Hooner Posted May 11, 2008 Posted May 11, 2008 I recently installed three Videcon IR cameras in an isntallation using Passive Baluns (from COP) The system is encountering some problems when the IR kicks in at night, knocks all camera signals off. I'm pretty sure the PSU is rated higher than the total max. current draw of the cameras. Is there a limit to the ampage that can be drawn across twisted pair? Hooner ________
lawandorder Posted May 11, 2008 Posted May 11, 2008 I recently installed three Videcon IR cameras in an isntallation using Passive Baluns (from COP)The system is encountering some problems when the IR kicks in at night, knocks all camera signals off. I'm pretty sure the PSU is rated higher than the total max. current draw of the cameras. Is there a limit to the ampage that can be drawn across twisted pair? Hooner Yes! There is a limit to the ammount of current any cable can carry. Measure the voltage at the camera both with IR on and IR off. You may find that putting the PSU local to the camera will resolve the issue.
Hooner Posted May 11, 2008 Author Posted May 11, 2008 Yes!There is a limit to the ammount of current any cable can carry. Measure the voltage at the camera both with IR on and IR off. You may find that putting the PSU local to the camera will resolve the issue. Sorry yes of course there is. I should have worded that better. ""What" is the limit to the current twisted pair can carry? I'm back there tomorrow to do some tests. Unfortunately we cant site PSU's anywhere near the cameras, we used twisted pair in this project as the client wanted minimum cable used (RG59twin was too thick apparently ..anyways will know more tomorrow. ________
djandysp Posted May 11, 2008 Posted May 11, 2008 Sorry yes of course there is.I should have worded that better. ""What" is the limit to the current twisted pair can carry? I'm back there tomorrow to do some tests. Unfortunately we cant site PSU's anywhere near the cameras, we used twisted pair in this project as the client wanted minimum cable used (RG59twin was too thick apparently ..anyways will know more tomorrow. Ive come accross this before strangely enough with videcon IR cams. Id recommend fiting a pcam 2 psu for each cam that should sort the problem
lawandorder Posted May 11, 2008 Posted May 11, 2008 Sorry yes of course there is.I should have worded that better. ""What" is the limit to the current twisted pair can carry? I'm back there tomorrow to do some tests. Unfortunately we cant site PSU's anywhere near the cameras, we used twisted pair in this project as the client wanted minimum cable used (RG59twin was too thick apparently ..anyways will know more tomorrow. To be honest it's probably not the current carrying capacity that is the issue here, it is the voltage drop which is a product of the cable resistance and the load of the cameras/IR illumination. I suspect that the cables are fairly long? Get back to me with the specific type of cable you are using and the approx length of the runs and I'll post some calcs for you. You really need to do some tests at the camera end rather than at the supply end but if you have any spare conductors double up on the supply pairs, this will halve the resisatnce and therefore reduce the voltage drop.
james.wilson Posted May 11, 2008 Posted May 11, 2008 i assume you have used all available cores for power? an alternative might be to send 24v ac on the power cores and rectify and regullate to 12v. securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount.
Hooner Posted May 11, 2008 Author Posted May 11, 2008 Theres only one pair of conductors being used at present, all cat5e runs are less than 30m each. Actually the cameras can operate on 24v so maybe thats worth a shot too. ________
james.wilson Posted May 11, 2008 Posted May 11, 2008 higher voltage will really help, just as much as adding more cores. I would always use all cores available as power securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount.
Hooner Posted May 11, 2008 Author Posted May 11, 2008 thanks redbull. The way I've done it is as per the below diagram. (Drawing two) http://www.cop-security-online.co.uk/secti...s/15-W414VP.pdf However that means the distribution block is handling the jumping of the power across the pairs meaning I cant double up the spares ________
james.wilson Posted May 11, 2008 Posted May 11, 2008 not opening the pdf i assume you have run the power over the same pair as the video? While this is fine for low current cams i wouldnt do ir for ir cams. do you have 3 spare pairs... if so just use them for the power. And it will be fine securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount.
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