power supply for 800 feet

[jmk 0]

I have a PTZ IR camera about 700 to 800 feet from my house to our gate. I have cat5 cable 24awg (4 twisted pairs) in conduit to the camera. I'm using 2 for video, 2 for PTZ and the rest for power. Of course it's to far for the power supply I have. Camera is 12vdc and 20w (1.66a?). The power supply is 12v 2a. I don't want to power the camera at the gate, because I would like to turn it off from the house. I have power at the gate. Unfortunately I can't run anymore or larger cable.

 

I'm considering using this power supply (http://www.powersupplydepot.com/36-Volt-Power-Supply,-4-2A,-150W,-Switching,-Hengfu/16034-PS/) at the house and then this (http://www.ebay.com/itm/COP-Security-15-AC24-2A-15-AC24-2A-AC-DC-AC24V-to-DC12V-Converter-Box-NEW-/111271023193?pt=LH_DefaultDomain_0&hash=item19e8451259) at the camera.

 

Will this work or am I crazy? I don't want to burn up the camera.

Any suggestions would be great.

[jazzar 0]

you could simply use the spare cable to switch a relay at the gate - that way you can pick up the supply locally at the gate and run the power through the relay contacs and use a simple 12v psu at the house to switch the relay coil via the spare cat 5 wires.

this will save costs on bulky psu's

don't have to worry about frying the cables then, sometimes old tech works.

[the toss 0]

Without a doubt your best course of action will be to power the camera from the gate , especially since it is a 12V dc and not 24Vac camera. So the problem you should be looking into is how to switch it on/off although I'm not sure why you would want to.

As jazzar siggested you could use a relay controlled over a spare pair or even easier get a single chan transmitter/receiver.

[jmk 0]

you could simply use the spare cable to switch a relay at the gate - that way you can pick up the supply locally at the gate and run the power through the relay contacs and use a simple 12v psu at the house to switch the relay coil via the spare cat 5 wires.

this will save costs on bulky psu's

don't have to worry about frying the cables then, sometimes old tech works.

 

I like your suggestion of a relay, however my electronic skills are very limited, so I have no idea what parts I would need to do that. A parts list and wiring diagram would be greatly appreciated (if you would be so kind).

 

Also, I want to turn the camera and dvr off because I don't really need it on all the time.

 

Thanks for the reply's.

[jazzar 0]

just google simple 12v relay or similar- you will get the idea.

basically you just apply 12v dc across the relay coil- this will then make the switch contacts of the relay change position. you just use this contact to break or make the connection for the power to your camera.

 

house gate

 

relay contact

switch relay

+12v relay psu _________/ ______________________________relay coil + 12v cam psu + __/ ___ to cam +12v

 

0v relay psu ___________________________________________relay coil - 0v cam psu ______ to cam 0v

 

view above in big windows explorer window it should look ok.

instead of the switch in the house you could just unplug the psu to kill the power.

[jazzar 0]

the above diagram is ok but the text mixed up after posting house to left , gate to right

top line at house shows switch, to right of switch is the relay coil then to far right is the relay contact.

sorry for poor diagram. the auto text width has mucked up the text lining up with the diagram- I'm sure you will get it.

[Horizon 0]

Hi there jmk. I like your approach here, but I think the loss through the cable will defeat you

 

The 24VAC to 12VDC converter will easily tolerate your 36V supply ( 24 x sqrt[(2] = 34 volts). The converter internally transforms AC to DC, so since it works on 24VAC, it must work on 34VDC.

According to an online calculator, a single 800 foot length 24awg has 22ohms of resistance, so double the resistance to include the return path, and then halve it because you are using two pairs.

Sketching about on the back of an envelope, it looks like more than a quarter of your power will be lost through the cable, and even 36V won't be high enough. It depends a lot on how low an input voltage that converter will work with. You might be okay if the length is nearer to 600 ft or less.

If it was me, I'd use a higher voltage - 60 volts is the maximum you can use without needing an electrician to do the wiring (or at least, it is over here), so I'd use something between 50 and 60V, and a different converter to step it back down to 12V. Choose one that can deliver at least 30 watts to the camera.

 

Or power it locally at the pole if that's possible. The PTZ will only draw 20 watts when it moving. When idle, it should be more like 5 watts or so, unless it has infrared LEDs or a heater. So your power bill shouldn't get too high

 

BTW, that open frame power supply (the 36V Hengfu) must be put into a box before you start experimenting with it. Stray wires are magically attracted to mains terminals, then you get zapped!

[jmk 0]

Jazzer,

Will this work? http://www.ebay.com/itm/90A-AGT-SSR-Solid-State-Relay-3-32V-DC-24-380V-AC-24V-380VDC-/320937686063