LED recommendations for 16 LED design /w lithium ion

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predatorcoder
 
Posts: 42
Joined: Sat Mar 25, 2006 10:37 pm

LED recommendations for 16 LED design /w lithium ion

Post by predatorcoder »

This is a question especially for those who have built some of the more powerful units on this forum. I'm toying with the idea of designing a 16 LED version. From what I've seen, it sounds like the TSAL6100 is the LED to use? Would you mix some other LEDs in with this (i.e. different spread) or is the TSAL6100 just so powerful that it would be best to use it for all 16 even though it's narrower throw? Is there a better alternative to the TSAL6100 in this application?

For power, lithium ion is obviously the way to go for both simple charging, and power per unit weight/volume. Any objections to using http://www.batteryspace.com/index.asp?P ... rodID=4315? 1.4 Ah, 11.5A max discharge (but since we're pulsing I wonder if this could be exceeded? the next size up is very large - 10 cm long - and if so, could a smaller Lipoly cell be chosen? this is not my area of expertise).

A USB battery charger could be used. E.g. bq24020 or similar (http://focus.ti.com/lit/ds/symlink/bq24023.pdf). Therefore a single USB connector would be used for both power and data. It looks pretty easy to get going. (I've played with another of the bq-series USB chargers, but not that one). Still pondering about what to use on the charging/protection end of things, e.g. if there's something that offers combined protection / charging at the needed currents.

For AVR, I'm thinking the AT90USB162 (http://www.atmel.com/dyn/resources/prod ... oc7707.pdf) would be a nice fit. It has 16 KB flash. Alternatively, the AT90USB82 would be a little cheaper with only 8 KB flash, but if there's room, an EEPROM far larger than 16 KB could easily be added to the board for < $1, to be used for storing oodles of remote control codes. I've worked with this chip before. The nice thing is they come from the factory with a USB bootloader, so you don't even need an AVR programmer, and the ISP header can be left out of the design to save space. I'm not sure what the USB would be useful beyond initial programming and charging, but I'm sure somebody can think of something to hack onto it.

In my opinion, there's really no reason the PCB has to consume much/any more area than the area of a cell phone battery. I can't believe how large the SHP TV-B-Gone is, it's just nuts how big it is for what it does... drive four 5 mm LEDs! They make cell phones smaller than that which are also power hogs when in use.

jasonx
 
Posts: 168
Joined: Wed Jan 16, 2008 5:41 pm

Post by jasonx »

You can get different angle versions of the TSLA6100 led
list from another post
oPossum wrote:TSAL6400 is the wide angle version. All the TSAL6x00 have the same tint.

IR333A 20 degrees
TSAL6100 20 degrees
TSAL5100 20 degrees

TSAL6200 35 degrees
TSAL7200 35 degrees

IR333C/H0/L10 40 degrees

TSAL5300 45 degrees
TSAL7300 45 degrees

TSAL6400 50 degrees
TSAL7400 50 degrees

IR-323/H0-A 60 degrees
TSAL7600 60 degrees
You have some great ideas will you be making your design public ?

predatorcoder
 
Posts: 42
Joined: Sat Mar 25, 2006 10:37 pm

Post by predatorcoder »

Yes, I have seen that list of LEDs. It's quite the list but I'd think there is probably a "best" or "most optimal" design that uses only one or two from that list.

I don't really see why not to put the design public. At the moment I'm just speculating on the design, I very well may do a schematic / board in EAGLE over the weekend to get a better feel on the concept and gather feedback. But it might be awhile before I actually build it, because there are several other fun projects competing for my attention. In the meantime, others would be welcome to work on the design.

At the moment I'm thinking:
* 16 of the 5 mm LEDs arranged in a 4x4 grid, directly on the PCB (to aim the PCB will face outwards)
* LED drive circuit will continue to be switched with the NPN transistors, unless someone can think of a better way (i.e. smaller with fewer components, not necessarily cheaper). I would like to find smaller ones though (i.e. less than SOT-23), if ones exist with the right specifications.
* Lipoly battery http://www.batteryspace.com/index.asp?P ... rodID=4315. I'm hoping this can source the needed 16A current bursts?
* AT90USB82 microcontroller powered directly off the battery
* External I2C EEPROM (undecided but there are lots of suitable choices < $1). 24AA64 from Microchip in a DFN package could be good.
* USB Micro-B port for charging, programming, and data. You'd be able to switch between European and American codes over USB (all codes would be in EEPROM; this would just choose which codes to start transmitting first for best performance). Adhere to the USB Battery Charging Specification using the resistive divider method described in the spec.
* MCP73831 Li-Ion charge controller - can be programmed with charge currents 100 mA to 500 mA, so the micro can restrict charge currents until a dedicated charger is detected or the host authorizes more current usage, as per USB battery charging specification and USB 2.0 specification.
* S-8241 for Li-Ion battery protection. Over-voltage, under-voltage, over-current protection.
* SE95DP-T for temperature sensor: to prevent charge of battery in wrong temperatures.
* Blue charge indicator light
* INA202 current sense amplifier to detect charge current. This will be needed for proper charge termination I think.
* Pushbutton and status LED, with controls similar to current TVBG implementations.
* A mechanism (undecided thus far) for switching to USB bootloader mode, for loading of new firmware.

Assembling all these SMT components is probably not appropriate for someone's first time soldering (unlike the original TVBG kit) but honestly, soldering leadless DFN/QFN packages is pretty easy. I actually prefer it compared to leaded SMT packages, because the chips tend to self-align better it seems, and solder bridges are more easily removed without solder wick.

A temperature-controlled soldering iron would be essential. Additionally I would strongly recommend having a hot air rework tool when doing any SMT work (especially leadless packages). You'll also want solder paste and some fine-tipped SMT tweezers. Also the finest 63/37 diameter solder you can find is very useful (see the Mouser catalog, mine is ~15 mil diameter if I'm remembering correctly). Hot air is the only practical way to remove SMT packages from a PCB without damaging the PCB or the SMT part, and it's really useful for soldering parts onto PCBs as well. I don't have either of these units but for those needing the tools, SparkFun looks like they have options: http://www.sparkfun.com/commerce/produc ... cts_id=609 and http://www.sparkfun.com/commerce/produc ... ucts_id=76.

My typical soldering procedure goes something like this:
* Put solder paste on all SMT pads.
* Place parts on the board. Order is not so important here as most are low-profile.
* Reflow the board. There are a number of ways to do this for people on a budget: hot air rework station (my favorite for one-off boards), hot plate method, toaster method, etc.
* Solder through-hole components, smallest parts first.

SparkFun has some excellent SMT soldering tutorials on their site. They've got videos on using hot air rework that will make you want to run out and buy your own! Turning up the hot air on a dead hard drive board or motherboard is really fun, because then you can get your tweezers and push all the components around, blow them off the board, etc. :D

I do not plan on kitting this board, because kitting SMT kits would be a lot of work! SMT parts typically are a pain to identify (e.g. SMT capacitors have no identifying marks!). So I'd have to individually bag and label each part. Plus they are easy for people to lose. I may be up for selling completely assembled boards though for people who just want something compact. It would be faster for me to just build it than kit the parts.

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