Good day, hope all is well

Requirements :
- I have an electret microphone that is given 3 different frequencies to give different commands to 2 individual motors.
At frequency 1 : both motors should be at the same speed
At frequency 2 : Motor 1 needs to be faster than motor 2
At frequency 3: Motor 2 needs to be faster than motor 1

Furthermore I am not able to use any microcontrollers.

From my understanding I would need to set up bandpass filter to isolate desired frequencies from the microphone. Then I would need some sort of decision making circuit ( possibly a comparator ). I would then need to set up a motor driver circuit.

Any sort of guidance and assistance would be appreciated.

 

Is this homework?

 

No, just a project Im working on

 

How about using DTMF (Dual Tone Multi Frequency) sender and decoder ICs which have been used in telephones since the 1960s to replace the older make and break telephone dialing?


each button generates two frequencies together, a fairly well proven technology using a total of 8 frequencies where two are combined together to convey one of up to 16 commands.

Cell phones still use DTMF, a technology developed over 60 years ago

 

DTMF chips are obsolete enough that they may be unobtainable.

MT8870D Data Sheet (microsemi.com)

 

What will be producing the different Frequencies that will be received by the Microphone ?
How far away From the Microphone will the "tone-source" be ?
How much Ambient-Noise must be tolerated ? ( SNR - Signal to Noise Ratio ).
.
.
.

 

How about using DTMF (Dual Tone Multi Frequency) sender and decoder ICs which have been used in telephones since the 1960s to replace the older make and break telephone dialing?

View attachment 319579
each button generates two frequencies together, a fairly well proven technology using a total of 8 frequencies where two are combined together to convey one of up to 16 commands.

Cell phones still use DTMF, a technology developed over 60 years ago

I am able to get my hands on the DTMF IC, how exactly would I be able to add this to an efficient circuit ?

 

What will be producing the different Frequencies that will be received by the Microphone ?
How far away From the Microphone will the "tone-source" be ?
How much Ambient-Noise must be tolerated ? ( SNR - Signal to Noise Ratio ).
.
.
.

The different frequencies (tones) will be generated using a "frequency sound generator app"
The tone source will be in close approximately to the Microphone ( less then a meter)
The SNR should be high

 

The thing is, we wonder about such an odd choice for a remote control. IR and RF are so much more common for good reasons. Early remote control TVs used ultrasonics.

 

WHAT IS THIS project, really???

Use an LM2917 tachometer IC to deliver a linear frequency to voltage conversion.
Then feed that voltage to two op-amps, one inverting and one non-inverting. Then use the outputs to drive power transistors to drive the two motors. At some frequency they will be the same speed. Raising the frequency will make on motor slower and the other faster. Lowering it will do the opposite.
This will be a rather silly scheme for a remote control.

 

DTMF chips are obsolete enough that they may be unobtainable.

MT8870D Data Sheet (microsemi.com)

They’re readily available at about $2USD℆ from AliExpress.

 

The different frequencies (tones) will be generated using a "frequency sound generator app"
The tone source will be in close approximately to the Microphone ( less then a meter)
The SNR should be high

It would be very helpful if you could explain why you are doing this. That is, what problem will be solved when you have a working version? Also, if not explained by “why”, where do the constraints “I am not able to use any microcontrollers” come from?

Right now, people are working blind. There are many ways one could do what you are describing but why one is doing it will be a big factor in choosing one.

 

In post #10 I described a scheme that is both noise independent and uses currently available devices, in addition to being easily adjusted. Also the ICs are much less expensive, and widely available.
So why argue about a scheme that was a poor choice to start with????

 

How about using DTMF (Dual Tone Multi Frequency) sender and decoder ICs which have been used in telephones since the 1960s to replace the older make and break telephone dialing?

View attachment 319579
each button generates two frequencies together, a fairly well proven technology using a total of 8 frequencies where two are combined together to convey one of up to 16 commands.

Cell phones still use DTMF, a technology developed over 60 years ago

This is how I would go about it. DTMF modules are inexpensive off the boat through Amazon. Both DTMF Encoders and DTMF Decoders. Awhile back, maybe a few years ago, I bought both encoders and decoders from Amazon. HiLetgo 2pcs MT8870 DTMF Voice Decoder Decoding Module Telephone Voice Module for Arduino at a cost of about $3.00 each. Those are decoders and here we have the encoders AE11A04 DTMF Module 5~24VDC Audio Generator Module Voice Dual Encode Transmitter Board for Dialing Keyboard. That affords 16 channels. I used an Arduino UNO but just about any uC will work having enough DIO ports. If you go this route I will be happy to post the code I used.

Now if you wish only a few channels, like 3 channels, the LM567 and LM567C are general purpose tone decoders designed to provide a saturated transistor switch to ground when an input signal is present within the passband. This way you can roll your own.

Actually the module(s) I linked to on the decoder it affords a simple BCD output so unless you want more those modules are all you need and just add a BCD to Decimal decoder chip, there is no need for a uC or micro-controller.

Ron