Sorry if this is the wrong site for the question.

How can I power this household lamp off the cigarette lighter in my car?

JANSJÖ LED wall/clamp spotlight, white

enter image description here

It comes with an AC adapter:

  • Intertek
  • 4005088
  • kmv-070-030-na-2
  • Input 100-120V ~ 50/60Hz 0.09A
  • Output 7V = 0.43A 3W

In this picture the bottom has the standard 2 AC wall outlet prongs. They are difficult to see, but are there. The top has the two female sockets for the detachable cord that runs to the LED lamp.


Is the output DC?

I suppose I could just plug it into an inverter, but was thinking there might be a DC adapter to go from the vehicle's 12-15V to the required 7V for the LED.

  • $\begingroup$ I don't know how you're planning to connect it, but do realise that LED's only have a voltage drop, and barely any resistance. Connecting it to a unrestricted source (without a resistor), will burn out the LED quickly. $\endgroup$ – Bart Jan 30 '18 at 21:51
  • $\begingroup$ Thanks, didn't know that. What is needed for a resistor? $\endgroup$ – Clark Jan 30 '18 at 22:46
  • $\begingroup$ Web has info for adding a resistor for naked/standard LED, which is not likely what is in the lamp. Also the currents discussed are 5 to 20mA. The spec on the lamp's AC adapter is 430 mA. $\endgroup$ – Clark Jan 31 '18 at 7:26
  • $\begingroup$ never mind, found youtube.com/watch?v=piET0Biqo0I $\endgroup$ – Clark Jan 31 '18 at 7:50
  • $\begingroup$ If more LED's are in parallel, more current is needed. Not all LED's support the same amount of current. $\endgroup$ – Bart Jan 31 '18 at 10:30

Yes, the output will be DC. Because LED's are (by name and nature) Diodes, they only allow current to pass through in one direction.

Further to this, the picture you supplied shows the symbol for DC current:

enter image description here

There are widely available DC-DC 'Buck Converters' available, which can accept a variable input voltage, and give a constant output voltage at a different level. The adaptors for charging your phone (5V) are a perfect example of this.

USB car chargers are available from 'pound shops' ('dollar stores'), so if you are on a very tight budget, and you can deal with your LED being slightly less bright, you could use one of these (and solder a male USB connector onto your lamp)

If you need that extra brightness, then simply buy the 'correct' converter, e.g. https://www.amazon.co.uk/DEOK-Synchronous-Rectification-Conversion-Efficiency/dp/B00HY3FWEK

I would still get a USB car charger, however, because it will have a ready-made reliable plug-and-play connection to your 12V socket. Just take the insides out and solder your new Buck Converter to the appropriate terminals.

Good luck!

  • 1
    $\begingroup$ I strained to look closely at the adapter. What on first glance looks to be an equals signs is indeed the DC symbol. And I now understand the tilda in the input specs to be the AC symbol. Thanks ! $\endgroup$ – Clark Jan 30 '18 at 16:43
  • $\begingroup$ So I'm glad I suggested that you provide the image, and sad that my answer does not warrant the recognition compared to some who came after. That being the case I will delete mine, before other phantom downvoters join the party. $\endgroup$ – Solar Mike Jan 30 '18 at 17:14
  • $\begingroup$ I'm sorry you feel I've taken your glory, as it were - This answer was written before the photo appeared, and later edited to include reference to the symbology. $\endgroup$ – Jonathan R Swift Jan 30 '18 at 18:50

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