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Mr.RC-Cam

The Ultimate Video Buffer

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This high performance video buffer design uses the Maxim MAX497 IC. The Maxim chip is rated at 275Mhz, so no signal degradation will be experienced when buffering NTSC or PAL video sources.

Each IC allows four buffered video outputs. Up to four IC's are supported on the custom PCB that was created (see photo below). Fully stuffed, it is a 4 x 4 buffer. That is to say, it has 4 inputs, and each input has 4 dedicated outputs (16 buffered video signals total!). You can daisy chain them too for other configurations.

Maxim's chip only needs +/-5VDC and a good board layout. I ended up using a DC-DC Neg Vreg for the minus supply. The power supply configuration shown in the schematic (see attachment) allows 7VDC to 16VDC operation @ 300mA.

For video buffer apps, the MAX497 is highly recommended.

vb_assy1.jpg

vb_schem.pdf

Edited by Mr.RC-Cam

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Ok, now I'm curious. What on earth is this thing? If you could explain in simple terms, I'm sure I could wrap my mind around it! :)

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An output of a camera or wireless receiver can only drive one video device at a time if you expect to maintain image quality. Some camcorders have a buffered output, so you can effectively drive two devices (i.e., camcorder and monitor) if yours is so equipped.

Regardless, this custom design is a buffer that will allow you to send video to several destinations at full fidelity. One example: Your ground station's video Rx needs to drive a monitor, a pair of video goggles, a VCR, and a PC capture card for some navigation s/w. That would require a 1 x 4 buffer configuration. This custom board, when fully configured, can do FOUR of those 1 x 4's.

More info about commerically made buffers: http://www.rc-cam.com/faq.htm#distamp

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Cool, thanks for the quick reply! Just another device I am drooling over! I definately want to record AND watch my flights at the same time, so this is something I'll need.

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I have two unstuffed (bare) circuit boards left over from the project. $15 (plus shipping) will earn you one.

As mentioned, this board is expandable. With one Maxim MAX497 IC you have a 1 x 4 video buffer. This is perfect for driving a VCR, HUD glasses, and a monitor or two, all at the same time. Stuff more MAX497's (up to 4) to create more buffered outputs (perfect for a home sports bar :)). It will run on the same battery that powers your Wireless Video Rx. Best of all, the video quality of the buffered outputs is as good as the original!

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I have two unstuffed (bare) circuit boards left over from the project. $15 (plus shipping) will earn you one.

As mentioned, this board is expandable. With one Maxim MAX497 IC you have a 1 x 4 video buffer. This is perfect for driving a VCR, HUD glasses, and a monitor or two, all at the same time. Stuff more MAX497's (up to 4) to create more buffered outputs (perfect for a home sports bar :)). It will run on the same battery that powers your Wireless Video Rx. Best of all, the video quality of the buffered outputs is as good as the original!

How do you want payment? Paypal, Check, I'll take one. I wouldn't mind sourcing those RCA blocks you have on your either.

And, how does it handle, (or does it) the Audio portion?

Dan

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PayPal would be best. I'll PM the details to you.

The connectors are Mouser #161-4219. I suppose that Line Level audio buffering could be done with any one of the 1x4 video buffer circuits found on the board. Or at least it seems to me that it should work fine for that.

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One board remaining.

Some handy hints:

For a minimal single MAX497 use (1 x 4 buffer), just install one at U1 and bridge all four of its inputs together (jump U1 pins 2,4,6,8). Do not stuff R8-R10. Input video at J1-1; outputs are at J3 and J4. However, if you install all four MAX497's then build as shown (4 x 4 buffer).

If you hack the board and use part of the buffer circuits for audio, then be sure to change the 75 ohm input terminator to something much larger. Perhaps 4.7K ohms. Also place a .001uF cap across this resistor. The MAX497's 75 ohm output resistors should remain as-is on the audio outputs.

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Sounds great. One board left.

EDIT: All boards are gone -- No more to offer.

Edited by Mr.RC-Cam

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