I recently came across the existence of arduino thermal printers and decided to try and make an instant camera. So far I have a project involving an ESP32-CAM that connects to a TFT display with some buttons.
My final project will use an 18650 battery and TP4056 for power. Prototyping is powered by connecting all components to a separate non-programmed ESP32's VIN. It's used purely as a USB port to connect to. This works fine, the problem starts when powering the printer though.
I bought a GOOJPRT QR204 58mm TTL printer. The printer needs 5V~9V and 2A. It doesn't work with direct power from a 9V battery as those have laughable amperage, direct power from an 18650 isn't enough, nevermind an ESP32's VIN. I also conveniently only have a 9V 0.5A barrel jack power supply and a 12V 5A one but nothing actually rated to power this printer. I've tried every method in my house to get it powered well enough to print a test page but nothing's worked.
I ended up buying a XL6900EL Step-up converter to test. It's supposed to be variable from about 1V to 32V and supply max 3A, but I ended up killing my printer with it because the converter doesn't show a consistent voltage when measured with a multimeter. I don't know why this is. I got it to 9V after an hour of fiddling only to have the printer explode on me and have the multimeter tell me it's actually outputting 30V now after measuring again. I followed the same measurement method as shown here: https://www.youtube.com/watch?v=iJxiM6mUqsY
Regardless, I have other concerns. To reiterate, I was powering everything through an ESP32 to test, and it had brownout problems when the step-up converter was connected. I'm very lost on simple ways to power this thing.
For the prototype,
- Does a USB port from a computer even supply enough current to power this printer? Should I be testing with a charging brick or so on? I don't have a desk power supply.
- Is the ESP32 even capable of supplying enough power from VIN to be used as a power source, despite step-up? Am I supposed to just get a dedicated board for breadboard power instead of going through another microcontroller to power my prototype?
And for the board version,
- What is the smallest component I could use to get the TP4056 output to be usable with the printer? The step-up I have is pretty big for the board I designed. I don't want variable power, just for it to go from the 18650's voltage to what I actually need.
If it's not obvious I'm not very good with power. I've never needed to cough up separate power boards to connect anything Arduino I bought. Why is amps not measured like voltage? It seems to be in terms of "maximum draw" (e.g. the step-up being rated for 3A) and not "output draw", like a 9V battery would be?