This year, for the holiday season, the lovely wife Morticia and I put these nifty LED candles in each window of our house. They have a flickering LED "flame" on top, two AA batteries, a switch on the bottom. The bulb screws into the candle shaft and has a circle in the middle of the bottom that contacts the + battery terminal, and an outer ring that contacts a loop of wire coming up the shaft when screwed in fully. They are nifty because they light for 5 hours from the time they are first turned on, repeating every 24 hours.
But we have some cramped passages in our house, and walking past the windows often knocked the candles off. Three of them ended up not working after taking a fall. Both Morticia and I tried taking them apart removing the batteries, replacing them and reassembling multiple times and we could not get them to light. These are new this year, and all of the contacts were clean and shiny.
So I took them upstairs to the lab for diagnostics. I set my bench supply to 3V and touched leads to the bulb of the first one. It lighted. So I connected my multimeter to the battery terminal and outer terminal and it read 2.8V. I reassembled the candle, and voila, it worked! Second candle exactly the same procedure and it worked again.
I now had a theory that the circuitry somehow got in a funny state that it would not come out of with 2.8V but would with 3.0V, so I set out to test this theory on the third candle. Just to make sure once again that it was not the disassembly / reassembly that fixed them (the obvious first guess), I redid this a couple more times with the third candle. Then, I thought I would check the voltage before applying a voltage from the lab supply. This one checked out at 2.5V. Now, I reassembled and, to my amazement it started working.
I can't help but think it is still the multiple disassembly / assemblies that fixed them. But three of them each working only after checking the voltage seems a bit too coincidental.
Any ideas?
Bob
But we have some cramped passages in our house, and walking past the windows often knocked the candles off. Three of them ended up not working after taking a fall. Both Morticia and I tried taking them apart removing the batteries, replacing them and reassembling multiple times and we could not get them to light. These are new this year, and all of the contacts were clean and shiny.
So I took them upstairs to the lab for diagnostics. I set my bench supply to 3V and touched leads to the bulb of the first one. It lighted. So I connected my multimeter to the battery terminal and outer terminal and it read 2.8V. I reassembled the candle, and voila, it worked! Second candle exactly the same procedure and it worked again.
I now had a theory that the circuitry somehow got in a funny state that it would not come out of with 2.8V but would with 3.0V, so I set out to test this theory on the third candle. Just to make sure once again that it was not the disassembly / reassembly that fixed them (the obvious first guess), I redid this a couple more times with the third candle. Then, I thought I would check the voltage before applying a voltage from the lab supply. This one checked out at 2.5V. Now, I reassembled and, to my amazement it started working.
I can't help but think it is still the multiple disassembly / assemblies that fixed them. But three of them each working only after checking the voltage seems a bit too coincidental.
Any ideas?
Bob