Does this device exist?

I'm looking for some type of semiconductor device that has a very high impedence gate that is OFF when high enough voltage is present. So a capacitor could be charged, connected to the device, and because the impedence is so high the capacitor is discharged very slowly. And while connected and the voltage is high enough the device stays off. When the voltage drops low enough the device turns on. Thanks, Eric

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etpm
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P channel Depletion mode MOSFET?

Jamie

Reply to
Maynard A. Philbrook Jr.

A diode with a resistor?:

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Better charger:

Schematic of the Solar Charger Circuit:

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Advanced:

DC to DC converter/smps? This can also be more efficient.

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Needs AC:

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Step by Step Hacking a Disposable Camera Flash Unit to Power a Geiger Tube:

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/Glenn

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Glenn

A Jfet is on with zero (gate-source) voltage. You need a negative voltage to turn it off. (Would that work? What are you trying to do?)

George H.

Reply to
George Herold

Greetings George, Wall warts are always using power even when the device to be powered is not connected. I know the amount of power used is small but I would like to be able to avoid it. So I was wondering how I could disconnect the wall wart from the mains whenever the powered device is turned off. So when the load is removed from the wall wart it disconnects from the mains and then reconnects automatically when a load is connected. I was thinking that maybe a cap could be charged which would keep the wall wart off. When the cap voltage drops too low the wall wart would turn on again, the cap would charge, and then the wall wart would again be disconnected from the mains. When a load was put on the wall wart it would keep the cap discharged. Eric

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etpm

Hi Eric, I'm thinking a wall switch is going to be the cheapest/ easiest approach. People are always trying to save these little bits of power... And the large bits are ignored. (Better windows and insulation, smaller cars... etc.) I wonder if the energy you'd save over the life of the wall wart would be more than the energy to make the parts that go into the "energy saving" add-on?

George H.

Reply to
George Herold

I don't know if the energy saved would cover the cost of the extra parts. I have done the major things to save energy. Even all the internal walls are insulated so that rooms can be kept at a different temps. Almost none of the receptacles are switched however. So the wall warts need to be unplugged. Eric

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etpm

ltage to turn it off.

t approach. People are always trying to save these little bits of power...

cars... etc.)

e more than the energy to make the parts that go into the "energy saving" a dd-on?

rotection is active.

Hi Eric, I'm sorry I didn't mean to imply that you were wasteful. (In fact it sounds like you are more dutiful than myself. We've got these big bay windows in the dining room, and I tell myslef each autumn, before t he cold weather comes, that I should go and have some extra internal window s made for them. They are double pained but still on those cold winter nig hts... oh they do have some thick curtains.... but enough of that.)

So I've got a box with power connectors and a 1 ohm sereis resistor. (I us e it to look at power draw from various instruments. I plugged in a Phihon g 5V /1A wall wart. It drew about 9 mA with no load. So call it about 1 W att of power. (OK for those experts I'm assuming I and V are in phase, but I have no proof of that.) Anyway if I left this on all year that's about

9k hours, so 9 kW-hours. It'd cost me a buck or so. (Does it matter that all my electricity comes from the nearby windmills?) For fun, a larger Astrodyne (~50W) brick on a rope draws about 40mA.

George H.

ection is active.

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George Herold

e big bay windows in the dining room, and I tell myslef each autumn, before the cold weather comes, that I should go and have some extra internal wind ows made for them. They are double pained but still on those cold winter n ights... oh (Grumble double **paned**, excuse my spelling.... maybe they're double pai ned when you break one and have to replace it :^)

they do have some thick curtains.... but enough of that.)

use it to look at power draw from various instruments. I plugged in a Phih ong 5V /1A wall wart. It drew about 9 mA with no load. So call it about 1 Watt of power. (OK for those experts I'm assuming I and V are in phase, b ut I have no proof of that.) Anyway if I left this on all year that's abou t 9k hours, so 9 kW-hours. It'd cost me a buck or so.

otection is active.

Reply to
George Herold

Your first mistake was living in Buffalo. ;)

Cheers

Phil Hobbs

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Phil Hobbs

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