@gunrunnerjohn posted:I don't know for sure, there are many designs of the inexpensive reverse boards. I know that several common ones use the TIP126/TIP127 combo.
I have a couple of Williams relay based reverse boards if you can't get that one running.
Hey John,
Just some insight on your very correct observations. The H bridge is like one I've never seen before. The PNP transistors have their emitters connected to + supply and the NPN's have their emitters connected to - supply. The bases of the totem pole are connected together with a high power low ohm resistor. A small resistor pulls the bases to + supply and the lower part of the power resistor is connected to TO92 NPN for control. The drive transistors have their collectors tied together to provide Motor1 and Motor2 .
The attempt is being made to force the drive transistors into saturation. Thus the lack of heat sinks. However with the base pull ups, the H bridge dynamically brakes the motors when it goes to neutral. Ouch!
This device was from Dave Ott/Ott Machne Services.
And my apologies to those who could care less.
Regards,
Lou N
