Thursday, February 4, 2010

RPM Sensor Mount

Yesterday I finished fabricating the mount for the two RPM sensors. Regular readers will remember that the older style sensor is guaranteed to work with the Zilla controller, but it interferes with my ability to use the tail shaft of the motor to run the A/C compressor. The newer one will allow me to use the tail shaft, but has never been tried with the Zilla. I'm going to find out if it will work.

This is a side shot of the motor's tail shaft with the RPM sensors attached. On the right hand side, closest to the motor you can see the sensor with the wires protruding toward the camera. that ring just in front of it is the exciter ring mounted on the shaft of the motor. You can see that the rest of the shaft would be free if the second, older style sensor were not mounted over the end of the shaft, which you can see on the left. It has a little black cup (which you can see) mounted over a magnet (which you can't see) that is screwed onto the end of the tail shaft. The whole point of having both mounted at the same time is so that once I get the motor spinning, I can simply swap which leads are attached to the controller and monitor the output from each.

The controller expects four pulses per revolution, which each sensor can do. I don't expect there will be a problem with either, but I'm really hoping the newer style one works, or it's no A/C for me!

I must have an RPM sensor on the motor. The motor's red line is 5500 RPM. It will tolerate higher speeds for short times, but not for sustained periods. The danger is that the all the copper in the motor will unwind off of the armature, thus destroying the motor. The controller has a feature that will allow me to set a red line that the controller simply won't pass. Of course I have to be careful and not drop the car in the wrong gear and over spin the motor. You can also set the controller so that it limits the RPM to a much lower number when the car is in reverse. That should be handy. But one of the coolest features is called Valet mode. All I have to do is press a button (yet to be installed) and it tells the controller to put it in Valet mode. I can set that up so that the controller limits current and RPM of the motor. Essentially keeping someone who isn't used to the car (a valet, mechanic, or teenager) from taking off like a nut.

After I finished that I got to work on the large battery box up front. I managed to get the brackets made and half the batteries installed and fastened down.

That was exceedingly difficult, the spaces are very tight. Notice that gap between the top of the battery on the right hand side and the bracket? I'll be shimming that somehow. You'll also notice that the terminals on the batteries are facing each other, which probably alarms the more astute readers. If they were to touch... It's kind of like crossing the streams. you don't want to allow that to happen. Well the brackets won't allow them to move closer than they are toward each other. But to be certain, I'll be placing some non conductive material between them just to be sure.

Today I had planned on finishing the battery installation on this box, but it looks like that's going to have to wait. I'm under doctor's orders not to lift anything heavy for two weeks. *Sigh* The other day I pinched a nerve in my neck and lost all feeling in my left arm. I can assure you that was a bit scary. But all is well. The Dr. has put me on anti-inflammatory medication and want's me to take it easy for two weeks. I'm sure lifting one battery at a time isn't a problem, but wrestling with stacks of 4 is probably not wise. I think progress will slow for a while. I'm going to see how much other stuff I can get done in the mean time.

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