25 meters voltage drop 12 V

M

matwh

n3wb
Jul 20, 2016
23
0
Hi,

I have dahua ipcam and I need to connect power 12 volts adapter power via 25 meters Cat5 Lan (not POE). How much voltage drop will occur? The camera requires 12 Volts and 0.5 Ampere. If voltage drops becomes 7 Volts at the end.. would the camera still run? Thanks.
 
What is your cable size? Cat5 comes in a few standard gauges and at low voltages it really makes a difference. If you can't see a gauge, strip a core and measure its diameter with a vernier or micrometer and calculate it out.

alternatively you can use a milliohm meter and measure a few meters. There are other neat hacks you can do with a car battery and a 12v bulb, but you need a vaguely accurate meter and a bit of ohms law. Not hard.

or just hook it up and see what happens.
 
Ya, not enough info to determine.

If you need more information, look at landscape lighting. Typically, these are low voltage systems running over large foot prints. An appreciation and understanding of voltage drop are explained nicely at those sites.

If you just need to get 12v those 25 meters, you could use a separate Cat5, just twist all the lines together to get one larger gauge? Or just run line you would find in landscape installs (looks just like speaker wire, usually burial grade).
 
Here is the spec of the lan cable:

http://www.belden.com/techdatas/english/1583a.pdf

Belden 1583A Cat5e DataTwist Five cable provides the ultimate option for your network needs.
PVC jacket. 1583A DataTwist Five cable is tested to 100MHz and meets or exceeds the TIA/EIA 568A standard and is third party party verified.
* 24 awg solid bare copper
* 4 twisted pairs
* Jacket sequentially marked at two foot intervals
CONDUCTOR : Number of Pairs: 4
Total Number of Conductors: 8
AWG: 24
Stranding: Solid Conductor
Material: BC - Bare Copper
INSULATION :
Insulation Material: PO - Polyolefin Number Color 1 White/Blue Stripe & Blue 2 White/Orange Stripe & Orange 3 White/Green Stripe & Green 4 White/Brown Stripe & Brown OUTER SHIELD : Outer Shield Material: Unshielded OUTER JACKET : Outer Jacket Material: PVC - Polyvinyl Chloride Outer Jacket Ripcord: Yes OVERALL NOMINAL DIAMETER : Overall Nominal Diameter: .195 in. MECHANICAL CHARACTERISTICS : Operating Temperature Range: -20�C To +75�C Bulk Cable Weight: 29 lbs/1000 ft. Max. Recommended Pulling Tension: 35 lbs. Min. Bend Radius (Install): 0.5 in. APPLICABLE SPECIFICATIONS AND AGENCY COMPLIANCE : APPLICABLE STANDARDS : NEC/(UL) Specification: CM, UL444 CEC/C(UL) Specification: CM IEC Specification: 11801 Category 5 TIA/EIA Specification: 568-B.2 Category 5e Other Specification: NEMA WC-63.1 Category 5e, UL verified to Category 5e FLAME TEST : UL Flame Test: UL1685 UL Loading CSA Flame Test: FT1 PLENUM/NON-PLENUM : Plenum (Y/N): N Plenum Number: 1585A ELECTRICAL CHARACTERISTICS : Nom. Mutual Capacitance @ 1 KHz: 15 pF/ft Maximum Capacitance Unbalance (pF/100 m): 330 pF/100 m Nominal Velocity of Propagation: 70 % Maximum Delay (ns/100 m): 538 @ 100MHz ns/100 m Maximum Delay Skew (ns/100m): 45 ns/100 m Maximum Conductor DC Resistance @ 20 Deg. C: 9.38 Ω/100 m Maximum DCR Unbalance @ 20 Deg. C: 3 % Max. Operating Voltage - UL: 300 V RMS - See more at:
 
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No. The camera may not run at all at that little voltage. What that number gives you is how much voltage will be at the end of the other line oopposite the source. You can do a few things easiest would be to Simply get a bigger gauge wire.
 
FrankOceanXray said:
No. The camera may not run at all at that little voltage. What that number gives you is how much voltage will be at the end of the other line oopposite the source. You can do a few things easiest would be to Simply get a bigger gauge wire.
Click to expand...

Do you know why bigger gauge wire would result in less voltage drop (in terms of electron propagation)? And why when I enter 2 ampere instead of 1, the voltage drop is more. Thank.
 
Check out ohms law. It will answer both of your questions.

Thicker wire reduces resistance. Increased current increases drop for the same gauge wire.
 
If you want to know the science, study up! V , I and R. Ohms Law.

If you want it to work, find yourself some thicker wire. Speaker wire could do the trick. Make sure all things meet applicable codes.. for your own safety.
 
The simple solution is to use an active PoE injector that conforms to at least 802.3af at the switch end, and an active splitter at the camera end, and you will be able to supply 12v at up to 1A at the camera end over up to at least 100m with zero voltage drop.
 
there is a reason why PoE is 48v.. dont try to send 12v down ethernet cables more than a couple of feet in length.

x2 for the active PoE splitter, I have several of them in play.. powering IR, Motion Sensors and Remote microphones.. Ive got one ethernet cable ran w/no network, just a PoE splitter on the end.
 
Only if you can guarantee the camera will always draw enough current to maintain the drop otherwise when consumption drops the voltage will spike.
 
If I use 16 volts DC adapter.. it should work.. isn't it.

Voltage drop: 4.21
Voltage drop percentage: 26.31%
Voltage at the end: 11.79
Click to expand...
Nope - that will never work - the current consumption of the camera varies a lot with it's status and activity, so the end-of-line voltage will be all over the place.
IR leds on - current goes up a lot - IR leds off - current goes down.
Processing load on DSP/CPU varies - current varies.
Camera reboots - starts with low current, progressively activates hardware and services, current changes accordingly.
And when current is low and the end-of-line voltage is correspondingly high, you could damage the camera.

The PoE active injector is the correct approach - no uncertainties.
 
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