felix123
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Is 5.71v too high a voltage?

Fri Jul 13, 2012 7:36 am

HI, I wired up a TP-link Power over Ethernet adaptor. It seems to work, but when I measure the voltage across the test points, I get 5.71v. Is this too high, will it shorten the lifespan?

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rurwin
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Re: Is 5.71v too high a voltage?

Fri Jul 13, 2012 7:58 am

Yes. The 5V power is required to be no higher than 5.25V. You will increase the heat from the regulators and may well cause damage to peripherals.

If you've built your own power lead, then put a (silicon) diode such as the 1N4001 in it. A diode drops 0.7V. Watch the current though; the 1N4001 can handle up to 1A and you probably want to de-rate for 100% usage, so don't power anything other than the RaspPi through it.

Jock in a Frock
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Re: Is 5.71v too high a voltage?

Sun Jul 15, 2012 2:12 pm

rurwin wrote:A diode drops 0.7V. Watch the current though; the 1N4001 can handle up to 1A and you probably want to de-rate for 100% usage, so don't power anything other than the RaspPi through it.
You could put 2 or 3 1N4001 diodes connected in parallel - this will share the current through them, while still dropping the required 0.7V.

Joe Schmoe
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Re: Is 5.71v too high a voltage?

Sun Jul 15, 2012 2:21 pm

Jock in a Frock wrote:
rurwin wrote:A diode drops 0.7V. Watch the current though; the 1N4001 can handle up to 1A and you probably want to de-rate for 100% usage, so don't power anything other than the RaspPi through it.
You could put 2 or 3 1N4001 diodes connected in parallel - this will share the current through them, while still dropping the required 0.7V.
Or use a 1N5400.
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

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jbeale
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Re: Is 5.71v too high a voltage?

Sun Jul 15, 2012 2:26 pm

felix123 wrote:HI, I wired up a TP-link Power over Ethernet adaptor. It seems to work, but when I measure the voltage across the test points, I get 5.71v.
The product page for that part claims a 5 V output. Assuming you have selected the 5 V output, I would question why it is so far out of spec, was it really designed to provide such an over-voltage? Is it unregulated, so it might go lower or even higher, depending on the load current?

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