Quote:
Originally Posted by apowers
maybe it is the bendix.
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I read the Wikipedia article on Bendix and I'm still not sure what exactly you are referring to. Bendix apparently refers to the way the sprocket is attached to the starter, specifically with a helical cut. I do not believe that is what you meant.
I will assume jackbauer got it right, and no I bypassed my starter solenoid.
I was hoping to use it initially as a safety cutoff. The problem is the solenoid and starter share a common ground, so it is not possible to turn the solenoid off separately. (without doing something fancy or mutilating the starter)
saand:
Yeah the meter would bring them together.. I suppose one could try to measure impedance across the ground connections. If they are connected it will be a short. If they float, then you measure voltage between the two and you should see the difference induced by the meter, 3V in my case.
Experimentation agrees with theory. I get open circuit measurement on ohmmeter and -1.8V on voltmeter, dropping to -1.7V very very slowly.
So they are isolated, and my ground wire between them is mandatory.
Thanks for confirming my gate resistor removal; I was sure everyone would tell me to but it back in since it seems almost like dogma at this point lol
Yep, the hands-on at university is so lacking. That's why I'm doing this project! Well that, and fun
Yep those oscillations are quite impressive, and they make me quite sad.
I see we have a problem with terminology which should be addressed at this juncture.
I consider having 3 main components:
1. The microcontroller board with outputs logic level PWM.
2. The mosfet driver board, one chip - takes 5v PWM input and drives 12V pwm output.
3. The controller, which consists of buss bars, capacitors, flyback diodes and mosfets.
I have those metallized polypropylene capacitors, only 4.7uF but with really low ESR and high ripple current capability.
Digi-Key - PF2475-ND (Manufacturer - ECW-F2475JB)
Two of them are on the controller between BM+ and B- along with the large electrolytics. Saand you suggest to add more capacitance here with low esr; do these caps not count? Or do you think I just need more of them?
The third is on the driver board since the wall wart powering it can't handle those kind of current spikes.
My microcontroller (you say controller card) has enough capacitance, but perhaps I should add some inductance as you suggest. There is a slight sag and oscillation, but not enough to be detrimental I think.
Just now I have begun to suspect the connection between the capacitor board and the buss bars. I epoxied them together with some two-part epoxy that claimed to be a solder replacement. (I knew soldering was going to be a pain)
The problem is that the solder was ineffective on the components; it was a weak physical bond, making an intermittent electrical connection. A fun story for another time.
The cap board is still connected to the buss bars with that epoxy.
The resistance across the epoxy is negligible, within the tolerance of my meter (it is a Fluke, but more electrician rather than electronics version)
As I said before, precharging takes several seconds so the capacitance is connected in a DC sense.
I suspect now that the AC connection is not as good; that the epoxy has a high ESR. This would keep the good capacitors from fulfilling their duty.
My only course of action is to replace this epoxy. I'll give it a try and cross my fingers!
I appreciate all of your help everyone. I hope I can give back to the community some day