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Difference between revisions of "LedFloor"
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PWM "natural" ability is prefered, but choice will be made depending on total cost of solution. | PWM "natural" ability is prefered, but choice will be made depending on total cost of solution. | ||
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+ | = Pré-étude = | ||
+ | Section rassemblant les infos de sourcing de composant & choix d'architecture, etc | ||
+ | == LEDs == | ||
http://cgi.ebay.com/1000-5mm-White-Diffused-LED-9k-MCD-Bulb-Lowest-Price-/360173855949pt=LH_DefaultDomain_0&hash=item53dc08e4cd#ht_659wt_113950$ fdpin 1000 leds blanches 5mm diffused (120°) 9000mcd | http://cgi.ebay.com/1000-5mm-White-Diffused-LED-9k-MCD-Bulb-Lowest-Price-/360173855949pt=LH_DefaultDomain_0&hash=item53dc08e4cd#ht_659wt_113950$ fdpin 1000 leds blanches 5mm diffused (120°) 9000mcd | ||
Ca commence à le faire :) | Ca commence à le faire :) | ||
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*I've 2 stm8s-discovery if you like to test. st-IDE run only on windows can be hacked to run on linux, i don't know ? | *I've 2 stm8s-discovery if you like to test. st-IDE run only on windows can be hacked to run on linux, i don't know ? | ||
+ | |||
+ | = Réalisation = | ||
[[Category:Projets]] | [[Category:Projets]] |
Revision as of 15:55, 24 March 2011
Contents
Description
How to turn the 11 windows of the hacklab into a big led display ?
- what have we got to do it ?
- Windows that are H189xW95.5 centimeters
- 1000 red leds
- FAIL: too narrow and not strong enough, need to buy ~1000-1200 Highly luminescent LED
- loads of RJ45 and old IDE/SCSI/floppy buses
- what we need ?
- a system to control each diode (or group of diodes) independantly
- that is not too expensive
Question: do we need on/off for each led, or more advanced modes (eg PWM for various intensities).
- on/off:
- is simpler as regard to schematics
- is simpler as regard to driving code (led bits per image, obviously)
- isn't as cool
- can still, to some extend, allow some variable intensities
PWM "natural" ability is prefered, but choice will be made depending on total cost of solution.
Pré-étude
Section rassemblant les infos de sourcing de composant & choix d'architecture, etc
LEDs
http://cgi.ebay.com/1000-5mm-White-Diffused-LED-9k-MCD-Bulb-Lowest-Price-/360173855949pt=LH_DefaultDomain_0&hash=item53dc08e4cd#ht_659wt_113950$ fdpin 1000 leds blanches 5mm diffused (120°) 9000mcd Ca commence à le faire :) (sinon check le reste de ses items) http://cgi.ebay.com/1000-5mm-Green-Diffused-LED-5k-MCD-Bulb-Lowest-Price-/360204432057pt=LH_DefaultDomain_0&hash=item53dddb72b9#ht_773wt_1139 par exemple, un poil moins cher (26$, 5000mcd en vert)
Solution #1
use a TLC5940NT that can control about 16 LED each
- datasheet: http://datasheet.octopart.com/TLC5940NT-Texas-Instruments-datasheet-153017.pdf
- schematic: http://webhome.csc.uvic.ca/~mcheng/samples/led_wheel/images/hack_schematic.jpg is it me or this schematic sucks big time ??? There are examples in the datasheet, way more reliable IMO --cq
- O(price) = $180 for the 64*TLC5940NT, so we'll need also several protoboard to be cut to bind them on.
Naturally leads to a PWM version
Solution #2
use the snootlab's i2c led driver solution that can control 16 LED each
- 64*i2c led driver = 9.95*64 = 636.80
- 1*i2c shield = 17.95
- 1 ardunio = 20
- O(price) = 674.75 euros
Solution #3
- use shift registers... ?
Solution #4
use two Peggy 2 board :
- 2* http://evilmadscience.com/tinykitlist/157
- O(price) = 95*2 = $180 --or far less as you won't need the giant PCB. They have a "parts kit" that includes the 328 and the IC's for $15. you'd still need LED's and transistors and other support components. --cw
looking at the peggyLE schematics, they are not using several of the outputs, it looks like a 32x30 grid is possible with the IC's included, and by adding another IC in place of the buttons 32x45 is possible. --cw => they use two 4 to 16 demux for highside driving. They therefore *have* to keep one output not connected, to allow an "off" state for each of these chips. One solution would be to use two such chips, plus two generic I/O, leading to a (quite ugly) 10 to 32 demux functionality. -- cq => that's only for the 74HC154's, the STP16DP05's can use all 16, so expanding that way there can 48x30 which gives 1440 LED's --cw
Solution #5
- Check with Electrolab, where another similar project is ongoing :-)
=> actually, the (current) project there is about a 8x8x8 led cube (and some pov, too). Which are a bit different. But hey, somehow these are still led based project, so why not.
Solution #6
So, the goal is to achieve a 1024 led screen, with, if possible, PWM on each led, for a total price <150€ (connectors, leds not included) ?
My proposal would be to mix #1 (eg use TLC5940 chips, for their ability to PWM their outputs) and #4 (actually, only reuse the 4 to 16 demuxes (74HC154) idea, with two additionnal GPIO from the uC to achieve a 5 to 32 demux). That is :
- two TLC5940
- drive each row in PWM mode
- can be daisy chained, and they take 8 I/O (or possibly less than that)
- cost about 3€ each at www.mouser.fr
- two 74HC154
- drive each column (one after each other)
- cost less than 1€ each
- some power stage:
- worst case is all 32 rows ON with 100mA each. So each column power driver should be able to sustain a 3.2 A continuous current.
- the evilmadscientist schematic proposes 1.5A pnp transistors ;)
- it'd be a better idea to get some (any) tougher pnp transistors (maybe few € total)
- This requires about 18 I/O for control
- it is out of reach of an Arduino (true only when all the features of the TLC5940 are used. There are solutions to use an Arduino anyway. Note that I consider UNO and similar boards, not mega ones - which are too expensive)
- it is quite doable with a Teensy (http://www.pjrc.com/teensy/ about $30, similar in functionalities to an arduino otherwise)
- or we could just use an naked Atmega chip, as I got a USBtinyISP Kit to program it (compatible with avrdude)
- some power input is required
- I suggest a computer PSU (reuse a standard connector to get 5v on the circuit)
- some connectors are required
- I suggest using standard RJ45 connectors (which stand 1.5A if I remember well. Meh...)
- some passives are required. As usual.
Total cost: O{100€ ?). Sounds good to me :)
issues/open questions
- will the TLC be well adapted to drive each column only 1/16th of the time ? That is, still work well when asked to somehow refresh data at (total refresh rate)*(number of columns)
- according to datasheet, the max required clock speed is 4096*(refresh frequency). Even with a *16 factor, it isn't out of reach of a simple uC
- will the leds give enough light when pulsed at max 1/16th of the time at 100mA ?
- my guess would be: yes
- how to make the board ?
- it can be done on a standard protoboard (quite small, I would even say)
- Check if standard PC power connectors fit on these. If not, use a wire + standard connector.
- it can be done on a standard protoboard (quite small, I would even say)
=> it will => do we have some at hand for the first prototype build ? --cq
- Check if there are thru hole RJ45 connectors available. Looks like there are some (quite cheap, O{10€} for a 8 port version) but pins won't fit on a protoboard.
=> otherwise, we can use female connectors from a patch bay (I got a dozen of them). => yup, that was the main idea ; the problem is that the pins of these things doesnt fit well on breadboards, from what I've seen. TBC... --cq
- Solid core cat5 wire will fit in a breadboard, so some keystone jacks and short lengths of cat5 can be connected
- if one want to really use 12 bit resolution for each of the 1024 leds, using a 8bit uC with 8k of RAM is... probably not the best choice
- I guess it'd be okay to downgrade the resolution to few bits per led, eg never drive LSBs for each led and use only 4bits resolution.
=> I cannot see any big flaw in this solution. Does anyone have a better view here ? --cq
- "it is really an issue to be unable to buffer data"
- wouldnt some usb to serial chips have some additionnal RAM ?
- "it wouldnt hurt to have some more processing power onboard"
- "you're such a p... to use monochrom leds"
=> we already have a stock of 1000 red leds.
- for diffusion, copy the tetalab's idea of using ping pong balls
Solution #7
Similar to #6, but instead of TL+demux, use a uC which has 64 I/O that can be dedicated to the led matrix.
- I cannot think of any chip that would be as cheap and as "simple"
- software layers would be easier
- additionnal power/interfaces would be required to drive the rows
One possible solution:
- use this : http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4114 + an ugly extension board (on a protoboard) with 64 pnp. Someone at Electrolab can provide that board
- then, in a second design iteration, design a full custom board with this chip + transistors, connectors, ...
Solution #8
- 42 ?
Solution #9
- Use the stm8s-discovery kit (~9€, farnell)
for 9€ you have two mcu: a stm32bits uC to upload the stm8its. The stm32b can be hacked ?
- I've 2 stm8s-discovery if you like to test. st-IDE run only on windows can be hacked to run on linux, i don't know ?