help needed - draw video transmitter power from lipo

[jodaboda]

Hi all. This should be a fairly basic question, but it's been many many years since my high school electronics class, and I don't really want to read a whole book on the subject (I learn more from reading forums anyway).

I have a draganflyer rc helicopter. I am attaching a camera and have wired its preview video to a small 200mw Hong Kong/ebay transmitter ( http://cgi.ebay.com/New-800mw-Transmitter-203C-Wireless-Color-CCTV-Camera_W0QQitemZ140041620925QQihZ004QQcategoryZ486 32QQssPageNameZWDVWQQrdZ1QQcmdZViewItem?hash=item1 40041620925 ). The transmitter shares housing with a small camera. They take a 9v battery. I believe the transmitter takes 8v and the camera 5v. Anyway, I want to ditch the camera and 9v battery, connecting the transmitter to the draganflyer's battery (3-cell 11.1 volt 1320mah Lithium-Polymer).

So my question is: what is the lightest way to do this? If the solution weighs more than 30-40g, I might as well just use the 9v battery.

any help is greatly appreciated. thanks.

[jeffs555]

You could try using a 9v low dropout regulator with a lot of filtering, but you are unlikely to get good results. Those cheap HongKong cameras are not very stable to begin with, and any noise on the power supply will show up in the picture. For mine, I bought two small LiPo's to power just the camera/transmitter, so it was completely isolated from the motor battery. Mine was also supposed to use a 9v battery, but seems to work fine with the two LiPo's in series. Two 200mah LiPo's will run the camera a long time, and weigh about 10 grams.

[jodaboda]

Thanks for the response. I didn't explain myself entirely well. I am not using the little Hong Kong camera at all. I am just using the transmitter to send the lcd preview from my larger camera. I won't be recording at the receiving end, just previewing and framing the shots. The larger camera will have a timer circuit to continually trip the shutter and record to a memory card. I don't really care if the downlink quality is a little crappy; as long as I get the idea of what the camera is looking at, I'm fine.

I will try a 9v reg. They're pretty darn cheap so I might as well. Is there anything else I would have to do, or could I just solder a couple wires to it and plug it in?

[jeffs555]

You will need caps on the input and output as specified on the data sheet for whatever regulator you use. Also, make sure you get a low dropout regulator.