I am using the Simple H as an isolator and amplifier for a standard Hobby servo, so that I can use the signal provided from the circuit inside a hobby servo to control the motion of a large DC motor, in this case, a wiper motor.
What I have done is to remove all the parts from a hobby servo. In this case, it was a HiTec HS‑805MG.
I pulled out the circuit board, disconnected the motor, removed the potentiometer, and connected the board to my servo controller card. This is not RC. This is a wired controller card. I measured the POT that was in the servo. It was a 5K pot. I got a full sized 5K POT and mounted it to the motor shaft of the wiper motor as a feedback control and wired it where the original POT from the servo was.
I took the two wires that were going to the 5VDC servo motor and connected them to inputs PA and PB.
I connected a ground wire from the power supply that was running the servo controller card to the GND pin on CN1 at the power outlets labeled (-). I know this was an input and I was connecting it to an output, but I needed the ground to be connected to the board so it would be in common with the GND from the 12VDC power supply I connected to the B+ and B- posts on the other side of the board. I connected a positive lead from the 5VDC power supply used to control the servo controller board to pin EA on CN1. The best I could figure out is that it was necessary to connect power there and to have the jumper on for EA in order to have the 2 power chips enabled so the motor could be bi-directional. I didn’t find the instrutions about that to be very clear, so I want to confirm that I have done the right thing there.
Finally I connected the two wires going to the wiper motor to M1 and M2.
the theory is that the board from inside the servo would send it’s output to what it thinks is the servo’s motor, but in reality is PA and PB on CN1 Those variations in voltage and polarity would be used to control the wiper motor in like manner. The feedback control POT is on the wiper motor, but the servo board still thinks it’s attached to the servo motor, so it should continue to run normally as an unmodified servo should.
I saw someone else doing this exact same thing in this video and I was trying to recreate this setup. Here’s the video: youtube.com/watch?v=2Ny33eoy3q0 The part I was looking at starts at about 1:31.
The video was such poor resolution, that I found it nearly impossible to tell what pins the wires were connected to, and he doesn’t tell that information. He also didn’t even identify the H Bridge, but I found it from pictures online. He explains the POT wiring pretty well, and says ythat the motor wires from the servo board go to the H Bridge, but doesn’t say which pins, and he completely leaves out mentioning anything about the other two wires I can see going into the H Bridge which I believe are the 5VDC and GND going to EA and - on CN1, but I can’t be 100% sure. He didn’t mention the jumpers at all, but I could see them on in the video, so I left them on.
I am hoping to get confirmation that so far, I am doing this correctly and can expect good results.
The problem is that I am having a great deal of trouble controlling the motor. It takes off the second I plug it in, and would break the POT if I had secured it tightly. I wondering what the trick is to setting it up so the motor will start at rest in a default position so I can protect the POT and get accurate motion on the motor.
Thank you, I hope to be able to finish this on the weekend.
