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

Comments

[SIRJAMES09]

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

...to some, a way of life(not so funny).

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

[saintneko]

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.)

[jimvandamme]

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?

[billbob]

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.

[saintneko]

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?

[billbob]

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)

[pxhughes]

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.

[saintneko]

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

[MarkSBurgunder]

Thanks for the tip. I'll have to try the blinking at some time.

[kscience]

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.

[jebecca]

Is your lamp Glowbal from Ikea?

[ShadowGirl]

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

[ferny121]

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(:

[sensoryhouse]

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.

[MarkSBurgunder]

That's a really neat job. Well done. Why did you add the blue LEDs?

[johnnyshaman]

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…

[constructor]

Nice project! Keep it coming!

[Spokehedz]

Cheaper LED strips: http://www.dealextreme.com/details.dx/sku.5312 - Although from the pictures, some of them are less 'white' than others. Free worldwide shipping.

[MarkSBurgunder]

Great find. I'll have to ad dealsextreme to my list of suppliers. In the past I have uses http://besthongkong.com for LED purchases.

[kscience]

Ouch. I used to buy from besthongkong via eBay- he got too busy, and the last time we did business I bought 100 white leds from an auction that in payment said blue led's. I emailed him, he said they were white. I b\got blue ones, that did not work as vu meter lamps on a 48 channel mixer. Ouch. topbright88 on eBay has all these leds, plus 100ma "straw hat" 140 degree leds. No heat sinking needed. I will post some desk lamps soon that run off of plain old 115vac asap..... Leds Rule, and they are here, now. Lets get our heads around them, I'bles sisters and brothers.

[Yerboogieman]

I have a blue florescent bulb like that!

[pravardhan]

I think these are low powered LED's. Try The Philips - LumiLeds LEDs like Luxeon I, III or the Rebel. It's mainly designed for lighting purpose.

[MarkSBurgunder]

Correct, they are fairly low powered. The whole strip of 30 LEDs is drawing about 200mA. All LEDs together only use 2.4W. I have used 5W Luxeon stars for a couple of bedside table lamps and they get a lot hotter! The one thing I found a bit of a pain with the Luxeon stars is that is quite hard to solder on connections as their base acts a bit like a heat sink and draws away a lot of the heat of the solder iron.

[STEVENSJDOG]

How did you attach led strips to inside the lamp?

[MarkSBurgunder]

Sorry. I realise now, that I missed this step. I used the double sided mounting tape to just stick the sticks on to the inside of the lamp. Before I did so, I check with a multimeter that the tape isn't a electrical conductor. The mounting tape I used is sticky on both sides and has a 1mm foam base which helps with any slight unevenness.

[ironsmiter]

nice 'ible, but OUCH at that cost!

For not much more, you can get a "designer" led desklamp from konceptech

I'd suggest looking for a string of line voltage powered led christmas lights. I got a nice, bright string for $4 a month ago, to replace the ccfl backlight on my lcd monitor. Probably even cheaper now that christmas is over.

[MarkSBurgunder]

Agree, if you went out to buy all the stuff new it would get relatively expensive. I already had most of the stuff and only needed to buy the LED strip. Even if you take into account the purchase cost of everything I used my lamp comes in at about $75 US compared to about $140 US for the designer lamp. That's still quite a difference to me. :-)

[mikedoth]

LEDs are great.