Although colour recognition systems are not new, until recently they would have been far too complex and expensive to feature in a PICAXE project. Texas Advanced Optoelectronic Solutions (TAOS) from Plano, Texas, have changed all that with their new line of low-cost colour light-to-frequency (LTF) converter ICs.

Fig.1: the complete circuit diagram for the Colour Sensor Module. 33kΩ resistors set the default conditions (high or low) for the sensor's input pins. Information on the function of the S0 & S1 inputs (here set for 100% relative frequency scaling using two 33kΩ pullup resistors) can be obtained from the TCS230 datasheet. A Mosfet (Q1) is used to switch the LEDs via the "L" signal on the connector.

The TAOS TCS230 LTF converter was selected for this project because it integrates all of the functions necessary for colour sensing into a single miniature 8-pin package, including a digital output for easy interfacing to our PICAXE microcontroller.

The project consists of two individual PC boards that plug together to form a complete colour recognition system. The first of these is the Colour Sensor Module, which includes the TCS230 sensor and a handful of support components. Revolution Education is supplying this board preassembled, as the TCS230 is only available in a tiny surface-mounted (SOIC) package that would be difficult to solder by hand.

The second PC board is a PICAXE-08M Servo Driver. Although primarily designed to control servos in robotic projects, this board is also suitable for use with the Colour Sensor Module.

In this article, we’ll describe how to assemble the Servo Driver board, as well as how to connect it to the Colour Sensor Module to build a complete colour recognition system. Naturally, we’ll also show you how to program it to recognise colours!