Hi all, bit of an amateur looking for some advice. Have done quite a bit of web searching but want to validate my proposed design. The project is a little garden watering system controlled by the raspberry pi. The solenoids will have a light load, probably switched on for 20-30 minutes maximum once every 3 days or so. We can skip all the logic and get to the electronics question - how to use the I/O from the pi to control the water valve solenoid. I found a basic circuit design here http://davidhunt.ie/?p=2770 Since ultimately I will want to control 4-5 solenoids (for watering various areas), I then found a darlington array on an IC that seems to make sense. It looks like it has the diode protection already built into the chip. It looks like it can handle 500mA per output http://www.ti.com/lit/ds/symlink/uln2003a.pdf Just want to check that all these parts will come together. The solenoids are 12V and pull around 320mA http://www.adafruit.com/products/997?gclid=CIW3k9qcwLUCFUWd4AodBl8Alg The pi IO control is 3.3V and can put out 16mA per pin to a total of 51mA. I'll put a separate 12V DC feed to the uln2003a. Questions: - Is the 3.3V from the pi enough to drive the chip? - Can I run several solenoids simultaneously, or will that be too much for the chip? I can run them sequentially if necessary. - I was reading that these solenoids have a large load to initially lift them, then a lower load to keep them lifted. Is there any sense to integrating some kind of capacitor(s) into the circuit, or is it overkill? - If for some reason the chip will not work, can you suggest the components for each individual circuit? I was thinking http://www.adafruit.com/products/976 http://www.adafruit.com/products/755 but don't know what resistor to use. Thanks for any advice, and please go a bit easy on me if my terminology is not too perfect.