Sorry to waste some of your time but I am a bit of a newbie trying to find out how to power a project.
The Drama department at school asked me the physics teacher to help them build a prop campfire. I thought I would just whack together 1m of addressable LED strip and an Arduino into a box and call it a day BUT I haven’t had to build something that needs rechargeable batteries before.
Looking for some advice on
battery - what size should I get if I go LiPo? the LEDs will almost always be coloured and because they are flickering they wont all be on full brightness
Battery charging - Is there something I can buy that will handle all the battery charging? possibly also something that can pump out 5V for arduino etc
A lot of the coding and other arduino stuff I know I’m just new to battery packs and to be honest after reading the warnings and the dangers of over charging Lipo scares me a little but it is the go to battery pack.
I would start here and pick through the list of components part way down the page on the right.
Grab the Pico, the LiPo battery, and then add in some of these for the LEDs as the Pico can drive them ok
and here is the ‘getting started’ guide for it all.
I am thinking through this for the in hall ‘campfire’ for my Cub Pack, as recharging should be as simple as plugging the system into a USB power charger - as used for mobile phones. Add a small switch that the Pico reads, to tell it to ‘do nothing’ i.e. charge only, or ‘go for broke’ and play fire. And then you can do away with the charger …
Hope this helps
Hi Matthew, Welcome to the forum!
Just to add to Murray’s excellent response, generally overcharging is prevented by the charging IC (LiPos are picky as you said, they want CV at the end of the cycle, so that’ll prevent overcharging, good video on this)
The problem is usually draining them too far. Basic charger ICs don’t have the ability to interrupt current to the load when the battery is empty. A way around this would be to construct a voltage divider to measure the battery voltage with the Pico’s ADC, and have it turn off the LEDs and go to sleep once the battery is empty, and have a switch inline with the Pico so you can eliminate the tiny left over current when storing these.
Hi @Matthew223092 and @James ,
Good pickup on the low voltage detection - so that’s possibly two switches - one that the Pico reads to tell it whether it is in charging mode or fire mode, and a ‘real’ switch to fully ‘disconnect’ the LiPo and the Pico in storage mode.
Is there an ‘inline’ switch available for the LiPo battery cable?
I’m guessing a bit here - I presume that to then bring the device up and ready to go from a discharged ‘cold start’, one would put the charge/fire mode switch in the charge position, connect the charger to the USB port (which wakes up the Pico), and flick the ‘real’ switch to reconnect the LiPo for it to accept the charge…
Then when it is charged (refer to the charge indicator LED) the charger can be removed, the fire gadget positioned in the the display place, and the charge/fire switch changed to the fire mode, thus turning on the LEDS … . .
I actually didn’t have a second switch in mind, just one after the battery and before the load, but I suppose that doesn’t mesh well with the PiicoDev expansion board.
Another option is to go with a Pico with built in charging, power switch, and protection:
If that is a real on / off power button then that would be great. And the PiicoDev non-recharging expansion board could be used instead
Nice that Pimoroni stuck with the ‘standard’ footprint for the Pico too.
Thank you so much for your input. I really do appreciate it. What I have read fills me with confidence but alas I must say I have gone down a slightly different route. I was recommended the Pimoroni LiPo amega pro
Murray did suggest the same brand and I went with this because it takes the thinking out of it, I hope. I also grapped some addressable LEDs so lets see how this goes.
Nice alternate route. There is often many ways to the end result.
I would add in the power detection concept from James to help protect the battery at the end of the discharge cycle as the voltage drops away. How you do this depends on the processor that you choose to use.
Finally starting the project now and trying to decipher this great suggestion.
I understand most of it except for why I would use a voltage divider. Couldn’t I just measure the voltage of the battery with my Arduino (my chosen processor) directly? (in parallel?)
My only thought about why i might use a voltage divider in case the voltage is too high for the board. The voltage of my LIPO is around 3.7V so not sure that would be a problem.
Am I missing the point?
Sorry for the late reply. Yes, you’re right. If your logic level (and thus in most cases, your ADC reference) is 5V, higher than the 4.2V a single-cell LiPo will get to, then there’s no danger in measuring the voltage directly. I mentioned it as most modern microcontrollers (like the Pico I brought up earlier) run at 3.3V. As time goes on you’ll see fewer and fewer sensors and microcontrollers that are happy running at 5V.