I've long toyed with the idea of installing automatic pophole controllers and I was wondering if Santa might slip one into my Christmas sock. Unfortunately this looks unlikely as with four houses to cater for, the cost of the commercially available units is prohibitive. However as I'm an electronics engineer by profession and worked in the control and computer industry for most of my working life I reckon if anyone can design and make one I ought to be able to. I've looked at photos of the Gizmo type and I reckon its not that sophisticated that almost anyone with a basic understanding of electronics can't produce one. Sourcing the parts looks to be the biggest issue.
I've a question however for anyone who has one and has looked at how they work in a bit more detail. How is the door held open once it has reached it's fully open travel? I assume that the motor drive is switched off by a reed switch operated magnetically, but is the motor braked or is there enough resistance through the gearbox to prevent the weight of the door falling and winding the unpowered motor in the reverse direction through the gearbox? If the resistance through the gearbox is enough to hold the door open it makes the design a whole lot easier than if a solenoid latch needs to be used to hold the door open.
I know there's been discussions on this topic previously and the ingenious use of a car aerial raise and lower drive has been used, rather than a DC motor and string arrangment, but I guess this requires a good deal of vertical travel space which might be available for a shed type of house but is not so convenient for an ark type of house.
Any suggestions or comments greatly appreciated.
HF