Mega board power receptical not working

S550Stang 2018-08-20 15:10:51 UTC #1

I tried to connect a 5v power supply to the mega board via the receptacle. The board wouldnt fire up. It will fire up when connected with the printer cable to the pc usb.. Why?

carefudundae 2018-08-20 16:43:52 UTC #2

how much current is your 5V PS capable of? may need upwards of an amp to turn the mega on...

S550Stang 2018-08-20 22:19:46 UTC #3

I will check. However i just looked at the spec sheet for the mega.. 7-12volts required.. lol.... so that "may" be the issue.. lol

jefbed 2018-08-21 07:51:24 UTC #4

Here's the official page covering the power supply requirements.

S550Stang 2018-08-21 12:08:07 UTC #5

Thanks for the info. I hooked up my power supply, similar to the one shown. and the board and lcd lit for a quick second. then out.. I measured the output of the 12vdc p.s. 14 volts... wtf.... hooked up thru usb, and board lit up so its still working. I then verified 12v from the printers power supply with a meter and connected to the board. no lights.

that spec you sent 14vdc shouldnt have affected the board. I'm thinking this is a chinesium knock off and not a hardier board which may be the issue. I'll probably order another board and pull 12vdc from the printer power supply which I should have done from the get go.

jefbed 2018-08-21 17:19:15 UTC #6

I run my 2020 Prusa i3 5v rails with USB power. I should have removed D1 from the RAMPS board. Trying to run the RAMPS with an LCD from the PSU is likely to fry the 5v regulator of the Arduino, which is what happened to mine. Everything else still works. It sounds like you may have the same problem I did. Was there a spark, pop or white smoke? On mine there was. On my newest build I removed D1 from RAMPS and never had any problems driving an LCD. I had a 7805 regulator wired to the power lines of USB cable using a custom perf board PCB to bypass the regulator, but I eventually just plugged it into a powered USB hub.

S550Stang 2018-08-22 17:27:31 UTC #7

I didnt see or smell anything odd and no sparks. You mentioned you removed D1, the pin itself? I'd still like to make this an independent printer if possible, but be able to connect to a pc if the need arises.

jefbed 2018-08-23 03:29:11 UTC #8

On the Folger Tech 2020 i3 I run an unmodified RAMPS since the regulator is already blown. D1 is a diode on the RAMPS board that shunts power from the 12v input to the Arduino's 5v regulator. Here's the reprap wiki page Removing it is a way to protect the regulator if you are providing your own 5v source. The LCD may have drawn too much current from the regulator and blown it quietly, even if it can handle the input power just fine. USB power bypasses that regulator, so you could use a powered USB hub with nothing else connected or wall charger to get the Arduino going, then just swap cables whenever you need to connect to a PC.

S550Stang 2018-08-23 12:07:12 UTC #9

I have a bunch of transformer plugs ( i tend to hold on to them after the thing they powered breaks) and a few are 5v, I could wire one up with a printer jack, that should work fine for 5v.