GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Fri Mar 16, 2018 7:19 pm


It was so simple  in the end !  Cool

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Tue Mar 13, 2018 6:11 pm

HI again,
i don't give up on the digitalised GDO , just that i have to delay that for now .
You remember the first GDO i ever bult from this site for testing security labels , somewhere in the first pages ?
Well it works ,we also bought  a whole security gate to double check the labels and the "GDO label tester" , actually it works so well that "they" (where i work) want me to build an other GDO to send it to the Chinese so they can send us the labels we want . (i think if i send it there , in a week i can by it  on e-bay or so, with free shipping  lol!   ) 
The thing is that i can't find double variable capacitor's (i could get some from the net but i also dislike them ) So i go with the varicap/zenner/led thing Using my experience with the digitalis-ed GDO attempt i made up the confusicus circuitus below

The main problem is the oscillogram i get in the scope  (i forgot to take a picture but it looks like in the drawing)
It's in the Khz range , thous it's the replica of the digitalised version . Actually there i used 100pF with the zenners , here i put only 10 pf in the hope that frequency will go up to 8 MHz range
The level output i wanted to use for triggering (with an other circuit , trigger Schmidt ..or something i don't know yet...  )  a LED for a good label that passes beside the coil . If i manage to make it to run good, i also intend to use a similar unit with trigger output to build a little sorter machine (unwind > nipp roll > GDO> rewind with a rudimentary tensioning system )
For now it is not oscillating right and i have no clue why, if you guys have an idea , that would help. I remember that the very first GDO put out a nice sine wave . It's not the zenners , i throw them out and put a 33 pf for each . Same form and same period . Oh and i also tried out LEDs instead of zenners . Leds are cool

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Fri Mar 02, 2018 3:20 pm

Hi ,
with the thin wire the f did go down... now i have an other trouble with the second fet. The drain signal is dc , about 6v with so little pulse that i can't see it . I managed to see  it  with the scope set on AC input 

with this setting (the scope was working but for some reason the blitz completely erased the green line from the screen )

The signal looks like this (with the blitz off )

I took the source of the second fet and put it to ground . This increased somewhat the signal (in AC) about 800mV pp
I introduced one more tranzistor in the circuit

It's more complicated as i intended .... now i have frequency reading on LCD. . Just that changing voltage on the zenners does not affect frequency

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Thu Mar 01, 2018 9:43 pm

Ok, I understand.

For "really" low frequencies I used the enamelled wire from relays. You can pile-wind then using an electric screwdriver, then it should bring the frequency down.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Thu Mar 01, 2018 7:55 pm

hi ,
no need for that . It's oscillating alright , i discovered that it's on high frequency . It goes well above 100 Mhz . It's so out of my intended range that it's no use . I don't know yet how to build proper air wound coils  to go down with  frequency (or if it works like that )
Any way  parts of the code are usable for other projects also. I tried to depict in a few lines what it does now. I intended to add a joystick to easily navigate through a little menu (also not donne) .  If you read the little description you can see that you may theoretically use the frequency meter part for your projects at higher frequencies also just by tweaking the gate timer , but i can tell that the  uc's electronic circuitry for some reason won't go higher than ~ 50 Mhz .

/*
 * JAKAB ZSOLT 14.022018 
 * SOMETHING GDO like ... something 
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 7
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD backlight control to pin 10 
 * boost PWM pin 6
 * boost feedback pin A3
 * dipp detection on A2 
 * timer one T1 input is port PD5 on the ATMEGA328P cip , that is in fact PIN 5 on ARDUINO NANO board , this will be the 2 byte counter register which can count up to 65536 .
 * Timer two is used to provide the time base for gateing T1 counter's input . I used 1 ms gate time  (for a frequency meter the user can make 
 *  this parameter vaariable for better acuracy / autoscaling) , so the frequency is 
 *  f = [ (65536 x number times that the register rolled over) + the register's acual value ] / 2000       [Mhz}
 *  The pid regulator is in paralell form , has self tuning included and uses 2 sets of P,I,D coeficients , one agressive set for large error and 
 *   an other set for "close to zero error "
 *   I dont program a lot, because to layzy for that... many subroutines are borrowed and modified  for my actual needs  , it's not finished and is in a raw form . Fel free to use what u need ( as i did)
 */
 
 #include <LiquidCrystal.h>
 #include <PID_v1.h>
 #include <avr/interrupt.h>

 LiquidCrystal lcd(12, 11, 7, 4, 3, 2);
 int dispcnt=0;
 float refV=2.10;   
 double Setpoint, Input, Output;                                         // PID vars
 double aggKp=50, aggKi=1.7, aggKd=0.8;
 double consKp=30, consKi=0.5, consKd=0.2;
 double gap=0;
 int btg=0;
 unsigned char sreg;

 byte smiley[8] = {
  B00000,
  B10001,
  B00000,
  B00000,
  B10001,
  B01110,
  B00000,
};

volatile unsigned long period=0;   
float frequency=0.00;           
volatile boolean       measurement_ready;
volatile unsigned char overflow_counter;     // number of overflows within gate_time
volatile unsigned int  time_so_far;              // number of ISR calls
volatile unsigned int  gate_time;      
 
 PID myPID(&Input, &Output, &Setpoint, consKp, consKi, consKd, DIRECT);
 double CNT=0;

void setup()
{
  delay(300);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, INPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(A3, INPUT);
  pinMode(A2, INPUT);
  digitalWrite(10,1);
  lcd.createChar(0, smiley); 
  lcd.begin(8, 2);
  lcd.print("hello!");
  lcd.setCursor(0,1);
  lcd.write("       ");
  lcd.write(byte(0));
  delay(1000);
  Setpoint = 2.5;
  setPwmFrequency(6, 1);                                                // 62500/1 = 62500 hz
  Input = 2*(runningAverageFeedback(analogRead(A3)))*0.0049;            // pid fedback
  myPID.SetMode(AUTOMATIC);                                             //turn the PID on
}

void loop()
{   
  Setpoint=2.01;
  
  //__________________________________________________________
  Input=14.1875*(runningAverageFeedback(analogRead(A3)))*0.0049;       
  gap = abs(Setpoint-Input); //distance away from setpoint
  if (gap < 0.1)
  {  //we're close to setpoint, use conservative tuning parameters
    myPID.SetTunings(consKp, consKi, consKd);
  }
  else
  {
     //we're far from setpoint, use aggressive tuning parameters
     myPID.SetTunings(aggKp, aggKi, aggKd);
  }                                           
  myPID.Compute();                                                     // run PID algorithm
  if(Output>200)Output=200;
  analogWrite(6,Output);  
  //____________________________________________________________
  measurement(1);       // 1 ms gate time   
  while (measurement_ready==false);
 
   //________________________________________________________
  dispcnt++; 
   if(dispcnt==250)
    {
      lcd.clear();
      dispcnt=0;
      lcd.print(Input,3);
      lcd.setCursor(0,1);
      lcd.print(frequency,3); 
      if(frequency<10)lcd.write("  ");
      if(frequency>=10 && frequency<=100)lcd.write(" ");
      lcd.write('M');
    }
}
//______________________________________________________
long runningAverageFeedback(int M) {
  #define LM_SIZE 18
  static int LM[LM_SIZE];      
  static byte index = 0;
  static long sum = 0;
  static byte count = 0;
  
  sum -= LM[index];
  LM[index] = M;
  sum += LM[index];
  index++;
  index = index % LM_SIZE;
  if (count < LM_SIZE) count++;
  return sum / count;
}
//---------------------------------------------------------------
void setPwmFrequency(int pin, int divisor) {
  byte mode;
  if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {
    switch(divisor) {
      case 1: mode = 0x01; break;
      case 8: mode = 0x02; break;
      case 64: mode = 0x03; break;
      case 256: mode = 0x04; break;
      case 1024: mode = 0x05; break;
      default: return;
    }
    if(pin == 5 || pin == 6) {
      TCCR0B = TCCR0B & 0b11111000 | mode;
    } else {
      TCCR1B = TCCR1B & 0b11111000 | mode;
    }
  } else if(pin == 3 || pin == 11) {
    switch(divisor) {
      case 1: mode = 0x01; break;
      case 8: mode = 0x02; break;
      case 32: mode = 0x03; break;
      case 64: mode = 0x04; break;
      case 128: mode = 0x05; break;
      case 256: mode = 0x06; break;
      case 1024: mode = 0x07; break;
      default: return;
    }
    TCCR2B = TCCR2B & 0b11111000 | mode;
  }
}
//_______________________________________________________________
void measurement(int ms) {

    bitClear(TIMSK0,TOIE0);     // disable counter0 in order to disable millis() and delay()
                                             // this will prevent extra interrupts that disturb the measurement
    delayMicroseconds(66);      // wait for other interrupts to finish
    gate_time=ms;                  // usually 1000 (ms)
  
    // setup of counter 1 which will be used for counting the signal impulses

    TCCR1A=0;                  // reset timer/counter1 control register A
    TCCR1B=0;                  // reset timer/counter1 control register B
    TCCR2A=0;                  // reset timer/counter1 control register A
    TCCR2B=0;                  // reset timer/counter2 control register A
    
    // setup of counter2 which will be used to create an interrupt every millisecond (used for gate time)

    TCCR2B |= B00000101;        // set prescale factor of counter2 to 128 (16MHz/128 = 125000Hz)
                                               // by setting CS22=1, CS21=0, CS20=1

    bitSet(TCCR2A,WGM21) ;      // set counter2 to CTC mode
                                              // WGM22=0, WGM21=1, WGM20=0                   
    OCR2A = 124;                      // CTC divider will divide 125Kz by 125 
   
    measurement_ready=0;        // reset
    time_so_far=0;                    // reset
    bitSet(GTCCR,PSRASY);        // reset the prescaler 
    TCNT1=0;                           // set frequency counter1 to 0
    TCNT2=0;                           // set gate time counter2 to 0
      
    bitSet(TIMSK2,OCIE2A);        // enable counter2 interrupts
    TCCR1B |= B00000111;        // set CS12, CS11 and CS10 to "1" which starts counting 
                                               // on T1 pin (Arduino pin D5)
 }
 //_______________________________________________________________________________________________________
ISR(TIMER2_COMPA_vect) {
 
  if (time_so_far >= gate_time) {          // end of gate time, measurement is ready
    TCCR1B &= B11111000;                   // stop counter1 by setting CS12, CS11 and CS10 to "0"
    period=0x10000 * overflow_counter;     // mult #overflows by 65636 (0x10000)
    period += TCNT1;                       // add counter1 contents for final value
    frequency = (float)period/2000;                  // frequency [Mhz]
    overflow_counter=0;                    // reset overflow counter
    bitClear(TIMSK2,OCIE2A);               // disable counter2 interrupts
    bitSet(TIMSK0,TOIE0);                  // enable Timer0 again // millis and delay
    measurement_ready=true;                // set global flag for end count period  
  }
  else {
    time_so_far++;                            // count number of interrupt events
    if bitRead(TIFR1,TOV1)  {               // if Timer/Counter 1 overflow flag = "1" then ...
       overflow_counter++;                  // increase number of counter1 overflows
       bitSet(TIFR1,TOV1);               // reset counter1 overflow flag
    }
  };
}

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Wed Feb 28, 2018 8:13 pm

... then try adding the 15pf + 15pf AND the zeners. See if the oscillations stop.

I would expect the frequency to increase when you use varicap/zeners, maybe 5x the frequency, but this circuit usually oscillates so easily.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Wed Feb 28, 2018 7:04 am

Hi, 
i removed the zenners , added the 15pF changed the BF245 with BF256 , same result.
Usually when i build an amplifier i get a wonderful oscillator.
I think it might oscillate , i put on a 10 Mhz osciloscope . It does show a very high frequency  signal , actually i can receive that with fm radio on 98Mhz .
That's bad i wanted a frequency range to be maximum 10 Mhz .
if i put back the zenners the signal is gone .
And also no matter what capacitor i put instead of the zenner  the signal is same , after capacitor increase, above 1nF the signal is gone .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Tue Feb 27, 2018 9:56 pm

Isolate the fault - is it the oscillator or the zener tuning?

Remove the Zener diodes and fit 15pf capacitors. Check if it oscillates then:

If it does oscillate then make sure you have the zeners the correct way round (DC volts across them, with +ve to cathode).
If it does NOT oscillate then you have a basic oscillator problem (wiring or defect device).

Assuming you have checked the circuit is correctly wired ?

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Tue Feb 27, 2018 6:40 pm

Hi ,
i put last parts on , fire it up and .... it's not oscillating 

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Tue Feb 27, 2018 2:36 am

There are large varicaps available for MW applications, but I have never used them.
The varicap-zener still gives you good capacitance ratio, so you can still have a reasonable frequency ratio - just a higher freq. range than the variable caps, thats all.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Mon Feb 26, 2018 8:25 pm

Admin wrote:The 16-V Zener has a capacitance of about 15pf at 2 volts, at least those I tried did.

LEDs also work as varicaps, but the capacitance is a little less and they seem to fail at higher frequencies (above 200MHz).

Good luck with the zeners.

BR Harry
hmm , so i could estimate max zenner capacitance about 30 pF  ... if i put 33pF for the fix capacitors in the end it would be really high frequency . Maybe i can take it down around 8 Mhz with the coil ..

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Mon Feb 26, 2018 8:14 pm

The 16-V Zener has a capacitance of about 15pf at 2 volts, at least those I tried did.

LEDs also work as varicaps, but the capacitance is a little less and they seem to fail at higher frequencies (above 200MHz).

Good luck with the zeners.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Mon Feb 26, 2018 7:35 pm

Admin wrote:It is looking good.
I am sorry but I don't have any 24-V Zener diodes or I would willingly send you a few.
It will be interesting to see how your unit works. Please keep us informed :-)

BR Harry
Laughing  thanks , the shipment of those 2 diodes  would be the cost of 100 diodes  lol!
I can purchase everything from tme.eu  what the local supplier don't has that's not a problem just that the shipment is from week to week , on Friday s (younger papanasos don't have patience ) 
I have bought several zenners , i put there 2 of 24 V . 
I also have capacitors from 33pF to 470 pF.  I don't know how to estimate the zenners capacitance . I know that with 2 series capacitor connection the equivalent is smaller than the smaller from both . Should i put there 100pF and see what happens ?
Or maybe 330pF ? if the zenner can go up to 330pF , than Cmax vould be ~165 pf and Cmin a little lower than the zenner can go , All most like the variable condensator u used .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Mon Feb 26, 2018 6:20 pm

It is looking good.
I am sorry but I don't have any 24-V Zener diodes or I would willingly send you a few.
It will be interesting to see how your unit works. Please keep us informed :-)

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sun Feb 25, 2018 4:00 pm

hi, today i had time for a little soldering . I put on a few parts

I don't keep many spare discrete components in stock . I need to buy two 24 V zenners as varicap diodes and the dc blocking capacitor for them . What would be a reasonable range for them ? 33pF ...100 pF ?
This i have on the board now + uncertainties  

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Wed Feb 21, 2018 7:57 pm

Hi again,
If you have files to add then I can host them for you. Just send me the files.
I also think it must be possible to create anb HTML server where guests can post pix and files, then link to them in the forum.
Hmmm ...  maybe the facility already exists ... will cheque.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Tue Feb 20, 2018 6:56 pm

Admin wrote:Yes, you must keep us informed. Code would be really appreciated.

As regards tubes, I am having a little nostalgia at the moment with tubes. I have the circuit of my oscilloscope to document, sitting here on paper awaiting to be drawn. Things to do every day :-)

Will post the circuits as soon as they are drawn and viewed.

BR Harry
ok , i'll need some help with the code thing , in principle i can copy / paste it here . But i'm using some header files and libraries pre-installed on my computer. So it wont be usable so directly as it is , one must download libraries i also downloaded and add  them to it's own library director  on C: Program files/ Arduino / libraries.......  (the boring stuff..) . Anyway one can post here questions so it should not be a problem helping out  Very Happy
Working with these  little useful boards is so easy , there are hundreds of examples on ''holly google" for absolutely everything , every module or peripheric  once invented and available on the market . I discovered these boards a few  years ago and i started to integrate them in industrial equipment . I can tell that in some particular cases (small and simple applications, not so fast processes ) they can successfully replace an expensive PLC .  (not to mention that programming doesn't need more than an USB cable ) 
Before them i was working with microcontrollers from microchip, i may still have some useful circuits for you radio amateurs  that i can share  , actually things i use some times , frequency meter , L C meter (i think this was probably made by a radio amateur because of the small values it can measure Smile ) , signal generator ... (don't know about precision or so , i just built them as found on the net )

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Tue Feb 20, 2018 8:59 am

Yes, you must keep us informed. Code would be really appreciated.

As regards tubes, I am having a little nostalgia at the moment with tubes. I have the circuit of my oscilloscope to document, sitting here on paper awaiting to be drawn. Things to do every day :-)

Will post the circuits as soon as they are drawn and viewed.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Mon Feb 19, 2018 6:02 pm

hi , i will post here all step by step ,also code or hex file , maybe someone wants to experiment  and it will not be "confusicus" it will be "simplicus"  Laughing  ... now  i have to find some FET s , most available that comes in my mind would be BF245 , but i can get some other types also. And i still have to get some of those diodes . For some reason it's  easier for me to get development boards  or even complete plc's than discrete components . 
Oh and i have a box full with valves , when i will have time to play, i think i will build something around here  , maybe a radio  Very Happy  .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Sun Feb 18, 2018 8:59 pm

Wow!! that looks fantastic.
It gives me a great thrill when someone can take one of my projects and "run with it".
Please DO keep the photo's coming. I would also be interested in a final "circuitus-diagramus confusicus" when it is finished.

Small comment about frequency range, there is absolutely no reason why you cannot use more coils to cover a wider range.

Another project I will phograph when I return to Sweden is a Tunnel-Diode oscillator. In principle it is two resistors, one capacitor and a 9-volt battery. If you connect the two crocodile clips to anything that resonates then it will oscillate at that thing's resonant frequency.

In my courses I connect it to a roll of URM67-U cable (with the far end shorted) and switch it on. It always oscillates at 1.1210MHz, because the cable length is 88.314 metres. I use a counter or a spectrum analyser to view the frequency.

This could be an altrernative to the GDO and may well work in your application. Pruning antenna centre-frequencies, coil resonance, cable resonance, cable-length ...

BT Harry - SM0VPO

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sun Feb 18, 2018 8:58 am

So far so good 

first row now is a voltage .
second row is frequency . I used a small dds signal generator i have (has only 0-65khz, and a few Mhz @ ttl level) to generate some signal
Also at the moment the circuit looks like this

Voltage feedback (first row, set point being 12V) on pin  A3 is the input of a discrete PID controller and pin 6 is it's output (Fpwm =65kHz). Frequency is counted by timer T1 configured as external clock sourced counter (pin 5) and internal timer 2 is used as 1ms gate for T1.
The boost converter need's some proper corrections (i used what i found) thous its behaving well thanks to the control algorithm , it still draws ~ 70 mA at full range 48 V  (12 V on output) for doing nothing (perhaps only for charging the 10uF and supplying the voltage divider circuits ?? )
The whole thing takes 100mA

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Thu Feb 15, 2018 9:16 pm

Hi IVAN 
i seee ...  Shocked  i'll get to that part later .
Now i just put together the boost converter, arduno and lcd . In first place i'll try to write a little program to see on lcd the voltage regulation for the varicaps . I'm using a PID regulator to control voltage . For the moment i close the PID loop with a voltage feedback . For the non linearity you mentioned i just came up with an other idea , in the end when things work a little bit i just have to close the PID loop feedback on the frequency reading instead of the voltage reading i'm doing now , so it's up to the PID to deal with the voltage  Very Happy  . This would be logic since in the end i want to control frequency process  not voltage . 
I will show up with some pictures when i put something presentable together .
At the moment  i have some trouble with finding an adequate  coil for the boost converter . I should have build the coil winder i wanted (and learn how to calculate coils for dc-dc converters )  bounce
I found an online boost calculator which gives me an approximation of the coil i need . The closest  store  doesn't supply coils at all (except for big  audio filter coils), i also throw away electronic scrap around the house ... this will take a while

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Ivan on Thu Feb 15, 2018 8:51 am

zsolt wrote:HI ,
I don't understand the term 3:1 frequency ratio , also 9:1 capacitance ratio . The ratio of f1/f2 = 3 , and C1/C2=9  ? If so what is f1,f2,C1,C2 ?
Hi,
f1 ... the lowest frequency of the range
f2 ... the highest frequency
C1 ... maximum capacity
C2 ... minimum capacity

The frequency is inversely proportional to the square root of capacity, so to get a 3:1 frequency ratio, you need a 9:1 capacity ratio with fixed inductance.

BTW, the dependance of diode capacity on DC voltage is very nonlinear, too. If you want to optimize the frequency search, you should use various voltage steps at different parts of the range.

BR from Ivan OK1SIP

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Wed Feb 14, 2018 7:01 pm

Admin wrote:Hi Zsolt,
The varicaps should not draw any current at all.

I also once read that you can use switching diodes to get a really wide frequency ratio. To get 3:1 frequency you need at least 9:1 capacitance raio. Using an ordinary 1N914 switching diode you can bias it to a specific voltage.

When the oscillations cause the RF waveform in the oscillator, the diode will conduct for only a part of the RF sine waveform, and switch in a bigger capacitor for only a part of the waveform. If you have trouble with frequency range then this could be a solution.Also cheap diodes, not varicaps.

BR Harry - SM0VPO
HI ,
I don't understand the term 3:1 frequency ratio , also 9:1 capacitance ratio . The ratio of f1/f2 = 3 , and C1/C2=9  ? If so what is f1,f2,C1,C2 ?
Oh and one other thing , what f/V ratio would be adequate to start with ? I'm just concerning that if the voltage increment is to big,  the frequency variation is to large ... I can express myself better like this : should i hunt  for Vout=Vout+0.1 ; or Vout = Vout+0.001 increments ? (since frequency is function of Vout i think this is important)     Laughing practical experience will tell i think . 
Maybe a big range can be covered with one single coil using these varicaps , this would be also a thing to hunt for 
First i'm going to build the boost converter with the arduino and an lcd to test the voltage regulation capability . Also the arduino's counter can't go higher than ~60 Mhz so this is also a limit . I read about some simple counter IC's that can be used to divide by 2 ... 10 .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Sun Feb 11, 2018 9:41 pm

Hi Zsolt,
The varicaps should not draw any current at all.

I also once read that you can use switching diodes to get a really wide frequency ratio. To get 3:1 frequency you need at least 9:1 capacitance raio. Using an ordinary 1N914 switching diode you can bias it to a specific voltage.

When the oscillations cause the RF waveform in the oscillator, the diode will conduct for only a part of the RF sine waveform, and switch in a bigger capacitor for only a part of the waveform. If you have trouble with frequency range then this could be a solution.Also cheap diodes, not varicaps.

BR Harry - SM0VPO

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Fri Feb 09, 2018 4:19 pm

Ivan wrote:Hi Zsolt,
the voltage converter seems to be an overkill to me. I would use a simple voltage doubler e.g. with 555. It should do. Or even simpler: two 9V batteries in series giving 18V! Mention that the varicaps take nearly no DC. Consider using two batteries for feeding varicaps and only one of these for the rest of the GDO. 

VBR from Ivan
hi ,
it's not about the voltage doubling , i can do that with one tranzistor .. the uC should find the dipp by itself (if you scroll down trough posts you can see the whole development how i got to this) .  On the drawing you saw i did not put the lcd , buttons ... and other things obviously needed. That's why you missed the intention . First i wanted to use an ADC to control the varicaps , than i came up with a buck-boost pair and now i consider to only use boost converter . The drawing with the potentiometer is just a suggestion to upgrade existing GDO's to benefit from remote controlled varicap's.
If the varicaps take so small current from the source is perfect  Very Happy It means that  i can consider as load only the voltage divider feeding the varicaps and the voltage divider of the feedback loop .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Ivan on Fri Feb 09, 2018 7:11 am

Hi Zsolt,
the voltage converter seems to be an overkill to me. I would use a simple voltage doubler e.g. with 555. It should do. Or even simpler: two 9V batteries in series giving 18V! Mention that the varicaps take nearly no DC. Consider using two batteries for feeding varicaps and only one of these for the rest of the GDO. 

VBR from Ivan

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Thu Feb 08, 2018 10:37 pm

PS: should i consider the varicap's circuit as a RC load ? What would be it's current (the 2 varicap's) ? Would be ok to aproximate  5 mA max current just to be shore ? 
I'm trying to tweak around the dc-dc source . My newest idea is that there is no need for the buck-boost pair . I believe that only the boost will do the job . If i use a 1/4 voltage divider to feed the varicap's than the boost converter should range from 9 to 48 V before the voltage divider .


I would also change the mosfet for a bjt tranzistor . What tranzistor would you suggest ? The operating frequency is <60kHz  ( Uce <60v , Ic <100mA i belive )

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Mon Feb 05, 2018 6:42 pm

Hi, 
i'm trying to get some documentation about how this is done in TV's (no need to reinvent the wheel  Very Happy )  . I'm curious how this search mechanism works in modern tv tuners , which algorithm is used . As i saw when i put my tv to scan, it goes through the whole range, and memories the frequencies where it founds a carrier or something i don't know yet . My uC should do the same just that it has to detect a dipp and display the frequency at which it happened .
I will take some time until i put something in practice from all this ... now in my ''free'' time  i'm mounting polystyrene plates , mounting doors ... house stuff . 
By the way have you thought about using also varicap's  just without a uC in your versions ?
 
I don't know about how linear this could be , but  i think it's easier to draw a dial around a potentiometer than a variable condensator ? Or there could be some other benefits / drawbacks ... ?   Oh or maybe a linear potentiometer can be used , those long ones like in dj mixers .
Now is somewhat hard to get new varicaps , i intend to use 24V zeners i have already  .
The dc blocking capacitor and the zenner capacitance equivalent  calculates like the case of normal series capacitor connection ?

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by John_1981 on Sun Feb 04, 2018 10:07 pm

Sorry, wrong thread!

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oscilloscope

Post by John_1981 on Sun Feb 04, 2018 10:06 pm

Have you thought of using a self oscillating half bridge converter to provide power for heaters and HT? I knocked one together one evening to power the heaters of some PL519 valves. I will dig out the circuit if you are interested. It used a ferrite core from a LOPT, a pair of TV horizontal output transistors, a small ferrite ring to provide the feedback and a handful of other parts. Efficiency is better than a standard Royer oscillator as only the driver transformer saturates, not the power transformer. Circuit is similar to a CCFL driver.

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Sun Feb 04, 2018 3:22 pm

Hi again Zsolt,
I think it is looking good. l will be really interested to hear how it works in practice. The tuning range will be a bit different, but your should go to much higher frequencies than mine due to the reduce tuning capacitance.

If you need more, then don't forget that you can put varicaps (or Zeners) in parallel.
BR Harry - SM0VPO

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sun Feb 04, 2018 1:47 pm

Hi,
for now i can only do theory ... i will make time for this later .
I added the dc dc convertor i mentioned . I'm not shore if it works like this , the buck part works for shore, i built an MPPT solar charger with it (and the small Arduino board) . 

An other option would be to build a separate (analog) boost to feed the buck converter .
When voltage below 9 V is needed , PWM1 is in zero state so the circuit is in Buck mode . When voltage above 9 V is needed PWM2 is in 1 state so the circuit is working in boost mode . At least this is how i imagined things so far . Also i used to do some rudimental digital filtering (running average Smile )  on adc conversion results , by this i managed to do voltage regulation with 2 decimal points (the load was a light bulb no coils or motors so probably is not a big deal )
I think , i will give it a try with the Arduino uno board . ( the pwm duty cycle control register is only 8 bit , this will be  a challenge Smile )

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Sun Feb 04, 2018 9:18 am

The picture looks good. You may have to increase the 10K to something a little higher if the diode bias damps the oscillations, but it should be ok.
Please do let me know how you get on this this. I am sure that all here are interested in this thread :-)

BR Harry - SM0VPO

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sun Feb 04, 2018 6:40 am

i,
i think i can easily generate the 2 ... 12 V control voltage with the uC itself , by using a suitable dc-dc converter and one of the uC's pwm pin. So i don't need to waste pins of the uC with the ADC module   .  Very Happy
I recently built a buck converter with a small  Arduino board (i found that pin 6 of that little board can work in pwm mode up to 65kHz ). I also found some simple buck-boost topology  in one single circuit
Now i only need to figure out the thing with the varicap diodes. For now i come up with the circuit below : 

I have found some connections on the net with these diodes . I actually never seen one . So the drawing is how i imagined that it could work (younger papanasos simply can't understand diods as capacitors  Laughing   )
I remember when i first built your circuit when trying to connect a frequency meter , all most everything i did it killed the oscillator , and now i'm talking about inserting 12 V in the middle of it .... if this works  bounce

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Sat Feb 03, 2018 6:36 pm

Hi Zsolt,
You are exactly correct.

As a matter of interest, varicap diodes only need a DC voltage that is higher then the peak RF voltage. If you are using a 9v battery for the GDO then a 12v supply would be fine. Also, vaicaps require the highr voltages to get the smaller capacitances. The maximum capacitance occurs at about 2V. You can also use ordinary zener diodes, which have a very high capacitance, compared to real varicap diodes. Just be sure the zener voltage is greater than the max DC you intend to apply.

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Wed Jan 31, 2018 8:51 pm

HI,
if i understand well , there is no RF on the source, but there is RF in the drain .
Anyway everything should be clear now, meantime i came up with an other crazy idea , the uC should first find the dipp by itself and then measure the frequency . Since i don't know how to use varicap diodes in your schematic i came up with the idea that the uC can drive a little stepper ganged with the variable condensator . 

Of course if i could use varicap diodes would be much better . I would use a 10 bit R-2R  DAC to generate control voltage for varicaps . I read that these diodes should get voltages up to 28 V . 

My grandmother uses everyday a cup of red vine for blood treatment. Could be something around this treatment ,  now  she is 88   Laughing   
Best regards .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Wed Jan 31, 2018 10:36 am

zsolt wrote:Hi,
I modified drawing again to depict what i understood



Is it right ? the trim pot would be the 22K you told to use 
Thanks  Smile

Hi again, sorry about the delay responding.
Yes, the picture is perfect with the extra FET. As one other pointed out, the source of the transistor has DC on it, so you don't need a diode detector. There should be little or no RF there.

Anyway, hafta shower and dress - off to hospital today to see how my blood is doing. I failed the blood test so they have to drain some blood. Probably why I am aways so tired.

Do you have all the info you need now?

BR Harry

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Mon Jan 15, 2018 3:09 pm

Hi,
I modified drawing again to depict what i understood



Is it right ? the trim pot would be the 22K you told to use 
Thanks  Smile

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Densil on Sun Jan 14, 2018 10:23 pm

And there is one more thing - harry wound all his gdo coils as one big coil. i used a resistor to feed the power in one end with no center tap and the current drawn is less dependant on the frequency. i put the resistor in the coil so i can have a different value for each coil. selected them on test.
/D

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Densil on Sun Jan 14, 2018 9:47 pm

Hi zsolt, i built harrys gdo and it works grate. i have a couple of comments that can help you.

if you want to feed the adc input then you only need a resister like 22k from the source without any diode at all. harrys design is a bit too sensitive with the meter in a bridge so i just had a voltmeter on the source of the fet. that works fine. i think harry uses very loose coupling so he has a smaller dip otherwise the external circuit pulls the gdo and he once described using a loop feeding a loop so he could push the second loop inside a can.

the parallel fet in your drawings looks good and i will give that a try myself.

ascii art is a bit naff on this forum because the characters are monospaced but spaces are not. you can use a - instead of a space and change the colour of them to white so they dont show the dashes. the dash - has the same space as a character.

ill let harry answer your other questions cos hes the expert. he said he made this circuit a few times for the last 35 years.
/D

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Wed Jan 10, 2018 7:51 pm

hi,
interesting things you say here maybe i ll give a try later on... what i wanted to do is to eliminate the big dial and the measuring instrument. I taught that both information s can be displayed on the LCD. And it can , at least the frequency gives no trouble . The dip gives trouble  , i tried to display a bar graph on the second row  , something like this : (hope the text is not otherwise formatted here when i post) 
_______________________
| frequency:  8.5 Mhz          |
| level : ||||||||||||||||||     |
|______________________|
When the dip occurs the bar graph should decrease. Actually it does . I discovered that the amplitude of the signal is very frequency dependent .
Oh and i discovered the the dip is not always negative . At some home appliances the amplitude  is increasing very much instead of decreasing .
Anyway it's interesting  how useful and versatile a little sensitive oscillator can be. It saved the day Smile  , from 100 labels 40 where bad . And i could also see that different labels are not behaving the same way . Probably your GDO should not be digitalis-ed at all  Very Happy , but I m shore that a stronger controller having a 40 Mhz clock could make it .

PS: i don't know how to parallel FET transistor in that scheme . Did you suggest to put an other FET in the circuit with Gate and Source in parallel with the existing transistor just that it's Drain should have only the micro-controller input and a load resistor separately  ? hope you don't mind i vandalized your drawing to show what i understood

Oh and an other question , where would you connect the amplitude detector circuit in your scheme ?

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Wed Jan 10, 2018 12:36 pm

Ok, I understand.

When I give my classroom demonstrations I usually have a 2-turn loop on the input to the counter. I feed the loop over the GDO loop, then use the GDO in the normal way. This is good for about 4 to 25MHz but the counter loop will have to be adjusted for higher or lower frequencies.

But this method is not suitable if you want to do as you do: have an integrated instrument.

Perhaps you could add a counter pickup-loop built into each coil? Then you can have a diffrerent and optimal loop for each band?

Just a suggestion.

Finally, have you thought about using a paralled FET (source of both FETs connected) to get an isolated output from the GDO? This could be an elegant solution.

BR Harry  - SM0VPO

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sun Dec 31, 2017 1:25 pm

hi , i managed to count the frequency with a 2 turn coil in the gdo , i was thinking about getting the amplitude into the mcu in order to display on lcd ... i found out that detecting the dip is already done in first place .When the dip occurs  the mcu shows zero frequency on the display (probably the level is to low for the input pin). So now i know when the dipp is present just that i don't know at which frequency  Very Happy  , I could tweak around the program to display the last non zero value for frequency when the dip is present . I don't think i can fully  upgrade your GDO to digital, the 2 events are antagonist for the mcu . It does the job anyway .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Admin on Sun Dec 31, 2017 11:18 am

Hi Zsolt,
One possibility for measuring the GDO is to take a series resistor (47K ?) and 1nf capacitor from either the gate or the drain to the input of your counter.

With the GDO there is about 10v P-P at those two points so you should be able to sniff off a little RF without affecting the frequency (much).

Anyway, I want to wish you a very Happy New Year.

Interesting fact, today, everybody who is legally an adult (over 18) were born in the 1900's. All "minors" (under 18) were born in the 2000's.

Vdry best regards from Harry - SM0VPO

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sat Dec 30, 2017 6:52 pm

hi , 
first of all best wishes for all . About the gdo 1 , since i'm using a self made frequency meter with 2x8 LCD i taught that i could display on the second row also  the amplitude in a form of a bar graph. With this i could eliminate the microampermeter ( i used a magnetoelectric device which is not performing quite so well ) .
I have an analog pin left free, and i can use internal 1.2V reference for ADC if needed.I have no idea if it can work or not, but where would you connect the analog input (with respect to GND) in the GDO1 circuit, in order to do this ?

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sun Dec 24, 2017 3:46 pm

HI,
it was a great time , and so fun . Actually i'm glad for having no computer back then  .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Ivan on Sun Dec 24, 2017 9:51 am

Hi,
3,5 MHz (80 m) band is not free. It is one of the hamradio shortwave bands. There are five distinct frequencies inside that band reserved for foxhunting. The "foxes" are allowed to send certain CW patterns only - perhaps E, I, S, H and 5 (. .. ... .... .....).

BR Ivan

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by zsolt on Sat Dec 23, 2017 6:16 pm

hi , indeed we have a radioclub ... it's complicated .What's with the 3.5 MHz frequency ? isn't that free ? i remember when i was a little kid we  used to play a so called game  fox hunting (don't know how to translate the term .)  Basically our electronics teacher used to hide some transmitter, usually 3, those where the foxes ,  and we had to find them with our receivers (hunters) .I remember that those receivers where 3.5 Mhz .

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Re: GRID DIP OSCILLATOR by Harry Lythall - SM0VPO question

Post by Ivan on Fri Dec 22, 2017 6:52 am

Hi Zsolt,
there is a central hamradio club in almost every country, and a governmentory radiocommunications regulator, too. You should get all the basic information on their webpages: hamradio bandplans, technical conditions (maximum radiated power, stability of frequency, spectrum purity,...), exams to pass etc.  To build or purchase your own transmitter legally, you must have a license and a callsign from the regulator office.

BR from Ivan OK1SIP

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