I have a few questions and also wanted to share some of what I’ve learned (concerning H-bridges), which may have been obvious to some but news to others. First off is yes I have read the SOR doc on H-bridges, but I was never sure if you could connect the (A,B) logic pins directly to the motor leads of the circuit in a servo(via 1KOHM resistor of course), until I found it on another web page. I had my hunches of course but didn’t want a pretty fire in my living room.
Great page:
http://130.94.182.150/mowers.htmThis page walks you through the steps of building an H-B and connecting it to an HS 805 servo.
I built this circuit and used it on a very cheap XL servo modified for 360, this servo was never good at returning to center before, and when I use the circuit with it, the servo would pass the center point and then return to center. Unfortunately I can’t try this on another servo for another few months.
Now for the questions: does this happen because of a cheap servo circuit or are there some modifications I need to make to my H-Bridge? How van I make it better. Also, In the SOR doc it says to increase the voltage, what should I increase it to and how do I do this. I am using a 2cell Lipo for the external power source to the H-B. I built two of these circuits but only had time to test one and I don’t remember which one. The MOSFET’s are (N-CH-FQPF16N15, P-CH-FQP15P12) and (P-CH-SPP15P10PL , N-CH-irf520). They have varying VGSS and (VGS)th voltages, VGSS from 20V+- to 30V+-, and VGSth from 2V to 4V and 1V to 2V.
Also I was wondering what gage wire to use in the circuit, on the one I tested I used 18G, the other I wired with 22G. I also took a look inside a GWS777 if anyone is curious just ask me.
I know this is a novel but thanks for reading and any advice would be much appreciated.
