Fault with LED strip lighting

[Captain Kernow]

I have some (self-adhesive) LED strips set up to illuminate my workbench. They are 12v, powered by a small plug-in transformer.

 

Despite having checked all connections, they have recently started not coming on when I turn the mains switch on. They have eventually come on, but only after several minutes have passed.

 

I don't know enough about how LEDs work but was wondering if this was symptomatic of a common fault?

 

There is no problem with the mains supply, as other things work fine from the same plug.

 

Many thanks.

 

 

 

[Stentor]

I’m not an electrician myself but after a quick bit of Googling this seems to offer a general insight into what it might be and a checklist to work through:

 

https://www.waveformlighting.com/home-residential/troubleshooting-led-strip-problems
 

Clearly LEDs are not without issues, hope this helps.

 

//Simon 

[MPR]

Hi Tim, 

I would be inclined to start with the power supply - if you have a multimeter, disconnect the strip and probe the output and check the DC voltage at start up. When you have eliminated the power supply, reconnect the strip and probe the end of the strip. If you can access the solder pads, you should read close to 12V, even at the far end. If you directly access an led segment, you should expect to read a forward voltage of around 3V.

Edit: my thought with the power supply is that there is an open circuit fault that clears as it heats up.

Edited January 22, 2020 by MPR

[Il Grifone]

I would go for the power supply as I have never had a LED that is slow to come on. There is a first time for everything of course....

[John ks]

I tend to agree with the previous 2 posts

I assume your work bench is for working on trains & you should have a 12V supply for testing locos

Connect the strip to that power supply & see how it behaves

 

For those that don't know, these strips are usually groups of 3 LEDs & a resistor in series & these groups are in parallel along the length of the strip

If a LED or resistor fail then only that group will not light & the rest of the strip will light

If the power supply is at fault then the complete strip will misbehave

John

[Captain Kernow]

Interestingly, what I have now established is that the longer you don't use the LED lighting, the longer it takes for it to come on.

 

If I use the workbench every day, or nearly every day, then the lighting comes on as soon as it's turned on.

 

If I don't use the workbench for a few days, then the lights have a delay coming on, but they do eventually come on.

 

I don't know why this should be, though.

 

[John ks]

I would tent to suspect the power supply

things to try

after a few days 

1      try a different PS (power supply). if the LEDs light immediately then the PS is the most likely suspect or

2      connect a volt meter to the PS & LEDs & switch it on. If the volts rise slowly then the PS is suspect

 

There's not much to fail in a LED strip, as I said a couple of posts back

 

The following is speculation 

If the PS is at fault it could be a capacitor  that loses its charge over a few days 

When it gets to a certain point it takes a while to recharge & turn on the PS

 

John

[gordon s]

Not sure if yours are similar to our, but also check the small connectors to the strip. We have them under our kitchen cupboards and occasionally the connectors play up and exhibit similar problems. From memory I think I hard wired one of them to prevent the connector gradually moving apart.

Edited February 14, 2020 by gordon s