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Discussion Starter #1 (Edited)
I have a question for all you electrical guru's. I have a 2.4ghz pin-hole camera that I am mounting in a Model Power Alco FA 2 Like this one:

http://www.bing.com/images/search?q=scale+alco+f3&FORM=HDRSC2&&id=7E75231950AC96A7B1D7368FE93D8E59F20C7F2D&selectedIndex=26#view=detail&id=7E75231950AC96A7B1D7368FE93D8E59F20C7F2D&selectedIndex=0

I stripped the motor and the drive gears out of this loco to create space, but I kept the power pick-ups to power the video camera.

The pin-hole camera fits very well, I removed the lower forward light reamed the hole out just a tad, Got very good test pictures!

My question is picking up power from the track. The camera requires 5vdc so I have a 3 pronged voltage regulator to step the track down from 12vdc-13.8vdc down to 5vdc.

Here is my question: what happens if I run it on a layout that has the polarity reversed? Or a DC layout and the polarity is switched to reverse the locomotive direction?

If it were a motor or a fan it would run backwards. I am not sure how to remedy this situation.
Other than that issue she works great!

Thanks for your help!

J.C.
 

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It would smoke it...ask me how I know...:eek:hwell:

Your best bet would be an onboard battery--steady current, polarity safe.
 

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Simple circuit.
Bridge rectifier to the voltage regulator to the camera.
You could also put some capacitors in before the regulator to maintain power during brief power outages.
 

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Discussion Starter #4
It would smoke it...ask me how I know...:eek:hwell:

Your best bet would be an onboard battery--steady current, polarity safe.
I thought if it reversed the polarity the camera would act like a spotlight...LOL!
 

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Discussion Starter #5
Simple circuit.
Bridge rectifier to the voltage regulator to the camera.
You could also put some capacitors in before the regulator to maintain power during brief power outages.
I like that Idea! Can you diagram the circuit for me?
 

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Discussion Starter #6
Or anyone (for that matter)have a simple circuit design you would share with me?
 

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Discussion Starter #8
Awesome! Thanks! Now if I can build it to fit in my Loco!
 

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GunrunnerJohn

Interesting circuit. Think I have a place
for it. LM7805 is an adjustable diode?

How physically do you adjust?

Also it appears to be designed for use on
a DCC layout.
The man with the camera asked
what would happen if used on a DC layout...and what
would happen if it hit a reverse polarity?

Don
 

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Actually, the LM7805 is a fixed voltage regulator, the requirement was for 5 volts.

The LM317 is an adjustable regulator. The regulators are actually power integrated circuits, not actually diodes.

The circuit shown will work with either track polarity, obviously if the voltage on the tracks falls below about 7 volts, the regulator will not be able to hold 5V, it requires about a 2 volt differential from input to output voltages.
 

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To have a stable power supply you need capacitors on both sides The term is filtered DC. Normally I have a cheep chip and wing the size of the capacitor. For a camera you may want to research a little. I see about 1000 to 3000 uf before the regulator and 1 to 10uf after. Coming from a DC transformer maybe you don't need one.
 

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The diagram GRJ put up is exactly what I had in mind, it works with DC, DCC, and AC.

Big4fan,
If you can't get it small enought let me know I can build them pretty tiny.
 

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Discussion Starter #13
The diagram GRJ put up is exactly what I had in mind, it works with DC, DCC, and AC.

Big4fan,
If you can't get it small enought let me know I can build them pretty tiny.
Sent you a pm... thanks
 

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To have a stable power supply you need capacitors on both sides The term is filtered DC. Normally I have a cheep chip and wing the size of the capacitor. For a camera you may want to research a little. I see about 1000 to 3000 uf before the regulator and 1 to 10uf after. Coming from a DC transformer maybe you don't need one.
Truthfully, you don't need input cap values nearly that large for filtering, the regulator has very good noise rejection. Obviously, it won't hurt anything, I might kick it up to something like 220uf, but I can't see putting a huge cap there. The cap after the regulator is to prevent it from oscillating under certain load conditions.
 

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Yard Master & Research
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I only went with what I have found for circuits and read in a few places. That is good to know.

I hope the camera survives.

John, you have an on board camera. What does that have for a power supply?
 

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I used basically the circuit I posted for the one time, that was after it ate several batteries rather quickly. I currently am looking for a likely locomotive to put the camera in, I'd like it to be hidden. I may try to put it into an RMT BANG.
 

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I'm using a 330UF after the regulator to act as a buffer for intruptions of power.
I am building this new one with all SMD chips so it will be very tiny, Hope to get it to be smaller than a 1/2" square.
 

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I'm using a 330UF after the regulator to act as a buffer for intruptions of power.
I am building this new one with all SMD chips so it will be very tiny, Hope to get it to be smaller than a 1/2" square.
Do you have SMT layout capability? If so, where do you get boards? I have a project or two that I'd like to get boards for. :)
 
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