What did I do?!?!?

[Overlord]

I have a prop1 and 6 wickleds that we got in the halloween special. I set up one wick a while back and it worked fine, today I was connecting the rest of them to see if they all worked. When they were all connected, I plugged in the power, they didn't light up! I've tried one by one and all the different output ports but there seems to be nothing working. The ULN2803 gets hot to the touch and the LEDs on the board are quite dim with the switch in position 2. Position 1 gives me a single LED as it is supposed to, but it's much brighter.

So, did I break something? I would have assumed you could connect all those wickleds to the board at once, but perhaps I overloaded it? Did I kill the 2803? Any ideas anyone?

Overlord

[JonnyMac]

Sounds like something got connected backward and may have shorted the ULN.  Replace it first, then test your candle again (you can use the GND and V+ posts for testing to make sure you have the right polarity before connecting to your OUTx terminals).

[Overlord]

The ULN does sound likely, I just am still new to this and wanted some more experienced advice. I have one other question now. If the ULN is in fact toast, should I still be able to light up the wickled as you suggest with the GND and V+ posts? Because it's not doing anything.

Overlord

[JonnyMac]

Yes, the V+ post is "hot" any time the power switch is set to position 2 (there should be an LED next to it).  You should pull the ULN before doing this as it may be shorted and putting a big load on the power supply.

[Overlord]

Sure enough. I removed the ULN and the LEDs went back to bright and the wickled lights up when attached to V+ and GND.

Thanks for your help.

Overlord

[Overlord]

OK, I have another question, The chip in question is a ULN2803AG. I want to know if any ULN2803 chip will work or if it has to be the AG. Also, could you tell me what the differences are? I can't find a datasheet for the AG.

Overlord

[JonnyMac]

You need to get a ULN2803A -- the G on the part you have indicates lead free.  If you can't find them locally, here are a few online sources.

-- http://www.efx-tek.com/topics/uln2x03.html
-- http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/txtSearch/uln2803/List/1/Default.aspx?SortField=ProductName,ProductName
-- http://beta.mouser.com/Search/ProductDetail.aspx?qs=FOlmdCx%252bAA1lVc%2fYEXA4pg%3d%3d
-- http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=1388756