Electronics PICs, Luxeons, PWM ...n00b in need of some advice!

These looked pretty reasonable... the luxeons I was looking at will pull about 350mA MAX so 500mA ought to be ample. I could spot anything about gain in the specs though.. ?

 

Those MOSFETs will be fine for a single luxeon, although they might get a bit warm. They are optimised for 10V gate signal, but should be fine with 5V from a pic.

I used farnell part number 327-2175 for my luxeon controller. I chose them mainly for their funny shape, as they are more compact than the TO92 shape. They're ludicrously over specified and will happily switch several Luxeon III LEDs.

 

hmm, well those seem a little OTT for my application, but perhaps something in-between. I need a pretty compact package (ideally) as I'd like to make these devices as small as possible. I'm only going to be driving a single Luxeon with each MOSFET - one red, one green and one blue (or would royal blue be better for colour mixing? I'm not sure so I'll try both). I'm aware of the heat problems with luxeons and as this is going to be quite a tightly packed device, something that runs cooler is more important than something that's tiny...

 

The Zetex ZVN4206A is a MOSFET designed for 5V gate voltage, so will not get as warm as the MOSFET you selected.

The bipolar transistor that I suggested doesn't appear to get warm during use with Luxeons.

 

Just put in a mahoosive order to farnell with all kinds of bits and peices. I got all 3 of the mosfets/transistors mentioned in this thread so I can have a play about and see what works / gets hot. Should be enough to get a bit more involved with all this stuff - Ziff sockets and breadboard is going to make life a lot easier!

Does anyone have any suggestions for a source of cheap lambartian emmitting luxeon emitters?

 

http://www.ultraleds.co.uk/ was pretty reasonable last time I looked, though I'm not sure if they sell those particular type or not.

 

Nice looking site - some good stuff on there, but unfortunately they don't have any red luxeons I found this site which appears to have luxeons of all different colours, but only the batwing emmitters. I was hoping to find the Lambartian emitters as they give more light straight out (better for this application).

I finally got TheAnimus's code working and sadly it's WAY too slow with the clock at 8Mhz. I'm trying to get the phase-locked loop setup working at the moment to see how it looks with an instruction cycle of 10Mhz. I'm starting to feel that this way of doing things just isn't fast enough.

I have some more / new PICs on their way with 3+ hardware PWM channels, so with a bit of luck, they'll be enough to cope with the higher speeds with enough cycles left over for me to load bits and pieces.

 

Which PIC's did you order? Only the 16F737, 767 and 777 have three separate PWM channels IIRC. Most of the other devices have more PWM channels but can only be used for the control of DC motors and similar applications (Half bridge and Full bridge).

 

try ebay for luxons.

As for PICs i think we have already covered that in this thread. A 10mhz PLL driven 18 series (gets effectivly 40mhz off 10mhz oscillator, giving a 10mhz instruction cycle) would probably make the coding the easyest. And the added current useage would be nothing compaired to the lights.

 

I'll have a look on ebay - maybe I'll find a bargain

I got a 16F767, 16F777, and 18F6520. The 18F one has 5 PWM channels Massively over the top, but since they're samples, I thought 'why not'

It's an 18F320 I've been using up to now - the same one I'm trying to get going using the PLL.

 

Yeh because this design is one off, and its the design cost thats going to be the highest, so wasting a whole extra £2 won't matter.

lots of people sell luxon's in their ebay shops, check the international sellers if the order cost is below 18 gbp (iirc) then import is free.

 

Won an auction this morning - 6 Lambartian Emitting 1W Luxeons are on their way as I type. Each one will draw 350mA which sounds like a lot to me. That's ~14x more than the LEDs that I'm using currently. I can't help feeling that 10 LEDs would be brighter, but I guess I'll have to wait and see. 1 luxeon certainly takes up less space than the equivalent (in terms of mA) 10 LEDs!

 

Hehe. That's what I thought when I first got my luxeons. So, I set up 20 'ultra-bright' LEDs from ebay. There was no comparison, the luxeon was so much brighter than the 20 LED array it was laughable.

 

I was going to do the same; 'great minds..' and all that Well that's certainly reassuring - cheers!

/me returns to watch the letter box - c'mon luxeons, arrive already!!!

 

Oh b*****... just found a cheaper site for Luxeons.

£6.52 per luxeon - all colours, all emitter types

 

Don't forget luxeonstar.com, they may actually be a bit cheaper, even if you have to pay VAT (which I haven't had to yet).

 

Foo! Why did I not find these sites earlier?! I googled 'n everything

 

Bah! My new 16F767's arrived only for me to realise my Olimex/IC-Prog programmer doesn't appear to support it. Can I just connect some wires to the appropriate pins? ..or use ICSP or something?

 

As an aside, has anyone got any good ideas about how to heatsink luxeon emitters? In particular, I want to mount several of them on a single heatsink, but can't work out how to do it.

The main problem is that the heatsink slug on the emitters is connected electrically to the die (and therefore finds an intermediate potential). Clearly, the individual emitters need to be insulated electrically from each other.

The problem is that the slug is so small that even the highest performing double-sided heatsink tape won't keep them cool. So, any ideas?

 

What about a mica shim of the sort you get in ATX PSUs etc. ? Why not just have 3 heatsinks?