Power supply questions.

mountaindew117

I bought a 9800 mha that has an output of 12volts. I bought a step down converter to drop the power supply down from 12 volts to 5 volts. I hooked everything up correctly and plugged it in to the mirror usb port on the pi and it powered everything but I have the little lighting bolt for low power supply. But I tried the setup without the step down and had a little puff of smoke come off the board and I'm thinking that was the fuse that protects from over current.

My question is would a 6volt step down hurt the pi in short / long term usage? To supply my build with enough power to use the lcd screen & and all other items plugged into it?

AlexMurphy

@mountaindew117 Is your Pi still working? You have blown the polyfuse. If it's still booting and running count yourself lucky.

mountaindew117

@AlexMurphy

Yes it is still booting and operating but I have like 5 odd these just laying around so to save myself another pi I was just wondering about the above question.

jsawhite

Yeah, you can't run a Pi off of 12 volts! I'm really amazed the thing still works.

More than likely, your dc to dc power supply (the step down you called it) cannot supply the current that the Pi needs. I'm sure there is enough power on the 12V side, but the supply has a current rating and it's likely too low. You need a better dc-dc supply. Something like this:

https://www.amazon.com/Ailavi-Converter-6V-24V-Output-Module/dp/B00XPZ7I4I

or this:
https://www.amazon.com/dp/B00O6R9PCC

both can supply 3 amps of current to the pi... Also, make sure to use a high quality USB cable between the supply and the pi, and make it as short as possible... minimizing the loss due to the cable.

Oh and to answer your question, no using the voltage converter is no problem long term. Technically, it's no different than the ones that step the 120V (ac) down to 5V... same concept. Just have to have one that can supply 2A or more at 5V.

mountaindew117

@jsawhite said in Power supply questions.:

Yeah, you can't run a Pi off of 12 volts! I'm really amazed the thing still works.

More than likely, your dc to dc power supply (the step down you called it) cannot supply the current that the Pi needs. I'm sure there is enough power on the 12V side, but the supply has a current rating and it's likely too low. You need a better dc-dc supply. Something like this:

https://www.amazon.com/Ailavi-Converter-6V-24V-Output-Module/dp/B00XPZ7I4I

or this:
https://www.amazon.com/dp/B00O6R9PCC

both can supply 3 amps of current to the pi... Also, make sure to use a high quality USB cable between the supply and the pi, and make it as short as possible... minimizing the loss due to the cable.

Oh and to answer your question, no using the voltage converter is no problem long term. Technically, it's no different than the ones that step the 120V (ac) down to 5V... same concept. Just have to have one that can supply 2A or more at 5V.

As for your last statement are you saying that a 12volt to 6 volt step down converter will not harm the pi as I have this one:

https://www.amazon.com/gp/aw/d/B00CXKBJI2/ref=yo_ii_img?ie=UTF8&psc=1

That supplies 3amps at 5volts but it gave me the lighting bolt as it didn't have enough power. So my question is would using this one:

https://www.amazon.com/gp/aw/d/B00CXKCRME/ref=ox_sc_act_image_2?smid=A2OCOGC9B25845&psc=1

That supplies 3amps at 6volts, would it hurt the pi as bad in the short/long run?

I'll look into the links you provided to see if one of these will solve my problem.

iggy

+6v will hurt your Pi....believe max tolerance on the +5v rail is ~+5.25v. Your step down will work....since the output is non-adjustable, the problem is your cables/wires....they are causing additional resistance and thus dropping your voltage below 5v. If you have a multi-meter, hook it to your PI +5v and GND lines and observe when it happen. You should see the voltage on the Pi dip below ~+4.85v. As the others have suggested, the quality of the wires and length will make a big difference....as a suggestion, since you are shooting for 3 amps, ensure your +5 volt/GND wires you are using (both standalone and inside USB cables) are at least minimum 24 gauge. I use this as a reference for determining wire size: http://www.powerstream.com/Wire_Size.htm

If you changed out wires / cables and still get the lighting bolt icon, you can try this as an alternative as it has an adjustable output:
https://www.amazon.com/Yeeco-Regulator-Converter-Converters-Adjustable/dp/B00XM8SM66/ref=sr_1_7?ie=UTF8&qid=1490741792&sr=8-7&keywords=yeeco+buck+converter

Let us know if you have additionial questions.

mountaindew117

@iggy

I like that power regulator you shared with me. It seems that I can set this at 5.2 volts and adjust how much amperage I can use, which should be more than enough power to control my setup for my portable gaming case. Only thing is now is finding out where to mount this board inside my case lol.

Thank you sir for the help ill update everyone when it comes in from amazon.

iggy

Cool and np....show us some pics of your proj when you are done. Also to note, those pentiometers will take a few turns before you start to see the voltage decrease....when you adjust it make you dont have your Pi hooked up to the buck converter output (cuz the voltage on the output will be set above 5v and thus destroying your Pi)....instead hook up a multi-meter and ensure your output is ~ 5v. Once you have it at 5v, power everything off, hook up the Pi, hook up the multi-meter to the Pi GPIO 5v and GND, and power everything on. Adjust the output in relation to what your multi-meter says (the buck converter voltmeter display is pretty darn accurate but use your multi-meter as your standard measurement tool).

mountaindew117

@iggy
http://i450.photobucket.com/albums/qq230/mountaindew117_08/17759069_10212795584590442_417353204_o.png

This is my current setup for my portable case. Everything will fit inside a pelican 1200 series case.

http://i450.photobucket.com/albums/qq230/mountaindew117_08/17622627_10212795602830898_1636030306_o.jpg?t=1491013230
I hope to be able to start putting everything together here in the next couple weeks. Have to wait on my face plates that im having 3d printed so i can mount everything to them that needs to be mounted.