My Motor Controller Project

Click this schematic for the big view.

Note: The charge pump diodes need to be fast recovery diodes. I used 1N4004 diodes in the schematic because I was too lazy to rename them before I created this page. I will also probably change the control logic before I actually get this to run.

First board layout.

Etched board for the motor driver. This was made with "Press-N-Peel Blue" toner transfer paper. I printed it from Eagle 4.0 PC board software on an HP LaserJet 4 at 600dpi. Then ironed the image onto a blank PC board. Then etched it in ferric chloride. I had to clean the blue coating off the traces after it was etched.

Click here to see backlit view of the board. You can see it is marginal. But it took me all day to make it, so I am going to use it anyway.

Update 02/12/01 - Dual motor controller module

I decided the traces on the PC board weren't large enough for the motor power. So I am going to use actual wires to connect the MOSFETs. This is a picture of the drilled heatsink with the terminal strip, current sense resistors and MOSFETs. There are only two MOSFETs in the picture but there eventually will be eight total.

The unwired heatsink module.

Closeup view.
(Notice the shorting wire so I don't zap the FET with static.)

I used TO-3 SilPads and cut them down to fit. Simply because ABC Electronics has them for $.05 and Digikey wants $.85 for the TO-218 SilPads.

I will attach a PC board or perf board with standoffs which will have the MOSFET driver electronics.

Update 02/13/01 - I have added some wires but haven't solder them to the FETs yet.

Module with some wires.

Closeup of module with some wires.

I've added some 12 gauge wires to the dual motor driver module. The wire is from a local auto parts store. Turns out 12 gauge wire is pretty stiff to work with. The ground bus bar is 12 gauge solid wire. (Romex house wiring)

I was rather pleased when I went to solder the 12 gauge stranded wire. The insulation didn't melt! That can be a big problem with a wire you haven't used before.

The next step will be to bolt down the FETs and solder the wires to the FETs. I will also add twisted pair cable from the gate and source of each FET to be connected to the controller board. I will add heatshrink tubing over each FET lead after it is soldered. Except for the source leads which connect directly to the current sense resistors.

Update 02/21/01 - The MOSFETs are soldered on.

Finished heatsink module.

This is a picture of the finished heatsink assembly. You can see the twisted pair wires which will connect to the driver board. The closeup picture shows two transistors of a half bridge. You can see the heatshrink tubing I put over the MOSFET leads.

I ohmed it out and the meter reads inifinity. On the diodes setting the built-in diodes read .446 volts. So it looks like all the MOSFETs are good. That is a relief, since I bought them used...

So the next step is to build a driver board to control the gates of the MOSFETs.

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