My first chicken gate worked, but I forgot to check the power draw – not very clever when you rely on batteries. After the battery went flat I measured the idle current at 65 mA. That’s a whopping 1560 mA hours over a single day giving me 20 days usage from 2 x 6V lantern batteries.
After rebuilding a new board I reduced the current to 9mA which means my batteries last 7 times as long. Here’s the bits I changed shown on the diagram:
- Buck mode power supply $1.65 – this used 6mA when idle and 9mA when also powering the 5V microchip. A huge drop from the original 22mA.
- Relay – this double pole relay physically disconnects both the 12V and the 5V from the motor driver board. Reducing 30mA to zero. A couple of FETs would also work but wouldn’t have a physical disconnection.
- Motor Driver $2.65 – cheaper than buying the components and much faster than rebuilding myself. Plenty of grunt for the 300mA that the motor uses.
- Capacitors – on the back of this board (where you can’t see it) is a small ceramic 100nF capacitor directly between the GND and +5V of the chip. This is a bypass capacitor(essential) which smooths power fluctuations and stopped the uChip rebooting that was occurring when I activated the relay. The large chunky capacitors on the front further assist the power smoothing.
- AXE029 – a genius component from Picaxe that lets you put header pins on your board and plug in the AXE029 for easy (really easy) programming and debugging.
If I had my time again I’d choose a 5V or even 6V gear motor to operate with this board. The closer voltage would mean easier power control and less wastage converting voltages.
All Hail Picaxe
Again my experience with Picaxe was flawless. The guys on the forum were more than helpful and very patient (thanks people). The documentation is accurate and helpful. The programming and debugging is the best I’ve seen. I work with a few development environments and this is by far the easiest and the most fun.