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Let's say there are 5 different loads, and I need a circuit to switch them on/off based on a pre-tunable delay. (E.g. first one immediately, second one exactly 2.78 seconds after the first one, third one 5.33 seconds after the second, the 4th load 0.24 seconds after the third, and the last one 1.05 seconds after the 4th). 0.01 seconds precision is enough.

The time delay between each one needs to be adjustable (not during the circuit operation, but using variable resistors ,manually, before turning on the main circuit).

Can this be done without oscillators or pulse counting stuff?

I can measure the circuit results precisely using other methods (to test if I've tuned the delays close enough to desired times.) I'll repeat the run-measure-tune cycle enough times to reach the 0.01s precision.

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    \$\begingroup\$ Assuming you want an accuracy of 10ms in a period of up to 10s, "Using variable resistors" is going to be a serious problem in itself! They're just not that accurate normally AND they suffer from temperature drift. You'll need special high-precision multi-turn pots with a vernier dial. If your constraint is no microcontrollers you need to say why. \$\endgroup\$
    – pjc50
    Commented Feb 12, 2021 at 13:05
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    \$\begingroup\$ you need a microcontroller, or lots of experience and patience. \$\endgroup\$
    – dandavis
    Commented Feb 12, 2021 at 13:09
  • \$\begingroup\$ @pjc50 I was considering costs. Seems I'm wrong. \$\endgroup\$
    – Elementronics
    Commented Feb 12, 2021 at 13:17
  • \$\begingroup\$ Back of the envelope assessment - you want a range of ~10s with a precision of 0.01s. That means your design has to be accurate/precise to 1 part in 10,000. This needs to be digital solution. \$\endgroup\$
    – SteveSh
    Commented Feb 12, 2021 at 13:18
  • \$\begingroup\$ @Elementronic analogue control systems went out in the 70s because, even then, doing anything with a precision of more than about 1% became very difficult and expensive. \$\endgroup\$
    – pjc50
    Commented Feb 12, 2021 at 14:14

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Can this be done without oscillators or pulse counting stuff?

Yes, but it's going to be difficult to get the precision you want. A circuit using several 555 timer ICs will do the job but you'll have to spend time trimming all your resistor and capacitor values to get the timing as you want. But "yes", it could be done.

If this were my problem, I'd opt to use a low cost microcontroller to do this.

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    \$\begingroup\$ ... well, until the temperature changes. \$\endgroup\$
    – pjc50
    Commented Feb 12, 2021 at 13:03
  • \$\begingroup\$ I guess I forgot to mention "temperature controlled chamber" to the mix! But yes, it's going to be very difficult indeed! Not impossible, just a lot of work for very little gain IMHO. \$\endgroup\$
    – jwh20
    Commented Feb 12, 2021 at 13:17

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