LED Design

giulianom · Jun 12, 2011

I have started to look for separate drivers, but the trouble there is finding one that can power 1500mA @ 30-34Vdc.

Found plenty that will do 1500, but at a max of 24V...

giulianom · Jun 12, 2011

The 555-timer circuit could probably work, though I'd have to figure out how to use the 30-34V coming from the constant-current driver...

A step-down voltage regulator, perhaps, to power the 555 circuit.

I'd like to still see if I can find a dimming boost driver that can take a input of 18-24V from a switching power supply, and output 1.5A @ 30-34V...

giulianom · Jun 12, 2011

So after doing some research, it looks like I may be able to use the "http://www.reuk.co.uk/LED-Dimmer-Circuit.htm">dimmer circuit for LED bulbs</a>" as listed before, with a higher-power NPN transistor.

The diagram isn't very clear...

This diagram is MUCH clearer:
[IMG]http://www.dprg.org/tutorials/2005-11a/index.html">http://www.dprg.org/tutorials/2005-11a/index.html</a>

I thought a TIP31A NPN transistor would work, being able to handle up to 60V and 3A:
[IMG]http://www.kpsec.freeuk.com/components/tran.htm">http://www.kpsec.freeuk.com/components/tran.htm</a>

Since it's just being used as the switching mechanism, the max of 60V is more important than the current...

Also I would need to regulate the 30-34V power coming from the LED Driver down to 5V-18V to feed the 555 timer.

A LM7805 can handle an input voltage of up to 35V, and outputs 5V max 1A:
[IMG]http://www.fairchildsemi.com/ds/LM%2FLM7805.pdf">http://www.fairchildsemi.com/ds/LM%2FLM7805.pdf</a>

Or, come to think of it, this MOSFET IRFZ46N is rated for 55V 53A, as suggested in the DPRG diagram:

[IMG]http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=669978&productId=669978&keyCode=WSF&CID=GMC">http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=669978&productId=669978&keyCode=WSF&CID=GMC</a>

Thoughts?

jbadd99 · Jun 12, 2011

http://led.linear1.org/led.wiz">http://led.linear1.org/led.wiz</a>

A useful link for LED info in general, including an array wizard...

giulianom · Jun 12, 2011

Thanks.. The led array chip has a 5x10 arrangement of 1w leds, prepackaged.

Designed to be driven at 1500mA, and between 30-34V..

The parts should be here by mid-July...

giulianom · Jun 12, 2011

I believe I have found a suitable dimmer that can take the 30-34V @ 1.5A from the LED driver, and output to the LED with dimming control:

http://cgi.ebay.com/PWM-DC-Motor-Speed-Controller-Board-dimmer-LED-Bulb-/300570730855?pt=LH_DefaultDomain_0&hash=item45fb696167">http://cgi.ebay.com/PWM-DC-Motor-Speed-Controller-Board-dimmer-LED-Bulb-/300570730855?pt=LH_DefaultDomain_0&hash=item45fb696167</a>

For $20, I believe it's worth a shot.

giulianom · Jun 12, 2011

Also available directly from the store:

giulianom · Jun 12, 2011

Here is the $20 LED Dimmer board I got from MDFly.com:

http://www.mdfly.com/index.php?main_page=product_info&products_id=792">http://www.mdfly.com/index.php?main_page=product_info&products_id=792</a>

The board is SMALL - less than the size of a business card.

I confirmed with the company that the duty cycle ranges from 1% to 99%, so I should be able to get some good dimming capabilities.

[IMG]http://i.imgur.com/t3fIT.jpg>

alt="" /></a>

The only thing I need for the board is a project box, and a 4.7K or 5K potentiometer - either linear, or logarithmic.

I figure I can get both at Fry's, and see which works better.

The 50W LED and power supply driver should be here in a week or two...

peaches7412 · Jun 12, 2011

How much did this all cost you?

giulianom · Jun 12, 2011

Here is the parts list, with costs:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250825245867&ssPageName=STRK:MEWNX:IT">1pcs High Power 50W White LED 4000LM Saving Lamp Light</a> (250825245867): $35.99

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250828846387&ssPageName=STRK:MEWNX:IT">Power 50W Waterproof Bulb Led IP67 30-35V 1.5A Driver</a> (250828846387): $26.99

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220738462299&ssPageName=STRK:MEWNX:IT">45mm Lens Reflector with Base for 20-50W LED Lamp Blub</a> (220738462299): $12.00

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130417087135&ssPageName=STRK:MEWNX:IT">4 Socket Intel LGA 775 CPU Cooler Fan Heatsink 20-825</a> (130417087135): $9.09

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300570730855&ssPageName=STRK:MEWNX:IT">PWM DC Motor Speed Controller Board dimmer LED Bulb</a> (300570730855)" $19.95 + $1.95


Total: $105.97


Effectively a 5 x 1w (50W) LED spotlight with 20,000K color temperature.

giulianom · Jun 12, 2011

GiulianoM;663028 wrote: Here is the parts list, with costs:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250825245867&ssPageName=STRK:MEWNX:IT">1pcs High Power 50W White LED 4000LM Saving Lamp Light</a> (250825245867): $35.99

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250828846387&ssPageName=STRK:MEWNX:IT">Power 50W Waterproof Bulb Led IP67 30-35V 1.5A Driver</a> (250828846387): $26.99

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220738462299&ssPageName=STRK:MEWNX:IT">45mm Lens Reflector with Base for 20-50W LED Lamp Blub</a> (220738462299): $12.00

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130417087135&ssPageName=STRK:MEWNX:IT">4 Socket Intel LGA 775 CPU Cooler Fan Heatsink 20-825</a> (130417087135): $9.09

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300570730855&ssPageName=STRK:MEWNX:IT">PWM DC Motor Speed Controller Board dimmer LED Bulb</a> (300570730855)" $19.95 + $1.95

Total: $105.97

Effectively a 5 x 1w (50W) LED spotlight with 20,000K color temperature.

[/QUOTE]

FYI - the link to the 50W LED above goes to a 6000-7000K version, not the 20,000K LED that I bought.

At least, I hope it's a 20,000K model. :)

Also, the heatsink arrived.

The aluminum core is about 22mm in diameter, with the fins having about a 3mm gap.

To attach the LED plate, I should be able to do one of two things:

<ol>
<li>Sandwich the LED chip in between the heatsink and the plastic backing plate - the opening in the plastic backing plate is just about 30mm square.</li>
<li>Attach the LED chip directly to the heatsink, using 3mm long bolts to go in between the fins.</li>
</ol>

[IMG]http://i.imgur.com/witJB.jpg>

alt="" /></a>

>

alt="" /></a>

giulianom · Jun 12, 2011

So it looks like the LED may actually be 6000-7000K... The seller changed the description after I bought one.

Still won't arrive for another week.

How can I tell the difference between 6000-7000K and 20,000K?

It's not like I have a spectrum analyzer...

giulianom · Jun 12, 2011

Try to save a few bucks, get screwed by eBay seller who ships a 7000K led instead of the 20000K one I thought I was buying... :cussing:

So I bought this 20000K led from another seller... Same one suggested earlier in this thread.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270738329590">http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270738329590</a>

Also ordered this 90 degree lens while I was at it...

[IMG]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220664135458">http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220664135458</a>

Should I keep the 7000K LED?

haninja · Jun 12, 2011

You might want to check my thread about these 50w LEDs.

giulianom · Jun 12, 2011

haninja;663955 wrote: You might want to check my thread about these 50w LEDs.
http://www.atlantareefclub.org/forums/showthread.php?t=55528">http://www.atlantareefclub.org/forums/showthread.php?t=55528</a>[/QUOTE]

Thanks for the link!

Good to see the pictures.

I'm going to try these 50W LEDs out and see...

I thought I saw some 20-30W LED chips that were listed as 16000K, and some 50W 10,000K models.

I might try a blend of different spectrums.

morganatlanta · Jun 12, 2011

Leave negative feedback for the eBay seller and see if they will make it right. Seller ratings are extremely important to them.

giulianom · Jun 12, 2011

The seller has offered to send me the 20,000K version, so I will see if I can do that.

I bought the other 50W and the LED driver from the seller in post #77, so maybe I'll eventually have a pair of LEDs to compare.

I figured I'd need more than one, anyway...

giulianom · Jun 12, 2011

GiulianoM;663020 wrote: Here is the $20 LED Dimmer board I got from MDFly.com:

http://www.mdfly.com/index.php?main_page=product_info&products_id=792">http://www.mdfly.com/index.php?main_page=product_info&products_id=792</a>

The board is SMALL - less than the size of a business card.

I confirmed with the company that the duty cycle ranges from 1% to 99%, so I should be able to get some good dimming capabilities.

[IMG]http://i.imgur.com/t3fIT.jpg>

alt="" /></a>

The only thing I need for the board is a project box, and a 4.7K or 5K potentiometer - either linear, or logarithmic.

I figure I can get both at Fry's, and see which works better.

The 50W LED and power supply driver should be here in a week or two...

So from what the seller has told me, I can use this dimmer with a 40V driver - but I would probably have to add a small TO-220 heatsink to the back of the MOSFET shown above, the one next to the big resistor.

Here's a pic of the back.

I would have to mount a small heatsink onto the solder pad.

>

alt="" /></a>

giulianom · Jun 12, 2011

The 60-degree lens has arrived.

Top

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Bottom

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alt="" /></a>

The instructions on the ebay page said to glue the lens and frame to the LED with 2-part epoxy glue.

I'm not sure I like the idea of a permanent bond with the optics, so I may try to make some kind of framework to hold the lens assembly in place.

morganatlanta · Jun 12, 2011

If you just use a little dab of epoxy, you would probably be able to pop it off it you wanted to.

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