Working on a flow sensor test setup the breadboard suddenly exploded! And I though blue smoke was the worst that could occur..

Yesterday I made a great step forward testing the flow sensor. I made a simple breadboard setup to run the pump when pushing a button, and stop it when the flow sensor read a set value (330ml for a normal Norwegian beer bottle). This worked, but I wanted to see the flow sensor readings so I added a 8 digit display to show the total milliliters going through the sensor. The display didn't work properly at first, showing strange outputs on the display, but after a while tweaking things it suddenly did what I wanted and I went to bed with a big smile knowing I made it work.

Today, the display suddenly didn't work, and after some tests using different codes and sketches I thought something had to be wrong on the breadboard. I also noted the pump motor was warm. So I did some quick reading about noise, de-coupling and capacitors. I have soldered a 0.1uF capacitor onto the pump and got an idea this was wrong, and added a 470 uF capacitor on the breadboard after the TIP120 transistor controlling the pump.

BOOM!

Apparently this was a big mistake. As it blew up in my face it was unsuspected and scary, but I sure learned something about using capacitors today. First of all being more careful, and I need to learn more about them.

I still don't know why the display doesn't work. And the circuit for the flow measurement doesn't seem 100% yet.

First tests using the flow sensor worked great. I could push the button and the pump filled a perfect 330 mL bottle. But after adding the display everything got more complicated.

The breadboard diagram shows how I have connected the pump and the flow sensor (black little thing with red-black-yellow wires). A 104 capacitor is soldered onto the motor (blue little thing). I have found an explanation on the adafruit site about using three capacitors on the motor, but I still don't have the knowledge to understand why and what it means.