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Velleman stroboscope kit problem

fundash

Jul 16, 2010
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Hi, I recently decided to buy some of these Velleman kits in order to improve my soldering skills. I made the IR light barrier and it worked fine...but that is only 9VDC. This one is the stroboscope (K5300)and it runs of 110VAC! I was scared but plugged it into that wall...AND IT WORKED!!! I was so happy as this is also my first high voltage and high current project! I used it for about 3 min. I smelled something funny then :( I move closer and noticed it was the board that was smelling, but I don't understand how it could work if there is a short circuit. I don't know if it is normal for this to happen or not, please respond :)
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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I wouldn't normally suggest something running from rectified mains (gasp) as an early project.

Alternatively you may have a capacitor around the wrong way, or put the wrong resistor somewhere.

The best bet is to locate what is creating the smell. Unfortunately, the normal low voltage means (finger test) could be lethal with the power applied, and rather painful even with the power removed due to the high voltages.

Perhaps first confirm that you have constructed it correctly.
 
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LTX71CM

May 23, 2010
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Depending on how roasted the part(s) got you may be able to do a visual search and find a discolored part or spot on the PCB. You can also see if the smell is persistent and sniff the board (unplugged and at a safe distance) to find the spot where the smell originates.
 

fundash

Jul 16, 2010
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well I checked it and all, and it works fine...there is a triac (voltage regulator?) as they call it on the pcb. I don't know if this is normal or not, and it caqn't be a cap, as the caps are the main parts that make it work, And it works fine...
 

LTX71CM

May 23, 2010
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Hmm... Maybe nothing is wrong, something just needs a heatsink. Any mention of heatsinks in the provided instructions?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Oddly enough it may seem to work fine with an incorrect value resistor or a capacitor around the wrong way, but unusual things might happen like burning smells...

As LTX71CM suggests, if something is getting really hot it may discolour the board, or it may itself discolour.

If it's the capacitor, you may not find out until it explodes.

Note that R4 is expected to get quite warm -- and you did mount it clear of the board, right?

Double check the orientation of C2, C3, and C4. There is a stripe down the side indicating the -ve lead. Make sure that this is oriented away from the side that should be +ve.

All the small resistors are 100K, so unless one of them is different, or all were supplied incorrectly, you shouldn't have been able to mix them up :)

The triac shouldn't require a heatsink. It's only discharging a 0.1uF capacitor.

The 22uF capacitors could be getting quite warm as their discharge current is enormous and would be limited by their internal resistance. The flash tube looks like an almost dead short once triggered. Currents exceeding 50A are by no means unusual, even in very small flash tubes, however these relatively long U shaped tubes generally operate at lower currents (10A - 25A as a guess)
 

fundash

Jul 16, 2010
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I'll just upload some pics... (within the week)
and I checked the caps, and they are in the right way (white stripe to negative)
 
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