My bad, pebe is right. The circuit in the schematic should work. It is hooked up to produce an output squarewave with an approximate 50% duty-cycle.pebe said:The original circuit shown for the 555 will work OK. It does not need the discharge pin connected. It is an astable oscillator with a unity mark-space ratio. The problem, as I said before, is that the output will not go to the +ve rail.
Wiring the driver transistor as in the attached circuit will ensure that the transistor is switched hard on and off and the output will swing between about 0.3V and 12V. The fact that the transistor inverts the signal doesn't matter.
Going back to your post #22, R2 (10K) should be connected to pin3 - not the transistor base, otherwise the 555 will not oscillate.3dchipmaker said:pebe thanks,
tried new output circuit the only thing i was not sure of was if led was wrapped in 1k or not. tried both ways voltage at output was 3.2 voltage before120 was 10v.but circuit would not oscillate
Now things are beginning to get clearer. Another couple of questions and it may be possible to come up with a rational explanation. When measuring voltage:3dchipmaker said:thanks again,
you are probably going to laugh but i will tell you how i measured output.voltage i measured with a multimeter but pulse rate i measured by attaching speaker and recording sound then cutting 1 second out of recording and decreasing time and counting pulses.
Then as JoeJester said, your meter is reading the mean level of the waveform.3dchipmaker said:Thanks,
It Was Digital And Was Set To Dc
You cannot make an accurate measurement of peak-peak levels of a waveform by measuring the mean level. a 0-12v pp level will give a 6V mean level - but so will a 5-7v pp signal. If the duty cycle is not known that will also give a false impression. The best way to take measurements practically is to use a 'scope. That will tell you the shape of the waveform, its pp levels and, if a square wave, its duty cycle. There are other ways to measure pp levels with a multimeter but they are laborious.3dchipmaker said:thanks for all your help!
would it be safe to say that the way im taking measurement would be an accurate reading of voltage output.and turning signal into audio and counting pulses per second an accurate hertz measurement?
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