John L Errington MSc

Experiments with an Arduino microcontroller


These pages detail the progress of my experiments with the Arduino microcontroller, aimed at the following projects:

1: the simplest, a recording voltmeter for testing for faults on computer power supplies.

2: a device to turn on a mains powered electric heater when there is bright sunshine (to take advantage of electricity from my 3.6kW solar panel array; and shows an approach that could be adapted to controlling most mains-powered devices.

3: experiments with speed control of a motor.

The first project requires a volmeter that will take accurate readings of voltage from the computer power supply connector, and store them onto an SD card.

The plan is that readings will start when a "go" button is pressed. This allows the psu time to settle.
All the psu voltage outputs ( +3.3, +5, +12, -12)will be monitored.
Initially readings will be taken and recorded to the card at short intervals (perhaps 0.1 sec). (file 1)
If they are within spec a set of green LEDs will be illuminated.
If they remain steady for 1 minute a new set of readings will be started, now at 1 minute intervals. (file 2)
Should any reading deviate from the average value by more than a pre-defined amount, or go out of spec, a red LED will be lit.

This device will allow soak testing of computer psu's and show faults without looking at the stored data - however this will be available if required to investigate any faults.

The second project will use a light sensor (photoresistor or small solar panel) to determine the amount of sunlight present. If this is sufficient an optoisolated Solid State Relay will be energized to switch on the heater. Issues here concern preventing excessive switching, and ensuring the whole system is safe.

A third project examines DC motors commonly used in instrumentation, control and robotics, and provides circuit diagrams and examples of ways the Arduino microcontroller can be used to control them.