Hello everyone. I have a simple idea, but I don't know how easy it would be to pull off.
In one line, I want to take a water dispenser from a fridge and hook it up to a weight sensor so that if thirty minutes pass and the cup on the weight sensor is empty, more drinking water is dispensed to keep me hydrated. (with other safeguards to prevent spilling)
How easy would this be to implement? I was looking online and the cheapest fridge pump I could find was $100 and the cheapest solonoid was $20.
IDEA: Wow, now that I think about it, I don't even have to use a pump! I could just use gravity! This is how it's done in a fridge isn't it...arg.
I was wondering if you could point me in the right direction in terms of what sensors/solonoid valves to buy.
Solenoid valve wise you just need something that you can control with reasonably safe voltages around water (12V would be pretty standard) but the key is going to be how much water pressure you have to open the valve. Most solenoid valves I've come across are NC (Normally Closed) valves that require the pressure of the water to actually open the valve once the solenoid is activated - they usually come with the pressure they need to open them eg these ones from Seeed Studio: http://www.seeedstudio.com/depot/electric-solenoid-valve-p-636.html?cPath=156_160
In terms of sensor for the water the most obvious is a ball float sensor not dissimilar to what is used to recharge the water in a cistern in a toilet. That could tell you if the glass is empty or full and then you just have a timer to go alongside it.
How's that?
Cheers
ajfisher
That sounds great. I like that valve from seedstudio, though I hope it's suitable for drinking water.
And for the sensor, I think it would be a lot cooler if I did it with something that didn't float in the water since I'll be drinking from it, especially since I'd have to have some kind of electrical contact to the ball sensor. (but I can use it in the tank!) I was thinking about the force sensor here: Force Sensitive Resistor - Square - SEN-09376 - SparkFun Electronics
I could attach the valve to something like this: Buy Cool & Funny Gadget Gifts at Bargain Prices and permanently press the button so that the water would rush to the solonoid which would open once every half hour. I guess I could also use some kind of IR sensor to tell whether the cup is actually there or not. How does that sound?
All sounds good - if you don't want something in the cup then you could do something natty with say an ultrasonic range finder pinging off the surface of the water (not sure if this would actually work or not) so you could determine the level of the water, then either use a force sensor on a plate to determine if the cup is there or not (weight on v weight off) - you could pop it all into a little unit to conceal all the gory bits and end up with an auto filling dispenser unit.
Of course the alternative would be to get up every hour with a 500mL bottle and fill it up at the tap so you get the benefit of going for a walk and a stretch too but that's just me 
and truly where would be the geeky fun in that anyway!
Cheers
ajfisher