Before I properly design my PCB I'm going to try and make a unit that works with a 18650 rechargeable lithium ion battery instead of AAs. I should be able to rip some out of an old laptop battery if they still work.
I haven't got many 3.3V boost thingies (needed for the temp sensor) for my current setup and they're not that cheap. Should be cheaper to use a zener diode/something else to drop the 4.2V for the RF24 radio.
12 of them in this battery :O I hope they work still.
And assuming they're genuine they're all Panasonic ones so should be decent quality.
Surprisingly that worked. With a normal diode, not a zener. Used the forward voltage of the diode to drop the Li-Ion voltage down to the voltage the radio works at. No voltage regulators needed now, and the DS18B20 temp sensor will work at all the voltages. I'll just have to be careful not to short circuit anything and blow up any batteries.
Do you need to be careful with Li-Ion batteries not discharging fully?
Yes, looks like it. Just looking it up and they shouldn't be discharged to under 2.4V. All the cells in the laptop battery are 2.2-2.3V so maybe I shouldn't be using them. The one I charged didn't explode though.
Do you have a 18650 battery charger?
Yes, just got one for my bike lights.
My !!/really exciting/!! Atmega 328p programming board.
It's got the 16MHz crystal and caps so I can program my chips to run at 8MHz off the internal clock before sticking them in my temp sensors (only have 1 so far though).
Forgot to upload the picture.