I am looking for a PIR sensor that will provide a 12 volt output to trigger a CCTV camera to start recording and I dont want to use a PIR that needs a 12 volt supply from batteries.
As far as I can see, most PIRs are 240 volt (in and out) and I want I want to use an existing PIR that currently turns on a couple of lights - hence the idea of using a relay between the PIR and the camera.
Is such a thing possible?
sure. 240vAC relays are common enough.
I'm sure it is possible but can you explain more fully what you have now. CCTV cameras do not generally record themselves there is a separate recording device.
Would simply powering the camera on when the PIR sees motion achieve what you want? If so why can't you use the switched output of a mains PIR to power the camera's PSU? (use a PIR that can switch an inductive load. Generally the kind that click)
You have mains.. use a 12v PSU. You probably want 12V for the CCTV anyway. Then you can use a 12V PIR, a 12V camera and no extra relay. The 12V pir is probably cheaper than a mains relay in a proper box.
A diy option is to take the PIR apart, they nearly all have a relay in them (probably 12V as it happens).. disconnect the mains input by removing the appropriate track to the relay and you can switch your 12V . you need a fair bit of clearance between the mains on the circuit board and 12V side to be safe.
If you wire the coil of a 240v relay in parallel with the lights, you can switch what you like with it - subject to its current capacity. The contacts are separate from the coil, so you can use them to switch 12v. You will, of course, need a 12v supply for the *camera* but not for the PIR. Not sure whether that's what you want!
My existing cameras are all POE powered network units. The internal ones are triggered by inbuilt PIRs or by motion in the cameras own adjustable motion (optical) windows.
The problem is with one external camera which suffers from an excess false motion triggers. This happens because there is a street light just outside the property and adjacent to this is a large tree on the pavement which overhangs the property.
The result is that whenever there is any wind there is movement in the branches and hence difference in light due to shadows on the ground and the building itself moving. Other false triggering is caused by car headlights - especially when drivers do u-turns after they find they took the wrong turn at the nearby traffic lights.
The cameras can be set to start recording if they receive a 12 volt input trigger - presumably from an external PIR.
At present I have an external PIR that is run at 240v and this switches on two halogen lights directly.
At present the one on the front is a Vivotek IP8332 and I am considering a FD8134V with a PIR looking out across the front yard.
Powering the camera on just when needed is a big problem - in terms of start up time. The cameras have their own memory cache and so are able to store and later record ( to the server) activity that takes place up to 10 seconds before the trigger happens. The camera gets its power ( low voltage) over Cat5 network cable from a POE switch.
VT
I guess I should have said that the PIRs are all external. Certainly all of mine are running on 240 volts. They are made by Steinel - model IS 1.
VT
Roger,
Sounds good.
As I my electrical knowledge is fairly modest, is there some guidance you might suggest regarding choice of relay eg something out of the Farnell catalogue?
Thanks
VT
As it's a signal (low current) feed to the recorder a relay with gold plated contacts would be a good idea eg:
Intended for a plug-in base (this one screw terminals):
or solder or use mini spade connections but beware of risk from mains connected spades falling/being pulled off. Insulate with heatshrink sleeving.
Clip avail to hold relay on base (I think this is the right one):
If you order today before midnight you get free post for orders over a tenner, follow instructions on main page of site, note that postage appears on screen but is deducted after the event, before your card is charged (crap but it works).
I'd suggest mounting the relay close to the mains wiring and run a low voltage cable to the recorder over alarm/security cable. CPC have cheap IP (outdoor) rated boxes if you need a separate housing.
This all assumes that the recorder records for all the time the 12V control signal is applied and stops when it is removed. This wouldn't work for a start pulse and stop pulse recorder (like a standard domestic recorder).
Fred,
Thanks for helping out. Based on what Geo says below are you in a position to home in on a final selection for the relay. I dont know the relative merits of each so your asistance would be much appreciated.
Quote from Geo
""Page 5 of the user manual shows the input diagram.
Much obliged.
VT
In article , Vet Tech writes
What makes you think I didn't make the perfect choice already ;-)
Seriously, the relay I pointed out is fine for the job, the gold (flashed not plated unfortunately) contacts are just what you need for a signal level application like this and are rare for a mains coil relay.
As pointed out by Geo, you will need to connect the common contact to pin 4 signal ground and the normally open contact to pin 3 Digital Input. You will also need to program the advanced settings of the recording software to activate recording when the Digital Input is LOW.
The relay is 4 pole but no matter, just leave the other 3 disconnected or use for some other purpose. Do not mix mains & low voltage on the contacts side, the pins are too close together for safety. Safety related points in my previous post still apply, ie insulation and sleeving.
Shame you didn't the RS account earlier, as that is where I bought my identical relay, code is 394-9116. I don't have RS codes for the holder and clip as I soldered my connections but if you want them from RS then search for them and I will check the codes if you post them but just checking, RS appear to place links to them on the page for that relay to save you looking. On this rare occasion RS appears to be cheaper for those bits and as you have an account, post is should be free.
Watch out for secure routing of your PIR link cable as it will fail to OFF if it is pulled down by a scrote. As an alternative you could wire to the normally closed contact on the relay and program the recording to record on active HIGH, this will fail to ON if the low voltage cable is cut or pulled down.
HTH
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