Hi all, I'm pretty new to electronics, apologies for the newbie question. I've been working on reading weigand signals from an RFID reader (MaxiProx 5375) with my Arduino Nano. Everything works as expected, I can read and interpret the signals. The data lines on the MaxiProx are 5v. I've based my project on [mod edit: link removed, the website linked to openly encorages building electronics for illegal purposes. OP, please do not post such links and do not use this forum to promote illegal activities. Thank you] I've just received another reader for different EM4X tags/cards and the data lines on this reader are 12v. After a few nights of searching online I believe I've realized that I can't use voltage regulator (my initial thought), but I need to use a voltage divider to step down the voltage to 5v, or could I use a zener diode? Below are the schematics of the circuit I'm working with [tastic] Could I simply add two zener diodes to the data lines? Please let me know if I've missed any information.

No problems, I'll draw up a proper schematic.

Then zeners should be all you need as long as the current going through them is limited. Your drawing is difficult to read, so I'll assume you know where to place them. I'm pretty sure I do, but I'll draw up a proper schematic and post it. Thanks for your help!

[image] tnikitin: I've just received another reader for different EM4X tags/cards and the data lines on this reader are 12v. That is a really strange choice of logic levels. To what is it intended to connect? :astonished:

Is that a 3.3volt-only SD card reader, powered by the weak 3.3volt pin of a classic Nano? Leo..

[image] Paul_B: That is a really strange choice of logic levels. To what is it intended to connect? :astonished: I agree, but that's what the datasheet says (it's a Chinese manufacturer, so the documentation has been a bit weird). I'm not sure what kind of controller this reader should connect to. I'll get access to an oscilloscope next week, I will be able to verify those levels. [Skärmavbild 2022-04-05 kl. 13.20.25]

It's powered by the Nano, but I haven't had any issues with the card reader. [image] Wawa: Is that a 3.3volt-only SD card reader, powered by the weak 3.3volt pin of a classic Nano? Leo..

[image] How to make a schematic you can post. Introductory Tutorials When you submit a question on the forum you will usually need to add a schematic (circuit diagram). The tutorial that follows will explain some ways to create a useful image; however lets start by explaining how to add the image to your post. Its easy. Having created the image all you need to do is : Save the image somewhere convenient - maybe your desktop Start your post, and place the cursor (insertion point) where you want the image to be shown; [upload image to forum] 3: click th…

[image] Paul_B: That is a really strange choice of logic levels No not at all for a Weigand output. These normally have a 12V signal or are open collector outputs. However the one thing that the OP seems to have missed is that there are two outputs to condition and read, not one. A simple voltage divider will be sufficient to cut the voltage down to a safe level. For those who have not met the Weigand interface, this link gives an explanation as to what it is and why it works, along with a project that uses Weigand output RFID readers. http://www.thebox.myzen.co.uk/Hardware/Crazy_People.html

[image] Grumpy_Mike: No not at all for a Weigand output. These normally have a 12V signal or are open collector outputs. To connect to what? :face_with_raised_eyebrow:

[image] Paul_B: connect to what An access control system.

Stepping down 12v to 5v on data lines

Other Hardware General Electronics

johnerrington April 6, 2022, 5:39am 12

Topic		Replies	Views
RFID-RC522 Was ist mit Spannung von Digitalen Nano-Pins Deutsch	16	312	August 4, 2025
I fried my Nano General Electronics	31	536	October 22, 2025
Question regarding 5.2v, an Arduino Nano and a MQ135 sensor Sensors	32	481	December 9, 2025
Arduino Nano not reading RFID (Works on ESP32 & Uno) General Electronics	32	1088	September 25, 2024
Arduino Nano e lettrore RFID-RC522 Generale	1	173	April 22, 2025

Stepping down 12v to 5v on data lines

Related topics