Sunday, January 2, 2011

More accelerating magnets

I've added a few more accelerating magnets. As noted before, I can't really enable them because my capacitors are too large. I've also found a new issue.

The main symptom was that the device failed to charge correctly. Specifically it went up to about 60V and would go no further. I'd seen this issue before where the optical sensors were receiving interference from the electromagnetically noisy charging circuit: They'd fire when there was no bullet and the charger would fight to charge them as they discharged. For some reason, that fight was always resolved between about 60V and 90V of charge. My old solution was to add an override that kept all the optical gates as max voltage when charging. This signal was daisy chained just like all the others from charging circuit to charging circuit. Clearly there was something wrong with this signal. Adding my oscilloscope to view it while charging actually made the device charge correctly! Damn quantum circuitry pisses me off every time.

That said, the scope really adds one of two things to a circuit: a big resistor to ground (which can sometimes fix errors where your voltage is floating) and a capacitor between the measured voltage and ground. I assumed that perhaps the daisy chaining of this signal was causing it to not reach the firing gates in time to shut them off before the charger went ballistic making electromagnetic noise (it is a bit of a race, since both at turned on by the same switch trigger). I added a cap between the signal and ground and sure enough the issue went away. For about 30 minutes. Damn it.

Around that time I stared to notice the display wander when the capacitor voltage was low and even didn't turn on at one point. Something was up but I was too dense to discover the real issue until fired the device wearing a shirt. Thing is, the stock of the rifle is where the battery (24V) and, more importantly the rectifier that brings it down to 5V live. It's also steel and in this case it was warm. Reaching inside, I found the heat sink of the 1.5A 5V regulator was piping hot. It was almost certainty producing low voltage.

I stepped out to buy a pair of new 5V regulators that should get me to at least 7.5A:

When I came back, the power supply was cooler and the device was charging correctly again.

Thing is, I didn't think I'd need more power. When all is said and done, the total consumption of 5V power should only be equivalent to a 5ohm resistor (or about 1A of power). That is 13 accelerator gates where each gate has a 200ohm resistor powering the optical sensor and a 100ohm resistor being pulled down on the mosfet that fires the little SCR (which in turn fires the big SCR). I only have like 8 of them installed so I should have even more buffer room. Something is sucking power.

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