Vernier Photogate

Contributors: bri_huang

Photogates

We started our original prototype design with these photo-interrupters that we found on Amazon. These little modules are great. They have 4 leads and there is a small IR LED on one side. The other side is an IR receiver.

The only drawback to using these devices is that the IR LED still needs a current limiting resistor. I figured that out the hard way! They aren't easy to mount, and they have a really small gate opening. Digging around in the closets at the school I discovered several drawers full of photogates from Vernier. I would guess that several other schools might be in the same situation.

These photogates are fantastic. The detectors each have a Schmidt trigger built in and a LED to indicate when the gate is broken. The only drawback is that Vernier has a special British Telecom connector on their devices. The photogate uses a left-hand version of this connector. We had an option to simply cut the ends off, but then these photogates would not be usable with the LabPro devices in our Physics lab. Thankfully, Vernier sells these breadboard connectors. Using these I could build an interface directly to an Arduino. I just had to figure out the sensor pin-outs.