Power supply with 5.35V / 2A safe?

[MarcelNL]

Hi there,

Merry Xmas.

I have a question about suppling power to my new R Pi2 Model B. Somehow my supplier forgot to include a power adapter and I still want to play..

Can I use one with 5.35V / 2A without burning up the board?

Thanks very much.

Kind regards,
Marcel

[rurwin]

Merry Christmas.

That is marginal. The spec of the Raspberry Pi is 4.75V to 5.25V. With my moderator hat on, I have to say no; don't do it.

However there is going to be some voltage drop in the power cable and in the "fuse", so it's likely that by the time the power gets to the RaspPi it is going to be below 5.25V. I wouldn't try it unless I checked that with a DVM across TP1 and TP2 though.

[MarcelNL]

Thanks, but how to test that withour connecting the Pi actually to that 5.35 power? And what are the tp1 and tp2 on model 2B? Were to connect my dvm?

thanks for helping me!

[gordon77]

Do you have a usb extension cable, maybe a metre or more, you could put in series with it to lose a bit more voltage, even if only whilst you test it?

[gregeric]

What uses 5V on the B+ / 2B & might put an upper limit on Vin? There's the onboard 3V3 / 1V8 regulator 2306KE that's got a recommended max 5V5, absolute max 6V5, so the BCM2836 will be safe.

Then there's HDMI & downstream USB to consider. The USB current limit switch 2552 again has max recommended 5V5, so as long as you don't plug any USB devices or HDMI monitor in you should be OK, at least as far as plugging in the PSU to see what the output voltage actually is with a light load.

Alternatively, load the PSU with a 5W 5R resistor & see what the output voltage really is. Oh yes, and as gordon77 points out, put the resistor at the end of your intended cable & measure there.

[MarcelNL]

Thanks all!

I just cut a spare USB cable and connected it to the 5.35/2A adapter and found a reading of max 5.05V on my DVM. Suppose the text on the adapter is not really to be trusted?

So I guess I should be safe?

[gregeric]

Good to go!

[pete_l]

Thanks all!

I just cut a spare USB cable and connected it to the 5.35/2A adapter and found a reading of max 5.05V on my DVM. Suppose the text on the adapter is not really to be trusted?

So I guess I should be safe?

You are assuming that you DVM is calibrated. What reading does it show for a nominal 5.00 volt source?

[MarcelNL]

Correct Pete,

But I do not have a nominal source. Maybe a new AAA battery?

Anyway the pi works but I will get myself the correct PSU soon.

Thanks all.

[gregeric]

I think you already have the perfect PSU for the Pi... something outputting a little bit over 5.0V to compensate for the small amount of resistance in the USB PSU cable & polyfuse. Stick with what you have.