cigar lighter voltage adapter

tadpole

New member
Joined
2 Aug 2001
Messages
65
Location
West Dorset
Does anyone know where to get a cigar lighter voltage adapter which has several different plug fittings with different voltages - from 3v to 12v - attached. I've been told they are available.
Thanks in anticipation,
Steve
 
G

Guest

Guest
Get a good one, and keep the packaging and receipt.

The one I bought melted after about 45 minutes use!

(and no, I wasn't overloading it, I was only running a walkman off it)
 

Footpad

New member
Joined
31 May 2001
Messages
84
Location
West Sussex England
How do they work?

I don't do electrics but when I was a kid my train set ran with a transformer
(AC 240 - AC 12) and rectifier (AC 12 - DC 12) I thought you could only transform AC and ships batteries give you DC? Explain please, in very simple terms.
 

bedouin

Well-known member
Joined
16 May 2001
Messages
31,723
Re: How do they work?

They use a clever little device called a 'Voltage Regulator'. This can reduce the input voltage. If you want a 9V output from a 12V input then the regulator holds its output at 9V and drops the remaining 3V across its circuit. (Note - a simple regulator cannot increase the voltage.)

This is very different to transforming. A transformer can be close to 100% efficient; a simple voltage regulator works by 'wasting' the excess voltage - in the case of getting a 3V supply from a 12V source three quarters of the power is wasted, and given off as heat in the regulator, so these are only appropriate for low power circuits.
 
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