After building the first prototype of our timer device and then making preparations to use the PICAXE 08M and save space by using a single NPN transistor as a NOT gate, we have finally completed our project using the PICAXE-08 Proto Board Kit. As usual, I purchased the Proto Board and PICAXE chips from those reliable folks at techsupplies in the U.K. For around 5 Euros, the PICAXE-08 Proto Board Kit with a PICAXE-08M microcontroller is a real bargain. It has almost everything you need to get going – the only extras you will require are a USB cable for programming the PICAXE and a battery box for holding 3 AA batteries to supply the circuit with 4.5v. I found the size of the prototyping area on the board to be ample for simple projects. Please note that the kit comes in component form, shown in the picture below, and has to be assembled using a soldering iron and a little bit of time – it is not complicated.
Moving the timer to the PICAXE-08M from the PICAXE-20M prototype was relatively straight forward. The new circuit uses pins 0, 1 and 2 to power the “minute/seconds LEDs” while pin 3, which is an input pin only, is used to select the device’s function (eggs or teeth) and pin 4 is used to power the piezo buzzer. On the prototyping area I placed the resistors to drive the LEDs and a voltage regulator to power the circuit from a 9v battery. In our circuit pin 3 is also pulled down to 0v using a 10k resistor. Below is the code for the device.
Luckily, as mentioned previously, we had prepared to save space in the enclosure – which is good because the space available turned out to be even smaller than I thought. The wiring to the LEDs and switches added quite a bit of bulk and as a result the whole circuit plus battery only just squeezes in. The image below helps to illustrate just how much bulk the wiring added to the internals of the device.
After many hours of work, the device is now completed and we used it tonight to time the brushing of our teeth. Tomorrow morning, we’ll use it for the first time to time our soft boiled eggs ;-).