12v Power Distance Through Cat5 Cable

[digitaleye]

Hi Guys.

Anyone know if i power a 12v cam down cat5 cable at 200m

[alterEGO]

Hi Guys.

Anyone know if i power a 12v cam down cat5 cable at 200m

i would not run power down the same cat 5 as video at 200m, i try not to do it at all if possible. Can you not use a power source local to the camera.

[arfur mo]

i'm with AE on this,

if you have no alternative then treble up on the spare cores, but imo 200 meters is going to push it a bit. you might have to fit an adjustable output voltage psu and jack up the voltage to overcome the drop.

either way fit a decent sized electrolytic capacitor say 2200uf @ 40 vkg at the camera end to act like a small battery and smooth any suden 'pulls'.

regs

alan

[luggsey]

A single 24 AWG (0.5 mm diameter) conductor has a resistance of ~ 9.4 ohms per 100 metres, voltage drop will be ~ 1 volt per 50 metres of Cat-5 Twisted Pair for a small load camera. (Quoted from a makers site)

Double up cores and get half the resistance.

Use ohms law (For DC) and get the volt drop.

[luggsey]

i'm with AE on this,

if you have no alternative then treble up on the spare cores, but imo 200 meters is going to push it a bit. you might have to fit an adjustable output voltage psu and jack up the voltage to overcome the drop.

either way fit a decent sized electrolytic capacitor say 2200uf @ 40 vkg at the camera end to act like a small battery and smooth any suden 'pulls'.

regs

alan

I would have thought the capacitance in 200m of cable would be pretty high to start with?

[camstop]

If you must try then triple up the spare cores as mentioned above and use a 13.8V PSU.

It will depend on the camera mainly as they vary a lot on what they will work with.

Personally i think you'll be struggling but best of luck all the same

[arfur mo]

I would have thought the capacitance in 200m of cable would be pretty high to start with?

comon mistake made here, i'll exsplain,

the resovior cap is to 'de-couple' the power supply to the camera. if the camera decides it needs more power suddenly for a short period the cable can't supply the demand current quickly enough over this distance, so we get a peek draw and then voltage drop at the camera and subsequent video quality issue's, so the capacitor helps fills in for these shortish power demands.

the inherent cable capacitance of the cable is only a few pico farads, for 'our' need's we require a few thousand UF's as an 'emergency' buffer say for the iris operation, so it acts like a small battery to smooth out the power 'troughs' and recharges as soon as the demand recedes.

the above is not meant as a technically exact example, more like using lay mans terms loike water and pipes to explain ohms law theory

i hope that helps, if so can someone please exsplain back to me what i just wrote fueled on 2 bottles of merlot - hic!

regs

alan

[luggsey]

comon mistake made here, i'll exsplain,

the resovior cap is to 'de-couple' the power supply to the camera. if the camera decides it needs more power suddenly for a short period the cable can't supply the demand current quickly enough over this distance, so we get a peek draw and then voltage drop at the camera and subsequent video quality issue's, so the capacitor helps fills in for these shortish power demands.

the inherent cable capacitance of the cable is only a few pico farads, for 'our' need's we require a few thousand UF's as an 'emergency' buffer say for the iris operation, so it acts like a small battery to smooth out the power 'troughs' and recharges as soon as the demand recedes.

the above is not meant as a technically exact example, more like using lay mans terms loike water and pipes to explain ohms law theory

i hope that helps, if so can someone please exsplain back to me what i just wrote fueled on 2 bottles of merlot - hic!

regs

alan

I should take water with it Arf, a decoupling cap removes AC/RF normally. think about it, the word gives it away, it "de-couples" ie. removes something see?

To make DC voltage more stable we are talking about a smoothing cap.

The capacitance of CAT 5 is pretty low I'll give you that, about 0.001uF for 200m, but more if the cores are "doubled" up.

The capacitance of some cables is "VERY" high, ask any sparks that Meggers long lengths of MI cable!

This guy needs to look at the volt drop as no cap will resolve that, also bear in mind that fitting a large cap at the end of a high resistance will have a detrimental effect on the protective device within the PSU, ie. it may go bang when turned on with a discharged cap!

!

[viper]

I should take water with it Arf, a decoupling cap removes AC/RF normally. think about it, the word gives it away, it "de-couples" ie. removes something see?

To make DC voltage more stable we are talking about a smoothing cap.

The capacitance of CAT 5 is pretty low I'll give you that, about 0.001uF for 200m, but more if the cores are "doubled" up.

The capacitance of some cables is "VERY" high, ask any sparks that Meggers long lengths of MI cable!

This guy needs to look at the volt drop as no cap will resolve that, also bear in mind that fitting a large cap at the end of a high resistance will have a detrimental effect on the protective device within the PSU, ie. it may go bang when turned on with a discharged cap!

!

Personally i would throw the DC voltage PSU and Camera in the skip and use an AC voltage PSU and Camera - job done!!

[arfur mo]

I should take water with it Arf, a decoupling cap removes AC/RF normally. think about it, the word gives it away, it "de-couples" ie. removes something see?

To make DC voltage more stable we are talking about a smoothing cap.

The capacitance of CAT 5 is pretty low I'll give you that, about 0.001uF for 200m, but more if the cores are "doubled" up.

The capacitance of some cables is "VERY" high, ask any sparks that Meggers long lengths of MI cable!

This guy needs to look at the volt drop as no cap will resolve that, also bear in mind that fitting a large cap at the end of a high resistance will have a detrimental effect on the protective device within the PSU, ie. it may go bang when turned on with a discharged cap!

!

here we go again

ok, if you decouple an audio amplifier pre stage you fit a small resistor, then say a 10 - 100uf a cap after it, both are close to and before the input supply to the pre-amp, this is done even on a short legnth of wire or instability may occur.

a 50 pf cap across the supply will act as a hi pass (or shunt) to high frequency 'buzzing' on the audio.

in this CAT5e situation, the 'small' resistor is the cable due to it's length, it will also (due to it's inherent capacitance) cause back EMF when power is initially applied, but given the suggested length of 200 meters the current passed into a 'flat' resovior cap will be limited by this cable resistance and coupled with the back emf will also act to reduce the current drawn.

even doubling/trebling up will not give capacitance for our needs, a 100 pair cable would not eather, when charging MICC you haver a thick copper sleeve and thick cables to act as plates and a descent air gap, thats why you can charge up a length of it and watch when a numty touches the open ends, scream's at the sparks and then is shown it's not connected to antything and head is scratched .

regs

alan

in operation