Free circuit schematics - wiparat.com

The circuit is not particularly susceptible to motor transients and supports FULL STEPS FORWARD, FULL STEPS REVERSE, ACTIVE HOLD, and POWER OFF aka RELEASED. If the motor does not turn then swap around the leads of ONE of the two coils. To reverse the sense of the EN signal simply rework the circuit around an [...]

The Tritium circuit was the first (to my knowledge) type 3 SE. As such, it is quite experimental, and should be regarded as a prototype rather than the ’state of the art’! Nevertheless, it does function reasonably well, and in some circumstances outperforms other solar engines such as the Freds that I have lying around. [...]