Driving doorbell (DC motor) with my Particle Photon - MOSFET problems!

I am in the process of wifi enabling my old fashioned doorbell (smartphone notifications, home automation etc.). My problem lies in the most basic feature of a doorbell – making the bell ring!

The originall doorbell is driven by two 1,5V DC batteries (D size). Powering the Particle Photon of a USB charger / USB cable I plan to power the bell of the 3V3 and GND pin. Connecting the wires directly to the pins makes a reel clean and powerfull ring.

My problem lies in controlling the ring with the Particle Photons digital pins. I bought a MOSFET N-channel transistor (irfz44n) but can’t get it to work!!

Connecting the transistor leaves the bell ringing half force and connecting the gate to a HIGH or LOW digital pin makes no difference in ring speed/force.

How do I control/trigger the bell using my Particle Photon? Any ideas?

Picture/Wire explanations:
BLUE Digital pin connected to GATE
WHITE deliberate shortcut of the original doorbell trigger switch

you might need to swap the Green jumper and the green wire going to ground.

The mosfet pin-out is (Gate Drain Source)

Gate --> D4
Drain --> bell
Source --> GND

It’s likely that current is flowing through the diode in the N-fet due to the current wiring, causing the constant ringing :wink:

Kenneth! You are completely right! Thanks … Unfortunally the D4 pin is not powerfull enough to open the gate. But if I connect the gate (blue wire) to the VIN pin the bell rings (even after I disconnect the wire) and stops when connected to GND. Any suggestions to this? Is my MOSFET the wrong choice or do I need a second transistor trigging the IRFZ44n?

What happens if you connect the gate to 3V3 instead of Vin?


The Vgs of the IRFZ44N is 4V so applying Vin which is around 4.7/5v turns it on fully, which makes sense…

Do you have an NPN transistor around? It might be a simpler solution since the current draw in this case shouldn’t be too high.

This N-fet might work well with 3V3 devices - https://www.sparkfun.com/products/10213

I tried using a 2N5401 That works (OFF on HIGH) - but it gets really hot an smells burned! Not good! I look for a NPN.

Is my wiring wrong? should a place the switch where the white wire is placed ?


Put a 10K resistor between Vin and the gate. When you switch your I/O pin (5V tolerant) to input, it will raise the gate voltage to 5V shutting it off. Switch it to output and low to ring the bell.