Before I mated the motor to the transmission, I wanted to try out the SPEEDO output on the DMOC445 that Beth at Azure Dynamics talked about in the previous post. I was really happy to hear that there's an RPM signal I could tie into. So, I got out the oscilloscope and tied it to pin 25 (SPEEDO_BUF) on the DMOC445 and spun up the motor.
Wait a minute, there's no pulses coming out. The signal is at ground. Azure said it was a push-pull circuit. The documentation said it was an open emitter output (implying a transistor that pulls up to 12V). Perhaps I didn't properly set the EE1SpeedoDiv variable in the controller. Okay, fire up the laptop and tap into the DMOC --- There's no variable remotely close to the name EE1SpeedoDiv! Argh! It's too bad that it's late Friday since the folks at Azure have already gone home, but I'll fire off an e-mail anyway and see if Beth will respond on Monday.
In the meantime, I have a (hopefully) working adapter hub and I can put the car back together and drive it. Perhaps I'll run down to Radio Shack and get an infrared emitter/receiver pair of LEDs to see if I can generate my own RPM pulses. I get frustrated when my hopes are dashed based on expectations. I guess that's just human. Ugh.
3 comments:
Tim,
Are you sure that you arn't supposed to take the +12 volts used in the drive then run that through a resistor and then through the output signal and it then pulls th1 +12 to ground?
Congratulations on the new hub. We will be waiting to see how it runs. Did you have time to look a the battery temperatures?
Paul
Hi Paul, I looked more at the output signal last night and tried to use a 1000 ohm pullup and then a 1000 ohm pulldown to see if the drive simply pulls up or down, but neither worked. Since the EE1SpeedoDiv parameter is not listed when I attach to the onboard computer, I suspect it wasn't in my version of the DMOC445 firmware. (version 1631)
I've been swamped with getting this thing running again that I haven't even thought of measuring battery temperatures yet. Do you have suggestions for particular places on the batteries to measure temp?
Tim,
Sorry about the tach signal-- who knows.
With regard to the battery temperature. I have this theory that given that the battery box is somewhat of an insulator and that during both discharge and recharge there is heat given off about equal to 20% of the energy used. This could mean that the cell temperatures will keep rising to some level where the DT may be as high as 20 Degrees or more above ambient. As you know the life of lead acid batteries decreases by a factor of 1/2 for each 18 Degrees rise above 78 Deg F.
An RTD exoxyed to the most interior battery would be really good. You could check it in the morning and evening with a VOM and look it up. A less sophisticated method would be to just put a glass thermometer in the cell.
I realize you are busy with other things so it is not urgent. Just something I am thinking about.
Hope you get it running again this weekend. When you do I am also interesed in your WH per miles. A voltage and current reading at different speeds would be interesting.
Paul
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