Rooter’s Sensor board, v2.0

I’ve been having some major trouble with my sensors lately on rooter, which has been holding me up for about 2 weeks. This week i decided to spend as much time as possible trying to get them to work, and eventually worked out why v1.0 wasn’t working… The IR LEDs were in the wrong way round! It appears i’d been taken for a fool by the QRD1114 datasheet, and managed to spec up a board where the phototransistors were in correctly, but the LEDs were backwards.

I went back to the breadboard, trying to get the LEDs working as they were meant to, and realised after half an hours testing that I have somehow managed to blow one of the output pins on my AVR, and then chosen that pin to drive the test LED!

After i had worked out that this was the problem, I quickly got an IR LED working, and managed to test it using my digital camera, which can pick up IR!


With this setup, and the output of the phototransistor tied to ground through a 150k resistor, this gives me a reading of between 100 and 350 on the ADC between 90mm and 20mm, which is perfect for micromouse applications.

After getting a working model on the breadboard, i refactored the schematic i had previously designed in eagle, this time hooking up the LEDs correctly, and improving the Resistor & connector placement, which had been interfering with the stepper board connector, as the two boards hang above each other!

I also added a ‘power OK’ LED, which i might switch for a white ultrabright one to give me a headlight!