Monday, November 8, 2010

High power analog is a little bitch and always has been

I've set it up to be able to fire on two of the magnets as a test.

It does indeed charge and fire. That said, the electromagnetic disturbance caused by just the charging system seems to be able to set off the SCRs that fire the magnets whenever it charges above 130V (the electromagnetic disturbance from the charger gets more agressive as the voltage increases. Indeed, you can hear it once it passes about 100V). The reason I get this pre-firing is that the magnets are set off by an infared beam sensor. When the round breaks the beam, the sensor gives a signal to the firing circuit. It seems that the disturbance is enough to cause bumps in the signal and thus fire the magnet before it's supposed to. At one point, when it fired while charging, the charger seems to have been able to toast one of the firing circuits.

My solution right now is to put a computer (microcontroller) between all the sensors and the firing circuits. The computer will be able to see when the signal is bouncing and discount it. I could also use a capacitor-resistor filter for this but that would provide less flexibility in the long run.

The computer will have it's own 5V power supply and need not share one with the charger. This should also help reduce jitters.

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