Opto Endstop Problem

Hi,

I'm having issues with one of my opto-isolators. When I originally built the thing it tested fine, but when I wired it up to my x-axis and tried to apply power to the stepper controller it would not work (no power light and drawing much larger than normal current). I tried swapping the end stop and it works fine so I've obviously got a defective endstop. Is it common for these things to blow and does anyone know where I get a replacement in the UK?

Milly.

If you hook it up backwards it will blow it.
There are extra caution notes to this effect in the wiki.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Hmmm, not possible with my setup as the connectors will only connect one way round. I've used the same lead on all the boards and its only this board, after a long lay off, that is now refusing to work!

Thanks for the tip though.

Milly.

Then perhaps a cold solder joint or really a bad component...

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Hmmmm, thanks for the replies, I don't really believe a component could just go like that so I am assuming that I either i didn't test it correctly in the first place or managed, at some stage, to short something or connect the board using the wrong lead. Frustrating, especially as the H21LOB is so hard to come by in the UK!

Well, I swapped the broken opto endstop for another one to test the x axis and was pleased to see the carriage motoring back and forth. Having now completed construction of the frame I had a bit of spare time to look at the broken board. Firstly, I checked all the joints and gave one a touch up with the soldering iron. I then ran the multimeter across the various components and found the LED had blown. Whether it was broken when i first installed it and I had failed to check it correctly, or it had blown after construction I do not know, but I replaced it with a new LED and the board now works fine. So if you find yourself in a similar situation check the LED!

Thanks for all the help,

Milly

Odd, I assume you mean the indicator LED, not the IR led of the opto.

The board should still function without it, or even it it was short circuited. And you said the board was taking a lot more current, but even with a shorted led it wouldn't take much more current.

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[www.hydraraptor.blogspot.com]

Yeah, was very strange, board was drawing more current and none of the lights would illuminate. And yes, I do mean the indicator LED, not the IR one. The diode had very high resistance in both polarities and was not lighting up. I've studied the schematic and can find no reason for this behaviour and can only conclude that there must have been a dry joint on one if the other leads that I rectified when I went over all of them.