The Lazy Destroyer
04-17-2007, 04:54 AM
So I'm running a bullet camera setup for my bike and decided to go a bit over-the-top and just build a power supply that can handle both my camcorder and two bullet cameras.
Built it and although powers up and spits out 12V, it does not power up even a lone bullet camera. With the bike running it powers 13.8-14.0V to the supply, and the supply spits out a pretty constant 12V. If I connect the supply to the camcorder while it is already on it will turn off and "blip" the power LED at a relatively quick(er) rate (than normal).
The camcorder has a power supply that is 12V and up to 1000mA. The one bullet camera I am testing with has a 12V supply rated at 300mA.
I used a schematic here:
http://www.mitedu.freeserve.co.uk/Circuits/Power/boosti.htm
to build a 78xx power supply that can handle more mA. It came up pretty frequently in my search for a schematic. I did things a little differently and want to double check that the design is right before going over everything yet again.
Input goes through a 4A fuse.
On +V-IN I put a 100uH RF choke. It has a max amp rating of 2A which is close to what I think I'd run w/ two cams (1.6A max) but okay.
The diagram shows 1R and 10R. I had 1K and 10K resistors laying around so I used those respectively.
The diagram lists 2955 as the power transistor. Couldn't find a 2955 so I went with a TIP42 available at Radio Shack.
www.ortodoxism.ro/datasheets/fairchild/TIP42.pdf (http://www.ortodoxism.ro/datasheets/fairchild/TIP42.pdf)
www.ortodoxism.ro/datasheets/unisonic/2N2955.pdf (http://www.ortodoxism.ro/datasheets/unisonic/2N2955.pdf)
Although they have similar properties, some of the values I am seeing are a little different. I wired this (left to right, when looking at the front of the transistor, pins pointing down): 1-base 2-collector 3-emittor, and I followed a PNP wiring diagram online here, second image:
www.geofex.com/fxdebug/trantest.htm (http://www.geofex.com/fxdebug/trantest.htm)
Instead of a 470u cap on the input side of the 7812, I used a 470u electrolytic and a .1u ceramic in parallel
Instead of a 470u cap on the output side, I used a 470u electrolytic and a 10u tantalum in parallel.
There is a 12v LED in parallel on the output of the power supply rated at 30mA. It does not dim when connecting either camera.
I double checked everything but with it spitting out 12v but still not seeming to power things up I'm stumped and wondering if maybe the TIP42 isn't working as a replacement or if maybe something else I did was wrong. The connectors for both cameras are wired right and and supplying proper + and - sides.
I'm not very experienced with power supplies and wanted to run this all by you all to see if maybe there is something obvious I am not seeing. Or if there is a good way to test something, that would also help me. I'm hoping to get things straightened out by this coming weekend. Thanks in advance...
Built it and although powers up and spits out 12V, it does not power up even a lone bullet camera. With the bike running it powers 13.8-14.0V to the supply, and the supply spits out a pretty constant 12V. If I connect the supply to the camcorder while it is already on it will turn off and "blip" the power LED at a relatively quick(er) rate (than normal).
The camcorder has a power supply that is 12V and up to 1000mA. The one bullet camera I am testing with has a 12V supply rated at 300mA.
I used a schematic here:
http://www.mitedu.freeserve.co.uk/Circuits/Power/boosti.htm
to build a 78xx power supply that can handle more mA. It came up pretty frequently in my search for a schematic. I did things a little differently and want to double check that the design is right before going over everything yet again.
Input goes through a 4A fuse.
On +V-IN I put a 100uH RF choke. It has a max amp rating of 2A which is close to what I think I'd run w/ two cams (1.6A max) but okay.
The diagram shows 1R and 10R. I had 1K and 10K resistors laying around so I used those respectively.
The diagram lists 2955 as the power transistor. Couldn't find a 2955 so I went with a TIP42 available at Radio Shack.
www.ortodoxism.ro/datasheets/fairchild/TIP42.pdf (http://www.ortodoxism.ro/datasheets/fairchild/TIP42.pdf)
www.ortodoxism.ro/datasheets/unisonic/2N2955.pdf (http://www.ortodoxism.ro/datasheets/unisonic/2N2955.pdf)
Although they have similar properties, some of the values I am seeing are a little different. I wired this (left to right, when looking at the front of the transistor, pins pointing down): 1-base 2-collector 3-emittor, and I followed a PNP wiring diagram online here, second image:
www.geofex.com/fxdebug/trantest.htm (http://www.geofex.com/fxdebug/trantest.htm)
Instead of a 470u cap on the input side of the 7812, I used a 470u electrolytic and a .1u ceramic in parallel
Instead of a 470u cap on the output side, I used a 470u electrolytic and a 10u tantalum in parallel.
There is a 12v LED in parallel on the output of the power supply rated at 30mA. It does not dim when connecting either camera.
I double checked everything but with it spitting out 12v but still not seeming to power things up I'm stumped and wondering if maybe the TIP42 isn't working as a replacement or if maybe something else I did was wrong. The connectors for both cameras are wired right and and supplying proper + and - sides.
I'm not very experienced with power supplies and wanted to run this all by you all to see if maybe there is something obvious I am not seeing. Or if there is a good way to test something, that would also help me. I'm hoping to get things straightened out by this coming weekend. Thanks in advance...