As a follow on from my previous post, i applied the PWM from the Arduino to cassette player. And... success! Well, sort of. I can hear a frequency of around 400Hz when the PWM is too weak to drive the motor. This is annoying, and I am wondering if there is a way to minimise this sound.
This is the same setup as last night, the only difference being that pins 1 and 2 of the ULN 2803 were tied together as well as pins 18 and 17. In the breadboard picture, these new connections are the small, red jumpers placed in line with the relevant pins on the ULN2803 IC (the only IC in the photo).
The reason for this tying together of pins is that i don't have any data for the motor inside of the tape machine. Thus, it might such more juice out of a single set of darlington transistors than they can deliver. Thus, more power can potentially be achieved by chaining multiple sets of the array together. This is a technique taken from page six of the Picaxe Manual (Part Three).
Below you can see a little video (27 seconds) of the thing in action.
For the record, the music on the tape in the video is an untitled number by Drowning Goldfish.