Making LED Poi

I thought I'd resurrect this old topic mainly, I admit, to try to get some information from the trailblazers who have gone before. But perhaps I can add my own pointers also.

I'm looking to build some LED Poi with a microprocessor (probably an Atmel) driving a Luxeon Rebel Endor RGB Star. Cree seem to be a preferred LED manufacturer but finding RGB Cree Stars is more tricky. The power supply will be a couple of AAAs for weight and simplicity reasons. The microprocessor will use PWM to control the three LEDs and mix the colour.

I have previous experience with an ATMega driving an array of 5V LEDs to make a static POV display, but these power-LEDs (Luxeons and Crees) seem to require a whole new circuit design to cope with constant (and high) current.

Most power-LED projects on the Internet advise some sort of an LED Driver to achieve this, which for our 2*AAA (3V) power supply means a "Boost Converter" that boosts the voltage up to that required by the LED, and outputs a constant current. You specify the current at purchase and so can potentially run your LED at a higher current (brighter, but shorter LED life). The consensus seems to be that by _not_ using an LED Driver (or equivalent circuit) then you risk blowing your LED. The only suitable LED driver I have been able to find that takes our 3V input is the LuxDrive MicroPuck (https://www.luxdrive.com/luxdrive-products/micropuck-2009a-single-led-driver/). Luckily a lot of people seem to want to upgrade their torches with high power LEDs, meaning that there is a market for small LED drivers that run off small batteries. I've found various cheap boards from China with various states of documentation that I may try as well, although "cheap" is a relative term for something that fries a £15 LED.

As an aside: LEDSupply (https://ledsupply.com/led-kits.php) do an interesting kit where you specify a single LED (eg a Cree XP-G), a MicroPuck of your desired current, and a battery pack, and free soldering for a very reasonable price. What you therefore have is a very bright torch (139 lumen even), or, to put it in poi terms: the guts of a single colour Hyperlight. Since it seems one of the big attractions of Hyperlights is the sheer brightness of them, I thought this worth mentioning. For some people a pair of very bright white glowing sock poi that you can see in the daytime might be all they need, given the cost and availability of the alternative.

So the MicroPuck is great, but it seems that to use it in an RGB microprocessor controlled poi we would need to have three of them, together with some transistors to switch them on and off with PWM. This concerns me since although these things are tiny, they _do_ have a weight, and a physical size. Not to mention they cost about $10 a pop. So suddenly our two pois are costing maybe $150 in electrical parts alone. And that's a lot for me to smash into a wall in a moment of abandon.

However, I've found a few projects on the Internet, including in this very forum, that seem to go with the old-skool LED approach of sticking a resistor in series with the LED as a method of limiting the current. Everything I've read tells me that this is crazy and just won't work with the power-LEDs, but _if_ it works at all (maybe at a reduced efficiency, increased heat, and shorter battery life) then it would be _far_ lighter and cheaper to use three resistors than three LED Drivers.

I've gone back through the archives and there have been a surprising number of people that have made their own LED poi, and gone through this very design stage. But information is sketchy. Links to promising "open source poi" websites are dead, and circuit diagram images are frustratingly missing.

So, yeah, I'm hoping for some of this lost information to be resurrected. But also on a less selfish note that we can perhaps update the technology that was around 4 or 5 years ago to that of today. Maybe find more creative uses for that accelerometer, add a mic for beat detection, or bluetooth our colour patterns to our pois via a handy iPhone app. smile

I feel that I must point out my interests here. I _totally_ respect Hyperlights. It's mindblowing that they were first mentioned in 2005, and everyone rates them as the best possible LED poi and desperately wants some, mostly going purely on a couple of YouTube videos and some long-exposure photography. The waiting list is (by my estimation) 4 years to get hold of them, and the price has at least doubled. Yet still they are quite simply a huge leap forward from anything else on the market. I rate myself a very novice spinner (think 5BW and a few isolations) who is likely to either brain himself or smash some expensive LED poi, and yet _I'd_ buy Hyperlights for £300 if I could get them tomorrow. But as I can't, I think it would be a great fun project to make my own programmable poi. Sure it's reinventing the wheel, but also I think it would be cooler to show off your super-bright poi and then be able to say that you made them yourself. Anyway, I have no plans to make commercial poi (hell, it's take Hyperlights the last 4 years to get to that point and I don't imagine all of it has been fun), or to undercut or poach sales from anyone else. I just fancy a little side-project that will encourage me to get on with learning some more poi moves in the process.

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