energy final : progress

by admin

The circuit for the final is almost done. It consists mainly of an Arduino Pro Mini 3.3V, the Real Time Clock from Sparkfun and the EasyDriver stepper controller. Connected to the Voltaic V15 battery, the driver can be powered by 5V and still provide the regulated voltage to feed the microcontroller. For the clock I had to use a 560Ω pull-up resistor from the 5V in order to not burn it (I saw some smoke when I had it connected without the resistor). I believe its internal resistance is set for low current sources such as the 5V from Arduino, so when I connected the 5V 1A from the battery it drew almost full current.

The deal now is to choose between having a code that will keep track of the time (in order to know the position of the stepper) or to make a really low-power system and rely on the battery. The first option can sound more appealing because of obvious reasons but, when thought through, it has some complications that might affect the power consumption and will make the code more difficult. If I choose to go down this path I’d have to keep the Arduino awake and writing information to some kind of memory (EEPROM or SD card) at all times. This is because, assuming the circuit could go out of energy at any time, I’d need to keep the memory updated with the most recent information. On the other hand, if I do the other way, I will have the Arduino in deep sleep, without anything going on, for intervals of 2 hours 44 minutes and 15 seconds, then it’d be on for half a second and go back to sleep again. Doing some rough calculations, I estimate that the battery would last approximately 150 hours without any sunlight, that’s almost a week without recharging, which is rather unlikely.

I still have to make some decisions, but that’s where I am right now.

Ps.: meanwhile I built the enclosure for the circuit. It will live on top of the paper.