A short silent movie on cassette player speed control

[@noisytim]

[@chrisbullock613]

I don't think I'll do much more with this one. Disappointingly because it works of PWM rather than directly driving the motor, there's a limit to how much I can change the speed. I wanted to make it really slow but even with a huge trim pot it won't do it.
I'm wondering if I can direct drive the motor, maybe bypass the chip entirely and feed it a variable voltage. Might work! Maybe I'll try that actually 😁

[@noisytim]

@@chrisbullock613 From the looks of it direct drive should be possible.
(If you want it to be hacky you could probably just unsolder the wires to the motor - then attach them to a lab-supply.)
Or if you want it stealthy: tap the input voltage and send it to a voltage regulator (something like an AMS1117 or LM317).
The IC itself is really tiny, so you can just hide it somewhere in the tape player.
It's usually just two resistors, a potentiometer and the IC.
You'll even find some calculators on the internet, that tell you which resistors to use.

[@chrisbullock613]

@@noisytim thanks for this it sounds like ideal. I just need it to move when I press play so should be simple. Or I can add a switch

[@peervalidated]

@@chrisbullock613 Any guess on the amount of slowdown this method resulted in? Thanks!

[@chrisbullock613]

@@peervalidated I can't put a number on it but very minimal since it's working with the existing trim. I think you need to directly control the motor to get a decent amount. I didn't do that because I don't know how to deal with the flyback, so I replaced the motor with a servo I could control with arduino - that runs very slow.