Saving battery power with an UNO: LMC555 + MOSFET?

I find the UNO controller great to work with but unfortunately it consumes a lot of power making long-term battery powered projects complicated. Has anyone tried to combine an UNO with a low powered timer like the LMC555 and a MOSFET switch to power the UNO on/off every so often? Thanks!

Why, what you need is built in. Try this link you might like what you find.

Interesting. How low power consumption can you get during this sleep deep/sleep? I think with the LMC555 it seems you can get 1mW at 5V operation (200uA) which I think is excellent. In my case I will be using an RTC module and an microSD module and they too need to power down during the resting period to save on battery power. Thanks!

Have you considered something like a Pro Mini? I have seen several threads here about driving down the power usage.

Another "XY Problem"!

No, the RTC module does not need to power down during the resting period to save on battery power. That is exactly what RTC modules are designed for, to operate from their reserve battery and wake up the main processor at the time that is set as an alarm (which can be as often or short as you need).

The problem is choosing an unsuitable main board - the UNO. It includes a USB interface that you clearly do not need for battery operation (and the same for the Nano). A Pro Mini can have the regulator and pilot light disabled so that sleep mode uses very little current and can be woken by the RTC.

Can't speak for the microSD module however.

Great points regarding the UNO itself. I just thought that if one has the UNO or nano (I have many of both) it would be nice to just deploy without going to another controller. But it is worth looking into for sure. Also, UNO and nano are also good as it is easy to get them with header pins attached already. But assuming we want to stick with an UNO, would it work with a MOSFET and a LMC555? I do not have a LTC555 yet so I will have to order some to try it out. But great ideas here. Thanks!!

With an Uno or Nano, you can put the processor to sleep, but you still have the USB adapter, voltage regulator and power LED drawing current. And depending on the card you use, the SD module may not go below tens of milliamps. So it may be best to switch the power to the whole circuit on and off with a DS3231 RTC, which would be powered at about 1uA from its own coin cell during power off periods.

But a lot may depend on what battery you'll be using. The INT/SQW output pin of the DS3231 is open drain, and the datasheet says it won't handle more than 5.5V.

The attached drawing was done for a different purpose, but it illustrates how the power might be switched from the RTC. The two diodes are intended to get the voltage on INT/SQW down to a legal level when using 4 AA batteries, but for a 5V Uno or Nano, it might be better to use a single LIPO battery and a boost converter to provide 5V.

Safe Time Lock.jpg

Safe Time Lock.jpg

Soldering headers onto a Pro Mini is not too hard - put the headers in a solderless breadboard and drop the Pro Mini down onto the headers ans solder away - press down on the Pro Mini and solder the corners - the header for the FTDI board is a bit more work - but if I can do it with my eyes and fingers most anyone should be able to also do the soldering -

Many thanks for sharing the drawing showing how to use the RTC to do this!!. Excellent!!! Will give that a try for sure. As for battery, yes, that is something I will have to decide what will be best. Great points!

Great idea with using the breadboard to hold the circuit while soldering the header pins! That should make it easier!!

Here is a really good write up on the various power saving technique's available along w/ measurements.

In this thread I show various power-saving techniques for the Atmega328P processor.

They include sleep modes, use of power-reduction registers, and other techniques. Applying all of them can result in a current draw as low as approximately 100 nano-amps (100 nA), well below the self-discharge rate of most batteries.