Simple DC circuit design help

Hi, I am building a trail camera where space (lack of) is a consideration in the case I an using.

So I would like to eliminate individual batteries for the components. I was actually an electronic tech about a zillion years ago, but have forgotten component values.

Here is my project...Camera=2 AA batteries =*3 volts. Flash/Video light = 2 AA batteries = *3 volts. Total 6 volts

  • may be rechargable batteries which will be 1.2 volts each x 2 = 2.4

The motion detector card requires Operating Voltage: 4V - 14V DC.

I would like to tap DC off of the camera and light, to power the Card. I suspect it will take a diode from each source, to prevent voltage to the other source. this would allow 6 volts for the card. If this is right, what value?

Next, I have a 6-volts solar charger I would like to somehow use to keep the batteries charged. First, I am not sure if it is intended for NIMH (nickel-metal hydrate) batteries and will work. I know it works on SLA (sealed lead-acid) . If it does work, how could I use it to keep 2 separate 2AA=3 volt sources charged? Is it even possible?

Any ideas are greatly appreciated


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Only if you connect the batteries in series.

You really only need 3 volts, so you could run both the camera and light from the same pair of AA (or, for longer life, C or D) cells.

Peter Bennett, VE7CEI  
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Peter Bennett

Thanks for the reply, yes, your recommendation is true. But the light and the camera already have built in battery holders, so It would not give me any more space. It is the controller board which takes external power.

Peter Bennett wrote:

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Put the camera and flash batteries in series to power the card. Connect the camera to the camera battery, and the flash to the flash battery. The isolation needs to take place at the output of the motion detector such that ground of the camera and ground of the flash are never connected together.

+---------+-------+---> to flash charger (+) | +| | Camera Battery | | -| +----> +6 to card +---o o--+ | / | o---------> to charger (-) | +---o o-------> to flash charger (+) | / | o----+ +----> (-) to card | +| | Flash Battery | | -| | +---------+-------+

As drawn, the charge/operate switch is in the charge position. Two charge control circuits are used, as the batteries will require different charge rates. It is assumed that you turn the camera and flash off when charging.


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first off I need to know if the flash/light is electrically connected to the camera. because if it is that's going to make a difference (exact details if how the connection is connected with reguard to the batteries in both devices would be good)

if not you can just connect the batteries in series.

being for SLA it's not going to regulate the charge correctly for NIMH. but if it has only a low output it shouldn't do too much damage.

easiest way is probably to take the bateries out of the devices before charging.

Bye. Jasen

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