First of all you need to find a motion sensor - of any sort , that either sends a signal or makes a noise .
The infra red ones seem to work best , the ones with a small hole in them are not so good in bright light - Be careful that you don't buy one with a ''dummy'' infra red screen on the front only to open it and find it is the cheap version with a small hole next to it [ ask me how I know :( ] .
I bought this "passive infra red detector" which is designed to work with an alarm system as a remote in a different room .
A door sensor with a chime will do just as well and it should be easy enough to follow the wires to the chime so you know where to pick up a power supply from .
Now you open it up and throw away your receipt because there goes the warranty ..... I saw the "S + - " and decided that must be the "Switch" output and possibly that little chunk of components is the wireless transmitter to the alarm system .
This is the business end of the wireless output of the motion remote .... apparently .
I tested that "S" wire and when the battery was connected , every time there was movement the red LED came on and I received a 9 volt feed there . I decided that it must be the output wire and so I un-soldered the three terminals , threw it away , and did something very simple ....
I took an earth feed from that "-" sign and since my positive output was 9 volts I fitted a 6 volt "zener" or 'avalanche' diode inline .
You must have the dark 'blocking' side of the diode pointing at the positive feed because if it is the other way you will get almost full voltage going to your remote which will fry it .
Now the remote : They all seem to work with 3 volt batteries so I selected a universal remote [ makes sense ] that will work with any camera ..... el-cheapo $16 ....
And the easiest way to get into the battery contacts was to grind the back away . [ If you are a perfectionist you could make a 'dummy battery' with insulated surfaces and solder some wires to it so you don't have to destroy the remote ] . You can see the "B+" and " B-" inside the body of the remote .
As you grind the plastic wipe the lumps of molten plastic away from the sides and try to maintain your composure when the molten plastic does a 'flash meld' with your skin and your workmates are watching .
Now solder the positive feed to "B+" and the negative feed to "B-" [duh ] ........
Then slide a piece of paper between the contacts - apparently if a zener diode pops it has a dead short across it rather than going open circuit = fried remote .
These are the zener diodes I bought - I wasn't sure so I bought a selection of voltages .... 600 for $30 = 5c each . In the local electronics store they are 38c each depending on how many you plan on using of course !
I don't know how strong they need to be , 500mw [ half a watt ] has worked for me so far but I don't know if it will be better to get stronger diodes . Maybe an electronics geek can step in and offer some advice - I'm only an auto electrician !
But anyway , my little two way radio is only two watts so maybe this is strong enough .
Since I removed the wireless transmitter from the motion sensor I don't see much problem with the motion sensor not being strong enough - it's probably doing less work than before .
It is really this simple : [ for how long though ? ]
I then took the soldering iron and made an 'exit' for the wires so I could close the box again .... one way to stink up the house !
And the finished product ! The crazy thing is that the $9 module comes with a free $10 battery ?
Now we go outside with it to try it out . I will find a better clamp to hold down the button for "Nikon" but this did the job for now .
Set the sensor and remote up , camera on tripod , I set manual focus this time because I was working with one second pulses , and then moved around in front of the sensor ....
The principle ?
When the sensor detects motion it supplies a 9 volt feed to the "S" contact which used to trigger the wireless signal to the alarm [ could be a speaker in a door chime as well ] , that 9 volt feed goes through the 6 volt zener diode which 'wastes' 6 volts and lets through 3 volts to the remote . Since the remote button is being held down it is ready to fire as soon as the battery supply gets a feed .
The motion sensor I bought has an added advantage in that it has a 'test mode ' . If the battery cover is off it sends a one second pulse each time it detects motion which is why I had my camera on manual focus for these tests . When you fit the battery cover a switch is held down which de-activates the sensor for 60 seconds and then after that each time it detects motion it sends a signal for 55 seconds which would give the possibility of having your camera in auto-focus mode and 5 frames per second [ or whatever your camera can do ] and let it focus and fire away when a subject enters the frame . [ I'm thinking wildlife photography here ] .
BUT : I haven't tested the system at 55 second triggering times , I don't know how much this zener diode can handle - time will tell . There is the option of simply using the power supply to switch a solid state relay interrupting the remote battery supply but that would just about double the costs :) .
For now the one second trigger times will do the job for me , there's a hawk living in the trees nearby , now all I need is one of those possums on the side of the road .........
As mentioned these plans are free to use , I tried setting up 'asdsense' to let advertising sponsor my research but it is taking a long time to happen so there is a donate button at the bottom if you feel that way inclined . Any proceeds will go toward replacing the gear I have destroyed so far and buying more things to hack into for photography [ as with my sound activated flash trigger ]
I see other possibilities as well . There are "driveway alarms" that consist of two units , one in the house and one outside giving the possibility of having your sensor in one place and your camera quite far way in another place triggered by that remote sensor . Perhaps the remote sensor by the finish line of a race with a 'snoot' to direct the pickup as to exactly where you want your subject to be when it fires the camera - you would have to calculate the time delay as well since it isn't instant .
I also see possibilities for weddings where "clicking" and "flash" aren't allowed - a compact in 'museum mode' tucked away somewhere .
These things would cost a lot of time and money to manufacture especially but they're sitting on the shelves for $9 waiting to be modified ! Just be careful what modifications you make :) my old remote didn't like 9 volts !