I do not know much about electronics and need some help reviewing the below circuit ASAP as it is for a light display I hope to launch on Thanksgiving.
I designed the attached circuit for some Bi-Color LED strands that I purchased at Costco. The way they work is they run off 120vac but use a full wave bridge rectifier to convert to 120vdc. With the polarity one way the LED's are white, and with the polarity reversed the LED's are color.
The purpose of the circuit is so I can use a light controller that outputs 5vdc to trigger the reversing polarity output to the light strand to switch between all white, or all color. I originally looked at using an H-Bridge but since I am dealing with 120vdc output it was more practical to use a DPDT relay instead to act as my H-Bridge. BTW, I am using this one from Digikey (http://www.digikey.com/product-sear...us&keywords=PB1059-ND&x=13&y=19&formaction=on).
I have tested the circuit and it worked great for about 25 cycles. Then the Relay started chattering when there was no voltage applied to the coil and the light strand was not lighting (before this the strand lit in white with no voltage applied to the coil, and in color with voltage applied). When I applied voltage to the coil the chattering stopped and the lights came on in color just fine but once removed they turned off and the chattering started again. After taking some voltage measurements I found that I blew one of the fuses on the AC input (The christmas light plugs have a 3A fuse on each leg of the AC input cord) and was getting a low AC reading. I replaced the fuse and the lights came on white with no voltage applied to the coil as they did before, then as soon as I applied voltage they turned color but when I removed voltage on the coil the fuse on the AC input was blown again! I found it odd that it was only blowing the fuse on one leg of the AC input cord and not both fuses as it usually does if you short the leads together. Anyway, after repeating this a couple times I assumed that I had fried the relay and that was what was causing it to keep blowing fuses.
Anyway, I have soldered 9 of these circuits and started testing the second one as well, it worked as it should for about 10 cycles but then I decided to stop messing with it and have you guys review my schematic before I burned out that relay and it started having the same chattering and blowing fuses as the first one.
I know with relays you can put diodes across the coil, and resistors and capacitors and what not but have no idea which to put in there, if it is necessary, and what size to use if I do add any of those. I also am not sure if that would have prevented the burning out of the relay and popping fuses on the AC input since adding those components across the coil is primarily meant to protect the coil source power (or circuit) not the other switched power source (in this case the wall AC input).
Any feedback would be appreciated, thanks in advance!
P.S. The circuit diagram shows 12vdc as the coil voltage, that is incorrect, I am using 5vdc!
- Matt
I designed the attached circuit for some Bi-Color LED strands that I purchased at Costco. The way they work is they run off 120vac but use a full wave bridge rectifier to convert to 120vdc. With the polarity one way the LED's are white, and with the polarity reversed the LED's are color.
The purpose of the circuit is so I can use a light controller that outputs 5vdc to trigger the reversing polarity output to the light strand to switch between all white, or all color. I originally looked at using an H-Bridge but since I am dealing with 120vdc output it was more practical to use a DPDT relay instead to act as my H-Bridge. BTW, I am using this one from Digikey (http://www.digikey.com/product-sear...us&keywords=PB1059-ND&x=13&y=19&formaction=on).
I have tested the circuit and it worked great for about 25 cycles. Then the Relay started chattering when there was no voltage applied to the coil and the light strand was not lighting (before this the strand lit in white with no voltage applied to the coil, and in color with voltage applied). When I applied voltage to the coil the chattering stopped and the lights came on in color just fine but once removed they turned off and the chattering started again. After taking some voltage measurements I found that I blew one of the fuses on the AC input (The christmas light plugs have a 3A fuse on each leg of the AC input cord) and was getting a low AC reading. I replaced the fuse and the lights came on white with no voltage applied to the coil as they did before, then as soon as I applied voltage they turned color but when I removed voltage on the coil the fuse on the AC input was blown again! I found it odd that it was only blowing the fuse on one leg of the AC input cord and not both fuses as it usually does if you short the leads together. Anyway, after repeating this a couple times I assumed that I had fried the relay and that was what was causing it to keep blowing fuses.
Anyway, I have soldered 9 of these circuits and started testing the second one as well, it worked as it should for about 10 cycles but then I decided to stop messing with it and have you guys review my schematic before I burned out that relay and it started having the same chattering and blowing fuses as the first one.
I know with relays you can put diodes across the coil, and resistors and capacitors and what not but have no idea which to put in there, if it is necessary, and what size to use if I do add any of those. I also am not sure if that would have prevented the burning out of the relay and popping fuses on the AC input since adding those components across the coil is primarily meant to protect the coil source power (or circuit) not the other switched power source (in this case the wall AC input).
Any feedback would be appreciated, thanks in advance!
P.S. The circuit diagram shows 12vdc as the coil voltage, that is incorrect, I am using 5vdc!
- Matt
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