I'm creating a payload that will need to be supported by a small structure. This payload contains a 555 timer which needs 5V. So far I've only found coin cell batteries and have been using a LilyPad Coin Cell Battery Holder that holds a 3V coin cell battery. On the underside of this, I've attached a 5V step-up breakout to supply a constant voltage to the chip.

This method is fairly heavy, though, and I'm looking for an easier, lighter way to supply 5V to the circuit. Does anyone have recommendations or ideas?

  • 5
    \$\begingroup\$ Not all 555 timers need 5V - it may be easier to redesign. \$\endgroup\$
    – pjc50
    Sep 9, 2016 at 16:07
  • \$\begingroup\$ It might be simpler to stick two CR2016 cells in the same holder and step down to 5V. But I'd probably look for a chip that will run off 3V. \$\endgroup\$
    – Ian Howson
    Sep 9, 2016 at 21:38
  • \$\begingroup\$ Look at Zinc-Air cells which have high mass and volume energy densities due to use of air as one reactant. \$\endgroup\$
    – Russell McMahon
    Sep 10, 2016 at 15:41

2 Answers 2


Why don't you use a CMOS 555 that will operate happily from a 3V battery, even at the end of (battery) life?

If you actually need 5V for blinky LEDs or whatever, you will need a circuit very similar to the ones you are showing.. so you could save mass by designing a very thin and small custom PCB. You can easily get 2-layer PCBs as thin as 0.4mm and you could probably cram that stuff into 1/3 or 1/4 the area, and use more compact components for the diode and the capacitor, so the total mass should go down by a large factor.

For the ultimate in reduction, pick a very high frequency switching chip that has synchronous rectification, as as the FAN4860, which operates at 3MHz with a tiny 1uH inductor and tiny 0402 ceramic capacitors. The chip itself is 1.2mm x 0.88mm x 0.5mm, almost an inhalation risk.

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Here is a comparison of the chip size vs. the (relatively) massive SOT23-5 package used by the vendor you linked to:

enter image description here

  • \$\begingroup\$ Thanks for your input, these are great ideas. I may go that direction or I'm considering using a TLC555CDR with an SO08 package and 0402/0603 components. That'll reduce my voltage demand to ~2V. Am I right in assuming that a coin cell battery is still my smallest power supply (without the 5V step up board) even with that reduction? \$\endgroup\$
    – F Young
    Sep 9, 2016 at 19:06
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    \$\begingroup\$ I think so- there are different sizes of button cells- the type used for hearing aids are very small (but check the voltage- you might need more than one). \$\endgroup\$ Sep 9, 2016 at 19:10

Sounds like an XY problem, better solved by designing to operate down to maybe 2.7v. However, to avoid a step up, you can use two miniature lithium batteries, and if necessary a linear dropper. http://www.powerstream.com/thin-lithium-ion.htm


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