I have a problem that’s been thwarting me for weeks.
—When my ESP32 is connected by USB to my computer, AND the Sparkfun Simultaneous RFID reader is powered from the Vin pin (~4.5V), the whole thing works well.
—If I try to power just the RFID reader with an external power source–and I’ve tried a number of them, around 5V and with plenty of amperage (up to 3A)–I get “BadCRC”. This is with ESP32 connected to my computer via USB.
—If the ESP32 is not connected by USB to the computer, and is powered externally, the RFID reader doesn’t seem to perform at all, although other parts of the sketch are clearly running.
Any ideas about what is going on? I’m using a Sparkfun Simultaneous RFID reader with an ESP32 using hardware serial, wiring directly to the TX and RX pins. I’ve mostly been using repurposed wall warts. I bought one power supply that goes up to 3A and has a knob to change V, fiddling with that got me nowhere. I have read mentions of a “burst” power supply in these forums–I know nothing about power supplies, how would I choose a more appropriate one, if that is indeed my issue?
The M6E NANO RFID is indeed very sensitive to a good power supply. Many of the wall warts have a very small capacitor and do not qualify. What you can try to do is use a real (charged) LIPO or add a large capacitor (> 1000uF) parallel to the Plus and Minus from the wall wart. As a test, you can also try to lower the RFID power below 500dBM. It will hard to get a reading even at small distance. If you want a strong supply, look for a 8A to 10A lab version not a wall wart.
Thanks Paul. This is meant for a puzzle in an escape room, so a giant lab bench supply isn’t really practical once it’s installed in the game. It will be in a difficult-to-access location, or I would try the battery. I will try adding a capacitor to my wall wart. Would the M6E NANO RFID be damaged if I used a 6V power supply instead of 5? I have a good one I might bust open and put a new capacitor into.
Thank you for your patience as I learn this craft. Is this the type of power supply I should be looking at? This could fit in the space. I was thinking you meant those huge boxes I remember from the lab bench of my school days, but this sort of thing could definitely fit where I need it to go.
I would expect that something like that would do the job. Be aware is when you increase the dBm the M6ENano will get hot very quickly and if too hot it will stop working, waiting to be cool again. You will have to add a cooling block in that case.
Thanks Paul. I have a heat sink, and I’ve also designed my application so it should only be reading for a few seconds at a time, with a timeout if it tries to read continuously for too long. Hopefully this will keep it in fine fettle.
I want to update in case anyone else has these issues. I tried many power supplies with very high wattage/amp maximums and they usually didn’t work. Even the one that did work ended up being inconsistent (ie it worked, but when I later bought more of the supposed same kind and brand, they didn’t). It is not a matter of voltage or current, but (I am now presuming) of being able to handle the spikes. I found out that the leviton outlet with built in USB can handle it and I’m going to stick with those, but if someone knows the particular specification to check when buying a power supply, I would still love to know that language.