Retro Fit a Desk Lamp With LEDs




This instructable details the steps I have performed to change a desk lamp I already had to use LEDs instead of a fluoro tube.

This project cost me at this time $49.95 Australian for the strip of 30 LEDs.
I already had the desk lamp. If i had to buy it it would have cost me ~ $40 Australian. As the LED strip is geared for 12V I used a power pack / wall wart I had spare. If I had to buy a wall wart I guess it would have cost me anoth ~ $20 Australian.

So I guess you could argue that this project really cost ~ $110 Australian which is roughly $75 US.

Check out the individual steps to see what I have done to end up with a quite passable LED desklamp.

Step 1: All the Bits

Just a quick list of all the bits I used.

- Ikea desk lamp (worth about $40 Australian)
- Old wall wart providing up to 1.4A at 12V (less amps will probably still work ok)
- Double sided mounting tape.
- Strip of 30 SMD LEDs

Step 2: Disassembling the Desk Lamp

First up I removed the cover on the lamp head to check out what's inside and what can be re-used for this project (or later projects).

Image 1
How the lamp head looks before the surgery.

Image 2
Remove the two screws and the wing nut. This will allow you to remove the bottom cover.

Image 3
The bottom cover is off and the switch and base for the fluoro tube can be clearly seen.

Image 4
As you can see, the switch has not got any srew terminals for the electrical connections. The terminals are of the type where the cable is pushed in and is locked in place automatically.
To release the cables I had to carefully push in with a small screw driver to release the cable lock.

Image 5
View of the switch and a short piece of cable I reused due to the new cable not being fat enough to lock in the switch terminals.

Step 3: Preparring the LED Bits.

The LED strip I bough was way to long to fit into the head of the desk lamp I had. Luckily the strip can be cut into shorter pieces at a number of locations along the strip. I cut my strip into three lengths of very roughly the size and re-soldered the bits back together in series the same as they would have been connected if I hadn't cut the strip into pieces.

Step 4: Threading the New Power Cable Through the Arms

Make sure that you attach a string of some sort to the old power cable before you pull it out of the arms. This string will make it so much easier to thread through the new power cable.

Once the old power cable has been removed and the string is in place, sticky tape the new power cable to the string and gently pull the new cable trough the arms.

Step 5: Connecting and Mounting the LED Strips

I now connected (soldered) the cable carrying the negative pole directly to the negative lead on the LED strips.

The positive lead from the wall wart and the LED strips I connected to the two terminals on the light switch.

Where ever I soldered two cables together I used some shrink tubing to provide insulation.

Lastly I wound the surplus cable neatly around the two posts provided to make for a tidier look.

Step 6: Test Drive

Next up some images of the test drive before final assembly.

Step 7: Final Assembly and Final Test Drive

After the initial test drive I screwed on the bottom cover again which made it all look neat and tidy again.

I have found during many of my projects that you can not have to many test drives. Some projects have worked through all the test drives but failed after the final assembly.

Step 8: Old New Desk Lamp Back on My Desk

And here you go. My desk lamp is now using LEDs It feels as bright as the old fluoro set-up.
The good thing though with the LED set-up is that I made it work... :-)

erm .... and it also uses less power. 2.4W as opposed to 9W.



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    29 Discussions


    Reply 3 years ago on Introduction

    That is true now. Maybe not so much 6 years ago.
    Plus the aim for me wasn't necessarily to save money, but to make something :-)


    7 years ago on Introduction

    why couldn't LED's be scavenged from elsewhere?? and then install them in the lamp?

    Here in America, Dumpster diving is a national past time LOL some, a way of life(not so funny).

    You would be surprised what you can find in a dumpster....


    10 years ago on Step 1

    Less amps should make the leds less bright and longer lasting, due to less heat being pumped through them - in fact anything you do to keep them cooler will lengthen their life span ( like if you make them blink at 60+ cycles a second - you can't tell the difference but they draw much less power and heat, but you have to make your own electronics for that.)

    8 replies

    Reply 7 years ago on Introduction

    COOL, that's what you want. They will last a little longer on DC, non-pulsed current. But if pulse width modulation is the only way you can get the total dissipation down, it's better than nothing. Don't think you can jack up the instantaneous amperage to get the light output back up; that just increases the stress. If you run them below their power rating, they will last longer than you will, but the power supply is what you have to look at next. Will the electrolytics dry out before 50,000 hours? Do the transistors run hot?


    Reply 10 years ago on Introduction

    dont LEDs have a lifespan of 25,000-100,000 hours running them at their rated specifications?(thats what makes them so awesome yea? along with durability and efficiency) unless you are overdriving them it might not be worth it to make them blink.


    Reply 10 years ago on Introduction

    if you blink them, you will reduce their power consumption, ambient heat, and increase their lifespan. If 100,000 hours is good why not go for 150,000?


    Reply 10 years ago on Introduction

    well if they survive 150,000 hours, driving them 8 hours/day the lamp would last about 50 years. by then i think it would be considered ancient technology. im just saying, unless you really really want the lamp to last half a century or more, it might not be worth the bother (also making them blink will make the overall brightness slightly dimmer)


    Reply 10 years ago on Introduction

    listen to billbob. That old stunt of strobing LEDs is left over from extending battery life in handheld calculators circa 1975. That technique also used to strobe them at a few thousand Hz with a duty cycle of around 10%. Strobing at 60hz will be very noticeable. Kept within specs, changing the duty cycle of a single PN junction won't noticeably change the espected operating life. It is still going to be about 100,000 hours MTBF. That aside, there is a basic flaw with the economics of this project in the first place. Assuming everything else was free, you want to spend AUS$50 for the strip of LEDs to save a whacking total of 7 watts. At my current rate of CAN$0.11 per kwh, thats about 1260 hours to save $1. On top of that, your are ignoring the inherent waste of the wall wart. Stick your hand on it. It is warm. That is 100% waste energy, and I will bet you that it is more than 7 watts. To re-engineer this project, don't use a flourescent as your donor carcase, but one of those older 'banker' style lights and dump the 75w bulb. Go to your local dollar store and by 4 or 5 of those battery operated stick on closet lights (net cost 4 or 5 bucks) with five LEDs. They operate on 3 AA batteries. Chop away most of the housing nad the battery enclosure until they fit your lamp. Wire them in parallel and use an adapter from a discarded cell phone as a power supply. These also are conveniently between 3.6 and 5 volts and every sentient being over the age of twelve probably has a drawer full of them. breaking down the project cost: $5 - Led lamps $5 - Bankers lamp from thift store. $0 - AC adapter from discarded cel phone. Power savings ~70 watts.


    Reply 10 years ago on Introduction

    Fluorescents cycle at 50 or 60 hz, if I remember correctly. Of course, they do have the phosphor that retains the glow so it's less noticable, but at the same time, white LEDs are UV LEDs making phosphors glow, unless the technology has progressed since the last time I investigated the technology, so the same should apply. Christmas-light LED light strings cycle. You can see it when you wave your eyes back and forth past them, the light streaks are discontinuous. Eagerly awaiting your instructable for hacking the bankers lamp, that sounds pretty awesome. :D


    Reply 10 years ago on Introduction

    reduce your filter cap in the power supply. Increased ripple is the 60 or 120hz "blinking" that will lengthen the lives of led's. Pure dc, over temperature, will change the color temperature of led's, and reduce their lives at higher temperatures ambient.


    9 years ago on Step 8

    Thanks. This is a project I'd love to try.


    9 years ago on Introduction

    WOW this is sweeeeet.i gotta try this wen i get the supplies for it.but is it really worth it to change from bulds to LEDs?do they use up less power os sumthing? thanks for posting this(:


    10 years ago on Introduction

    Thanks for the idea.

    My brother gave me this old ikea lamp. The bulb was burnt out. Instead of buying a bulb I decided to add LEDs instead.

    I removed the 12v transformer and added a 3.7v inside the base.

    11 White 10mm LEDs
    6 Blue 5mm LEDs

    Click here to see it in HD.

    1 reply

    10 years ago on Introduction

    Sorry to be devil’s advocate – but it is my understanding that florescent lights are more efficient for a significant light output than LEDs. I don’t know where the trade-off between the light level takes place; if I figure it out any time soon I’ll post it. If your looking for MTBF then the LEDs win hands down. Another thing – many modern ballasts are actually pretty complicated electronic devices; they no longer cycle the lamp at line frequency. I have one sitting on my desk (for a customer’s system – not a desk lamp) that cycles at 2kHz or so…