| Backlight |
updated Thursday, July 29th, 1999
Contents:
1. Connectors
2. Pin Configuration
3. Timings
4. Voltages
Molex (Waldom/Molex) Micro-Miniature 1.25mm connectors
Molex Part # 51021-0300
Digi-Key part # WM1721-ND (p. 46 in the January-March 1998 Digi-Key catalog)
(These are the receptacle housings for the following (required) crimp terminals:
Molex (Waldom/Molex) crimp terminal
Molex Part # 500-50-8000 (note that Molex and Digi-Key just put their dashes in different places for this part number: Presently I'm reading from the delivery bag).
Digi-Key part # WM1775-ND
A word to the wise would be to get more of these than you need: The kind of wire you will need to hook into the crimp terminal is very thin and you will find that it will be easy to hook it up so that it looks solid, but will break right after you plug it into the backlight assembly.
I used AWG 30 hookup wire that I got from Jameco, for which, unfortunately, I was unable to find a crimp tool. I had to *solder* the things together, which is painstaking, given the tendency of the capillary effect to wick the solder right into the hole where the thing is supposed to plug into its socket. Do crimp tools for this guage even exist?
Nate Caine tells me the cryptic '8 microsecond' backlight pulse width referred to in the MCL0712A03 data sheets occurs during the horizontal blank periods in the NTSC specification-- so this should give you what you need to synchronize the pulses to whatever drive circuitry you build. Given the NTSC horizontal frequency and the 8 microseconds, almost everything is determined.
Julie S. Porter has subsequently discovered that the cathode blanking interval signal, available from the CD22402 video sync generator chip, can be set to 8 microseconds width, and drives the backlight just fine. The NTSC color bar generator featured as a construction article in _Nuts & Volts_ (April 1995) uses the CD22402; just adding a TTL inverter chip like the 7404 to the circuit gives you a driver to test the backlights with. The URL is http://www.delectra.com/anavid for Julie's version of the circuit. Nuts'n'Volts is http://www.nutsvolts.com.
The three connectors of the backlight are simply the positive supply, ground, and control pulse lines. (See above)
The MN83803AK provides this pulse as well as the MCL0712A03 control signals, synchronizing on an NTSC sync signal that is extracted from the composite NTSC video signal by other circuitry, or generated directly (when there is no need to sync to an external video signal).
Supply: 5 (or in camcorder data sheet, 4.5) volts;
Sync: 5 volts peak to peak, not zero-crossing (you can drive 'em with TTL, e.g. with CD22402 plus a 7404 inverter, as noted above).
Rich Diehl has informed me that applying the DC supply voltage to the backlight in the absence of a sync pulse may damage or destroy it.
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