b_have Posted July 3, 2008 Share Posted July 3, 2008 Need a 7.5V 300mA feed to an on board camera (ideally ignition switched) what are the options? Quote Link to comment Share on other sites More sharing options...
Andy Blyth Posted July 3, 2008 Share Posted July 3, 2008 (edited) Something like this will probably be the easiest bet. Has wires going in instead of a moulded cigar lighter plug too, means it will be easy to splice into your cars' wiring. You could design and build your own DC-DC converter, but probably not for a total cost of around a tenner. Getting a switched feed will be pretty easy. IIRC, the lighter socket is already switched. Just hook into the two wires going to that. EDIT: This one is a little closer to home! Edited July 3, 2008 by Andy Blyth (see edit history) Quote Link to comment Share on other sites More sharing options...
SimonB Posted July 3, 2008 Share Posted July 3, 2008 Permanent or temporary? You can get cigarette lighter adaptors from Maplin that output various voltages - pretty sure 7.5V is one of them. I have one I rigged up as the power supply for my bullet cam. Quote Link to comment Share on other sites More sharing options...
b_have Posted July 3, 2008 Author Share Posted July 3, 2008 Probably a stupid question, but I've seen a few of the cig lighter adapters outputing 7.5V but no mention of the 300mA part. What is contained in the box? Quote Link to comment Share on other sites More sharing options...
b_have Posted July 3, 2008 Author Share Posted July 3, 2008 Something like this will probably be the easiest bet. Has wires going in instead of a moulded cigar lighter plug too, means it will be easy to splice into your cars' wiring. You could design and build your own DC-DC converter, but probably not for a total cost of around a tenner. Getting a switched feed will be pretty easy. IIRC, the lighter socket is already switched. Just hook into the two wires going to that. EDIT: This one is a little closer to home! Many thanks Andy, will the Output of1500mA cause an issue or is that just the max draw? (god I hate being a dunce ) Quote Link to comment Share on other sites More sharing options...
JustGav Posted July 3, 2008 Share Posted July 3, 2008 300mA is fairly low to be honest... an electrical device will only draw as much current as it needs, so in theory even if you strapped 1000A powersupply to it, it would still only draw 300ma (unless you put a metal bar across it, then 1000A suddenly turns it to molten metal Quote Link to comment Share on other sites More sharing options...
Andy Blyth Posted July 3, 2008 Share Posted July 3, 2008 Probably a stupid question' date=' but I've seen a few of the cig lighter adapters outputing 7.5V but no mention of the 300mA part. What is contained in the box?[/quote'] 300 mA is the current that your camera will draw from a 7.5 V power supply. All you need to do is ensure that your converter can supply at LEAST 300 mA. It's not a problem if it can supply more, even much more. In fact it's better to have some margin to play with. Re: what's in the box, not a lot to be honest! Probably less than a dozen components, whose purpose is to reduce the (12-14 V) voltage present in your car to the (7.5 V etc.) voltage that your camera needs. Quote Link to comment Share on other sites More sharing options...
b_have Posted July 3, 2008 Author Share Posted July 3, 2008 Thats exactly what I needed to know. Many thanks guys Quote Link to comment Share on other sites More sharing options...
JustGav Posted July 3, 2008 Share Posted July 3, 2008 For additional reference if something is quoted in Watts, it is very easy to calculate current draw. Watts = Volts * Amps So the cam would be 7.5v * 0.3 = 2.25W Quote Link to comment Share on other sites More sharing options...
Digsy Posted July 4, 2008 Share Posted July 4, 2008 300 mA is the current that your camera will draw from a 7.5 V power supply. All you need to do is ensure that your converter can supply at LEAST 300 mA. It's not a problem if it can supply more, even much more. In fact it's better to have some margin to play with. Re: what's in the box, not a lot to be honest! Probably less than a dozen components, whose purpose is to reduce the (12-14 V) voltage present in your car to the (7.5 V etc.) voltage that your camera needs. If you do end up using a power supply that can push out a lot more than you need then its best to put a fuse inline. That will save you from having to use heavier cable than you really need. Its good practise to use one anyway to protect the PSU and the wiring. Quote Link to comment Share on other sites More sharing options...
bignum Posted July 4, 2008 Share Posted July 4, 2008 The problem i found with running camera`s directly off the cars output is interference due to the fluctuation on the alternator, i run mine through a 12/240 unit which is regulated then whatever psu you need to feed the camera/recorder which should also be regulated. Quote Link to comment Share on other sites More sharing options...
stevie_b Posted July 4, 2008 Share Posted July 4, 2008 ... (unless you put a metal bar across it, then 1000A suddenly turns it to molten metal Yes, I remember hearing a story whereby someone dropped a massive spanner across the terminals of one of the batteries that powers a diesel-electric submarine. There was a big flash..... and they never did find the spanner afterwards. Quote Link to comment Share on other sites More sharing options...
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