Electromagnet - hqwitty/UCSD-HPS-Electronics GitHub Wiki
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19 small 2.7mm for height, 5mm diameter
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16 medium small, 2.65mm for height, 6mm diameter
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7 mediums, 2.8mm height ,8mm diameter
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1 medium large,2.7mm height ,10mm diameter
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15 large,2.8mm height ,12mm diameter

The electromagnet works with potentially full strength with a simple button circuit and a 12V battery pack, but works with very weak strength and a delay with the Deadman Buoy circuit.
UPDATE: Now it works for unkown causes.