How do you make phase matching circuits without microcontrollers ?

[MathWizard]

Say you have 2 copies of some 1kHz wave, a sine or square wave if that's easier, but they are at some random phase, how do you make a circuit with BJT's and/or some basic logic IC's and/or comparators, that would give you both waves now in phase.

Then for example, if I sent a 1kHz squarewave as 5MHz AM signal to an RC car, I could have a reference 1kHz osc onboard, and it would compare any the incoming signal with the ref 1kHz signal. Then I could also do the same with say 17kHz signal to be another command like turn right.

Even if this is not a good way to send commands, how do you make low frequency phase lock circuits ?


Ok for squarewaves anyways, I can do it with 1 inverter, 2 AND gates, and an OR gate, and make a new 3rd signal in phase with the 1st.

[ejeffrey]

Say you have 2 copies of some 1kHz wave, a sine or square wave if that's easier, but they are at some random phase, how do you make a circuit with BJT's and/or some basic logic IC's and/or comparators, that would give you both waves now in phase.

You need to be more specific


If you have two copies of the same single with different phases and guy want to produce in phase signals you just throw one away and duplicate the other.

If you have a tuna le _oscillator_ that you want to lock to a reference, that's a pll.  The simplest phase detector is an xor gate or an analog multiplier.

The simplest way to do am detection, often used by simple remote controls isn't phase sensitive at all, it's just looking for the presence or absense of modulation at a particular IF.  So you do AM detection, then feed the signal to some audio frequency bandpass filters, then rectify and filter the audio frequency out.

Another approach is to use a frequency to voltage converter.  This can let you demodulate FM modulated subcarriers.

[Andy Chee]

Use the phase comparator(s) in a jellybean CMOS 4046.

https://www.ti.com/lit/an/scha003b/scha003b.pdf

[MathWizard]

Yeah the circuit I tried does not really work the way I hoped, and sort of just copies the original signal.

I was worried about the changing strength of the carrier and audio, around my house. So I though maybe it's better to try and look for an audio signal, by comparing it to a reference frequency somehow. Also if I send a few different frequencies as commands, and using passive filters, it might be hard to separate the ranges of detection, and keep out RF like radio stations. For now I'll just try and make narrow bandpass filters for different frequencies, and see where that goes.

I don't have any of those PLL IC's. But I have lots of shift register's, comparators, binary ripple counters, 555 timers.

[PCB.Wiz]

Say you have 2 copies of some 1kHz wave, a sine or square wave if that's easier, but they are at some random phase, how do you make a circuit with BJT's and/or some basic logic IC's and/or comparators, that would give you both waves now in phase.

Then for example, if I sent a 1kHz squarewave as 5MHz AM signal to an RC car, I could have a reference 1kHz osc onboard, and it would compare any the incoming signal with the ref 1kHz signal. Then I could also do the same with say 17kHz signal to be another command like turn right.

Even if this is not a good way to send commands, how do you make low frequency phase lock circuits ?

If you want radio signaling, you need to also worry about signal to noise.

What you describe is still available in the SO8 single tone decoder NE567/LM567 (and '567 Asian clones), and also still available is the 16 state, SO18 dual tone decoder MT8870 and '8870 clones.
Those have good noise immunity and are suited to low speed command decoding.
The data sheets on those explain how they work.


The 4046 family is a CMOS PLL, but it lacks a sync detector, so you could look at the 74HC7046, which has a lock detector which might be good enough for simple command decoding.

So I though maybe it's better to try and look for an audio signal, by comparing it to a reference frequency somehow. Also if I send a few different frequencies as commands, and using passive filters, it might be hard to separate the ranges of detection, and keep out RF like radio stations. For now I'll just try and make narrow bandpass filters for different frequencies, and see where that goes.

What you describe there, is very close to the '8870. If you are OK with up to 16 commands, it would be well suited.