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Kaboom! How screwed am I?

I just finished building my Open EVSE 40A Advanced kit. Seemed straightforward enough, but when I plugged it in, nothing happened. No matter how I adjusted LCD contrast, I just had a blank panel.

So I started measuring with my meter, to see if I could identify a problem. I started with power input. I touched probes to the incoming power at the screws on the big relay, expecting to read ~240VAC. Instead, BOOM!, big pop.

Somehow, one leg of the AC_Line connector block shorted out. Questions:

1. Any idea what happened? By touching the probes to the relay I created an additional circuit through my meter, but I can't see how that could have caused the short on the controller. I'm quite certain that both legs into the AC_Line block were well seated and didn't have exposed wire.

2. What now? I expect that the controller is toast (plus I don't know if it was working to begin with).  I could buy another one ($90, ugh), but without some idea what went wrong the first time, I'm reluctant to throw good money after bad.

Note that one difference between my build and the build guide was that my kit lacked the lugs for fitting the slide connectors. I just cut off the slide connectors, stripped the insulation ends, tinned the wire ends with solder (mostly so I could bend them into nice loops) and connected them that way.

Also, I have a four-wire power cable, so I wire-nutted off the neutral line and just left it inside the box. In the "pre-boom" photo, you can see it running up the left side of the box and curling around the top of the controller. The neutral line's insulation is blackened from the nearby short explosion, but undamaged.

I can't see any way either of those choices could have been related, but I include them for completeness.


I can only guess as to what happened... Perhaps a stray strand of the AC line shorted out? Clean the board well with a solvent like rubbing alcohol, and then see if any traces were involved in the kaboom!  If so you will have to add jumpers to replace the fried traces.  From what I can see in your photos I think that the PCB is ok once you remove the carbon form the event.

You said that you were getting no display.  Perhaps you did not have the line ac voltage on the pcb (the scorched) wires properly connected to the relay and your probing actually connected it, then because of the stray wire strand you got the kaboom?

Clean it up, dry it out and then post more pictures and your testing of the ac traces.


connector side of the PCB:


solder side of the pcb:


Newbie here -- I just completed an advanced kit, and (thanks to this weekend's successful build) recognize your components and layout.

Looking at the "Pre-Boom" layout, I see that the purple pilot wire is correctly connected, but there seems to be no ground wire connecting the board to the ground bus.  That ground wire should connect from the ground bus to a terminal next to the pilot terminal. 

Apparently the power supply of the board does use the ground, since the little UBEC power supply connects between 12 volts and ground.  If this is true, then perhaps the lack of a ground can cause real problems on the board; perhaps this was the cause of the flash.

Another problem that appears in the "Pre-Boom" photo:  The GFCI sensor coil is on the output side, rather than the input side.  In your setup, the fat red and fat black wires (in the left of the photo) should be routed through the GFCI coil (the on labeled with "21917" in the photo)   

I suspect that this latter problem did not cause the pop, however.  

Finally, are you certain that your meter was set to "AC Volts" and not "current" ?   It's a mistake that I've made all too often...

Best of luck,


Thanks for the reply, Cliff.

Indeed you're correct that I failed to connect the ground from the controller to the ground block. I'm not sure how I missed that. It is surprising that the ground would actually be used in normal operation.

Re: the GFCI sensor coil, the output side is where the build guide places it. Putting it on the input side would mean you're measuring current used by the EVSE unit as well as current fed to the vehicle. The difference in those will be negligible, but it still seems like the output side is what you really want to measure.

And, yes, I definitely had the meter set to AC voltage :-)

I guess I'll order another controller and try again. I'm not sure if failing to connect the ground had anything to do with the boom, but it seems like it was probably the cause of the failure to operate that led me to start poking around.

The pictures look okay except for the missing ground. That would not cause a boom, just a No Ground error on the LCD.

The ground is needed at the OpenEVSE Controller because it is the reference for the pilot signal and it provides a path for the welded contactor test and ground test. Without a ground you do not have a complete circuit to the vehicle.

Its hard to see in the picture but it looks like the LCD contrast was not set. Was there any relay clicks on startup or any color on the LCD?

I think Cliff is onto something, if the boom happened when the meter was applied. It was likely on the current setting or the probes were in Common and Current. You may want to test your meter. If this is the case the fuse in the meter may have blown.

You are welcome to send your board back, we will test is and replace it if necessary.


OpenEVSE Support 

I bought a new controller board and reassembled the EVSE, this with the missing ground. No boom this time, but no joy either. I measured at various points and everything looks good (my meter is just fine, and I'm quite certain it wasn't the problem the first time around), but I cannot get anything legible on the LCD no matter how I adjust the contrast. I do see the contrast changing when I turn the pot, and when I turn it one way the LCD does change to where I can see the outlines of the display segments but no text.

I verified that the LCD controller is getting 5VDC.

I'll attach photos of the assembled unit, the LCD display with the pot turned so that the outlines of the top segments are visible but the bottom segments are fully black, and measurement of power from the EVSE controller pins that feed the LCD controller.

Suggestions? I think I probably need to swap out the LCD controller. I might blame the EVSE controller, since I'm sure it has the CPU and sends the text to display, but since I've seen the same behavior with two EVSE controllers, that seems unlikely.


FYI, this was operator error.

I needed to power cycle the whole EVSE after adjusting the contrast pot. I had been disconnecting the LCD, making adjustments, and reconnecting it. But if the LCD is not connected when the EVSE controller powers up, it doesn't initialize it.

Has the LCD contrast problem been solved. Seems I have the same issue here. No matter how i adjusted it, just cannot see the text. 

I was able to adjust the contrast, but I had to connect everything then plug it in to see the results of the adjustments.

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