bugs said:
I had one of the aqua-medic ones and returned it coz it got just as hot as the normal one...
I must admit I don't understand how a pulse operated solenoid can be integrated into a system which maintains the load and holds the device at an "energised" state without pulling current. The only way I can think that it works is that it energises the coil, pulls in the solenoid, senses that this has been done and uses some clever electronics to resist the spring pulling the valve back into the normally closed position. I wouldn't call this a pulse operated valve myself, more like an energy efficient solenoid valve!!
But.. having looked at another way of doing this the only option is to utilise an electromechanical approach. Using another type of solenoid or small stepper motor (e.g. servo from RC vehicle) to act on a mechanical pneumatic valve. The drawbacks to doing this are:- A - The valve does not have a failsafe for problems such as supply failure or controller problems, if anything goes wrong it will keep piling the CO2 into the planted environment. B - electromechanical combinations are never reliable if made on a budget. Which brings us to C - it is very expensive to make this type of setup from scratch using new parts. :?
From what I can see it is far more prudent to stick with the existing technology. Incidentally I have recently seen the "Aqua-Medic Shut-Off CO2 Pulse Valve" for £58, which (if it works as well as they say it does) will pay for itself in approx. 4 years. What should be taken into account is (again if the manufacturers claims are correct) that the running cost is a third of the standard solenoid. From my calculations (and they are as rough as the proverbial dog's bottom) the cost of the pulsed solenoid is £5 per year, versus the standard which comes in at around £15. Dont let these figures startle you too much - they are assuming eights hours daily dosing with CO2 i.e. valves on permanently during day and all the calculations have been averaged up.
Right, now that's all sorted I'm off to sell some crap on ebay to pay for one of those "pulse" solenoids. Caveat Emptor and all that!
