RF remote control circuit
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RF remote control circuit
First topic message reminder :
Hi,
I'm also in search of a RF control circuit . The circuit should activate a relay while the transmitter is transmitting .
Recently i added a motor to my gate. Now it's operating from IR remote control and working fine , just that i need to wait until the gate opens . With a RF control i could open the gate from about 100m so when i get there the gate is open . At least in my theory .
I do have some RFM12 B radio modules and i could operate them with an arduino , but anybody can do that .
I would like an analog circuit instead , the transmitter would be installed in my car. So the supply is 12V and the antenna would be shared with the existing antenna from the radio , if possible. The receiver would be installed at the fence , supply and antenna is not a problem . Also security related problems are not an issue . (as i see now days it's enough to put an analog circuit and only a few know how it works )
I did try this circuit https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/27MHz_RX-TX_Remote.gif , i built the circuits. I can't make it work more than 10 cm .
I tried to tune the circuits to 2.5 Mhz , but i am not shore what i did is ok . I think the receiver is on neutrodyne principle . So i put the scope before the sfr choke and adjusted the coil until 2.5 MHz , then the same with the transmitter .
Simply i am not able to make it work . Maybe someone knows better circuit ?
Hi,
I'm also in search of a RF control circuit . The circuit should activate a relay while the transmitter is transmitting .
Recently i added a motor to my gate. Now it's operating from IR remote control and working fine , just that i need to wait until the gate opens . With a RF control i could open the gate from about 100m so when i get there the gate is open . At least in my theory .
I do have some RFM12 B radio modules and i could operate them with an arduino , but anybody can do that .
I would like an analog circuit instead , the transmitter would be installed in my car. So the supply is 12V and the antenna would be shared with the existing antenna from the radio , if possible. The receiver would be installed at the fence , supply and antenna is not a problem . Also security related problems are not an issue . (as i see now days it's enough to put an analog circuit and only a few know how it works )
I did try this circuit https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/27MHz_RX-TX_Remote.gif , i built the circuits. I can't make it work more than 10 cm .
I tried to tune the circuits to 2.5 Mhz , but i am not shore what i did is ok . I think the receiver is on neutrodyne principle . So i put the scope before the sfr choke and adjusted the coil until 2.5 MHz , then the same with the transmitter .
Simply i am not able to make it work . Maybe someone knows better circuit ?
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
12 m is quite enough if the TX antenna is inside a car. If both antennas are in free space, far (more than 10 lambda i.e. 7 m) from conductive bodies and there are no obstacles between them, the range may be up to 100 m or even more. Fog naturally increases the atmospheric absorption, decreasing the range.
You will not be happy with possible solutions: use a more sensitive receiver (limited by external, not own noise), transmitter power up to the legal limit for license free ISM, directive antennas with as much gain as you can afford and maybe math processing of the received signal to receive the information below the noise level.
VBR from Ivan
12 m is quite enough if the TX antenna is inside a car. If both antennas are in free space, far (more than 10 lambda i.e. 7 m) from conductive bodies and there are no obstacles between them, the range may be up to 100 m or even more. Fog naturally increases the atmospheric absorption, decreasing the range.
You will not be happy with possible solutions: use a more sensitive receiver (limited by external, not own noise), transmitter power up to the legal limit for license free ISM, directive antennas with as much gain as you can afford and maybe math processing of the received signal to receive the information below the noise level.
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Re: RF remote control circuit
hi
the rf meter seems to be useful so far.
I modified code so that the Tx is always on . I have 60 mv @ 50 cm away and about 20 mV @ 1 m away from tx antenna. Beyond that the meter is not able to show something .
Now what i do to increase range?
I observed that when is fogg outside the system is not working at all. When is clear i can open the gate ~12 m away
the rf meter seems to be useful so far.
I modified code so that the Tx is always on . I have 60 mv @ 50 cm away and about 20 mV @ 1 m away from tx antenna. Beyond that the meter is not able to show something .
Now what i do to increase range?
I observed that when is fogg outside the system is not working at all. When is clear i can open the gate ~12 m away
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi Zsolt,
I would try a stub of coax (or maybe a whole comb structure of stubs) as a filter. The indicator itself is really wideband, ranging from LW to microwaves.
VBR from Ivan
P.S.: Do not worry that the device looks ugly. Get it to work first, tidy it up later (or maybe never )!
I would try a stub of coax (or maybe a whole comb structure of stubs) as a filter. The indicator itself is really wideband, ranging from LW to microwaves.
VBR from Ivan
P.S.: Do not worry that the device looks ugly. Get it to work first, tidy it up later (or maybe never )!
Ivan- Posts : 772
Join date : 2012-11-25
Re: RF remote control circuit
I did a little modification to the display after studying the LM3914 datasheet and a lot of absorption rf meters from the net.
A lot of the schematics use 100 ....250 uA needle instruments . In analogy with that i modified the LM3914 circuit that i found to measure from 0 to 114 mV.
For this i modified the pcb ... now the whole circuit looks so ugly that it hurts eyes , but it seems to work
The schematicus i ended up is pictured like this:
I say it seems to work because meantime during a phone call i saw (almost scared ) that all LED's light up and flicker.
I found that i can even trace wires in the wall with this thing. Tomorrow i will make some time to see what is happening with the TX from the car. So far so good.
Since this circuit seems to react to everything i would make it to react to 433 MHz only . Some schematics where using some kind of resonator instead of the diode which goes to ground. I do have 433Mhz cristal from an other transmitter
The eye hurting product looks like this
A lot of the schematics use 100 ....250 uA needle instruments . In analogy with that i modified the LM3914 circuit that i found to measure from 0 to 114 mV.
For this i modified the pcb ... now the whole circuit looks so ugly that it hurts eyes , but it seems to work
The schematicus i ended up is pictured like this:
I say it seems to work because meantime during a phone call i saw (almost scared ) that all LED's light up and flicker.
I found that i can even trace wires in the wall with this thing. Tomorrow i will make some time to see what is happening with the TX from the car. So far so good.
Since this circuit seems to react to everything i would make it to react to 433 MHz only . Some schematics where using some kind of resonator instead of the diode which goes to ground. I do have 433Mhz cristal from an other transmitter
The eye hurting product looks like this
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
looking at the LM3914 block diagram i see a 20k rezistor on the signal input. From the whole document i can't find what is the input impedance. With this i will deal later. I plan to use 2 glass case diods. If not working i will try schotky. Meanwhile still searching for parts
I did a little test with 2 cooper rods as antenna.
Of course it des not work.
If i take away the potentiometer completely the leds light up when i get close to a monitor or even the soldering iron
The LM3914 is more like a voltmeter measuring the voltage drop on the potmeter . On the original rf meter the indicator is directly an ampermeter. Maybe that's the difference.
If i put a DVM on the potentiometer i get 40 mV when i approach the thing to the monitor. Maybe an amplifier is needed . Or the needle instrument needs to go..
Anyway now i know that the transmitter is rally week.
I did a little test with 2 cooper rods as antenna.
Of course it des not work.
If i take away the potentiometer completely the leds light up when i get close to a monitor or even the soldering iron
The LM3914 is more like a voltmeter measuring the voltage drop on the potmeter . On the original rf meter the indicator is directly an ampermeter. Maybe that's the difference.
If i put a DVM on the potentiometer i get 40 mV when i approach the thing to the monitor. Maybe an amplifier is needed . Or the needle instrument needs to go..
Anyway now i know that the transmitter is rally week.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Probably no microammeter has 500 Kohm internal resistance. I expect somewhere about 1 Kohm. The trimmer in your device should have similar value.zsolt wrote:Hi,
i started building the rf meter ....
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Re: RF remote control circuit
They are pretty old. The upper right is almost surely a germanium one. Germanium diodes have forward voltage drop about 0,3 V only. Check them with your meter.
VBR from Ivan
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Re: RF remote control circuit
Yes, that looks nice.
VBR from Ivan
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Re: RF remote control circuit
Hi,
i started building the rf meter .... i think this will be a separate thread for me. I can't break a 10uA indicator . I will use a scale with 10 led's to display signal strength . I found a ready made display like that with a LM 3914 on it.
I found some diod's in glass case . No inscription on them . One has a yellow marking near to a terminal . They might be rf since i have them from a radio receiver .The schematic i made up looks like this.
I also found a broken cable tester so i will be using that case to build this device in it.
I thought to make the dipole from 2 telescopic antennas which i can take of from broken radio receivers .In this way i could adjust the dipole to other frequencies also
i started building the rf meter .... i think this will be a separate thread for me. I can't break a 10uA indicator . I will use a scale with 10 led's to display signal strength . I found a ready made display like that with a LM 3914 on it.
I found some diod's in glass case . No inscription on them . One has a yellow marking near to a terminal . They might be rf since i have them from a radio receiver .The schematic i made up looks like this.
I also found a broken cable tester so i will be using that case to build this device in it.
I thought to make the dipole from 2 telescopic antennas which i can take of from broken radio receivers .In this way i could adjust the dipole to other frequencies also
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
with or without, it seems to make no difference.
ps the plastic case has a little ferrite ring inside.
ps the plastic case has a little ferrite ring inside.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,zsolt wrote:meanwhile should i put this ferrite on the rg174 cable?
it is impossible to guess the magnetic properties and losses at 433 MHz from a photo. Try it and you will se.
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
zsolt wrote:"i did not use any shielding or filtering." Wrong!
"i might have impedance mismatch!" At my first guess it is not critical.
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
Yes, they are, but there are loads of them in hamshacks. A pinpoint germanium diode is needed. The transistor may have big parasitic capacitance, I do not know the MP40 type. If you cannot find a germanium diode, use a silicon Schottky one, they should be available with no problem.zsolt wrote:the germanium diodes are quite obsolete. I found some germanium tranzistors. MP40. Do those do the job instead of the diods if i connect base to collector
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
i did not use any shielding or filtering. Everything gets power through a 5 v regulator. Looking at the tx schematic i might have impedance mismatch https://www.google.com/search?q=fs1000a+schematic&oq=fs1&aqs=chrome.1.69i59l2j69i57j69i60j69i61.2910j0j8&client=tablet-android-huawei&sourceid=chrome-mobile&ie=UTF-8#imgrc=PL7aZOlHypbECM:
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
the germanium diodes are quite obsolete. I found some germanium tranzistors. MP40. Do those do the job instead of the diods if i connect base to collector
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
No. To evaluate the radio channel, disconnect the MCU and test the bare TX - RX pair, with proper antennas of course. After it works O.K., add the MCU.zsolt wrote:i forgot to say how my tx works. I have a spst button. When i press it the circuit gets supplied. Then the microcontroller waits a little, sends some ascii characters and after that it turns on a beeper. When i hear the beeper i let go the button.
I don't know is this affects range or not
Btw the MCU on the TX side may be negatively affected by the EM field and/or RF on power supply rail. Do not forget proper shielding and filtering.
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
You compare the value shown on the meter at a certain distance from the antenna under test (AUT), when the AUT is in free space / on a metal roof / inside a car, turned at various angles etc. Or you can compare various types of AUT and what you like. The measurement is comparative only, not absolute.
VBR from Ivan
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
i forgot to say how my tx works. I have a spst button. When i press it the circuit gets supplied. Then the microcontroller waits a little, sends some ascii characters and after that it turns on a beeper. When i hear the beeper i let go the button.
I don't know is this affects range or not
I don't know is this affects range or not
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
how do i use that instrument? What to look for?
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
I found an improved version with voltage doubler here https://ok1fcb.webnode.cz/konstrukce/jednoduchy-vf-indikator/zsolt wrote:why does the car not steal the rf signal from the key when i open/close the door?
It probably steals some decibels. The range needed for a car lock is quite small. And I have no clue where the lock receiver is, its placement may be optimized. My car has no radio lock...
I do have a microampermeter with needle. I wil search for diode but how does that circuit look like?
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
why does the car not steal the rf signal from the key when i open/close the door?
I do have a microampermeter with needle. I wil search for diode but how does that circuit look like? The diode in parallel with the uA and al that in parallel with the 17 cm +17cm cooper rod?
Also i think i found the drawing of the tx that i have https://www.google.com/search?q=fs1000a+schematic&oq=fs1&aqs=chrome.1.69i59l2j69i57j69i60j69i61.2910j0j8&client=tablet-android-huawei&sourceid=chrome-mobile&ie=UTF-8#imgrc=PL7aZOlHypbECM:
I do have a microampermeter with needle. I wil search for diode but how does that circuit look like? The diode in parallel with the uA and al that in parallel with the 17 cm +17cm cooper rod?
Also i think i found the drawing of the tx that i have https://www.google.com/search?q=fs1000a+schematic&oq=fs1&aqs=chrome.1.69i59l2j69i57j69i60j69i61.2910j0j8&client=tablet-android-huawei&sourceid=chrome-mobile&ie=UTF-8#imgrc=PL7aZOlHypbECM:
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi Zsolt,
"the car steals from the rf power" -exactly so! Absorption and shielding take place inside a (metallic) car. Placing an antenna outside the car body is much better.
"some way to quantify how well my antenna is emitting and how well the other is receiving" - try a simple RF indicator. It should be a wire dipole tuned into the band attached to poles of a microampermeter (an old taperecoder indicator will do) and bridged by a RF detector diode. A Schottky or germanium one will give you more sensitivity. Use the reciprocity principle to measure the receiving antenna, use it as a transmitting one temporarily.
"an amplifier is at 433 mhz" - be careful not to exceed the power and spurious limit for ISM devices!
VBR from Ivan
"the car steals from the rf power" -exactly so! Absorption and shielding take place inside a (metallic) car. Placing an antenna outside the car body is much better.
"some way to quantify how well my antenna is emitting and how well the other is receiving" - try a simple RF indicator. It should be a wire dipole tuned into the band attached to poles of a microampermeter (an old taperecoder indicator will do) and bridged by a RF detector diode. A Schottky or germanium one will give you more sensitivity. Use the reciprocity principle to measure the receiving antenna, use it as a transmitting one temporarily.
"an amplifier is at 433 mhz" - be careful not to exceed the power and spurious limit for ISM devices!
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
i found out that the coax between the tx module and antenna is 50 ohm , it is called RG174, has 30.8pF/foot, 17 db /100 feet attenuation. I use only about 20 cm so i don't think it's a problem.
The system works sometimes, sometimes not. At short distance works always, then i when i go further away not at all and if i go more it works at a distance that i would not expect. If i move about 50 cm from that spot it doesn't work again.
When i was holding the module in my hand and tested the whole thing i had all most 100m, after i mounted the tx module in the car everything got bad. Somehow the car steals from the rf power. The car has also a radio for the lock system. I don't know at which frequency but when i put new battery in the key it works more than 50m.
i think i need some way to quantify how well my antenna is emitting and how well the other is receiving.
Some on the internet write that the tx module could operate from 12v to increase range. It did not work at all, i suspect that there is an issue regarding voltage levels with the microcontroller so i got back to 5 v.
i wonder how doable an amplifier is at 433 mhz, what tranzistor could do that, or should i buy one.
The system works sometimes, sometimes not. At short distance works always, then i when i go further away not at all and if i go more it works at a distance that i would not expect. If i move about 50 cm from that spot it doesn't work again.
When i was holding the module in my hand and tested the whole thing i had all most 100m, after i mounted the tx module in the car everything got bad. Somehow the car steals from the rf power. The car has also a radio for the lock system. I don't know at which frequency but when i put new battery in the key it works more than 50m.
i think i need some way to quantify how well my antenna is emitting and how well the other is receiving.
Some on the internet write that the tx module could operate from 12v to increase range. It did not work at all, i suspect that there is an issue regarding voltage levels with the microcontroller so i got back to 5 v.
i wonder how doable an amplifier is at 433 mhz, what tranzistor could do that, or should i buy one.
Last edited by zsolt on Sun Nov 17, 2019 7:30 pm; edited 1 time in total
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Well, improving an antenna is usually better than pumping big power into a bad one.
VBR Ivan OK1SIP
VBR Ivan OK1SIP
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
i don't know about this things. I found on the internet that i have to use a 1/4 dipole antenna. Then i googled just like that how to make one. I found a page that says that 2 pieces of 17 cm tube make a dipole like that.Ivan wrote:Hi,
first, what do you name as "1/4 dipole" ? Do you mean a dipole with 2x 1/4 wavelength (lambda) radoiators? Its overall length is then 1/2 lambda and THAT is its usual name.
Its impedance is real, cca 72 ohm balanced at resonance. I expect the TX output impedance is somewhere in that region, but unbalanced, suitable for a coax feeder. If this is your case, quite good and simple matching can be achieved by a ferrite bead(s) on the coax, just at the dipole. The bead brings inductance into the outer surface of the shield, stopping unwanted currents in it.
VBR Ivan OK1SIP
Then i built one and put it on the roof. I used tv cable to connect it to the receiver.
Today i mounted the same antenna in the car also
the results are slightly better.
I believe that there is no more to get out of this modules.
It did not work while the car is under the roof so i connected both, this antenna and cars radio antenna.
Now the remote works inside of the garage and about 50 m outside.
There may just not be enough rf power, in the end the tx works only from 5v. Maybe a tranzistor before the antenna would increase tx power
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
first, what do you name as "1/4 dipole" ? Do you mean a dipole with 2x 1/4 wavelength (lambda) radoiators? Its overall length is then 1/2 lambda and THAT is its usual name.
Its impedance is real, cca 72 ohm balanced at resonance. I expect the TX output impedance is somewhere in that region, but unbalanced, suitable for a coax feeder. If this is your case, quite good and simple matching can be achieved by a ferrite bead(s) on the coax, just at the dipole. The bead brings inductance into the outer surface of the shield, stopping unwanted currents in it.
VBR Ivan OK1SIP
first, what do you name as "1/4 dipole" ? Do you mean a dipole with 2x 1/4 wavelength (lambda) radoiators? Its overall length is then 1/2 lambda and THAT is its usual name.
Its impedance is real, cca 72 ohm balanced at resonance. I expect the TX output impedance is somewhere in that region, but unbalanced, suitable for a coax feeder. If this is your case, quite good and simple matching can be achieved by a ferrite bead(s) on the coax, just at the dipole. The bead brings inductance into the outer surface of the shield, stopping unwanted currents in it.
VBR Ivan OK1SIP
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
Yes , i will try the 1/4 dipole also .
And an other interesting fact i observed that the remote works even if the car is in the garage . Shouldn't the metallic roof stop the radio waves ?
I have no matching circuit . Do i need that for the 1/4 dipole?
And an other interesting fact i observed that the remote works even if the car is in the garage . Shouldn't the metallic roof stop the radio waves ?
I have no matching circuit . Do i need that for the 1/4 dipole?
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,zsolt wrote:made some progress. I had to try the antenna of the car. So i hooked everything up and tested the system. I don't even have 50 m range now.
i wonder why. The antenna is 75 cm . For 433mhz i have 69.24 cm wave length.All most the same. How could the range go down so quick. Because one antenna is a 1/4 dipole and the other is vertical whip? I will try to rotate the rx antenna with 90 degree to see what happens.
the antenna is more than one wavelenth long. You must expect high and not purely resistive impedance at the feedpoint, which is a bit hard to match to the TX output. What matching circuit do you employ?
And there is a cross-polarization issue (I have already warned you about that!). A horizontal dipole is horizontally polarized, while a vertical whip is vertically polarized. Turning the dipole to the vertical position solves this issue.
On the other hand, different profiles of antennae (wire vs. tubing) makes no problem.
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
made some progress. I had to try the antenna of the car. So i hooked everything up and tested the system. I don't even have 50 m range now.
i wonder why. The antenna is 75 cm . For 433mhz i have 69.24 cm wave length.All most the same. How could the range go down so quick. Because one antenna is a 1/4 dipole and the other is vertical whip? I will try to rotate the rx antenna with 90 degree to see what happens.
i wonder why. The antenna is 75 cm . For 433mhz i have 69.24 cm wave length.All most the same. How could the range go down so quick. Because one antenna is a 1/4 dipole and the other is vertical whip? I will try to rotate the rx antenna with 90 degree to see what happens.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
cooper tape peals off because the sun. I had issues with some led strips.Ivan wrote:hi,
I opt for the copper tape, for the sake of safety. IMHO the rods would exceed the frame of the mirror and they could cause a serious injury in the case of an accident. Soldering the tape is nearly the same as soldering a PCB. To avoid overheating the glass (and possible rupture), you can solder first, attach to the glass later.
VBR from Ivan
if i put the antenna right on the back of the mirror it exceeds only about 5 cm.. I found a better place anyway. close to the glass. I already have a flipping support for a tablet on the ceiling( like knight rider, but only for waze or google maps). I attach the antenna in front of that. So it will be way behind the rear view mirror almost touching the window It does not take anything from visibility. That part of the glass is already masked with some kind of black paint from the factory. Actually the whole top region of the window is darkened. Till now i did not even realised that. I think is something design related
Anyway i hope i will not have to rebuild the receiver antenna with the 3mm rods instead of the thick cooper pipes, that's my biggest concern with this for now.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
hi,
I opt for the copper tape, for the sake of safety. IMHO the rods would exceed the frame of the mirror and they could cause a serious injury in the case of an accident. Soldering the tape is nearly the same as soldering a PCB. To avoid overheating the glass (and possible rupture), you can solder first, attach to the glass later.
VBR from Ivan
I opt for the copper tape, for the sake of safety. IMHO the rods would exceed the frame of the mirror and they could cause a serious injury in the case of an accident. Soldering the tape is nearly the same as soldering a PCB. To avoid overheating the glass (and possible rupture), you can solder first, attach to the glass later.
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
hi,
i opt for the cooper rod antenna. Soldering wires to that paint on the glass i think will not hold much (i don't do off road on the mountain like mr Harry..but still)
Also i found some cooper like metal with 3mm diameter that i think is good.
The 2 antennas wil not be the same so i probably redo the antenna from the receiver (the one made of cooper pipes) if results turn out bad.
i opt for the cooper rod antenna. Soldering wires to that paint on the glass i think will not hold much (i don't do off road on the mountain like mr Harry..but still)
Also i found some cooper like metal with 3mm diameter that i think is good.
The 2 antennas wil not be the same so i probably redo the antenna from the receiver (the one made of cooper pipes) if results turn out bad.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
conductive paint is e.g. here:
https://www.amazon.de/dp/B00LTWQWXW/ref=sr_1_1?crid=111HFYX7Z5J3X&keywords=leitf%C3%A4higer+lack&qid=1573496739&sprefix=conductive+%2Caps%2C324&sr=8-1
or you can use self-adhesive copper tape e.g.
https://www.amazon.de/dp/B075R35B7X/ref=sr_1_17_sspa?crid=3OJBJ5N27BXAH&keywords=kontaktkleber&qid=1573496530&sprefix=%2Caps%2C240&sr=8-17-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFQTDNTOUZYSTRLSCZlbmNyeXB0ZWRJZD1BMDgyMDAyNDFTNkpFN1hSSE4wSFgmZW5jcnlwdGVkQWRJZD1BMDgwOTM5MzFBVElLS1JPSTlTV1omd2lkZ2V0TmFtZT1zcF9tdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
VBR Ivan
conductive paint is e.g. here:
https://www.amazon.de/dp/B00LTWQWXW/ref=sr_1_1?crid=111HFYX7Z5J3X&keywords=leitf%C3%A4higer+lack&qid=1573496739&sprefix=conductive+%2Caps%2C324&sr=8-1
or you can use self-adhesive copper tape e.g.
https://www.amazon.de/dp/B075R35B7X/ref=sr_1_17_sspa?crid=3OJBJ5N27BXAH&keywords=kontaktkleber&qid=1573496530&sprefix=%2Caps%2C240&sr=8-17-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFQTDNTOUZYSTRLSCZlbmNyeXB0ZWRJZD1BMDgyMDAyNDFTNkpFN1hSSE4wSFgmZW5jcnlwdGVkQWRJZD1BMDgwOTM5MzFBVElLS1JPSTlTV1omd2lkZ2V0TmFtZT1zcF9tdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
well, i finished the receiver for now.Ivan wrote:Hi,
"both antennas are not on the same axis" - it does not mind, the radiation pattern of a dipole is wide enough.
"the TX antenna is cca 10 cm under the roof" - maybe this is a problem, maybe not. The car roof is in the antenna's near field.
You may also try to glue two thin wires forming a dipole directly on the front glass or draw the dipole on the glass with silver conductive glue. Experiment and have fun!
VBR from Ivan
the antenna is made of 2 cooper pipes 17cm long each of them. i did not find information about the distance needed between the 2 pipes so i made a 5mm spacer. Actually the spacer is an axis having different diametral sections so that the two pipes go on it but not closer then 5mm. i used a plastic rod to make the spacer. In the end i put the whole thing in a plastic tube which i fixed on the roof and painted black.
I don't know about conductive paint. As i heard for an antenna the surface is important due to skin effect so drawing the antenna on the glass seems to be a good alternative.
When i first tested the modules with no antenna they worked just a few meters. When i soldered 2 pieces of wire range increased a lot. So i believe that matching the antennas does worth the effort. I already have a range of about 100m and the transmitter is still a piece of wire.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
"both antennas are not on the same axis" - it does not mind, the radiation pattern of a dipole is wide enough.
"the TX antenna is cca 10 cm under the roof" - maybe this is a problem, maybe not. The car roof is in the antenna's near field.
You may also try to glue two thin wires forming a dipole directly on the front glass or draw the dipole on the glass with silver conductive glue. Experiment and have fun!
VBR from Ivan
"both antennas are not on the same axis" - it does not mind, the radiation pattern of a dipole is wide enough.
"the TX antenna is cca 10 cm under the roof" - maybe this is a problem, maybe not. The car roof is in the antenna's near field.
You may also try to glue two thin wires forming a dipole directly on the front glass or draw the dipole on the glass with silver conductive glue. Experiment and have fun!
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
hi,Ivan wrote:Hi Zsolt,
the picture looks like you want to mount the TX dipole vertically,while the RX one horizontally. That would be bad, cross-polarization decreases the range significantly. But maybe I misunderstood the picture.
Nearby conductive objects cause loss of power, impedance changes and deformation of the radiation pattern of any antenna. Placing an antenna inside a car may make it useless due to the shielding effect. Perhaps the trial and error method is the best.
VBR Ivan
my drawing is not very accurate... but both antennas are horizontal. The rx antenna i built is about 10 cm above the metallic roof.I will make a photo in the morning.
I experimented with the tx which now has just a piece of cable instead of an antenna. It seams to work.
The antenna inside the car is not ready yet. The inside rear view mirror is horizontal. I plan to build the tx antenna on the back side of that. So the 2 antennas see each other directly through the front window (like i see the road or the rx antenna on top of the roof). The antennas are not on the same axis because for that i would need to put the rx antenna above the middle of the road. That is not possible, but they are both horizontal.
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi Zsolt,
the picture looks like you want to mount the TX dipole vertically,while the RX one horizontally. That would be bad, cross-polarization decreases the range significantly. But maybe I misunderstood the picture.
Nearby conductive objects cause loss of power, impedance changes and deformation of the radiation pattern of any antenna. Placing an antenna inside a car may make it useless due to the shielding effect. Perhaps the trial and error method is the best.
VBR Ivan
the picture looks like you want to mount the TX dipole vertically,while the RX one horizontally. That would be bad, cross-polarization decreases the range significantly. But maybe I misunderstood the picture.
Nearby conductive objects cause loss of power, impedance changes and deformation of the radiation pattern of any antenna. Placing an antenna inside a car may make it useless due to the shielding effect. Perhaps the trial and error method is the best.
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
i made a dipole antenna found on the internet. My construction is like a stick .
The orientation would be like this
I din't know how the metallic roof affects the antenna. The same antenna would be in the car . I found a place on the top side of the window on the back of the inside rear view mirror . Also i don't know how that affects the antenna.
Yagi i found hard to use because i don't know where to hide it on the car .
The orientation would be like this
I din't know how the metallic roof affects the antenna. The same antenna would be in the car . I found a place on the top side of the window on the back of the inside rear view mirror . Also i don't know how that affects the antenna.
Yagi i found hard to use because i don't know where to hide it on the car .
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
433 MHz has wavelength 69 cm, so many types of antennas are feasible. I would start with a 1/4 lambda vertical whip for all-direction coverage. If you want directivity (e.g. forward direction at TX and the direction of the way to your garage at RX), use a short yagi. Keep the polarization on both sides identical.
VBR from Ivan OK1SIP
433 MHz has wavelength 69 cm, so many types of antennas are feasible. I would start with a 1/4 lambda vertical whip for all-direction coverage. If you want directivity (e.g. forward direction at TX and the direction of the way to your garage at RX), use a short yagi. Keep the polarization on both sides identical.
VBR from Ivan OK1SIP
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
hi,
27 Mhz is much better , 433Mhz is even better.
Doorbell circuits don't last long . For some reason the chip burns out on tx side.
I bought a cheap tx rx pair for arduino , they run on 433Mhz .
My problem now is with the antennas.
What types of antennas could i make for longest distance?
For the beginning i plan to mount the receiver on the top of my garage because it's the highest place . I am afraid to put it higher because of lightning .
27 Mhz is much better , 433Mhz is even better.
Doorbell circuits don't last long . For some reason the chip burns out on tx side.
I bought a cheap tx rx pair for arduino , they run on 433Mhz .
My problem now is with the antennas.
What types of antennas could i make for longest distance?
For the beginning i plan to mount the receiver on the top of my garage because it's the highest place . I am afraid to put it higher because of lightning .
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
I will try to adjust my existing circuits to 27Mhz to see what happens
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Generally, two parameters of any transmitting antenna are crucial: matching to the transmitter last stage and so called radiation resistance. If the antenna is badly matched, the RF power reflects at its input and cannot be radiated. Short antennas (short relative to the wavelength in use) are usually hard to match. They are very capacitive, which requires big inductance in the matching network to compensate. Making a big inductance with big Q is often a hard problem. Ferrite cores are no good for power transfer on HF and higher.
The ratio of the radiation and loss resistances corresponds to the ratio of RF power radiated and converted to heat. Short whips (again relative to the wavelength) and thin wire loop antennas have a low radiation resistance, so the thermal losses dominate. These antennas may do for receiving at good conditions, but not for transmitting.
VBR Ivan
The ratio of the radiation and loss resistances corresponds to the ratio of RF power radiated and converted to heat. Short whips (again relative to the wavelength) and thin wire loop antennas have a low radiation resistance, so the thermal losses dominate. These antennas may do for receiving at good conditions, but not for transmitting.
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
Yes. Improving the TX antenna for 3 dB is equivalent to doubling the TX output power. Improving it for 10 dB is equivalent to increasing the power 10 times. Therefore several kilowatts connected to a short whip makes the same range as a single transistor working into a fair matched antenna...zsolt wrote:So now if i get it right and have that little transmitter connected to the antenna of the car radio, transmitting that audible tone , it should work if the receiver at the gate is sensitive enough. Just that for bigger distance that car radio antenna is not enough.
What if that little transmitter would have more rf power with same antenna? There are CB radios for cars which have also small antenna ( don't know about frequency)
i did not even tought about cooper tubing loop antenna, that reminds me about 'fox hunting' receivers. I did use a receiver like that
CB in Europe works in the 27 MHz band, generally the same as old radio remote controls. Other bands are possible on different continents.
When MW broadcasting was common, car radios used cca 2 m long whips as antennas. Such antenna could be well matched on 27 MHz. Antennas designed for FM only are probably too short.
A good ste about transmitting magnetic loops is e.g. at https://www.btv.cz/mla-t
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
hi,Ivan wrote:You are right,
although the arragement with two full size antennas has the best efficiecy, when you do not need a two-way communication, you can use a small receiving antenna and a sensitive receiver with good results. But, unfortunately, this does not work on the transmitting side. A magnetic transmitting loop made from copper tubing is possible, but still clumsy.
A wifi based solution is well possible, if your AP covers the area around your garage. Thanks to much higher frequency, the wifi antennas can have simply the form of meander on the PCB. To transfer the commands via internet is IMHO an overkill.
VBR Ivan
it's not such an overkill at all, for example one needs an arduino uno, a wifi shield and all sw can be found in various instructables on the net. The sw for an android operated smartfone can be found on googleplay. ( and so much about security) There are also aplications for those 'smart lightbulbs' and 'smart switches' that can be used..
So now if i get it right and have that little transmitter connected to the antenna of the car radio, transmitting that audible tone , it should work if the receiver at the gate is sensitive enough. Just that for bigger distance that car radio antenna is not enough.
What if that little transmitter would have more rf power with same antenna? There are CB radios for cars which have also small antenna ( don't know about frequency)
As i see the receiver, the rellay will clamp only when that audible tone is detected.
Yes the dorbell is at 433.9 Mhz.
i did not even tought about cooper tubing loop antenna, that reminds me about 'fox hunting' receivers. I did use a receiver like that
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
You are right,
although the arragement with two full size antennas has the best efficiecy, when you do not need a two-way communication, you can use a small receiving antenna and a sensitive receiver with good results. But, unfortunately, this does not work on the transmitting side. A magnetic transmitting loop made from copper tubing is possible, but still clumsy.
A wifi based solution is well possible, if your AP covers the area around your garage. Thanks to much higher frequency, the wifi antennas can have simply the form of meander on the PCB. To transfer the commands via internet is IMHO an overkill.
VBR Ivan
although the arragement with two full size antennas has the best efficiecy, when you do not need a two-way communication, you can use a small receiving antenna and a sensitive receiver with good results. But, unfortunately, this does not work on the transmitting side. A magnetic transmitting loop made from copper tubing is possible, but still clumsy.
A wifi based solution is well possible, if your AP covers the area around your garage. Thanks to much higher frequency, the wifi antennas can have simply the form of meander on the PCB. To transfer the commands via internet is IMHO an overkill.
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
hi,
wait a moment , now i see
"1/ To use a tuned full-length vertical at 2,5 MHz, it should be 30 m tall. Three or more radials should be about 30 m long each, too. The same antenna should be both at the tramsmitter and the receiver. Not much practical, am I right? With some sacrifice in efficiency, several metres long whip loaded by the proper coil may do the job.
"
why should i have 30m of antenna ? Remember my radio with the loop antenna? that is 20 turns on two 50 cm sticks in X form .That receives well a local station on 1330 kHz (1.33MHz)
that is the max i thought about , and maybe 2 m of wire stretched on the fence .
And why must be identical antenna on the rx and tx if both operate on same frequency ? Isn't a radio signal a radio signal for each?
For example my loop antenna again , i bet that the local radio station doesn't transmit with an antenna like my loop antenna but i am still getting the signal.
And anyway i just need between 50-100m range .
Don't get me wrong, i could attach a wifi module to the existing circuit and operate the gate with my smartphone over internet in 30 minutes (i have mobile data on that) ...... but a gate operated with a crappy radio ? how much people has that
( maybe james bond )
I don't know much about what i call "analog radio" because on the wifi and rx/tx modules i buy and use i don't get to that part . The only thing i ever looked up in a datasheet is how the information is serialized , timing and which address a few special registers have .
wait a moment , now i see
"1/ To use a tuned full-length vertical at 2,5 MHz, it should be 30 m tall. Three or more radials should be about 30 m long each, too. The same antenna should be both at the tramsmitter and the receiver. Not much practical, am I right? With some sacrifice in efficiency, several metres long whip loaded by the proper coil may do the job.
"
why should i have 30m of antenna ? Remember my radio with the loop antenna? that is 20 turns on two 50 cm sticks in X form .That receives well a local station on 1330 kHz (1.33MHz)
that is the max i thought about , and maybe 2 m of wire stretched on the fence .
And why must be identical antenna on the rx and tx if both operate on same frequency ? Isn't a radio signal a radio signal for each?
For example my loop antenna again , i bet that the local radio station doesn't transmit with an antenna like my loop antenna but i am still getting the signal.
And anyway i just need between 50-100m range .
Don't get me wrong, i could attach a wifi module to the existing circuit and operate the gate with my smartphone over internet in 30 minutes (i have mobile data on that) ...... but a gate operated with a crappy radio ? how much people has that
( maybe james bond )
I don't know much about what i call "analog radio" because on the wifi and rx/tx modules i buy and use i don't get to that part . The only thing i ever looked up in a datasheet is how the information is serialized , timing and which address a few special registers have .
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
I recommend you to use the doorbell including the coder. The receiver selectivity is fairly low. Most doorbells work in the 433 MHz ISM band, so any ham station working at 70 cm, any PMR or remote control module can provide the carrier. The encoder/decoder pair can prevent most cases of false triggering.
VBR from Ivan
I recommend you to use the doorbell including the coder. The receiver selectivity is fairly low. Most doorbells work in the 433 MHz ISM band, so any ham station working at 70 cm, any PMR or remote control module can provide the carrier. The encoder/decoder pair can prevent most cases of false triggering.
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
hi
could this circuit work on 27 Mhz if i change only the LC ?
I did open up a doorbell and i found 2 digital cips , one encoder at the button and one decoder at the bell, both with TTL input/outputs as i saw later in the datasheets.
The radio circuit interfacing the encoder is made with just one tranzistor in a topology that looks like the simple FM bugs that can be found on the internet .
At the receiver side the decoder cip is interfaced with 3 tranzistors. The first one has a topology just like the transmitter on the encoder side (where the button is placed) and the second 2 tranzistors look like an amplifier or a trigger , probably it adjusts the signal level to TTL for the decoder.
The doorbell is a good idea .
could this circuit work on 27 Mhz if i change only the LC ?
I did open up a doorbell and i found 2 digital cips , one encoder at the button and one decoder at the bell, both with TTL input/outputs as i saw later in the datasheets.
The radio circuit interfacing the encoder is made with just one tranzistor in a topology that looks like the simple FM bugs that can be found on the internet .
At the receiver side the decoder cip is interfaced with 3 tranzistors. The first one has a topology just like the transmitter on the encoder side (where the button is placed) and the second 2 tranzistors look like an amplifier or a trigger , probably it adjusts the signal level to TTL for the decoder.
The doorbell is a good idea .
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi Zsolt,
did you consider adapting a wireless doorbell for your purpose?
VBR Ivan
did you consider adapting a wireless doorbell for your purpose?
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
Your transmitter has a small ferrite antenna only? Its efficiency for transmitting is very low. No wonder you bridged a small range only.
VBR Ivan once more
VBR Ivan once more
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
Hi,zsolt wrote:1/ i did not try 27 mhz only 2.5mhz
2/ security is absolutely not an issue here where i live. I can even leave without closing the gate, nothing will hapen.
3/ I wonder what frequency those toy boats have.
1/ To use a tuned full-length vertical at 2,5 MHz, it should be 30 m tall. Three or more radials should be about 30 m long each, too. The same antenna should be both at the tramsmitter and the receiver. Not much practical, am I right? With some sacrifice in efficiency, several metres long whip loaded by the proper coil may do the job.
2/ Be really happy!
3/ Old RC cars and boats use 27 MHz. The channel is selected by changing the crystals on both sides. Airplanes use an exclusive 40 MHz band. Modern RC models and toys usually work in the 2400 MHz band with automatic free channel selection (a Wi-fi similar technology).
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
i did not try 27 mhz only 2.5mhz because i have now just a bad scope. As i mentioned security is absolutely not an issue here where i live. I can even leave without closing the gate, nothing will hapen. Also i never bothered with ciphering and deciphering. Usually i send over some text with a cyclic redundancy check attached to it. (and don't bother with that neither at the receiver side.. if the first and last characters match it s ok.. ) The modules i have work well about 20 m. I want at least 100m. And the soil is not flat. Down the lake i saw a fisher with RC boat, it could go from one side to the other. I wonder what frequency those toy boats have.
Also i'm not in hurry to make the circuit work. As i built the circuit from the link below i can build an other one if it works better.
There is no documentation provided for the circuit but i am shore it should do much better then 1 m range. I checked components and everthing is fine
Also i'm not in hurry to make the circuit work. As i built the circuit from the link below i can build an other one if it works better.
There is no documentation provided for the circuit but i am shore it should do much better then 1 m range. I checked components and everthing is fine
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi,
everybody can know the SPI protocol of the modules, but nobody knows the clever ciphering/deciphering algorithm you implement into the attached MCU. The TRXes provide a serial communication channel up to 115,2 kb/s. The safety can be really high! Using these or similar modules is faster than making a transceiver from scratch.
27 MHz has the wavelength more than 10 m. How is your antenna and counterweight long?
VBR Ivan
everybody can know the SPI protocol of the modules, but nobody knows the clever ciphering/deciphering algorithm you implement into the attached MCU. The TRXes provide a serial communication channel up to 115,2 kb/s. The safety can be really high! Using these or similar modules is faster than making a transceiver from scratch.
27 MHz has the wavelength more than 10 m. How is your antenna and counterweight long?
VBR Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
Re: RF remote control circuit
Ivan wrote:Hi Zsolt,
what do you mean saying "analog"? AFAIK any radio transmission by itself, i.e. generating and receiving a radio wave, is analog. Modulating and processing of the signal can be digital, anyway.
I recommend you to make use of ready-made modules in the ISM band 433 MHz or 2,4 GHz. There are loads of them on the web at moderate prices. Use either a specialized chip or a MCU (Arduino etc.) to implement a floating code on both ends for safety.
VBR from Ivan
Hi,
i have RFM12B modules , those communicate with a microcontroler by serial peripheral interface (SPI) that's what everybody has. I also have modules which comunicate over I2C . I will not use them. A circuit like that from the link will do the job . I don't know why i can't make it work.
The relay clamps if the distance less then 1 m
zsolt- Posts : 209
Join date : 2017-12-19
Re: RF remote control circuit
Hi Zsolt,
what do you mean saying "analog"? AFAIK any radio transmission by itself, i.e. generating and receiving a radio wave, is analog. Modulating and processing of the signal can be digital, anyway.
I recommend you to make use of ready-made modules in the ISM band 433 MHz or 2,4 GHz. There are loads of them on the web at moderate prices. Use either a specialized chip or a MCU (Arduino etc.) to implement a floating code on both ends for safety.
VBR from Ivan
what do you mean saying "analog"? AFAIK any radio transmission by itself, i.e. generating and receiving a radio wave, is analog. Modulating and processing of the signal can be digital, anyway.
I recommend you to make use of ready-made modules in the ISM band 433 MHz or 2,4 GHz. There are loads of them on the web at moderate prices. Use either a specialized chip or a MCU (Arduino etc.) to implement a floating code on both ends for safety.
VBR from Ivan
Ivan- Posts : 772
Join date : 2012-11-25
Age : 64
Location : Praha, Czechia
RF remote control circuit
Hi,
I'm also in search of a RF control circuit . The circuit should activate a relay while the transmitter is transmitting .
Recently i added a motor to my gate. Now it's operating from IR remote control and working fine , just that i need to wait until the gate opens . With a RF control i could open the gate from about 100m so when i get there the gate is open . At least in my theory .
I do have some RFM12 B radio modules and i could operate them with an arduino , but anybody can do that .
I would like an analog circuit instead , the transmitter would be installed in my car. So the supply is 12V and the antenna would be shared with the existing antenna from the radio , if possible. The receiver would be installed at the fence , supply and antenna is not a problem . Also security related problems are not an issue . (as i see now days it's enough to put an analog circuit and only a few know how it works )
I did try this circuit https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/27MHz_RX-TX_Remote.gif , i built the circuits. I can't make it work more than 10 cm .
I tried to tune the circuits to 2.5 Mhz , but i am not shore what i did is ok . I think the receiver is on neutrodyne principle . So i put the scope before the sfr choke and adjusted the coil until 2.5 MHz , then the same with the transmitter .
Simply i am not able to make it work . Maybe someone knows better circuit ?
I'm also in search of a RF control circuit . The circuit should activate a relay while the transmitter is transmitting .
Recently i added a motor to my gate. Now it's operating from IR remote control and working fine , just that i need to wait until the gate opens . With a RF control i could open the gate from about 100m so when i get there the gate is open . At least in my theory .
I do have some RFM12 B radio modules and i could operate them with an arduino , but anybody can do that .
I would like an analog circuit instead , the transmitter would be installed in my car. So the supply is 12V and the antenna would be shared with the existing antenna from the radio , if possible. The receiver would be installed at the fence , supply and antenna is not a problem . Also security related problems are not an issue . (as i see now days it's enough to put an analog circuit and only a few know how it works )
I did try this circuit https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/27MHz_RX-TX_Remote.gif , i built the circuits. I can't make it work more than 10 cm .
I tried to tune the circuits to 2.5 Mhz , but i am not shore what i did is ok . I think the receiver is on neutrodyne principle . So i put the scope before the sfr choke and adjusted the coil until 2.5 MHz , then the same with the transmitter .
Simply i am not able to make it work . Maybe someone knows better circuit ?
zsolt- Posts : 209
Join date : 2017-12-19
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