We have one of those cheap drop spiders that drop down when you clap right over our door and would really like to be able to trigger it remotely. Is there a specific sound or device that would allow you to do that?
You can do it to any prop you just bypass the motion sensor and add it to a wireless trigger. You have to use a multimeter to find which wires set off the motion then bypass them to a remote relay. Usually these are poorly labeled so you have to probe around. If you have a battery operated prop you can also hard wire an adjustable voltage adjuster to give it the correct voltage. You need to solder two leads from the battery pack and add one.
Or
If you know for sure there is motion or sound in front of the prop at that exact moment you hit the wireless relay button you could just add a relay to the battery pack/power adapter and when powered on it will activate. This is the simple way.
Some of the sound activated props are not as easy to mod as the light (shadow) activated ones. I have been meaning to look into what's required to reliably trigger them.
My idea right now is a mini bluetooth speaker behind it triggered by a sound from an ipad. These spiders are pretty cheap and I'm not sure I could even find the sound sensor its using. The question I have now is what sound to use to trigger it.
Can't say if this will work for every sound activated prop but it has worked for me in the past. Remove the sound pick-up mic and connect the leads to the NC terminals of the remote relay. Use a 10K resistor on one of the leads. This creates a normally closed circuit with the 10K resistor taking the place of the mic. When that loop is opened (by momentarily energizing the remote) the prop should trigger.