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Old Apr 01, 2004, 10:56 PM
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Wiring a DC-DC converter for 12v Camera!

Ok I need a little help here. I have a couple of 12v mini cams that I want to put on some airplanes. I bought a couple of the DC-DC converters from TI Here's the link if interested http://focus.ti.com/lit/ds/symlink/pt5041.pdf

Anyhow I have a 12v camera and a 12v transmitter. How do I wire this thing so I can input 4.8v from a small battery pack and then supply the converted 12v to the camera and transmitter?

If you have pics of previous projects that would be appreciated.

Thanks

Chris
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Old Apr 02, 2004, 07:40 AM
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Crestwood, KY
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Doc:

This seems pretty straight forward. The PT5041 uses an input of approx 4.7 volts to 11 volts. The output is constant 12 volts. The hardest part is getting connectors to work with your 12V mini cam and transmitter. I wouldn't even use a switch between the battery and the PT5041 just use any connectors that you have available. That way you can just plug them together when you are ready to power up. Looks like the PT5041 is good to 1 amp so just about any connector will work. The output of the PT then needs to supply power to both the transmitter and camera. Lots of options here. Use a "Y" cable coming out of the PT, one end goes to the transmitter the other end to the camera. Or, if the camera will plug into the transmitter, perhaps you can get by without using a "Y" and a standard cable will work. You might want to wire the camera, transmitter and the PT together with no connectors. I have no idea what type of power input connections are on your transmiter and camera. You will have to be a bit creative here to get power to these two.
Just remember, the PT common is your negative or "Black" lead from the battery. The Vin is the 4.8 volts + , red lead from the battery. Vo is the 12 volts + out going to the 12 + power in to the camera and transmitter.

I hope I haven't confused things.
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Old Apr 02, 2004, 07:52 AM
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Doc:

One other thing. I hope the combined load of the camera and transmitter is not more than 1 amp, as that appears to be the upper limit on the PT.
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Old Apr 02, 2004, 09:22 AM
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s,port
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Gene,

Thanks for the input. I am not an electrical engineer so I want to make sure I am doing things correctly. I can figure out which wire goes to what connector my question was mainly about splitting the outgoing 12v? I will try a makeshift y connector to see how that works.

Thanks for the help
Chris
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Old Apr 02, 2004, 02:13 PM
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Quote:
If you have pics of previous projects that would be appreciated.
The PT5041 was used in the old RC-Cam3 project. There may be something there to help you out: http://www.rc-cam.com/rc-cam3a.htm

This project is the one that introduced the PT5041 for wireless cameras. It is a nice way to obtain 12VDC from a standard R/C bat pack.

RC-CAM
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Old Apr 02, 2004, 03:03 PM
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Madison, WI
Joined Jan 2002
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Could you use the battery pack to run the motor and the video rig? I've been trying to use a 12V pack to run a motor and a wireless video system. The rf interference feedback through the 12V line is really bad. Would this converter "filter" the noise from the motor?

Thanks
Dennis
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Old Apr 02, 2004, 03:23 PM
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Quote:
Would this converter "filter" the noise from the motor?
Its transcient response spec is about 2KHz, so motor ripple/noise (and any other nasty supply rail issues) is not going to be fully filtered out. However, many 12V powered cameras and Tx's have internal Vreg's and filtering, so sometimes the result is acceptable. You'll have to build it up and test it to see if it works with your equipment. Keep in mind that the currents that are experienced will quickly overload an ESC's BEC output.

DC-DC converters, like the PT5041, are not always slap-'em-in-and-go sort of solutions. They operate at near-RF frequencies and have magnetic components. So, they can create EMI/RFI that will affect video quality. If the applied assembly technique is really goofy then R/C glitches are even possible.

So, build it up like a typical RF circuit. That is: good quality decoupling caps (low ESR), short component leads, single point grounding, short/heavy wire harness connection to battery, etc.

RC-CAM
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Old Apr 02, 2004, 04:24 PM
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United States, CA, San Diego
Joined Jul 2003
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Has anyone come up with a small PC board that could be mounted to the PT5041 so that leads and caps can be mounted more easily and neatly? I have one of the units now (from DigiKey.com), but have not built it up yet as I have not decided the best way to mount the three caps and input and output wiring. Any suggestions would be appreciated. Thanks.....

Joe
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Old Apr 02, 2004, 04:33 PM
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I believe that Yb2normal has a board available. It is the one he stuffs & sells with his ready-to-fly system.

RC-CAM
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