Unrealcpu wrote on 2021-03-21, 21:47:
Opto-coupler..
It's the safest method I can think of.
The PC speaker would turn on/off the internal LED (don't forget adding the resistor) of the opto-coupler instead of a speaker's magnet.
Inside the opto-coupler, the signal is then received via a photo transistor/diode thing.
What happens then with the signal is up to the user, the PC speaker is out of danger.
I've wanted to try using one for this purpose for ages.
Unfortunately, I haven't had enough free room space for experiments since a while.
The problem is, the PC speaker is no real sound source.
It's not outputting any real AF signals, but rather rapidly switches between +5v and 0v.
So the results are square waves, at TTL levels.
Not sure if you can use DC blocking caps here to ged rid of noise, because the signal itself is DC.
What's also very troubling : The PC speaker IS the PC's timer.
Any damage to the timer chip and the PC is toast. 😢
Though normally, the PC would just crash if something is wired falsely.
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In what to one race is no time at all, another race can rise and fall..." - The Minstrel
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