David_Dickson

I have a camcorder I would like to run in the car without needing the battery. It comes with a mains adaptor and lead. The adaptor output is 6v at 1.8A so if I could replicate this in the car I could just use the lead to replace the battery and run it from the cars power.

Any ideas?

ta

chiark

Use a 6V voltage regulator

If you know which end is the hot end of a soldering iron you could make one pretty easily, or you may find that maplins sell em?

With 1.8A draw you probably are looking at a switchmode rather than linear regulator. If you find nothing pre-assembled, National Semiconductor have some "Switchers made simple" software that'd work out what you need to build one.

Cheers,
Nick.

David_Dickson

hmm, im handy with a soldering iron, show me what to build and Ill build it!
Its the theory thats my weak-point, I have pretty much no idea what you are talking about!
Ill take a peek in Maplins tomorrow.

dr_ming

Most camcorder manufacturers sell such items as accessories, and there are a number of independent video accessory manufacturers who do the same. These have the benefit that they come ready made in a nice box.

If you want to make your own, the Chiark is spot on, the Nat Semi simple switcher range will do exactly what you want, and you can even download some s/w from their web site that will do all the design calculations for you: gives you a complete parts list and circuit diagram. However, you need to be careful, as there are some extra precautions you need to take if you are going to plug it into your car. In particular, you need to add protection against voltage transients. The usual way to do this is with a big, fat (>5A) zener diode across the fused side of the 12V input to the regulator. 36V is a good choice because (IIRC) the simple switchers have a max Vin of 40V. This will protect against negative transients (normal diode conduction), and positive transients >36V (zener conduction). Have fun.



[Edited by dr_ming - 11/16/2003 9:58:30 PM]

AndyC_772

iTrader: (2)

IMHO you're much better off buying one than building it. I've used the 'simple switcher' devices before, and although they're straightforward enough compared to other ways of designing a switch mode power supply, make no mistake - you're still into electronics degree territory here. Making it work, making it reliable and making it safe for your equipment (not to mention yourself - switch mode supplies can and do explode!) are different things.

To drop 6V at 1.8A, that's still within the realms of a linear supply provided you fit a nice big heatsink. This would be easier to get going and more predictable in its behaviour. Even then, I doubt you'll find someone willing to put in the time and effort to do all the design for you and provide step-by-step instructions.

It sounds like the sort of thing you should be able to buy ready made anyway - try Maplin or Farnell for starters.

A.

David_Dickson

Yeah, buying one is the obvious option but its an older camcorder so parts availability isnt too great.

Looks like building one is going to be more hassle than Im willing to spend.

Thanks guys

dr_ming

David, Transient protection applies whether the power supply is switched mode or linear, but as Andy points out, making things like this is hassle. Check out

http://www.keene.co.uk/system/keene.htm

Look under power products, car power cords. I think you will probably find what you want.

[Edited by dr_ming - 11/16/2003 10:19:53 PM]