Guest PaulR Posted December 8, 2004 Share Posted December 8, 2004 Or use one of these SCART plug adaptors: with a BNC to phono adaptor. You can then just plug your BNC into any Euro SCART plug on your TV or VCR. A compromise though. Always best to use a proper CCTV monitor really, if possible. Link to comment Share on other sites More sharing options...
Doktor Jon Posted December 8, 2004 Share Posted December 8, 2004 Just a minor point on the voltage drop issue. With 12v DC cameras, depending on whether the manufacturer has included a voltage regulator in the power supply section, or indeed just down to the basic circuit design, most cameras have differing requirements in terms of drive voltage. So for example, a camera which is spec'd to run at 10.4 - 13.2v DC input, will still work quite happilly with a fair degree of voltage drop. If you use a model which requires 11.6v - 15v DC, then obviously this will become a problem quite quickly (or should that be shortly ). They are obviously both described as '12v DC' cameras, but even with a moderate length of power supply cable, one will work and the other may not. Also, I have seen problems in the past where a camera has been bench tested with a specific length of cable using a manual iris lens, and then the installer took it to site, fitted an auto iris lens, and guess what .... camera worked, but the lens didn't! Incidentally depending on the application, in the past I've used either twin 0.75mm flat mains cable, or heavy gauge 'figure 8' 32/0.2mm or 53/0.19mm for longer runs. Link to comment Share on other sites More sharing options...
Guest aeading Posted December 15, 2004 Share Posted December 15, 2004 OK, i am new to CCTV really, I have installed some systems supplied by the wholesaler, but have a question.What type of signal does the standard CCTV give via the BNC connector?? Can this be conected to a standard TV via the composite input?? How do you calculate possible volt drop on the 12vDC feed to cameras?? and what cable to poeple regularly use to feed them (I have seen flex, alarm cables 'doubled' up, and speaker cabel.) 33979[/snapback] ok its 1 volt peak to peak 0.7 volt video level 0.3 volt sync pulse the colour is chroma burst @ 4.43 mz the total bandwidth of 5.5 mz if you connect a camera to a scope you can see all the above set your scope 20 us @ .2 v per division you may need to ajust your trigger level.This wayyou will see the whole video siginal dont forget to load the video siginal with 75 ohm terminator at scope end. volt drop use ohms law goto google and type in ohms law dont just pick a cable like .75 flex without ohms law you will never know the volt drop.dont forget to use regulated a smothed power supplys theirs a lot a **** out their yes you can connect a cctv camera to a standard tv via the scart connector but if you camara has a tvl of 500 does you tv have the same or higher tvl? most tvs dont have a under scan button all tvs over scan the picture so you will not see the edges of what the camera can see this is not so bad because the highest res is @ the center of the picture due to lense quallty if you want to learn the trade i would sugest that you attend a cctv course ive found TAVCOM are the boys type tavcom into google good luck you have enterd the world of cctv fact 65% of cctv engineers cant back focus a camera the right way Link to comment Share on other sites More sharing options...
Guest Peter James Posted December 16, 2004 Share Posted December 16, 2004 ok its 1 volt peak to peak 0.7 volt video level 0.3 volt sync pulse the colour is chroma burst @ 4.43 mz the total bandwidth of 5.5 mz if you connect a camera to a scope you can see all the above set your scope 20 us @ .2 v per division you may need to ajust your trigger level.This wayyou will see the whole video siginal dont forget to load the video siginal with 75 ohm terminator at scope end. volt drop use ohms law goto google and type in ohms law dont just pick a cable like .75 flex without ohms law you will never know the volt drop.dont forget to use regulated a smothed power supplys theirs a lot a **** out their yes you can connect a cctv camera to a standard tv via the scart connector but if you camara has a tvl of 500 does you tv have the same or higher tvl? most tvs dont have a under scan button all tvs over scan the picture so you will not see the edges of what the camera can see this is not so bad because the highest res is @ the center of the picture due to lense quallty if you want to learn the trade i would sugest that you attend a cctv course ive found TAVCOM are the boys type tavcom into google good luck you have enterd the world of cctv fact 65% of cctv engineers cant back focus a camera the right way 34736[/snapback] The perfect answer, I wondered how long it would be before someone mentioned ohms law well done. aeading you have my vote for acceptance as trade as the above post proves you most definately are. Pete Link to comment Share on other sites More sharing options...
Guest Posted December 16, 2004 Share Posted December 16, 2004 The perfect answer, I wondered how long it would be before someone mentioned ohms law well done.aeading you have my vote for acceptance as trade as the above post proves you most definately are. Pete 34773[/snapback] so much for the vetting process pete anyone could have re-typed that quote from a book...no disrespect to aeading..tho id expect more from a mod... Link to comment Share on other sites More sharing options...
ian.cant Posted December 16, 2004 Share Posted December 16, 2004 fact 65% of cctv engineers cant back focus a camera the right way There is a good reason for that, you generally dont need to these days. When was the last time you needed to back focus a camera "correctly"? In these days of fully functional domes there is no need and lets be honest, unless you doing large sites or city center systems your not too likely to come across tv zooms too often. So in terms of facts, the fact is 90% of cctv engineers dont need to know how to rack a camera correctly. The same as most engineers wouldnt know what a cs ring was for! Most of todays alarm engineers wouldnt know how to do castled foil, correctly! That all due to the technological advances not because todays engineers are ignorant or anything, just needs have changed. Link to comment Share on other sites More sharing options...
Guest Peter James Posted December 17, 2004 Share Posted December 17, 2004 so much for the vetting process pete anyone could have re-typed that quote from a book...no disrespect to aeading..tho id expect more from a mod... 34790[/snapback] Yep your absolutely right Gaz but my vote is only part of the vetting process. All Mods have to agree that the prospective applicant is trade as well as the usual security checks. Though his post could of been re-typed straight out of a book, you still would need to know what ohms law is in the first place. Pete Link to comment Share on other sites More sharing options...
Lectrician Posted December 17, 2004 Author Share Posted December 17, 2004 Yep your absolutely right Gaz but my vote is only part of the vetting process. All Mods have to agree that the prospective applicant is trade as well as the usual security checks. Though his post could of been re-typed straight out of a book, you still would need to know what ohms law is in the first place. Pete 34834[/snapback] You still need to know the resistance for the cable, per meter when using ohms law. I am fully conversant with that. I wouldn't know where to get the figures from for alarm cable, which is what I have seen used most often. I just wondered if you guys used a 'rule of thumb' with this sort of thing. I am looking to diversify a bit. I am becoming more interested in alarms and cctv, but I don't want to loose the sparky side either. But you can't specialise in both Thanks to all that have replied. My reasoning on asking if I could connect a standard CCTV to a normal TV - I was asked by a mate if it was worth him buying one from EBay, he wanted it for his flat. Email : martin@askthetrades.co.uk Link to comment Share on other sites More sharing options...
Guest Posted December 18, 2004 Share Posted December 18, 2004 Yep your absolutely right Gaz but my vote is only part of the vetting process. All Mods have to agree that the prospective applicant is trade as well as the usual security checks. Though his post could of been re-typed straight out of a book, you still would need to know what ohms law is in the first place. Pete 34834[/snapback] thats me told then Link to comment Share on other sites More sharing options...
Guest Peter James Posted December 18, 2004 Share Posted December 18, 2004 You still need to know the resistance for the cable, per meter when using ohms law. I am fully conversant with that. I wouldn't know where to get the figures from for alarm cable, which is what I have seen used most often. I just wondered if you guys used a 'rule of thumb' with this sort of thing.I am looking to diversify a bit. I am becoming more interested in alarms and cctv, but I don't want to loose the sparky side either. But you can't specialise in both Thanks to all that have replied. My reasoning on asking if I could connect a standard CCTV to a normal TV - I was asked by a mate if it was worth him buying one from EBay, he wanted it for his flat. 34842[/snapback] 12AWG wire has a resistance of 1.62 Ohms per 300 metres. However, we wherever possible would fit the psu close to the camera in the 1st place to avoid current loss. If this is not possible it is always better to over specify the cable (Its the cheapest bit of the installation but can become the most expensive). It is a bit horses for courses and if your psu,s arent local how much cash would you save by using alarm cable over 1m flex? Pete Link to comment Share on other sites More sharing options...
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