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Topic: Arduino Pong (Read 45 times) previous topic - next topic

nootropic

@robinh: what was the behavior before you added the 75ohm resistor?  I've been trying to figure out what circumstances lead to the need for the 75ohm resisotor.  How does one know they need it?  Which TVs would require it?  Thanks.

robinh

The behavior was no picture, only sound (I have added some basic audio out through RCA as well).

I knew it worked with 75 Ohm, cause I had used it when I breadboarded the circuit. But when I moved it over to a protoboard I tried without 75 Ohm since several people here mentioned that it wasn`t needed.

The tv is a Full HD 37"

ChrisS

@nootropic:

in German:
"Ein Abschlusswiderstand hat die Impedanz des Übertragungsmediums und sorgt dafür, dass am Kabelende keine Reflexionen auftreten. Dadurch würden reflektierte Schwingungen und Stehwellen entstehen, die in das Kabel zurücklaufen und das übertragene Signal beeinträchtigen. "

i would try to translate it.

An "End-Resistor" (75Ohm) has the impendancy of the signal-way (wire) to get rid of signalreflections on the singal-way ending. The Resistor is killing signal destroying by eliminating returning singnalwaves and errors.

End-Resistor ist Standard by old professional Pal/BNC Video connections...

Middle down...
http://www.itwissen.info/bilder-klein/bnc-komponenten.png

So, if your Signal is destroyed by returning SignalWaves and the resulting Signalerrors or "Signalcrashes" this resistor eliminates the signalreflection on signal-way-ending to corret the signal.

Result is a working or better signal, which now possibly work on your tv. If there are to much errors the signal maybe unusable for your tv.
So, if you have Signalproblems on Pal, you could try a 75Ohm resistor to enhance the signal by eliminating signal "interferences"?1? errors.

Hope i am understandble, hard to explain with german motherlanguage.

Greetings Chris

Sturmfabrik - mediale Dienstleistungen
www.sturmfabrik.de

nootropic

Thank you, robinh and danke, ChrisS.  It sounds like the 75 ohm resistor is required for at least some TVs.  I'm considering making a product that generates video and I'm trying to figure out if I should include the 75 ohm resistor (at least as an optional component) and the diodes.  I did experiments with diodes and they degraded picture some, and I was told that they were not strictly required.  I'm just trying to design a device that would work on the *most* TVs possible.

ChrisS

mmh, i am not very experienced in electronics i can't help you much more. I wish you good luck with your new Design... keep on!

Greetings
ChrisS
Sturmfabrik - mediale Dienstleistungen
www.sturmfabrik.de

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