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I am reparing a mirror which has IR triggered LED strips in it. I have no data on the LEDs - I can only work from what is written on the components themselves. I know the IR sensor/switch is working.

I am sure the LED driver has stopped working too - 230Vac is going in but no voltage is measured across the o/p (even with no load).

I want to test the LED strips.

The driver primary 230vac and the secondary says 12V 416mA Max 5W.

I figured that I could test the strip of LEDs by connnecting a 12 dc supply across it (th +/- are clearly labelled). I want to be sure though before I try since I don't want to destroy the LEDs and have to fork out for another set of strips.

So is that ok to do?

Many thanks

E

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    \$\begingroup\$ Have you tried with a 9V battery? it works. Kinda dim, but it works. \$\endgroup\$ Apr 12, 2018 at 20:48

2 Answers 2

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LEDs are current controlled, so you'll want to determine if the current limiting resistor is good, because applying an uncontrolled 12V supply with a failed-closed resistor will fry your LEDs. If you determine that your resistor(s) are good, apply your 12V supply.

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  • \$\begingroup\$ thanks for that. I had this memory of something about frying due to current. \$\endgroup\$
    – maxelcat
    Apr 13, 2018 at 14:17
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If you're using a bench power supply, it would be a good idea to set the current limiter to around 400mA.

Otherwise, use something that won't produce an excessive current, such as the 9V battery suggested by Sredni Vishtar in a comment.

LEDs need current limiting to prevent them blowing. Some LED strips have current limiting resistors built in. Others don't, and require a current limited power supply.

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