I'm working on a project that uses 6 RC522 rfid readers attached to an Arduino Mega. I can get it to work fine with 3 or 4 readers, but when I plug in 5 & 6 everything stops working.. After checking the voltage requirements the RC522 has a working current of 13—26mA/ DC 3.3V. Which would put 4 readers current consumption at 52ma. The Mega has a 50ma output on the 3.3v pin.
I need advice on how to power the other 2 readers. Am I going to have to use a second 78-156ma/ DC 3.3V transformer to run the 6 RC522 rfid readers? Or does anybody have ideas on using the transformer supplying the mega to accomplish this?
Brittio:
The Mega has a 50ma output on the 3.3v pin.
Make that 150mA.
I saw peak currents of 60-100mA in the datasheet.
How do you supply the Mega now.
Maybe a simple 5volt to 3.3volt lineair regulator will do.
Don't know if sensitive RFID receivers like switching regulators.
Leo..
How do you supply the Mega now.
Maybe a simple 5volt to 3.3volt lineair regulator will do.
Don't know if sensitive RFID receivers like switching regulators.
Leo..
I was using a 12vdc 50ma transformer. Swapped to 12vdc 1200ma and didn't see any improvement.
Swapped to 12vdc 1200ma and didn't see any improvement.
That is because it has to go through the same 3V3 regulator on the Mega. You need a regulator that can provide extra current, as well as a power supply that will provide more.
Grumpy_Mike:
You need a regulator that can provide extra current, as well as a power supply that will provide more.
Are you saying 12vdc 1200ma isn't large enough?
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Grumpy_Mike:
Got any supply decoupling?
Also how far apart are these readers? They interfere with each other if they are too close.
I haven't done any decoupling.. These readers are temporarily very close because I'm testing. Again, they work fine as long as I don't have 5 or 6 plugged in.
None of the data shows performance of 3.3V output with 5v input, only 7, 12 and 36V. You'll be fine with 12V, and get more efficient operation (longer battery life) with 7V.
Got the voltage regulator installed and now it will operate 5 of the 6 readers.. In the picture you can see I'm connecting them using network cables. I can rearrange all my readers and it works fine so long as i only have 1 long red cable. (the 6th reader was also on a long red cable) I plan on running all 6 on longer cables once i'm done testing.. Is this something Decoupling would help with? (again i've never decoupled)
The key here is to do some measurement of the voltage. Is it holding up? You say:-
Got the voltage regulator installed
Is this a single pre built block, or have you made it from components. If so you should have used decoupling capacitors as part of the regulator circuit.
