May 28, 2012
about 3 years ago
A Jacob’s ladder rerquires a continuous lf AC arc, it climbs the ladder due to thermal effects of the air the arc is discharging in.
Immerse the carcass in a mixture of Methyl-Ethyl-Keytone and GP laquer thinner. Cover container tightly and wait. I about 2 days the epoxy will begin to swell and soften. Keep picking off the softened compound and returning the device to the bath. I estimate in about 7-9 days the module’s innards will be 90% clear of potting compound. I use the same method for depotting Ford Electronic ignition modules for repair.
To make your display operate as you intended, common connect all intersect electrodes, add 2 additional electrodes to the midpoint of each segment fed via 1 Meg 2 Watt Carbon resistors.(Carbon due to the historical behavior of Metal film resistors suffering from arc bypass under high voltage transients.) The resistors will allow for arcs to form to both end electrodes in a given segment, as well as extend the arc event time, also reducing radiated EMI due to lower arc current. Experimentally determine the maximum forward input voltage that can be applied without triggering an arc discharge cycle with the module fed via a MR755 or equivelant diode. This is to get the internal HV supply in the CDI module near to but not in excess of the firing point. By use of a second supply, (5VDC), supplying high side drivers controlled by the Uno and outputting to the segment’s CDI unit downstream of the MR755. Drive the segment @5V only long enough for one discharge event. Sequentially strobe the segments in a round robin fashion to minimize overal power dissipation.
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