PSU - 5.2V Ok?

Any technical questions about the Epiphany chip and Parallella HW Platform.

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PSU - 5.2V Ok?

Postby AndyC » Mon Aug 04, 2014 10:10 am

Hi Guys,

I have a 4A switching PSU here with variable DC 5-15V.

I just tested it with a meter and the lowest it goes is 5.2V, just checking that this should be ok with the board?

Cheers

Andy
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Re: PSU - 5.2V Ok?

Postby sebraa » Mon Aug 04, 2014 12:52 pm

Did you measure while the PSU was loaded? If not, try again with a load attached. Usually they need at lease some load to have the correct output voltage. Transformer-based PSUs are worse, though.

On the other hand, 5.2 volts should not be a problem.
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Re: PSU - 5.2V Ok?

Postby AndyC » Mon Aug 04, 2014 1:01 pm

Hi,

Thanks for the reply.

It was tested unloaded. When I manage to get my heatsink attached I will give it a go and test it loaded.

Thanks

Andy
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Re: PSU - 5.2V Ok?

Postby timpart » Mon Aug 04, 2014 1:08 pm

I have a power supply for two boards and with one board attached it supplies 5.1V. I had a look at the board schematic and traced the 5V line. I looked up the specs of the chips I found attached and they all had a max operating voltage of 5.5V. (Absolute max of 6.0 or 6.5 volts, but you don't want to go there.)

I may have missed one or misread a spec though. Perhaps someone from Adapteva could make an official comment.

With a 4A supply there is the risk that if you accidentally short out the board you could blow one of the 4A fuses. (The supply might be able to send out a bit more than 4A briefly.)

Tim
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Re: PSU - 5.2V Ok?

Postby AndyC » Mon Aug 04, 2014 1:22 pm

Actually on closer inspection this thing outputs 5A at 5V.

If I put a 3A fuse in the plug would that go before the board fuse?
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Re: PSU - 5.2V Ok?

Postby sebraa » Mon Aug 04, 2014 5:40 pm

AndyC wrote:If I put a 3A fuse in the plug would that go before the board fuse?
Depends on the characteristics of both fuses. I wouldn't count on it.

But this is only a concern if you create a short circuit somewhere. Shouldn't happen if you are careful.
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Re: PSU - 5.2V Ok?

Postby AndyC » Mon Aug 04, 2014 5:48 pm

Thanks for the info, I will give it a go and see.
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Re: PSU - 5.2V Ok?

Postby timpart » Tue Aug 05, 2014 6:57 am

AndyC wrote:If I put a 3A fuse in the plug would that go before the board fuse?


If you mean the mains plug, I wouldn't rely on it. The current out of the power supply could well be higher than the current in. (It is converting power V * I but with less than full efficiency) It might well be able to do 4A out on 3A in.

I've not heard of anyone shorting their board, but two forum members have put too high a voltage in and one with wrong polarity

Tim
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Re: PSU - 5.2V Ok?

Postby AndyC » Tue Aug 05, 2014 7:12 am

Thanks for the info.

I will use it for the moment, when I manage to get some kind of breakout for the GPIO I will get another PSU, just incase!
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