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by **Frank_Cox** » December 7th, 2011, 1:41 pm

Interesting approach on the electromagnet. what exactly do you have in mind? are you thinking of using a solenoid type valve or something else? a ball valve would also work well
I would actually use a ball valve with an actator on it instead of a selanoid type valve since the selanoid valve has a very smoall port in it that closes with a needle. a ball valve with an actuator will have an full port in it. also the actuator can be driven by a controller to open and close part of the way instead of full open or full closed

by **brkemp** » December 7th, 2011, 3:33 pm

I was originally thinking about using a small actuator but I don't know too much about electronics so I was trying to keep it simple. I wanted to use the power that is sent to the fan and it seemed like an actuator would need something to tell it to open and close. I ended up getting an electromagnet ( magnet with 2 leads coming out). It is 12v dc .33 amps and has 25 lbs of pulling force. I believe my fan also pulls .33 amps so I figure it should work because digiq supplies 2 amps.
I have a simple plan that will hopefully work. I'll have to post pics cuz I'm not using the BBQ guru fan, I made my own. I basically wanted to build the drafts door inside a 3x3 square tube only 3-4 inches long. It will simply have a hinged door hanging from the top with extra weight at the bottom. The magnet will be mounted on the top of the tubing and wired Into the fan. This way when the fan has power it will also power the magnet pulling the door up out of the way ( the air will also aid in blowing the door up out of the way). Once the fan is off the fan will swing down in place preventing the draft.
The only possible problem I see is that because the fan "pulses" it may affect the performance of the magnet. I think that the pull strength of the magnet (25 lbs) should be no problem for the very light door and the airflow will keep it up. Let me know what you guys think

by **Rick** » December 7th, 2011, 6:07 pm

How about just let gravity do it? (i.e. multiple top-hinged doors like a dryer outlet on the side of a house)- skip the actuator. Digi has addressed this on their fan with a hand-closable gate on the outlet so you can meter it at the fan end. ... at least that's my hunch...

by **brkemp** » December 8th, 2011, 5:19 pm

The problem with the draft door on the BBQ guru fan is that it is still manual... I wouldn't be able to just "set it and forget it". You still have I watch the temp and if it over shoots close it off and watch it until its back down to open it back up. Also with hinged doors if the draft is strong enough it will lift the door enough to get the air in. I was just trying to have it completely automatic