Here in Hong Kong we have geckos. These are small lizard like creatures that can run up and down walls as well as doing the same in the azimuth plane.
They are quite useful creatures and will eat mosquitos and attack cockroaches so it's better not to kill them. But they are also lazy and if they can scavenge food in any form lying around the kitchen they will go for that before eating mosquitos.
There are one or two big ones – probably well fed - that haunt my kitchen and worst of all they leave crap behind which is a hygiene hazard.
For several years I have searched the Internet looking for gecko catching machines and to this day have never found one.
A year or two ago I made up an electro mechanical circuit which used an infrared beam to trigger a relay which then triggered a solenoid so that a trap door would close on a cage holding the trapped gecko. It was a Heath Robinson affair and after one night's use the 12 volt battery would run flat.
Just recently I contacted our resident genius (Ghurd) and enquired if he could offer any ideas to replace the relay part of the circuit, and, after triggering, kill the circuit to preserve battery power.
I am delighted to report that Ghurd came up with a P-Fet and N-Fet circuit that does exactly what is described in the foregoing paragraph.
Photographs of the machine are shown below and most readers should be able to observe how it works. The cork stopper at one end is where tempting food goes in on a small tray made out of tinfoil. At the other end is a trap door which the gecko has to walk through until it is around 80% into the tube to reach the food. Before the food is an infrared beam and if the gecko breaks this the door closes before the gecko has time to think of escape. When a gecko is captured it is taken to a country location some miles away for release.
To avoid magnetizing the reed switch contacts at the trapdoor end, the door can be removed from the slide and turned 180 degrees and re-inserted into the slide when not in use. This distance should avoid magnetization.
The circuit design is credited to Ghurd.
The next job is to try catching geckos.
The only thing I do not have an answer for is whether or not geckos can see infrared light.
The system can be modified for all sorts of other uses.
David in HK
