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digital ain't happy with me

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mstechca

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I have got to admit it too!

anyways. What I have going is my superregen that produces a visual output based on the incoming signal. The schematic shows the circuit without the superregen portion which connects to the input.

The problem I am having is that I cannot get the input of a 4077 XNOR gate to recognize the signal. The gate always takes the input as a logic "0".

I tried connecting the logic input to the collector of the NPN where the LED's cathode is.

If I reduce the 120K resistor, the output could be stuck at "1".

I think there is an equation with the resistor and capacitor in series that I don't know about.

I want to use my working PLL with this circuit to detect pulses.

How can I do it?
I want it so that when the transmitter outputs a logic high, I want the XNOR input to be a logic high.
 

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Hi MStechca,
I modified your circuit and maybe it will work better:
1) An input cap is added to keep Q3's bias from being messed-up.
2) Your Q1 to Q3 amp is great but surely only Q3 would do the same job.
3) R2 is removed since it doesn't do anything.
4) The value of C1 is increased a lot to pass low frequencies.
5) The value of R4 is reduced to avoid attenuation.
6) 100k resistors are added to make sure that Q4 and Q5 turn off and fairly quickly.
7) 2.2k is added across the LED to make sure the output goes to a logic high.
8) An important supply bypass cap is added.
 

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audioguru said:
Hi MStechca,
I modified your circuit and maybe it will work better:
1) An input cap is added to keep Q3's bias from being messed-up.
2) Your Q1 to Q3 amp is great but surely only Q3 would do the same job, without the diode.
3) R2 is removed since it doesn't do anything.
4) The value of C1 is increased a lot to pass low frequencies.
5) The value of R4 is reduced to avoid attenuation.
6) 100k resistors are added to make sure that Q4 and Q5 turn off and fairly quickly.
7) 2.2k is added across the LED to make sure the output goes to a logic high.
8) An important supply bypass cap is added.
 

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I didn't bother adding a resistor between Q4 and Q5, with a high signal level the smoke will be awesome! :lol:
 
I didn't bother adding a resistor between Q4 and Q5, with a high signal level the smoke will be awesome!
haha :lol:

thanks. I'll see if it works.
 
audioguru said:
I didn't bother adding a resistor between Q4 and Q5, with a high signal level the smoke will be awesome! :lol:

He's not joking, I would insert a 3k3 between the C of Q4 and the B of Q5.

Also, Q3 is configured as a transresistance amp. so its input resistance will be low. What is the output impedance of your audio source?
 
Why would there be smoke coming out when the current supplied to the base of the PNP is well under 100mA?

As it stands, I can pick up the audio through a 4.5W, 8 ohm speaker by connecting it in series with a 220uF capacitor. I then connect that to the point where the emitters of both transistors meet. The other end is grounded.

So as long as I can hear something at full volume through the speaker, I should be able to obtain the proper logic levels.

Audioguru, your resistor-capacitor values did NOT help. In fact, they made my LED stay on forever at full brightness. Still, there is NO SMOKE :wink:

Maybe I need more diodes.

The only other thing I can think of off the top of my head is to somehow make an ADC circuit.

I think the impedance is 27K because the last audio amplifier stage output before this circuit is connected to a 27K pull-up resistor and the collector of the NPN.

Should I enforce voltage division alot more?
because it seems that when I create more voltage dividers, Audioguru's circuit works better for the logic gates, but when I use the speaker, the results are worse. At least the volume is alot lower.
 
mstechca said:
Why would there be smoke coming out when the current supplied to the base of the PNP is well under 100mA?
You are correct! :lol: Almost.
If R4 is 10k then it will have a max of 1.5V across it, supplying 150uA as base current for the PNP. If the PNP is a 2N3906 with a typical current gain of 135, its collector current is "only" 20mA. The NPN should be able to withstand "only" 20mA into its base. The battery won't like the wasted current.

Audioguru, your resistor-capacitor values did NOT help. In fact, they made my LED stay on forever at full brightness.
Your circuit has an input cap to the rectifier so there is no way the LED will stay on unless the capacitor or transistors are shorted or another signal continues to be rectified when the signal is off!

Isn't the receiver a super-regen? Doesn't a super-regen oscillate all the time? Won't the oscillation be rectified and keep the output low?

I think your super-regen is missing a lowpass filter on its output.

I think the impedance is 27K because the last audio amplifier stage output before this circuit is connected to a 27K pull-up resistor and the collector of the NPN.
Then the stage with the 27k load resistor is being loaded down by the low input impedance of this amp. It doesn't matter, this amp has plenty of voltage gain.

Should I enforce voltage division alot more?
because it seems that when I create more voltage dividers, Audioguru's circuit works better for the logic gates, but when I use the speaker, the results are worse. At least the volume is alot lower.
Your amp doesn't have negative feedback so the speaker is loading it down. Amps with negative feedback work the same with or without a load.
 
Your circuit has an input cap to the rectifier so there is no way the LED will stay on unless the capacitor or transistors are shorted or another signal continues to be rectified when the signal is off!
...
Isn't the receiver a super-regen? Doesn't a super-regen oscillate all the time? Won't the oscillation be rectified and keep the output low?
...
Then the stage with the 27k load resistor is being loaded down by the low input impedance of this amp. It doesn't matter, this amp has plenty of voltage gain.
...
I think your super-regen is missing a lowpass filter on its output.
...
Your amp doesn't have negative feedback so the speaker is loading it down. Amps with negative feedback work the same with or without a load.
The receiver is a superregen, but it is tuned into the transmitter's frequency, so the superregen is mostly off. because a low frequency pulse is being sent through the transmitter.

I guess your circuit works in an inverted fashion.
I wonder if just adding a single stage common emitter amplifier (with the LED in the collector of it and a resistor in series) where the speaker connects (coupled by a capacitor) would give me better results.

I will try it and find out experimentally. and Yes, I still DO NOT have a real oscilloscope!
 
mstechca said:
The receiver is a superregen, but it is tuned into the transmitter's frequency, so the superregen is mostly off. because a low frequency pulse is being sent through the transmitter.
I think your super-regen has a squegging oscillation where it builds up its gain due to positive feedback then the moment it oscillates it gets cutoff and builds up its gain again. The squegging occurs at an ultrasonic frequency that you can't hear. The ultrasonic frequency is rectified by your rectifier which turns on the LED. Your supre-regen needs a lowpass filter at its output to reduce the ultrasonic frequency, passing only the modulation.

I guess your circuit works in an inverted fashion.
I wonder if just adding a single stage common emitter amplifier (with the LED in the collector of it and a resistor in series) where the speaker connects (coupled by a capacitor) would give me better results.
With a capacitor-coupled rectifier feeding a single transistor, the sensitivity will be reduced since a single transistor has much less current gain than two cascaded transistors like before. A single transistor will work the same as two cascaded transistors before if its the resistor feeding the rectifier is reduced, and its coupling cap increased, since your audio amp is able to drive a low resistance.
 
So we've now got a five transistor buffer circuit, to feed the multi-IC 555 based 'PLL' (which I still see no reason to assume will work?), all to try and replace a single 8 pin IC NE567.

Perhaps you might be learning something?, but it seems doubtful? :lol:
 
Nigel Goodwin said:
So we've now got a five transistor buffer circuit, to feed the multi-IC 555 based 'PLL' (which I still see no reason to assume will work?), all to try and replace a single 8 pin IC NE567.
I didn't show my ENTIRE circuit. :lol:
But the transistors closest to the audio input are transistors that amplify the signal.

Perhaps you might be learning something?, but it seems doubtful? :lol:
I learn from hands-on experience. :wink:

I think your super-regen has a squegging oscillation where it builds up its gain due to positive feedback then the moment it oscillates it gets cutoff and builds up its gain again. The squegging occurs at an ultrasonic frequency that you can't hear. The ultrasonic frequency is rectified by your rectifier which turns on the LED. Your supre-regen needs a lowpass filter at its output to reduce the ultrasonic frequency, passing only the modulation.
I think I've hit a jackpot!!! :lol: :lol: :lol:

It must be a low pass filter. I added a 33nF capacitor and a reverse-biased diode in parallel between the NPN's base (of the left-most transistor) and ground. This must be my low-pass filter. It seems that the higher the capacitor, the lower the noise. It must do a good job at cutting out the high noise.

And I was thinking a while back when I showed a capacitor at that spot (without the diode). and someone here (I think audioguru) thought that the capacitor was unnecessary, but all along, it helped a tremendous deal.

Without the pair, the volume was ridiculously low!

and this one is for audioguru: :shock: :lol:
 
I don't know where you added a capacitor.
Here's a super-regen receiver for a toy car. It has 3 lowpass filters.
 

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Look at where you circled 727Hz

I constructed a stage like that, except that the capacitor is connected from base to ground. My resistor is 470K and my capacitor is 33nF.
 
Since your capacitor is from base to ground, it isn't in the negative feedback loop like this one. A capacitor from base to ground forms a lowpass filter in combination with the resistor driving it, the collector resistor of the stage ahead of it. The low impedance of a transistor's base increases the calculated frequency of the resulting lowpass filter.
 
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