I am working on a project for my aquarium. I am away from home at school most of the year, so I want a way to easily change some water in the tank without being around. Essentially, I want a solenoid valve to drain water out of the tank until the water drops below the level of a float switch, then have the valve close and a pump start until water level raises to another float switch. The switches are simple digital inputs, but the other two pieces are a bit more complicated. I was hoping you all could look at my schematics and make suggestions if possible.
Solenoid- I’m using a 12VDC, 150mA solenoid, so I have basically copied my schematic from http://www.arduino.cc/playground/uploads/Learning/solenoid_driver.pdf. The only question I have is the difference between a 1k and 2.2k resistor? Is there any difference? I chose 1k for now, because that is what I have.
Pump- The pump is a small 10W guy. I am however very uncertain how I want to control this.
i.)For starters, I’m not 100% if I should be choosing a SSR over electromechanical. I like the SSR, because they don’t require a transistor, but is there any other reason I should choose one over the other?
ii.) If I do go with an SSR, is the Panasonic AQG12105 (http://www.mouser.com/ProductDetail/Panasonic-Electric-Works/AQG12105/?qs=sGAEpiMZZMuYaq4aOfOV%2bDt0xZYR48dC) going to be okay? The 5VDC control voltage is good, and 1A and load voltage range is acceptable, but they do not list a control current. I know most SSR are in the range of 10mA, so can I assume this one is okay? I picked it mainly because of cost. Does anyone have any suggestions for alternative relays?
iii.) My setup with switch the relay maybe twice a week for a few years. Do I need to be concerned about failure? Worst case is it fails closed and the pump stays running flooding my floor. Is having two relays in series going crazy?
Outside these questions, I would love to hear some other feedback and suggestions.
Thanks in advance for you help and comments!
Water Change Schematics.pdf (187 KB)