Circuit design help?

Hey, I've worked with a 555 circuit before but always at 9 volts or so. I'm looking to throw together a quick blinker circuit to help test coatings. I'm looking at the icm7555ipa. It can run off a supply voltage as low as 2v. I'm looking to make an LED blink at ten seconds intervals and run it off of a coin battery or two. Any input? Would the same astable circuit layout I'd use with a normal 555 work?


  • Long story short, yes it should be pretty much the same circuit and work.

    Medium length story:
    There are some minor details about the current you can draw from cmos chips when operated at the lowest possible voltage. And the comparators internally may not be quite as accurate and give like a few percent "wrong" timing. But since your timer is in the range of 10 seconds you probably work with very low currents to begin with so it's not much of a problem (unless you use giant caps to do timing). You probably end up with something like 47μF and 500kOhm ish.

    Needlessly sequal of the Medium length story:
    If you can solve the problem with 74-Logic you have the choice between a whole bunch of different types. Using cheap Schmitt triggered Hex-inverters you could build simple timers. 74 HC 14 would be one examplen which works down to 2V. There are the AUC and AUP families which go as lows as 0.8V but they have pretty low maximum operating voltage, tend to be ESD-prone and no clue if they have the 14 in a hand solderable package or not.

    The overengineered still way too long story which may be interesting if you'r into microcontroller stuff:
    MSP430L092 will get you 0.9V and the full load and bloat of having microsecond precise timing. You could hypothetically save a few microamps of current compared to the 555 version. But then you have LED's which eat many times more than that. Still if you feel like it, sure why not.

    Last but not least the mc gyver version:
    use regular 555 a joule thief, a single AA or AAA battery and use an LDO or so to get a stable and high operating voltage. Lasts way longer than coin cells. (overengineerd variations of this sollution exist as well)

  • ^^^ All true. Do the thing.

  • Thanks! Ok. I'm now looking for a schematic incorporating these suggestions.

  • Lm909 is no longer being made.

  • I've found some ultra low power schematics now, but apparently the led isn't very bright

  • Where would I put the ldo in the circuit? And I've seen some "micro joule thief" which don't have the big torroid.

  • My knowledge of ee is so minimal it's pathetic. To be honest, I don't know enough to take advantage of these suggestions.

  • @Cassox would you be interested in learning more about ee? I've got a great program that comes with some good guides on the basics, and even gets into some of the more complicated stuff. I can post the link up later this afternoon.
  • Totally. I built a few variants of the 555 circuit but I'm probably just going to go with an LED with a built in flasher.
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