Board test

Hi,

I have done a silly thing, I could not get the mech end stops to trigger on my ramps1.4, so after trying everything else I swapped the ground/ positive to the negative on the end stops on ramps (Yes I know about the law of nature : "The dumb will suffer", I was dumb, I suffer. It was like 2am and I had been at it all day). There was a tiny little click and some smoke came out of the Atmega2560. My question is this, how do I figure out if all the components are fried, or only some of them, or all of them are still working?


After smacking my self a few times, and getting some sleep, I pulled the ramps of the atmega board, and plugged that into the usb serial connection of my pc. The LEDs on the 2560 are on. One steady amber, another higher up steady green and another, next to the steady amber is flashing around 3 time per second. It seems to connect and it seems to be taking gcode. Is the some sort of test script I can run on the board to see it it is functional? And if it is, how do I test the rest of it?

The ramps board's fuses seem ok

The easiest test is under menu examples. Blinking LED. If you can upload that sketch and it blinks, than the MCU is okay. That is the first thing I test when I get a new Arrduino.

Files>Examples> 01 Basic> Blink

If you've connected + to - on the endstop connector, you've probably blown the regulator on the Mega 2560. There may be a fuse on your 2560, but I don't think there is one normally.

You "should" be able to run it directly connected via USB (as you've proved). You will find that you can't power the Mega 2560 via the barrel jack or from the RAMPS board (via D1).

Thanks for that. Tried blink and it works a treat.

And I just did a web search on regulator and it is the bit that was smoking. Also, it is reasonably easy to replace, so I may have a go at it.

Cefair,, do you think I would have done damage to the ramps board or motor drivers?

Shorting out the + & - rails will only blow the regulator, as it's trying to pull too much current. All the other components should be fine.

The amount of current required to fry the regulator should be well within the tolerances of the tracks on RAMPS, and there are no components that such a fault puts in danger.

Basically, since you shorted the +5 and Gnd together, all you've done is remove power from all the other devices.

If you remove the regulator from the Mega board, you could try loading your firmware again (Marlin?), connecting your power supply, and then using Pronterface on a PC to control the machine. You won't be able to print without a PC (the PC's USB will be powering the Mega, the end-stops and the logic side of the stepper drivers), but otherwise it should work fine.

Just make sure the end stops are wired correctly! If you're only using 2 pins, get some jumper headers and cover the + pins (they're all the same voltage, so joining the + on a N-min to a + on it's matching N-max will cause no problems). This will definitely stop you accidentally shorting + and - together again, without resorting to desoldering the pins or cutting them off.