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!

Here are some pictures of my completed micromouse chassis, along with all the boards.

Everything on the chassis is mounted using velcro, for easy attachment and removal.

There are 4 seperate boards that make up the control circuitry:

• Sensor board, containing 4 IR photoreflectors, which attaches to the main control board.
• The stepper driver board, which uses an ATTiny2313 to sequence 2 step / direction into the correct outputs to drive the motors.
• The Power regulation board, which carries an LM1084 3.3V regulator, to drive the motors, and a LM2940CT 5V low dropout regulator, to drive the electronics.
• The main control board, which contains an ATMega16, and controls all the running of the robot, and controls all the maze searching and running algorithms.

Got the AVR code for the stepper motor drivers working today, and the Voltage regulation for running from a battery, at this rate, I’ll have the mouse moving by wednesday / thursday

Heres a sneak peek of my uni dissertation, my micromouse robot

Fingers crossed, it’ll be up and running by RoboTIC 06!