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Discussion Starter #1
I want to replace the motion sensor on my 6' Jack-O-Lantern man (bought from Home Depot) with something that is more sensitive so that I don't have to be 6 inches away for it to trigger. I am puzzled because the existing sensor only has two wires so I am not sure what is happening electronically. New PIR sensors are all three-wire sensors. Can anybody explain how the existing switch works and recommend a sensitive, compatible replacement, or alternatively explain how I can adapt a PIR motion sensor to replace my two-wire sensor?
 

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Typically they're triggered either by sound or light. If it's a light trigger, I've put a spotlight across from the prop so that TOTs walking between the light and the prop will trigger it. If it's sound triggered, I've not found a good solution, since I have fairly loud background sound-effects.

Does your prop have a 'try me' button? If so, then simply swapping the switch for something that closes the circuit will trigger it.

You could use a trigger mat (that closes a switch when you walk on it) to trigger it. Alternatively, I've used an outdoor motion light fixture to replace the 'try-me' button. I've installed a screw-in outlet, then used a 110V relay that I've attached to a cord that plugs in to this outlet (WARNING: Don't try this if you're not comfortable working with 110V - safety precautions must be taken!). The relay contacts then replace the try-me switch. There are other ways, but electronics knowledge is required.
 

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I want to replace the motion sensor on my 6' Jack-O-Lantern man (bought from Home Depot) with something that is more sensitive so that I don't have to be 6 inches away for it to trigger. I am puzzled because the existing sensor only has two wires so I am not sure what is happening electronically. New PIR sensors are all three-wire sensors. Can anybody explain how the existing switch works and recommend a sensitive, compatible replacement, or alternatively explain how I can adapt a PIR motion sensor to replace my two-wire sensor?
The existing prop sensor you're referring to is not a PIR, it's a photo cell. It does not work on motion, it detects changes in light intensity. Hence rowlandharris's suggestion of using a spotlight on the sensor that someone will walk in front of. Unfortunately the "try me" button connection is usually not a good choice to trigger the prop due to a second "trigger" of the contacts will result in stopping the sequence before it's finished. There are tutorials here for using the cheap Harbor Freight driveway alarms to trigger these types of props.
 

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Good point about the re-triggering of the sensor, J-Man. I make use of the built-in timer switch of the motion sensor using the 'test' position, which keeps the circuit closed for about 15 seconds, thereby not re-triggering until that time has elapsed.
 

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Discussion Starter #5
Thanks for the explanation rowlandharris. Knowing this is a photocell explains a lot. I tested the sensor with a flashlight and it worked just as you said it would. I would like a wider trigger radius however so I need to go in a different direction. Let me throw an idea out and see if you or J-man have an easier solution or can shoot my idea down before I build it.

First I will remove the existing photocell and temporarily replace it with a 1 Meg potentiometer. I will lower the resistance until I trigger the prop, measure the resistance and replace the pot with a fixed resistor of that value.

Next I will replace the sensor with a PIR which has adjustable range and delay. I will connect the output of the PIR to a small solid-state relay. I will connect the normally open contacts of the relay in series with the new resistor in the trigger circuit of the prop. When the PIR detects motion the relay energizes and the prop is triggered.

Any reason why this won’t work? Is there a simpler way?
 

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Highly doubt that will work but you can try. Most props will trigger via the photo cell when there's a change in light intensity, up or down. If the prop is in a dark environment, light will trigger it, when the light is removed, it will trigger.
 

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Since it looks like you're comfortable with electronics, here's what I did for two of my props. I used a modular PIR that has two trigger modes, a sensitivity pot, and a timing pot, running off a 4 AA battery pack. The PIR runs off the 6V, but the output is about 3.5V, not enough to power a relay (I purchased some high impedance reed relays - about 600 ohms), so I made a simple 2N2222 transistor switch circuit to turn on the relay (with a reversed bias diode across it). The relay then triggers the 'try me' prop input. I put everything into a plastic conduit box with a power switch (on back - not visible in photo). The PIR fits nicely into the hole (facing the camera), and the other hole is for the sensor wire and a rod to stick into the ground to hold the sensor in place. The two small holes on the side (shown on top in photo) are for the pot adjustments. Hope this makes sense!

prop sensor.JPG
 

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Discussion Starter #10
As the expression goes, " great minds run in the same channels". I have already ordered parts (including the 4AA battery pack) to do exactly what you described except I had not decided on a housing yet. Love your idea to use the conduit box. In particular, one of my concerns was whether or not the PIR sensor, with a 100 degree field of view, was going to detect people too soon. By recessing the sensor back in the box, I suspect this likely narrows the detection angle to something more appropriate. Has that been your experience?
 

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The box provides a rain cover and reduces the angle. Here's what I bought from Home Depot:

conduit box.jpg

If you still need a narrower field, just add a pvc pipe or cardboard tube over it to restrict it even more. BTW - I used a square battery pack instead of a flat pack to fit into that housing. Hopefully, you ordered the square one. Good luck!
 

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Most animatronics on the market have a place on the controller to plug in a floor matt trigger (i.e STEP HERE) Our Seasonal Visions 6' Lunging Reaper has what looks like an 8mm aux or head phone jack. Ours has a 3 position switch to select the mode All the floor matts are doing are closing the circuit to trigger the prop. MOST are LOW VOLTAGE 5-12vdc so it's safe and easy to do the following: Buy a 10 foot aux cable, cut one end back and strip back the wires, plug the aux in to your animatronic, stand back and touch the two colored wires together MOMENTARILY. Your prop should come to life.

I attach sensors to an arduino and
then trigger our reaper using a 5vdc Relay.
 
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