I’m building this pretty simple little frequency counter using a pic chip. Chip can take max 5 volt input. I’m mostly going to be under that but in case I want to measure a stronger signal I’m thinking I need to have some way of attenuating the signal. A simple voltage divider with a pair of resistors? I guess I could have a rotary switch and choose different levels of attenuation or something like that.
Is there some other smart way of achieving this circuit protection? A way to “cap” the signal? A pair of zener diodes as shown below?
I’m showing my ignorance here but hoping for some help! 🙂
One solution could probably be the use of a buffer/amp stage before the input (something like one or two transistors) and let that take the abuse. After all, it is far cheaper and easier to replace a failed transistor that an MCU
One solution could probably be the use of a buffer/amp stage before the input (something like one or two transistors) and let that take the abuse. After all, it is far cheaper and easier to replace a failed transistor that an MCU
I’ll read up on that, thanks for the tip!
Just a thought, I feel like using Zeners in that arrangement would cause the waveform to square off? In addition, you would have the forward of one diode and the reverse of the other (5.6 volts for example above) contributing to the limiting voltage. I don’t have any practice in that area, but those are thing that come to mind for me.
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@radtekman Pretty much what I was thinking, so maybe using a 4V to 4.5V zener would be better.
Note that you’d be clamping the output and thus injecting harmonics into the output, which might confuse the frequency counter. Most likely though it’ll latch onto the fundamental frequency, but it’s something to be aware of if you get some weird results from the counter.