- Joined Jan 6, 2018
Is it safe to use a resistor divider to output approximately 5v AC from the 120v AC line voltage without a step down transformer to clock my CMOS counter?
What I've done in the past is use a series of resistors to bring down the appropriate current and voltage to drive an ac optoisolator (such as the SFH620A-3) and then use its output as a clock signal. That would be a safe way of doing it.
NO!!!, at least not under most conditions. Aside from a shock hazard there are noise issues and other potential grief possibilities.
NO, it is not safe. I’m an industrial electrician and play with big power all day, but at home on my bench, anything that comes out of the wall is isolated.
Probably in the USA you will not find such a transformer, but evidently in other parts of the world such things are common. So any transformere should be qualified for constant duty.Not only that its not safe, but you can burn the house if you do not know how to calculate the power dissipation over the components.
Why not use a standard transformer for long hour work and a Gretz rectifier after it? If the transformer is not made for long hour work it will overheat and burn the house down also. Something like a bell transformer from the old bells will work, since its made to be active every day the whole day.
I don't think the generators at the power plant are changing in speed.With the frequency changing unexplained I am sure we are dealing with the spirit changing the 60 Hertz line frequency by changing the theory and physical constants because it is limited by time.
That was my first thought too, after reading Richard's comment. Seems like the hysteresis a Schmitt trigger provides would be very helpful here, but the transistor totally defeats it.Get rid of the transistor ahead of the schmitt trigger - it just makes a mess of things by providing gain for noise.
Disagree with all of that.Get rid of the transistor ahead of the schmitt trigger - it just makes a mess of things by providing gain for noise. Limit the current into the protection diodes at the input of the schmitt with a series resistor in the range a 100k.
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