Bruce Robinson explaination about this circuit:
- I did a few revised drawings for Ian quite a while back, so he could place them up at beam-online. However, they did not get posted inside the midst of the a lot of revisions he was doing.
- Attached (begging Ian’s indulgence), will be the two versions of the circuit, one which turns on having a Positive input, the other (for quadcores) having a Negative input.
- Ian shows 100k input resistors. I’ve been applying 47k resistors with success. Tilden’s report recommends nothing lower than 50k (I assumed 47k was near enough) and up to 20 Meg or so.
- I’ve also observed a slight drop in speed when I use these bridges, but only about 10% or so.
- Until 800 mA capacity (working with PN2222 and PN2907 transistors)
- Not “smoke-proof” (i.e., it cannot deal with drive voltage in both directions at once)
- 30 connections per bridge (so, 30 holes in case you make a PCB)
Original Tilden H-Bridge article can be found here. Read the article for detailed ecplanation and recommendation.