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Originally Posted by HKZ Bob
Dear all
I have a lot of noise on the Schmitt Trigger on point Base T2. I assume it causes misfire. Can that be?
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This is caused by the high voltage converter generating a "noise" at about 3 kHz and this is normal. This is normally without consequence if the slope of the input signal if not too slow.
Quote:
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How do I evaluate The correct value for R5. selected resistor? The owner before placed 50k resistor at R5/R6
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The R5 value is not to be modified. The R6 value is determined at factory to set the triggering voltage at the zero crossing of the negative slope of the input signal (a bipolar pulse)
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I am using a 2 V peak to peak sinus signal a a trigger. I s that appropiate.
If I increase that value to 8V pp the box works better due to a better signal to noise ratio.
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This is not appropriate as the slope of such a sine wave is not fast enough not to be disturbed by the 3 kHz spurious signal.
See the attached oscilloscope picture of a simulated appropriate signal showing the triggering signal at the gate of the SCR at the correct time.
