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.
I've got a couple of 328ps but couldn't get them to work. Need to try again.
They're pretty easy to get working. Everything on that board will get it detected by AVRdude. You do need a USBasp to program it or upload a bootloader if it doesn't come with one.
But it should have have some caps and resistors and other bits to properly connect it all up.
I think I've got some of the correct caps and a ceramic resonator but couldn't get it working last time.
Still cheaper to buy an Arduino nano though!
Maybe it's cheaper to remove a load of the voltage regulator bits off a pro mini.
Really? Cheaper to buy a fully assembled board than a single chip? How much do you buy nanos for? My 10 Atmegas cost £20 so £2 each.
I did try disconnecting the voltage regulator and power LED from a mini but couldn't get the power consumption down far enough. Much easier with the DIP chips if you want to go low power.
I bought 5 Nanos for £9.57 early this year. £1.91 each.
I think if low power really is essential then the chip is the way to go.
Wow, that's crazy cheap. How much do the official ones cost compared to that?
Cheapest I can find the chips on their own is about £1 each. No caps or crystals with that though. My other ones came with all that sfuff but I don't use them, and a DIP socket and reset button.
They're so cheap I pretty much see them as disposable now.
I might see what sort of power a pro mini uses with regulator and all LEDs removed. No USB chip to consume energy either.
I have seen that before, but forgot about it!
Soldered up another board with a Li-Ion battery now. It's powering up but not sending the temps for some reason. I'll have to try and fix it tomorrow.