EG's "Ventilator 3000", part 2

Here's some more components used to construct the automatic coldframe opener. This first item is called a coupling nut, and is threaded the whole way through. It's the cheapest, but most critical piece to the entire construction, and was ordered through my favorite store on the internet - McMaster Carr . Since the other coldframe might be  fixed the same way later - I went ahead and bought a couple of them for around $1 each.

Photo below - here's my little window air conditioner thermostat that was salvaged from an inoperable window unit, and has exactly the temperature control range that is needed for the coldframe on a sunny winter day. Because most junked out window units usually fail for reasons other than a broken thermostat, luckily they are in good supply. A person can usually get one from an appliance repair shop for free, if you remove it from the defective appliance yourself.

Photo below - here's an overhead view of the coupling nut sandwiched in between 2 pieces of flat steel. This provides a good connection between the drill and coldframe door, and effectively raises/lowers the window by running up and down the 5/16" all thread rod as the drill turns the allthread rod clockwise and counter - clockwise. As you can imagine, alot of thought went into this little homemade piece, and I changed my mind at least 6 times while trying to come up with the right one. It was definitely the most time consuming part of the overall design, and my brain hurts. Ouch! See? I thought about this little thing for days......

Photo below -  here's a pretty good picture of the micro switches in place. The lower one shuts off the power to the drill as soon as it reaches the completely closed position, and the top one is activated by the deck screw that is screwed into the window frame - which shuts it off when going open. They came from the website above, too , and were around $8 each. When activated by something pushing against the little lever on each, things can be turned on or off - based on which set of contacts is wired to a device.

Photo below - Here's the thermostat, which automatically tells the drill to open or close the window based on internal temperature. The sensing bulb of it enters the enclosed space through a hole drilled into the side of the coldframe. Since the temperature control range of it is somewhere between 50 and 90 degrees - it's perfect for controlling the ventilation system in a greenhouse, hoop cover, or coldframe. This thermostat was previously used to control the ventilation fans of the propagation chamber before the new system was implemented.

Lastly, here's a shot of the complete unit with the 2 little wheelchair batteries connected to the control system. They supply 24 volts to the relay, and also 12 volts to the drill. I won't go into the details of how this is done, because I feel it might be confusing. I'll also refrain from showing the electrical schematic that I designed for this system, because I wouldn't want to be liable for anyone else's shortcomings in working with electrical controls. Not everyone has the ability to understand industrial motor controls, or even relay ladder logic - so EG will be the only one with this information. I hope you understand.....

The final amount invested in this system is about $20, because most things were already on hand. Sometimes it's good to have lots of junk laying around. Hehe...Anyway, i'll show a video of it in action later this week, and hope you like it! Oh, it works.....and works very good...hehe. In the mean time, i'll keep an eye out for a 12 volt drill that is better than this one. This one is really noisy, because it's pretty worn out.....

Take care, and happy building!

EG