3.3V Nano Every BLE, driving an relay.

Dear Folks,

I'm currently busy on a project that has brought me a headache. Since the nano every BLE only has a 3.3v on the IO pins, i can't connect it to a 5v relay. (like a normally would.) So my next question is there a clear and easy to understand electrical wiring scheme about a 3v3 micro controller that drive's an 5v relay?

Best Wishes, Jeff.

Most 'Arduino' relay modules can be powered (coil/opto) with 5volt, and switched/controlled with 3.3volt logic. Post a link to the module if you have already bought one. Leo..

thanks for you reply!

Well, that's the point i need a scheme because i need to make a pcb with the relay soldered on it. In my case a already designed pcb with a 5v relay on it doesnt work in my case. So i'm currently designing a pcb that must work without a flaw for atleast 2 years.

Lots of standard relay circuits on Google (images). Base resistor value depends on coil current (?) and logic voltage (3.3volt). Do you already have a relay (link). Leo..

This is the relay i want to use Link.
The thing is that with all the scheme that can be found on the internet are different and i’m just stuck with my hands in my hair. and don’t actually know how they have done it. And i have to do it in just one run because we are running out of time for this project.
Normally i will figure this sort of things out by myself, but now i just can’t do it on my own.

Best wishes, Jeff.

The maker world seems to think we need overly complicated relay drivers. This does mean that they work in a variety of situations but it seems a constant puzzler to those not fluent in electronics.

A simple option is to just use a couple of parts with your relay that should be easy to obtain. Any general-purpose NPN transistor will do, provided it can handle 100ma. The BLE has a pin marked 5V... use it to power the relay. (not the best idea... but it is what is immediately available)


Relays CAN cause problems with microcontroller circuits as they do sometimes cause brownout and electrical noise issues.

Just use the diagram in my link, or the above diagram. Can use a BC547 or BC 548 for the transistor (easy to get where you are). Can use a 1N4148 or 1n4004 or 1N4007 for the diode. Base resistor should be about 560 ohm (for ~5mA base current). Power for the coil (one relay only) can be tapped from 5volt pin of the Every, if you're using USB power. Leo..

PS Er is een Nederlandse sectie in dit forum.

Thanks for you reply! I know enough for now, you guys just helped me out alot of trouble, and i hope that people that are facing the same issue are going to read this forum post.

P.s. ik weet dat er een nederlandse sectie is! alleen praat ik nogal makkelijk in het engels haha. Dankjewel voor je bericht!