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Old March 8th 04, 06:33 AM
James W
 
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Default Using a power mosfet to select from various power sources for HFrig

Anything I should be concerned about with my plans to use a power mosfet
to choose amongst various 14V sources to power an IC706. This is for
automotive use. I want to use my deep cycle batteries while the engine
is off, and use the engine/battery/alternator while the engine is
running. Thought I'd use a couple of big mosfets to select one or the
other.

thoughts?

- jim

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Old March 8th 04, 11:13 AM
Gregg
 
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Tried it. Save yourself some grief and use relays ;-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
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Old March 8th 04, 11:13 AM
Gregg
 
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Tried it. Save yourself some grief and use relays ;-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
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Old March 8th 04, 03:33 PM
James W
 
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Care to expand a bit on this?

Gregg wrote:
Tried it. Save yourself some grief and use relays ;-)


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Old March 8th 04, 03:33 PM
James W
 
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Care to expand a bit on this?

Gregg wrote:
Tried it. Save yourself some grief and use relays ;-)




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Old March 9th 04, 12:05 AM
Gregg
 
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Behold, James W signalled from keyed 4-1000A filament:

Care to expand a bit on this?


Sure!

I found that the RDSon was too high with most MOSFET's. The best I could
attain was a 1/2 volt drop at 1 amp load. When the CB linear came on, it
increased the drop to 6 volts (60 amp draw).

So, I went to the auto wrecker and got a couple of 30 amp relays and a 100
amp contactor for the job and it worked perfect.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
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Old March 9th 04, 12:05 AM
Gregg
 
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Behold, James W signalled from keyed 4-1000A filament:

Care to expand a bit on this?


Sure!

I found that the RDSon was too high with most MOSFET's. The best I could
attain was a 1/2 volt drop at 1 amp load. When the CB linear came on, it
increased the drop to 6 volts (60 amp draw).

So, I went to the auto wrecker and got a couple of 30 amp relays and a 100
amp contactor for the job and it worked perfect.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
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Old March 9th 04, 12:59 AM
budgie
 
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On Sun, 07 Mar 2004 22:33:12 -0800, James W
wrote:

Anything I should be concerned about with my plans to use a power mosfet
to choose amongst various 14V sources to power an IC706. This is for
automotive use. I want to use my deep cycle batteries while the engine
is off, and use the engine/battery/alternator while the engine is
running. Thought I'd use a couple of big mosfets to select one or the
other.

thoughts?


Why not a pair of BIG Schottky diodes?
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Old March 9th 04, 12:59 AM
budgie
 
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Default

On Sun, 07 Mar 2004 22:33:12 -0800, James W
wrote:

Anything I should be concerned about with my plans to use a power mosfet
to choose amongst various 14V sources to power an IC706. This is for
automotive use. I want to use my deep cycle batteries while the engine
is off, and use the engine/battery/alternator while the engine is
running. Thought I'd use a couple of big mosfets to select one or the
other.

thoughts?


Why not a pair of BIG Schottky diodes?
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