-1
\$\begingroup\$

There are countless applications for delays of a few hundred milliseconds up to a few seconds. I have not been able to find some elegant solution, but I am sure that there must be a way, and that some of the expertise in here has a neat little circuit that is much better than whatever I can come up with.

And before I get the obvious answer: A 555 with a 1000uF cap is a fun breadboard experiment, but the huge electrolytic capacitor is absolutely impractical on any "real" miniaturized PCB's. Surely there must be a more practical/professional way.

I find it really strange that the big IC manufacturers doesn't have a simple sot-23 delay timer. Components such as TLP5010 is real close, but not quite bullseye. It can be coerced into a functional circuit with some additional components, but it still feels like a square wheel. So without any off-the-shelf options: Please share your favorite timer circuit.

\$\endgroup\$
6
  • \$\begingroup\$ A 555's timing depends on the capacitor and the resistor, so you can use a smaller cap with a big resistor. Still it's not a great choice if you need precision or low power consumption. There are timer/counters that run by counting pulses from a crystal oscillator. Maybe look into those? \$\endgroup\$ – Hearth Jan 9 at 14:03
  • 2
    \$\begingroup\$ "Share your favorite circuit" is not how this site works. You need to be very clear and specific about what you need, and don't just ask for an "elegant" solution. \$\endgroup\$ – Elliot Alderson Jan 9 at 14:07
  • \$\begingroup\$ Please take the Tour to learn how the site works. \$\endgroup\$ – Transistor Jan 9 at 14:07
  • \$\begingroup\$ Requirements? Input characteristics (active low/high, pulse width)? Output characteristics? Accuracy requirement? Some least to most accurate choices: 74AC14 with RC & diode, 555, MCU w/o crystal, MCU w/crystal. \$\endgroup\$ – Mattman944 Jan 9 at 14:12
  • \$\begingroup\$ You can use a microcontroller with internal factory-calibrated RC to get much better unadjusted precision than is possible with a 555. Or a CMOS 555 with a high value resistor. Or a 74HC123. A million solutions are possible. The right one depends on the application and other factors. \$\endgroup\$ – Spehro Pefhany Jan 9 at 14:17
3
\$\begingroup\$

find it really strange that the big IC manufacturers doesn't have a...

But they do! Analogue Devices TimerBlox. There's a lot of them and they can do many things, but in a nutshell, they'll do 1 us to 39 days. Better than a 555.

Simple application from one of the data sheets:-

timer

'programmed' like so:-

programming

\$\endgroup\$
2
  • \$\begingroup\$ Power up. | Wait 39 days for output to go high. | Adjust trimpot. | Cycle power and repeat. I think some of the others in the series might let you monitor the internal clock. This would make calibration much faster. \$\endgroup\$ – Transistor Jan 9 at 14:33
  • \$\begingroup\$ @Transistor I'm absolutely sure that you're right, but I have to get to the off licence... \$\endgroup\$ – Paul Uszak Jan 9 at 14:36

Not the answer you're looking for? Browse other questions tagged or ask your own question.