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black 'n white into white 'n black

C

Cumin' Up

Jan 1, 1970
0
I am New in electronic and I would to design a circuit that will
inevert a white paper with black letters into a black paper with white
letters. With my little knowledge that I get from from electronic
within my three years in the field of Electronic, I think if I use a
Camera circuit and modify it with a Class A amplifier i can be able to
get it, bt I am still struggling to get there. Can somebody help me or
give me a better idea on how to go on with my project, because this
project will help people with eyes promblems who cant see black in
white. Pls Help me my colleagues in the field of electronic
 
M

martin griffith

Jan 1, 1970
0
I am New in electronic and I would to design a circuit that will
inevert a white paper with black letters into a black paper with white
letters. With my little knowledge that I get from from electronic
within my three years in the field of Electronic, I think if I use a
Camera circuit and modify it with a Class A amplifier i can be able to
get it, bt I am still struggling to get there. Can somebody help me or
give me a better idea on how to go on with my project, because this
project will help people with eyes promblems who cant see black in
white. Pls Help me my colleagues in the field of electronic

first you need to seperate the video syncs from the video picture

http://www.national.com/search/search.cgi/main?keywords=lm1881

see figure 3 in the data sheet. The video is now referenced to ground.
Then use an inverting amplifier, gain of -1, this will turn black to
white .You need a bandwidth of at least 5MHz, Then you can resistively
mix the syncs from the LM1881 with the inverted video to feed the TV


martin
 
E

Electric dabbler

Jan 1, 1970
0
martin griffith said:
first you need to seperate the video syncs from the video picture

http://www.national.com/search/search.cgi/main?keywords=lm1881

see figure 3 in the data sheet. The video is now referenced to ground.
Then use an inverting amplifier, gain of -1, this will turn black to
white .You need a bandwidth of at least 5MHz, Then you can resistively
mix the syncs from the LM1881 with the inverted video to feed the TV


martin

Hi



I Did this once, to make a simple reading system for someone who was
visually impaired.



It consisted of a nice fast op-amp (Elantec?) wired as an inverter, with a
4066 analogue switch driven on a line by line basis by an LM1881 so that the
active video period got inverted and the sync stayed the right way up. I
think I had to do some messing to get the DC levels right and there was
possibly an adjustable monostable in there somewhere to get the timing
right.



Philip
 
T

theJackal

Jan 1, 1970
0
I am New in electronic and I would to design a circuit that will
inevert a white paper with black letters into a black paper with white
letters. With my little knowledge that I get from from electronic
within my three years in the field of Electronic, I think if I use a
Camera circuit and modify it with a Class A amplifier i can be able to
get it, bt I am still struggling to get there. Can somebody help me or
give me a better idea on how to go on with my project, because this
project will help people with eyes promblems who cant see black in
white. Pls Help me my colleagues in the field of electronic


Some B/W TV circuits I've seen use a Schmitt trigger to detect
whether a black/white components are present in a video signal. So
I'd imagine reversing the polarities of the trigger would do the
trick.

"Go easy with the whisky"

theJackal
 
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