The control system for the greenhouse door opener

Fist of all, i'd like to say "thanks" to all the people that threw their broken appliances away for me to pick up! Most of the parts for this control system came from just that - broken appliances....Oh, they're jam-packed with all kinds of electrical goodies....yeehaw!
This automatic ventilation system is constructed with salvaged components from a broken printer, personal computer, 2 microwave ovens, and of course a window air conditioner - and I hope you like it!

Since the greenhouse will be located in the garden, wheelchair batteries will be used to power everything, and the voltages used will be 24 volts dc (for both relays), 12 volts dc (for the little fan in the top), and of course 5 volts dc (for the little motor on the door opener). To get the most capacity for the system, i'm using 4 batteries - which means the automatic coldframe opener will have to do without this winter (unless I can come across a couple more batteries).
I made an electrical drawing of the control system with autocad the other night while the wife watched tv (EG thinks tv is a complete waste of time), and I fully understand that most people don't comprehend it - but, for those of you that do, I hope you like this EG original control design. This only shows 2 batteries for the power supply....

Now, i'd like to show you some photos of the actual system. In this first picture, you can see the limit switch that shuts off the power to the little motor as the door is closing. It was salvaged from a microwave oven, and only has "normally closed" contacts.

Photo below - here's the limit switch that shuts off power to the motor when the door is cracked open to a pre-determined amount. This switch is the same as the previous one - but was quite tricky to actuate. The small white gear was fastened to the shaft of the door opener drive with super glue, then the homemade arm was attached to it with tiny screws. Those little screws were really hard for these big fingers to hold!

Photo below - The thermostat.....It came from a defective window air conditioner, and was mounted in one of the back corners of the greenhouse. Its' contacts make on temperature rise, and the range of adjustment is perfect for this application. I'll eventually set it to ventilate the greenhouse when the temperature inside rises to around  70 - 80 degrees. (which should only be necessary on sunny days)

Photo below - This blue relay is the one that reverses the polarity of the voltage going to the little door opener motor, and the tiny black one is the one that turns on the ventilation fan mounted in the top of the greenhouse. Switching the polarity of voltage to the little motor reverses its' rotational movement - thus opens and closes the door.....

Photo below - The voltage divider.....using 2 small resistors, this little homemade circuit takes 12 volts dc and reduces it to 5 volts dc @ 200 milliamps of current. The aluminum piece that they are mounted to is for dissipating the heat created from the opposition of current flow that the resistors provide. With the right values of resistors installed, a person can convert a dc voltage into any lower voltage they want (and also the current capacity, too).

I'll try it out this weekend and see how it performs - although I expect to maybe have a problem with at least one of the little limit switches. There will surely be a bug or two to get worked out, but it shouldn't be a big deal. After it is working, i'll shoot a video of it in action, of course...
My main focus for Saturday will be on the squirrel trap - as it has got to be completed very soon. Anyway, it should be an exciting weekend for working outside and watching my Auburn Tigers in the afternoon, and I hope the shoulder doesn't give too much problems...

Take care, and happy gardening/tinkering!

EG