A remote control

And that's the reason for D2 as well.

The receiver consists of an IR receiver module and was originally a Vishay TSOP4838, which is a 38kHz receiver, and that means the 7555 in the remote should be adjusted to give exactly 38kHz, and not around 40kHz as previously stated (like I said, warts and all...).

The power supply to the remote control receiver circuit is best provided by a 5V regulator, and we'll see that a 1 amp rating will suit it best.

The IR receiver will work from 2.5V to 5.5V and is best decoupled from the rest of the power supply by the typical 100 ohm series resistor and 100nF capacitor (on the datasheet ). Just to be sure, I used a 4.7uF electrolytic capacitor.

The output has to be inverted to be the right polarity for the HT12D decoder, and this is done by using a BC327 transistor with base connected to the TSOP4838 output via a 4k7 resistor. Its emitter to +5V and collector to pin 14 of the HT12D, which is data in (DIN). A 4k7 pull-down resistor from pin 14 to supply 0V acts as the BC327 collector load, ensuring proper switching.

The outputs from the HT12D are the same pin numbers as the encoder's push button pins, so if 10's up and 11's down, then 10 on the HT12D is up, and 11 on the HD12D is down.

The HT12E oscillator is set by one resistor and as it transmits at 1.5kHz, then for the HT12D 5V supply its resistor has to be 75kHz (because it needs to be 50 times and 1.5kHz x 50 is 75kHz) and the corresponding resistor value is 120k, but somehow my prototype uses 100k and works OK.

Except for the HT12D supply pins, the only one left is VT pin 17, which flags a valid transmission by going high (logic 1).

So, we have up on pin 17 and down latches on the output pins matching the button press. The button press outputs latches, but pin 17 only stays high during the button press, so that acts as the stop.

We can then take this as a logic truth table to a quad half H driver chip which is interlocked and when one output is high the other is low, and vice versa, and the pot motor sits between these two outputs!

These driver chips can deliver 1 amp per output, and we can parallel two Half H's together to reach 2 amps. We don't need that much current for the motor as its maximum is 150mA with end stop clutch slipping. But it means the chip runs cooler.

We then only need 4 diodes to soak up the motor back EMF, and that's that.

I'll draw it up next post, but for now I'll comment that I've seen other remote receiver circuits and they're so over complicated it isn't real. Now, they might (or might not) have sufficient logic to bring the motor to a halt instantly, and this receiver circuit simply doesn't and cannot. But how long will it take for the pot motor to stop? It hasn't a flywheel so it must be pretty instant, and I can only guess that it might take 0.1s, and if so it will run past by 2.5 degrees of rotation, which is less than 1%.

We can also experiment by placing a resistor in series with the motor to slow its rotation speed.

Yes, but the pot that's easily available is 100k, unless you're going for an AC30. The choice is yours.

This one interests me https://mou.sr/3UplN3q

I don't know how you'll house it but keep the wiring short.

Error on pin 8 L293 corrected (thanks Bruce)