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SCR controlled bilge pump
Lynn Coffelt wrote:
Quickly, this isn't going to be any help, but once an SCR fires, (in a DC circuit), it isn't easy to halt it's conduction without interrupting the current flow by introducing another switching device.... Well, yes, that can be a problem, but I think SCRs can be shut off by changing the bias of the gate circuit. They have to have a minimum current flow to work. Trouble is, all my semiconductor experience was with transistors, diodes, and ICs, and I cannot find much about their DC application on the net. (And whatever twit named a series of boats "SCR" is begging for a kick in the shin.) The other (non-helpful, I know) question is that if there is backflow from the discharge hoses, shouldn't there be checkvalves to prevent seawater from entering (especially during a moderate heeling turn?) The check valve would have to be right at the pump, or close to it, to keep the water flowing back out of the hose from floating the switch. I'm wondering about the same pump control techniques, but this is at my house when we have more than a little rain. Like this past week! Should work fine in a sump, where the hose emptying back into the sump would be even more a problem. You are talking about a house, so you have a bit more room for spare parts. Here's what I figure for a latching relay circuit (if you don't need it, sure as anything someone else is going to ask): Need: Pump, relay with at least two normally open switches, two float switches, bunch of wire. Radio Shack has at least one 12VDC relay, and at least one 120V relay that will work. Watch out, they look exactly the same and you have to check the label on the package. (They are DPDT.) Place the upper float switch in parallel with one of the normally open switches. One side of them goes to one side of the power, the other goes to one side of the relay coil. The other side of the relay coil goes to the lower switch, and the other side of the lower switch goes to the other side of the power supply from the first set of switches. The remaining normally open switch controls the pump. I think the Radio Shack relay is a generic automotive module, and I know I've seen bases for it around somewhere, so you could solder the float switches, power supply, etc to the base and just plug in a replacement relay when the old one goes bad. Of course, it would be handy to add a third float switch even higher than either of the first two, and wire it to an "OH,****" alarm G. |
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