Intro: Catproof Remote Control
So, You get home from work and decide to relax by watching your favorite detective show. You plop onto the couch, turn on the TV and set the remote down next to you. It's an OK episode. Near the end, just as the detective is about to reveal the killer, your cat decides he wants some petting. He jumps up to the couch and his paw lands right on the channel button of the remote. Instead of finding out whether the killer was the ex-stripper trophy wife or the business partner with the drinking problem, there is a fat guy yelling at you that you can get three extra bottles of Super-Duper Scrubber-Upper if you order now for just $39.95.
You pay the cable bill. You should decide what's on.
Fortunately, cats don't have thumbs, so it isn't that hard to make a cat resistant remote.
I wanted one that didn't require any extra attention or effort on my part, so it had to be enabled just by picking it up. When I first thought of this, It seemed much harder than it turned out to be.
Fist, I thought of putting power switches on each side of the remote. I had to reject this because a lot of remotes keep their programming in volatile memory.
Second I thought of putting an enabling switch on the side so that the keys couldn't be activated with just a paw on top. This was unworkable because the keys are on a matrix instead of each key being a separate input to the chip.
I gave up on the idea for a while and then suddenly it occurred to me "Duh! All you need to do is prevent the LED(s) form emitting. You're such a dope!"
What you are basically going to be doing is using a switch to open the current path through the LED(s) when the remote isn't being held by a human.
Materals cost: about 50 cents if you don't have a good scrounge box, nothing if you do.
Step 1: Gather Materials
Pretty much all you need are:
Basic electronics (really basic).
Tools and materials
A micro-switch (preferably a normally closed but it is much easier to find an SPDT).
Basic soldering stuff.
A little bit of wire.
Some small screwdrivers.
A utility knife.
Step 2: Determine Physical Switch Placement.
The first thing you need to consider is where to put the switch. This depends upon how you hold it and how you put it down. This decision will be somewhat constrained by the placement of the components and voids in the case. For me it was on the bottom of the remote near the nose.
Step 3: Open It.
This is never as easy as it should be.
Remove the batteries.
You have to find screws (if any) that are frequently hidden. Check in the battery compartment, under any stickers and feet.
If you are lucky it will easily open after removing the screws. This is not likely. You'll, probably, have to pry it open. Use a couple of small screw drivers and take your time.
Step 4: Determine Electronic Switch Placement.
Next you need to figure out is the current path through the LED(s). If it is the single LED type, no problem. If there are two you need to figure out if they are in series or parallel. Once you have that figured out you can decide where in the circuit it is best to put the switch. I've indicated with blue dots on the schematics where it could be done for the various configurations. In my case it was the middle dot on the middle schematic.
Step 5: Solder in the Switch
Put the switch in the circuit using the wire if needed. In my case I just cut the leads from the board and soldered some wire to them.
Step 6: Mount the Switch
Use the utility knife to cut a hole in the case to put the switch.
Use the hot glue to secure the switch in place. One thing about hot glue, it doesn't stick to anything, but it is good for squirting in a mechanical/friction fitting. Note the huge globs.
Step 7: Finish.
Close it up, replace the batteries and you're done.
Once again, some regular schlub has to fix what the professional industrial designers failed to design correctly in the first place.