# How do you hack a store prop's motion sensor?



## Rascal (Sep 24, 2008)

I did some searches and found one helpful post, but it was old so I wanted to see if anyone has found a new solution.

Is there a way to hack the motion sensors typically found on the store bought props? I think I read that they are the PIR and that they respond to changes in light.

That in itself is helpful, but I'm wondering if there's a way I can bypass the motion sensor, or trick it to always be on)? I have two props that use these and it would be better if they just always stayed on.

Thanks and only 5 days left! :googly:


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## Scottzilla (Jun 13, 2007)

They're actually a CDS cell (resistance varies with light) rather than a PIR. 

You could try replacing the CDS cell with a fixed resistor, but I think the circuit requires changes in resistance to trigger it. Maybe if the resistance drops low enough it will just keep running. I haven't actually tried it, but it's a place to start. Perhaps I'll try it as I'm modding skulls later today.


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## Steve Filpansick (Sep 19, 2007)

Have you tried just bypassing the sensor?


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## Scottzilla (Jun 13, 2007)

Yep, just tried it. I tried shorting the wires together and disconnecting them completely. Neither one worked. I think the problem is that it looks for something to change. You could make a 555 circuit to continuously retrigger the circuit, but I'll bet theres an easier way yet.


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## Rascal (Sep 24, 2008)

Steve Filpansick said:


> Have you tried just bypassing the sensor?


That's what I was wondering but was afraid of damaging something instead. I am no wiring expert.

Thanks for looking into this guys.


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## Turbophanx (Jun 30, 2008)

I wanted to do this with my Gemmy JASON animated prop, but didnt want to hack a $200 prop.


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## Scottzilla (Jun 13, 2007)

But you HAVE to hack your props, no matter the cost. It's like the law or something.


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## Severin (Aug 5, 2007)

You try putting a small, battery powered, blinking LED in front of the sensor. It might trick the light sensor into activating constantly.


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## Rascal (Sep 24, 2008)

Severin said:


> You try putting a small, battery powered, blinking LED in front of the sensor. It might trick the light sensor into activating constantly.


That's a good idea, thanks.

It will work for one of my props as the sensor is on a long wire that I can bury in the chest. For the other one, I don't really have a place to hide a light as the head has moving parts inside. Hmm...


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## Dr Morbius (Sep 21, 2004)

Scottzilla said:


> But you HAVE to hack your props, no matter the cost. It's like the law or something.


LMAO!!! That is true. HAck or DIE!!


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## robp790 (Jan 8, 2008)

You know, two of my store bought props have a try me jack or demo jack built into them it is my goal to try building some sort of a parallax brand PIR circuit, with 5.5v battery pack, attach it to a 2.5mm or 3.5mm jack plug it in to the prop and get activation that way. It is my winters goal to solve this problem, as I was disappointed in the sensor that the prop comes with in near darkness.


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