Building The Ultimate Cat Trap- Behind the Scenes of “How to Stop Cats Forever”

There was a lot of  tech “stuff” going on in my cat deterrent video “How to Stop Cats Forever”,  which is only skimmed over in places  -I didn’t want the video to drag out for too long  plus it was meant to be more of a parody, fun instructional video.

However i do get a lot of questions about various tech aspects of how the set up worked. So if you are a little more tech minded and craving a little more detail, I have prepared this post for you!

However I may still skim over some  stuff…but with extra pictures! Everyone loves pictures? – A complete written instruction set is still to come (for the Water Spray version)

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It’s all fun and games until someone has to clean up the mess.

Each time the “Extreme party popper” was activated it took about an hour to clean up and reset it. The flour was the biggest pain but it looked awesome, so I had to go with it. Overall I only had about 3 false activations which is pretty good considering IR motion sensors are pretty “trigger happy” in a garden setting.

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Packing the 4 “shells”: Newspaper wadding + Streamers + Flour + confetti + cling wrap

The streamers had to be individually rolled as They are too big straight from the packet.

When rain was expected each of the pipes had to be covered in cling wrap with a rubber band – because flour + water = blergggg.

Also what I found interesting if one of the pipes wasn’t packed as tightly as the others, when it would fire It would actually inhale the streamers, I guess due to the slight Venturi effect in the sections of pipe at 90 degrees.

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Cameras ready & overlooking the setup

A lot of people  have commented “Weren’t you worried that someone would steal the cameras”.  It’s not seen in the video but the actual setup had all of the cameras inside looking out through a glass sliding door.  If anything it was mainly just to protect them from the weather.

Wires “stabbed” into position for the shutter release – You don’t even want to ask how I powered these up to run all night without a battery

I didn’t actually have the right plug connector for the shutter release to plug into the Canon DSLRs on hand.  So I managed to work out which two pins where the actual shutter and basically just slipped the wire over the individual pins – Perhaps you  shouldn’t try this at home 🙂 I had to carefully work out the exact Focus Point and exposure for both cameras. This was set up for a night exposure which is why the dove images are a bit over exposed.

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Hydrostatic pressure testing  to make sure the tank isn’t going to explode – That’s how much confidence I have in my welds .

The air tank which was pretty much made from scratch (as seen in the video) I figured just to be safe should be pressure tested (Probably overkill though).

I used a method that is common in industry for such things which is done by filling the vessel with water and then applying pressure to about 150% of the pressure you plan to operate it at normally.

This is called a hydrostatic pressure test.  It’s handy as if it does fail it’s not as Catastrophic as if it is full of air.

I guess the simplest way to explain this would be to imagine pressurising air being like compressing a big long spring, then imagine compressing water to be like compressing a really short hard spring. Even though you are using the same amount of pressure to squash them both down  when the pressure is released the big long spring is going to travel a lot further to get back to it’s original length.

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Testing – Applying 150% of the planned operating pressure and monitoring it remotely. Hey I don’t want to get a face full of Thomas the Tank shrapnel.
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Yep I even did the testing in a concrete well liner. Better safe than explody.


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First tests in my dads workshop with just newspaper. Note- my dads crazy inventions also visible. (Right) -Cray pot tipper with car starter motor winch. Also (Left) – Speed record attempt fixed wing land yacht.


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I wonder what the mechanic & his customers next door thought when they found their cars covered in flour Monday morning…opps

The first tests with flour and only a couple of streamers worked a treat. Without a roof overhead they actually go really high! Higher than what I wanted in the home camera set up as they would have just disappeared from shot.

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A full lighting test.

I was always a bit disappointing with the lighting in my original “How to stop cats pissing on your car” video, so I went all out on this one. The more light the better for a using a high shutter speed! Also a light behind the cats as a “rim light” to laminate the flour.

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Lots of people have asked – Yep, I did actually test this on my sister 🙂


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There is literally hundreds of photos of me just testing the spray each night. Each time it is set off it takes about 10 to 15 photos on each of the cameras. I should really do a Timelapse just of these shots.


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The mess of wires linking everything together. Hmm, things really did seem to escalate after my first video.
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Here you can see both the positioning of the stills cameras and the video camera on the right. There is also a few small infrared spotlights just for the video camera.
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The “extreme party popper” loaded and ready to go with rain covers (cling wrap) on each of the pipes



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The timer module for the stills cameras and relays housed in a plastic box.


Now this wasn’t covered in the video but I actually used a separate timing relay kit for the DSLR cameras.  This was to allow them to keep taking additional photos after the water spray had stopped, this to capture the glorious aftermath.

Also visible in the above image is the separate relays for the popper’s reticulation solenoid,  the240 volt AC lighting trigger and the actual hose spray.

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The relay setup to trigger the lighting actually worked out really well- better that I expected. This would actually be useful for a whole bunch of different projects.

Although in the video I showed that I used a bore water pump relay , I ended up supplementing this with a new, solid state one from the shops. Partly because I still needed my sprinklers to work, but also because the solid state relay has no moving parts and is that  little bit quicker to trigger the lights for that all important first photo.

I found that unfortunately the fleeting half second that the lights took to glow to their full brightness, was too long and the first photo taken would often be underexposed.

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The strings on party poppers were pretty crappy in the end and and seemed to fail a lot as seen in the video.

I may have been able to persevered and combined this with the final setup however I realised it probably isn’t a good idea to have an ignition source (the party poppers),  firing next to a huge flammable dust cloud of flour. It could have been a pretty big Fireball, yeah it would have been a funny fireball,  but  still a fireball- Right next to my house.


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Other applications for the cat spray I have found include child / TV deterring.

When my 3 year old son decided he would start a habit of standing really close to the TV and hitting the screen when watching it,  I found that I could use part of the cat spray setup… minus the “spray” part.

Utilising the motion sensor connected to a small 12 volt air compressor, This would make a noise for a couple of seconds when he was too close, it seemed worked a treat.

Yeah I could have tried “parenting” or “discipline” or whatever New age witchcraft is in fashion at the moment,  but I don’t really care for doing things that don’t involve wires and electricity and stuff.


Kristen’s parent’s being a good sport helping with filming one of the “cut-away” scenes.


So that is it for now. I will probably add to this post in the future as I stumble on more photos, but I hope this gives some interesting insight for now.

If you do have any questions about the setup feel free to leave a comment below!

The video:

Part 1

Part 2


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