LED strip lights stopped working

Thread Starter

soopytwist

Joined Dec 23, 2016
42
About 18 months ago I fitted LED strip lights behind my computer desk while moving in new furniture and an LED controller lead with an infrared receiver connected to a free USB port at the back of my PC. When I got Oculus Rift I had to disconnect the strip lights because I needed the USB extension lead I was using (as the LED controller lead is too short) and I left it off for a long time unused. I've now got a new USB extension and plugged the strip lights back into the PC but the LED's no longer light up.

I've tried the extension lead with my mobile phone charger and the lead is fine. I've tried replacing the battery in the remote control to actually turn on the lights, since it's the only way I can, but still can't turn them on. I have no idea if the remote controller even works as there's no other way to test it but with a new battery in it's probably fine.

I've also tried plugging the strip lights directly into a USB 0-2 4A connector on my power socket extension, thinking that perhaps the USB ports on the back of the PC aren't working. But then I've also tried plugging a memory stick into the extension lead and that works just fine.

So either the strip lights have mysteriously stopped working because I've not used them for nearly two years or the LED controller lead is faulty or the remote controller is faulty. Either way I have no other means to test them to see what the culprit is. Other than buying new strip lights of course but then I'd have to dismantle half my bedroom to get at the back of the desk now!

https://imgur.com/Q1pgH0j
 

iONic

Joined Nov 16, 2007
1,662
Would be nice to see the LED strip connection point. The LED's are likely just fine but confirming this by applying power to the strip alone would point more solidly to the controller or remote.
 

Thread Starter

soopytwist

Joined Dec 23, 2016
42
Would be nice to see the LED strip connection point. The LED's are likely just fine but confirming this by applying power to the strip alone would point more solidly to the controller or remote.
My apologies for the late reply. Also sorry for the rubbish photo but it wasn't easy getting my iPad down there to take this picture with a torch! So I've got 4 pin holes, if I connected a 12v transformer to the bridge between the strip and the LED controller which pins do I connect the negative and positive to?
https://imgur.com/kHMO2z5
 

ian field

Joined Oct 27, 2012
6,536
About 18 months ago I fitted LED strip lights behind my computer desk while moving in new furniture and an LED controller lead with an infrared receiver connected to a free USB port at the back of my PC. When I got Oculus Rift I had to disconnect the strip lights because I needed the USB extension lead I was using (as the LED controller lead is too short) and I left it off for a long time unused. I've now got a new USB extension and plugged the strip lights back into the PC but the LED's no longer light up.

I've tried the extension lead with my mobile phone charger and the lead is fine. I've tried replacing the battery in the remote control to actually turn on the lights, since it's the only way I can, but still can't turn them on. I have no idea if the remote controller even works as there's no other way to test it but with a new battery in it's probably fine.

I've also tried plugging the strip lights directly into a USB 0-2 4A connector on my power socket extension, thinking that perhaps the USB ports on the back of the PC aren't working. But then I've also tried plugging a memory stick into the extension lead and that works just fine.

So either the strip lights have mysteriously stopped working because I've not used them for nearly two years or the LED controller lead is faulty or the remote controller is faulty. Either way I have no other means to test them to see what the culprit is. Other than buying new strip lights of course but then I'd have to dismantle half my bedroom to get at the back of the desk now!

https://imgur.com/Q1pgH0j
That type of mysterious failure can be dodgy electrolytic capacitors. It was a common thing in consumer electronics servicing - a householder would flip all the main breakers before going on holiday, on their return - various 24/7 devices go bang when they reset the breakers.

Dodgy lectros tend to run hot in SMPSUs, to some extent this can mask the symptoms of lost electrolyte. When powered up cold - some of caps pretend to not even be there. the result can be anything from not starting up, to starting up too much all at once. If it doesn't go bang straight away - just keep flicking the on off switch till it does...……...
 

iONic

Joined Nov 16, 2007
1,662
Do you have a multimeter? Plugging in the USB device into a working USB port and using the remote should yield a voltage on two pins Ground and R, G, B. Selecting white on the remote should activate all channels so you would get 5V from ground(not sure which pin that is, probably one end or the other) to another pin. Not voltage detection will definitely confirm that either the remote or USB device is not working.

Is this remote using IR to signal the USB device. There may be a way to tell if it is functioning.
 

Thread Starter

soopytwist

Joined Dec 23, 2016
42
My apologies for not replying sooner. I had to wait until I could dismantle my desk to remove the strip. Here's a couple of photos. When I plug the USB into my PC I don't hear the usual "bing-bong" sound that plays when a USB device is connected. Perhaps you don't if there's just a v5 and GND wire...?

Anyway this strip doesn't work and I still don't know why.

 

Tonyr1084

Joined Sep 24, 2015
7,853
Do you have any electronics stock you can use to make a 5 volt tester with? Such as an LED and a 330Ω resistor? Having such you can put it across the red and black leads and see if the LED lights up. If it does - you have power. There IS the possibility of a broken wire inside the insulation. It happens. Rare, but it can happen. Especially if a cable is stressed accidentally.

Other things you can use would be a small motor. Solder some leads to it and touch the ends of the leads to the red and black wires. If the motor runs then you have power. Even an old speaker can tell you something. By tapping the speaker leads to the red & black, you should get a click or a pop. Do that repeatedly to determine if you have power. In my car, when I was faced with a nest of wires going to speakers I just used a 9 volt battery and tapped it to each lead. Whichever speaker popped I knew I had the two right wires for that speaker.

Looking around on my desk, asking how would I verify if something had power. The thing with the LED - that you have to get the wiring right or you can possibly blow the LED. Not necessarily, but it all depends on the LED. A small motor, and by small I mean no larger diameter than that of a quarter. Something NOT bigger than a C Cell battery. It may be 5 volts, may be 12 volts. Could even be 24 volts. The point is that if the motor spins at all - you have power.
 

Thread Starter

soopytwist

Joined Dec 23, 2016
42
I'll see what I can use, other than than I'll have to buy a multimeter. Incidentally I removed the USB lead and soldered on a new one but the lights still don't work so that rules out a break in the lead.
 

Thread Starter

soopytwist

Joined Dec 23, 2016
42
Hmm. The motor test gave some interesting results. So with the new lead I soldered on (red and black wire) the motor doesn't spin. If I connect the motor to the old USB lead (while plugged into my PC) the motor spins. The newer lead as two more wires, white and green so maybe the red and black I used are the wrong ones? Anyway, even if I solder the old lead back on which does spin the motor the LED strip still doesn't light up.
 

Ya’akov

Joined Jan 27, 2019
9,079
Hmm. The motor test gave some interesting results. So with the new lead I soldered on (red and black wire) the motor doesn't spin. If I connect the motor to the old USB lead (while plugged into my PC) the motor spins. The newer lead as two more wires, white and green so maybe the red and black I used are the wrong ones? Anyway, even if I solder the old lead back on which does spin the motor the LED strip still doesn't light up.
You can check the IR remote by pointing it at your iPad or other digital camera. The sensor can see IR and it will appear to be blinking though you don’t see it unaided.

You might try replacing the batter(ies) in the remote if you don’t get anything from it and you haven’t already.
 

Tonyr1084

Joined Sep 24, 2015
7,853
Anyway, even if I solder the old lead back on which does spin the motor the LED strip still doesn't light up.
Sorry, I have to ask this question. We all make mistakes. Is it possible you got the polarity wrong when you soldered the wires back? I ask this because I've done this. It happens.

A few months ago I fixed my CB Radio. Initially I plugged it into power backwards and blew the reverse current protection diode. THAT diode went short, so that when I tried plugging it in correctly it just blew the fuse. So I figured out that the diode was shorted and I replaced it with the same value and capacity diode and it still blew fuses. Perplexed as to what I did wrong - I finally noticed I put the diode in backwards. I think it's safe to say we ALL have made similar mistakes before.

Now - DON'T go swapping the wires to see what happens. You MIGHT just blow out what may otherwise be a good circuit. This is where experience and knowledge comes in to play. You have to make sure you're connecting the right polarity BEFORE you apply power. Otherwise you may end up buying new lights. I'm just saying - be careful.
 

Thread Starter

soopytwist

Joined Dec 23, 2016
42
I soldered the old USB lead back on (in the right place, as it was before). If I plug that in and hold a motor to the red and black wires it spins up but the LED strip doesn't work. Neither does it if I change the batteries in the remote. And I've tried looking at the remote though my iPad's camera and I can see it flashing so the remote is all good.

So either the LED's are all blown, or the controller is fried.

I can understand this thing maybe not working after using them for a long period of time but I only used them for a few months before unplugging the USB lead because it wouldn't reach the back of my PC. Left unplugged an unused for more than a year, when I finally come to use them again they just don't work. I can't understand it.
 

Tonyr1084

Joined Sep 24, 2015
7,853
Well, if memory serves, you changed the cord between the last time they worked and now. I continue to be suspicious whether you wired it backwards or not. I'm also now wondering if during soldering you damaged a pad and have lost connection to part of the circuitry. Bottom line - may be time to buy new. And if you DO buy new, have a look at how the new one is wired. If you've wired yours backwards then you have the answer to why the original unit failed.

If we haven't asked for a closeup of the connections to the board along with the board circuitry, can I please ask for such? It's possible we may see a fundamental problem that can be easy to overlook.
 

djsfantasi

Joined Apr 11, 2010
9,156
I soldered the old USB lead back on (in the right place, as it was before). If I plug that in and hold a motor to the red and black wires it spins up but the LED strip doesn't work. Neither does it if I change the batteries in the remote. And I've tried looking at the remote though my iPad's camera and I can see it flashing so the remote is all good.

So either the LED's are all blown, or the controller is fried.

I can understand this thing maybe not working after using them for a long period of time but I only used them for a few months before unplugging the USB lead because it wouldn't reach the back of my PC. Left unplugged an unused for more than a year, when I finally come to use them again they just don't work. I can't understand it.
But there’s a MAJOR difference in your test.

Motors spinning is not polarity sensitive (excluding direction). They’ll spin no matter how you connect the wires. Just in different directions.

The LED strip and controller IS polarity sensitive. If connected backwards, the least that will happen is they won’t light. At most, you can blow them or the controller.
 
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