1ea Motor Power Battery:



This typically is the battery that came with the cordless screwdriver. One should obtain a cordless screwdriver that also comes with a 120 vac-input (plug-in) charger for the battery.



The battery charger should not be powered up and connected to the battery when the door is operated. This can cause some chargers to shut down and not recover (unless the charger power input is cycled).



A straightforward (if crude) solution is to leave the charger connected but operate it from a timer. The timer is set so that the charger is not "on" when the motor runs. A more sophisticated design (not shown) is to have an additional relay (or additional contacts on relay K1) to disconnect the input to the charger when K1 is energized.





2ea Relay, DPST (Double-Pole, Single-Throw) (K2, K3):



Note that all relays (in the schematic) are shown in the "Normally Open" or unpowered position. The dashed lines show mechanical linkages.



The contacts on K2 and K3 must be capable of handling an inductive load (the motor). As a very rough rule-of-thumb, is they are at least 3/16 in. dia. they should be adequate for small to medium-size cordless screwdriver motors.



1ea Relay, SPDT (Single-Pole Double-Throw) (K1):



K1 must have a 120 vac coil, since it is shown used with a 120 vac timer. The contacts are not critical (unless K2 and K3 are very large relays!).



2ea Microswitch, SPST normally closed (SW1, SW2):



The switches should be rated for at least the K2, K3 coil voltage and current. The best type is spring-blade actuated. The spring blade provides enough flexibility to make adjustment easy.



1ea Fuseholder (F1):



Rated for 120 vac operation. a one amp fuse should do it unless you're using a very large relay for K1.



1ea Fuseholder (F2):



Fuseholder rated for K2, K3 relay coil voltage and current. Fuse size: One amp should be adequate unless K2, K3 are very large relays.



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That's the BOM for the major electrical parts. Don't skip the fusing! Fuses are important to protect the wiring and to prevent fires.



One other very important part. Probably the most important part: One sees many Chicken House (CH) automatic doors made from a piece of wood sliding in slots. This type of design is prone to fail due to wear and moisture (humidity). High humidity can cause the parts to swell and stick. An alternative design that I have implemented is to use a pair of heavy-duty drawer slides (such as the type found on file cabinet drawers). (Light-duty drawer slides will not function in a vertical position.) I'll try and post a picture of the slide that I've used.