(Correction: It is 8x10W not 8x50W!)
For an aging member of my family who have eyes sight issue I wanted to create a powerful light source, so here I am, my first experience with LED. Big thank you to the Instructable users steveastrouk for his expert guidance and to the young Yonathan24 for the inspiration.
The device is composed of 8 x 10 Watt white LEDs mounted in series on an aluminium frame. Total cost is about 80 US$ half of it coming from the LED power supply driver itself that cost me 44 US$. I found cheap LEDs on the Net (0.78 US$ a piece), probably not the best quality but I am not building a spacecraft. Using another method, one small driver per LED, you can probably made it for about 50 US$ (I will try this alternative solution, keep posted!)
Sktechup model can be found here, not factory quality design but close to what I made.
Nothing complicated, you will need about 4 to 5 hours to completion.
In advance I apologize for my Frenchglish...
Step 1: What You Need
This is what I used:
- A tap handle
- A 2mm single pass tap
- A 1.6 mm drill
- A tube cutter
- A small plier/cutter
- A small screw driver
- A rule
- Something to marque before drilling (English translation welcome)
- 2x 500x6mmx2 aluminium tube
- 50cm 0.8 mm copper wire
- General purpose oil (cutting oil better)
- Thermal past
- Epoxy glue
- a #11 and a #14 key
- "Super" Glue
- A wire cutter
- Some wire
- a 100K potentiometer
- 8 x small heat sinks
- 8 x 12V 10W white LED
- 2 x female connector
- 2x male connector
- Soldering past
- A multimeter
- 16 x 2 / 3 mm flat head screws
- A soldering iron
- A driller
- A LED driver
- A small box for the dimmer
The LED specification is:
- Model: 10W
- Color: Cool white
- Forward Voltage (VF): DC 9-12V; Forward current (IF): 1050mA
- Out put Lumens: 800-900LM
- Color temperature: 6000-6500K
- Beam Angel: 140 degrees
- Life span: >50,000 hours
The LED power supply driver model is: Mean Well ELG-100C-1050BLED power supply, 1050mA, 48-95v 99.75w PI67, CC 3 in 1 dimming.
Step 2: Fixing the LED on the Heat Sink
Fixing the LED on the heat sink is probably the most difficult but the most important of the project.
My LED have two 2.5mm holes, perfect to fits the 2mmm screws. Most of the 10W LED I saw are built on the same layout
- Mesure the hole positions on the heat sink and use something to mark before drilling them. (my "something" is show next to the heat sink on the first photo, a "pointeau" in French, translation suggestion welcome)
- Drill with a 1.6mm drill. I used a 1.5mm drill and move the piece around the drill to make the hole bigger. Not ideal but a 1.6mm drill is not easy to find. 1.5mm is too small for the 2mm tap.
- Clean and make the thread holes using the tap. Slow and steady, turn a half tour and back a quater, this is the move. Better to try first on a spare, it could be a bit tricky if you never did before, especially that small. You can find a guide here. Aluminium can be sticky on the steel tap, check after each drill
- When done clean the surface and remove the blue plastic protection sheet if as like me there is a thermal patch on your heat sink
- Clean around the hole, you may find some metal scrap that will prevent the LED to stick correctly on the surface of the sink. I used a small screw driver
- Put some thermal compound, it cannot hurt even if there is already a thermal patch. You can spread it a bit before installing the LED
- Install the LED and screw it on the surface of the heat sink with two 2x3mm screws. The aluminium base of the LED is about 1.5mm tick it is very rigid and will transfer the pression on all the surface of the LED base ensuring a good contact with the heat sink.
- Only 7 assembly to go
You may use only a thermal adhesive if this is too complicated for you but I am not sure if it will be strong enough
I am using a Dremel 3000 tool on its workstation to drill the hole. Much easier and precise than doing without and with a bigger driller.
Step 3: Fixing the Heat Sink/LED Assembly on the Alu Tubes
I could have made a better job here and use a more formal method or a different way to fix the heat sink on the tube or a different support. I did it a straightforward simple and a bit dirty way.
- Align and space your 8 sink/LED assemblies, LED down. Remember to alternate the orientation of the LED to allow the wiring in series as show in the first illustration.
- Use a space heat sink to space them
- Align the heat sinks pushing then laterally with a rule or any strait guide
- Place the two 500mmx6mm aluminium tube on the top of the aligned heat sink, then should space then self automatically finding their place between the row of the heat sink construction
- Prepare a small amount of epoxy glue and apply it on the side across the heat sink edge and the aluminium tubes. The glue I used start to get harder after 5 minutes. I was able to glue two sinks per epoxy preparation batch
- Wait, how long depends of the glue you use.
The result was a bit messy, see the photo. Somewhere it ruined my efforts of trying to get something aesthetically appealing. I tested with super glue, it it much cleaner but remember you cannot make any adjustment, it requires much more precision and preparation. You can also screw the tubes to the heat sink as show in the illustration or use a completely different way.
On the sktechup prototype I flatted the extremities of the aluminium tube making a nice end to fix the rampe. In practice to need a small press, using a hammer give a ugly result, see a test on last photo, so I keep my tubes intact.
About 20 minutes plus the time for the glue to harden
Step 4: Wiring
During the previous step you fixed the sink/LED assembly alternating each by 180 degres so the plus + connector face the minus - of the previous or next assembly. Check the first above illustration again. To connect the LEDs I used a 1mm thick copper wire, it look less messy than more flexible ones and it is supposes to offer less resistance.
The rest is easy.
- Cut 7 pieces of about 55 millimeter long in of copper wire.
- Ply each end at 1 mm at right angle on the same plan
- Solder the wires on the LED. I used a 30 watt soldering iron, largely enough, don't burn the LED!
10 minutes and it is done
Step 5: Wiring for the Power Supply
Following the expert advice of steveastrouk I use a Mean Well ELG-100C-1050BLED power supply, 1050mA, 48-95v 99.75w PI67, CC 3 in 1 dimming. See above the photo of the sticker. AC on the left, DC on the right to the LED ramp and a wire for the dimmer (explanation next step)
I could have soldered the power supply directly to the ramp but I choose using a connector. Easy steps
- Using a small L shape aluminium profile super-glued on the aluminium tube, I mounted a female connector
- A small piece of wire (here in orange) connects the male pine of the connector to the male pot of the first LED
- I connect a black wired to the negative pot of the last LED. I passed the black cable inside the tube. Just drill a 3mm hole through the aluminium tube at each end and pass the cable. A bit tricky but you can handle it ;)
- Cut and sold are required
Done after 30 minutes
Step 6: Dimmer
The dimmer is installed on the white and blue cable of the power supply. As you can see on the photo the drive have one power input cable on the left and two cable on the right The thinner cable, blue and white is where you will have to install the dimmer. (it is the blue and white cable of the dimmer, on the photo inside the small box its is red and green) The dimmer is use is just a potentiometer. It is a 100K potentiometer in a small box, no electronic just sold the two cables on the central and one external connector of the potentiometer. It is possible to install a 10V PWM (Puls Wave Modulator) but I do not have one. With a PWM it maybe possible to obtain a smoother dimmer more gradual dimming. I could have fixed it on the LED ramp but like this my ramp is entirely independent of the power supply. The illustrations above are self explanatory. As far I can can understand it does not matter were to connect the plus or minus on the potentiometer just use the middle and side connection pot.
Step 7: Test and Conclusion
Time to try your ramp. It is very bright protect your eyes.
The LED light at about 35 volts and are stable around 48 volts. I get 76.4 volts at maximum power (89V without anything connected to the power supply) so each LED get 9.5V a perfect safe voltage for a 12V LED (10 Volts is nominal for a 12V LED)
There is 9 LED cells in each of the 8 LEDs. I used an old radiography to check the LED quality at low power (the black image above). As you can see not all of the small individual LED light at the same power, it is due to impurity in the LED substrat. Remember these are 0.78 US$ a piece LED! In the electronic shopping center they propose me LED with the same spec at 8.8 US$ a piece! Not sure but I guess the quality must be a bit different (or not...)
Job done (but on the photo Bob the cat don't care, snobbish boy)
Step 8: What's Next
In order to reduce the cost by about 45% I will try with one mini driver per LED as illustrated. Waiting for the spares I got 8 x 12V 10W LED plus the drivers for US $20.72 on the Net, I wish I could get it from a flesh and bones shop but at US $71.00 the difference is to big! Design prototype here