Current Sensor

[Jay Lundy]

Originally Posted by Rurouni

So does anyone understand how those pwm connections are working? Like I said before, either we're reading the schematic/picture wrong, or it looks as if we're going to have to cut the pwm cables to make them fit where they're supposed to. I hope someone can get back to me on this one.

Well the PC board came with 3 rows of 3 pins. Each row is obviously connected together.

The first row (closest to center) is for the chip itself. It should fit snug in those 3 holes with the big leads in the holes on the other side of the board.

In the next row we put the capacitor. I can't remember exactly what pins it should go in, refer to the sheet included in the kit for that (pay attention to polarity).

The last row is where we put the pwm cable. You may have to trim a few strands from each wire to get it to fit in the holes. Make sure you get the wires in the right pin (white -> output, red -> Vcc, black -> ground). See the datasheet for what each pin on the chip is for.

One problem we had was soldering. The small pins were easy, but the bigger leads were more difficult. It was impossible to do with some of our 850 F irons, but mine at home was hot enough to do.

We also were not sure how to solder the 10 AWG wires in those holes (which are much bigger than a 10 AWG wire). We ended up running a wire through the holes and along the back of the PCB. Then we removed the insulation around where the wires touched the metal rings and soldered it there. Then we cut the wire short and added connectors on the ends. Finally we used liquid electrical tape to seal off the bare metal. Once again it was difficult to solder, but we managed.

I think this thing is great. The first day we set up a simple experiment where we had the CIM reverse directions at full speed (no load) every 500 ms. When the motor changed directions, we were reading current of up to around 60 - 70 amps. Then the 30 amp breaker started getting hot and it started tripping. We plan on doing more experiments and hopefully use it to determine problem spots in our drive train (tripping breakers has always been a problem with us).