I thought my first project was finished until I connected it up to a 12V LiFePO4 battery through the barrel jack and fried an Arduino Leonardo, but I am not sure why. All worked fine with a 9V power supply. Measured voltage of the battery before connecting was 13V, which I know is higher than recommended, but seemed within tolerance. I connected it and it worked for about 5 minutes. When I unplugged it and plugged it back in, it no longer worked. The only thing I can think that did it was I also plugged it into my computer to change some code. I'd done that a lot with the 9V power supply, but maybe the higher voltage caused the issue? I'd like to figure out a battery plan without frying anything else. Or, you know, worse.
Edit: I figure I probably need to put something between the battery and Arduino to prevent this, but I am not sure what. A buck converter and bring it down to 9V? Something else? Thank you for any insight you can provide!
Yup, totally. My question is why and how do I avoid frying the next one, ideally using this battery. Just don’t plug in usb at the same time and it will be fine? Or use something between the battery and arduino?
To me it looks like you fried the internal voltage regulator. The higher the input voltage the more heat is dissipated. So you need to be aiming for the lowest possible voltage into the Vin barrel jack. So about 7.5V.
The fact that it failed when you unplugged it, is just a coincidence.
So I would use a buck converter to reduce your voltage down from your source voltage.
I have tried my hand at drawing a schematic. (Sorry for the poor quality, still need to learn a tool to do this digitally.)
It is an instrument, using the Adafruit Music Maker Shield. I’d think the 2 speakers (4ohm 3w) connected to that would be the biggest power draw through the Arduino, but I don’t see a way around that. Their documentation suggests using vin/barrel jack rather than 5v/usb because of that issue, which I have done.
There are also 8 piezo electric sensors connected to analog input pins. They are in parallel with a resistor and a zener diode which I intended as some protection in case the voltage generated by the piezo is too high, but maybe I have done that wrong.
There are 4 buttons connected to digital inputs and one digital output for some addressable leds. The leds are connected to the battery through a buck converter to step down to 5v, so they should not be drawing power through the Arduino.
Splendid job.
(Stuff that people slap up digitally figuring it's genius looks like spaghetti typically to people trying to figure out what's going on.)
That's potentially 1.2A (plus) drawn from the Leonardo's 5V rail. Not good! Even at a fraction of this you could burn the onboard regulator to a crisp.
Yeah, that doesn't really work well, but it's not likely the source of your problem.
The LDO ('1117) is supposed to have current-limit and thermal-shutdown features. ...protection against a combination of
high current and ambient temperature
If I switch these out for 8ohm 1w speakers am I correct that they would draw .4A, so I’d be back to relative safety? Or is there something else I need to consider?
Correct it is supposed to have one. But we have found from members experiences, that often that a large voltage kills the onboard regulator, before it has time to warm up and shut down.
Yes if you drop the voltage down to a lower rate then 0.4A is still way more that the internal regulator can supply.
Look at the data sheet for the regulator and see for your self. Bare in mind that the heat sink provided by the tracks around that regulator are not very good.
However, as you already have a buck regulator on that circuit to drive the LEDs, then why are you not using that to power the 5V side of the circuit instead of using the internal regulator? As I said the current you can get out of that is about 100mA at the most.
Thanks to @Paul_B for pointing your already present buck converter.
