Wireless programmable light

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Wireless programmable light

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lurks

I'm mainly using JeeNodes to control electronic greenhouses with LED lighting but I thought I'd do something fun with some leftover parts. Enter the wireless programmable light.
It consists of a pentium heatsink in a re-used glass shade. It's got a triple luxeon rebel board fixed to the main heatsink slug, recycled from a dive torch upgrade. While glued onto the veins around the side are three red, three blue and two green power leds. They're 3W leds but I'm only driving them at 350mA on account of limitations of the heatsink and ULN2003 darlington array (I'm using two channels to drive the white leds at about 750mA).
The ULN2003 sinks current from LM317 regulators configured as constant current sources. I'm using the dimmer plug on a JeeNode because I found software pwm was a bit crap. In retrospect I could have easily used the pwm lines from the arduino and done away with the dimmer plug.
The sketch running on the jeenode listens for hope rf packets as you'd expect, the first byte being a command byte with a few different options such as toggling full white and off, instant colour set and a cross fade as well as an alert mode which ramps up to the selected colour and back down to the previous colour.
A python server script acts as a basic web server that only understands get arguments. It runs a serial thread talking to a jeelink. I use the standard rf demo sketch, just sending it the same thing as you'd type to it. Works surprisingly well. I'm using the same mechanism for my greenhouses.
I set up a desktop script to select colour from my lounge/media PC. My Android phone also has a simple toggle full white/off widget on it and of course it sends different coloured alerts to the light from Tasker, if it knows its at home.
Picasa stills showing pics of the unit and light head (it's got two more LEDs from that picture) and super dodgy skint student cardboard box electronics enclosure: https://picasaweb.google.com/mat.bettinson/ArduinoLight?feat=directlink
Here's a video of a fun random mode: http://www.youtube.com/watch?v=EaglutCHDso
Things that came up/to be fixed:
I'm passing a simple loop delay value to change the crossfade speed. It's not super smooth most likely because of delays in the loop checking of RF and maybe I2C as well. I should use a proper timer I guess.
I bought a jeenode to save a few bucks, then scratched my head for ages on why I couldn't program it with an FTDI bub I had. Turned out to be that reset is presented where as the Arduino ide sends a DTR to reset. So at the moment I have to press a ground wire quickly to program it. I also found the cap on the reset line is really rubbish, possibly why my jeenode USB is so unreliable at programming. The cap seems to take forever to discharge so it will reset again. So I ground the reset line directly to program...
One tip I can share: Cheap universal power supplies from China ($18 from ebay) make for awesome power supplies for projects like this. Selectable voltage from 15 to 24v, serious amps out output power, physically handy in-line design rather than fat wall-wart and USB ports which is ideal for grabbing 5V to power the arduino where regulating 15v is a bit naughty and 24v would probably smoke your regulator.

Posted 13/02/2011 03:01:10
tankslappa

Very very neat... I love the coloured squares it projects due to the offset of the LEDs.
IIRC, certainly in windoze, you can configure the serial port the USB BUB creates to use DTR as reset. It's in the advanced config for the port in the hardware manager. Sorry I can't be specific as right now I don't have an FTDI lead to hand, and that means the port doesn't exist on this machine. Hopefully this will make some sense! I certainly use USB BUBs to program my JeeNodes, and it always works smoothly.

Posted 13/02/2011 08:39:37
lurks

DTR is default behavior. The problem is a lot of FTDI leads break out reset, not DTR. I've Googled hacks, there's some on linux. You can also supply some switches to avrdude to burn to use reset. The arduino ide doesn't have any such setting that I can see. The windows drivers have a setting to hold reset on close, which doesn't seem useful to me?

Posted 13/02/2011 10:31:29
tankslappa

What BUB are you using? I've got the moderndevice USB-BUB that JC sells here, and also a TTL-232R-5.0V lead from moderndevice (which I don't think they sell any more), both of which certainly reset my JeeNodes when I program them, but I do need to make the setting change... I'm going to dig out one of the leads, plug it in, and see what settings I have.

Posted 13/02/2011 10:43:07
lurks

Yeah these ones are fine because they breakout DTR. I thought I could try get by with one I had from 4D systems. Turns out the FTDI cable/bub with reset on them instead of DTR is not actually uncommon. It's Arduino being weird and deciding to use DTR...
I didn't know you needed to change any settings. The built-in USB on JeeNode-USBs resets. Well, some of the time it resets anyway... It'd actually be fine if I had a little push-button reset.
I've got a spare WiFy RN121. I'm thinking I'll organise some sort of adapter plug and work out how I can drive the reset on a TCP connection. Then I'll have a programmer bub that I can just jack into any JeeNode without a cable in sight. That'd rule.

Posted 13/02/2011 13:10:29
kafka82

Hey LURKS Your project is really cool! I'd like to do somthing with similar with jeenodes and leds array but I don't know really where to start about how to build an LED array and control it wirelessly. Do you know where I can look for?

Posted 26/02/2011 22:47:11
lurks

They are two separate issues. Controlling wirelessly, the Jeenode will do that for you. Jcw has provided a bunch of example code, there's even an RGB node sketch. Of course you still need to send it wireless data from a 'bases station' neenode or JeeLink, which is what I use.
On a host server I lashed up a Python script which opens a serial port to the JeeLink in one thread and serves a web server on another. That way I can issue web calls to the script and it will happily relay them out to the JeeLink. I'm actually just using the stock rf12 demo on the JeeLink. So I send byte,byte,byte,node + s out via serial and the standard demo sketch will transmit my data. It could be better with a dedicated relay sketch, or even something that maybe uses an ethernet shield to totally bypass my server/script solution? That'd be a very interesting project.
To drive LEDs, I'm using LM317 regulators configured as current sources, switched by a ULN2003. jcw actually has an output plug which has a similar darlington array right on it so you could skip that, but you still need the current sources.
jcw also has current source plugs. They'd be fine for driving most high power LEDs if you're not using too many. This is more expensive and in my experience far less robust than using your own regulators. Also the problem you have with the current source plug is that it is plugged into IOs which aren't all PWM capable on the Arduino, meaning you're going to have to either use software PWM or do a custom wiring job, which probably negates the point in using a 'plug' in the first place.
I'd also say that software pwm dimming is pretty crap for LEDs. This means that if you want non-flickery dimming, you're going to have to use the PWM digital pins on a jeenode or you can use the jcw dimmer plug which is excellent and has a multi channel dimmer output. It's a good price too and will nuke any issues you have with running out of ports.
Of course if you're not doing anything too bright, or you're driving LED strips say (RGB strip etc) then you don't even need a current source. LED strips have resistors to drive them at 12v so you could just switch those directly with jcw's output plug, assuming the draw isn't more than 500ma.

Posted 27/02/2011 02:31:01
lurks

Oh, one benefit in just shoving a cheap ULN2003 on breadboard over the dimmer plug is that if you DO need more than 500mA, you can simply rig up any of the 7 darlington pairs in parallel to increase your current handling.
The dimmer plug is cool but it's connected to a i2c chip for each of the outputs so... you can't just electrically parallel the pairs. Maybe you could 'pair' them up in software but that sounds a bit iffy to me. $2 ULN2003 is the go :)

Posted 27/02/2011 02:34:44
kafka82

Hi Lurks thank you for your insight! I particularly like the idea of creating light pattern on the ceiling. How is that accomplished? does the leds position affect the pattern or is done with code?
Anyway my wip idea is to use temperature+humidity sensor on few jeenodes to build a network of 3-5 lamps that talk to each other. I'd like to read temperature/humidity data and change light condition accordingly (or use your light pattern in addition).
The only problem is that I am quite a newbie and this task will be quite challanging! I am using as temperature sensors the DHT22 and I hope to test it tomorrow on a jeenode.
Ive seen you using 8 leds in total. I was thinking to use maybe 6 RGB LEDS to have enought brightness but not sure about the quantity. It is a prototype to test the idea then I could modify it.
Can you maybe suggest me some schematics to buils such a prototype with leds? What is the easiest way in your opinion to build this small prototype and what components I would need ?
The final idea is to have this small table lamps (or hanged from ceiling) in a public place which change color shades/brightness according to temperature; they also indirectly interact with people as in more/less croded place temperature is affected as well.
If you like the idea I would be happy to have suggestion/advice from you and share my outcomes!
Giulio

Posted 27/02/2011 17:47:15
lurks

Ah the light pattern is something of a happy accident! The LEDs are affixed around a CPU cooler and the CPU cooler is pointing 'up' from the bottom of a square frosted glass tube. So you see patterns just because the different LEDs cast different light squares on the roof.
RGB LEDs... let me tell you about a mistake I made... The green LEDs in my light are actually RGB LEDs and I'm just using the green. Why? Well, because I originally intended to use a number of RGB LEDs but I inadvertently bought LEDs which have a common cathode. That makes it impossible to chain the RGB LEDs together in series. Doh!
You can buy RGB LEDs which have ALL of the pins on the case, so you'd have six pads/pins instead of four. That's what you need to do it properly. So before you buy any you may want to check that! This only applies if you wanted to use multiple RGB power LEDs in series. It sounds like you actually might just want to use one in each light, which wouldn't be a problem.
If you're talking about RGB power LEDs they're 350mA each. That's enough current that you're going to need some constant current solution. If you don't mean power LEDs, you just mean the standard 5mm RGB LEDs, they're very very dim. You may also find individual power LEDs easier, they're extremely cheap from HK suppliers and allow you to change the positioning to get shadowing effects like you see on my light. (It's actually cheaper to buy separate red, green and blue LEDs - search on ebay for 'prolight', these are good LEDs made by a firm in Shanghai - user 'angeldeal' sells them very cheaply and I've bought something like 200 off them without problems)
Are you looking to control multiple lights from one jeenode? You may run into a lack of ports - so then again jcw's great 'dimmer plug' will save your bacon.
BTW on temperature sensors, I'm a big fan of the dallas 18B20s. You can chain a whole load of them on exactly the same wire and they report back their temperature via serial. Getting them running in code is pretty easy. There's people on ebay selling them cheap, I bought another five just now for $10 or so.

Posted 28/02/2011 08:33:00
kafka82

Hi Again,
very useful info - thank you very much! The idea is to keep design as simple as possible as I am learning while I am doing. So I think I would use - according to your suggestions - 1 3W power RGB LED for each jeenode. I found this http://tinyurl.com/64dwn7v .
According to you - what is the simplest design/schematics to implement this on a jeenode? Do I still need a MOSFET+DIMMER PLUG?
One idea is use this rgb led as actuators reading temperature/huidity data. So for instance the light intensity is regulated by temperature data while the colour from the humidity.
On the other hand - following your project- it would be nice to have the light to be more interactive. So for instance it would be nice to interface the jeenode with twetter and change the colour of leds by sending tweets. I think this bit is just a matter of code isnt it, and it hasnt to do with hardware - has it? The idea is to control each node indipendently from the others... is this feasible (let's say 3 nodes in total)?

Posted 28/02/2011 19:57:00
lurks

That's an excellent RGB LED, you can get cheaper ones if you just want to use one per device. That prolight is good for using several per device though because it is a proper six pin on.
The prolights I really meant were the individual red,green and blue ones. You can buy bags of them in 5, 10, 20 or whatever and they're really cheap.
Incidentally, for mounting I recommend using thermal silicon glue. I've used a few ways and this is by far away the easiest and the best bit is you can pry off the LEDs if you need to anyway. Folks on ebay sell it.
It's certainly possible to have every jeenode control an LED but it's actually more of a hassle organising the power for an LED. I might suggest that you run the wires out to several light heads from one set of drivers and a Jeenode. It's not really any hardship to run cable that's basically just four wires (ground, red, green, blue) than power right? Of course if they're well apart then the wireless pays off.
The problem with driving a single power LED is that you're talking about a fairly low voltage but it's critical that you have some sort of current control. The red LED on an RGB LED will be about 2.4v at 350mA or so. The cheap and easy way to create a real constant current source is to use a linear regulator like an LM317. Here's a good page which explains it very nicely: http://users.telenet.be/davshomepage/current-source.htm
The fairly crap thing about an LM317 is that the voltage drop across it has to be about 3V. (theoretically a 'low dropout' reg would be much better but I've not really looked into this)
Using a regulator you need to provide 5.4v in, 3V will get dumped in heat and 2.4V used - so it's pretty inefficient and in fact it's worse because you have to plan for the blue LED which is about 3.5... so your red led is going to be a problem. The regulator is going to get damn hot.
It makes more sense to use a linear regulator when you're using several LEDs in series because the drop across it less than the power going to the LEDs. With RGB leds you have the annoying situation where a regulator solution will waste more power for those because of the lower forward voltage.
For these reasons, it's not great using linear regulators. To illustrate what it would look like, you'd have a breadboard with a number of LM317s soldered into it with decent heatsinks each, and when the LEDs are on, the heatsinks will get very hot. It's not a terminal problem but it also means you have to make sure you put it in the right box so you don't melt stuff...
The simplest suggestion is to use jcw's current source plugs. They're a bit on the pricey side but they have proper buck regulators that are much more efficient than just throwing the heat away. They are the daddy for this app.
Thinking about it, I'd be tempted to just try it a dirty great current limiting resistor for each colour. The reason these are bad in power LEDs is because they waste a bit of power, they have to be the sizable wire wound resistors and because they're still not that accurate for current.
For a single RGB power LED though it'd probably be okay because 350mA isn't a huge amount. So the simplest would be to use either a ULN2003 (that's what I'd use), jcw's 'output plug' or mosfets. Anything that's basically an electronic switch that can handle at least 350mA per channel.
Then have that switch each LED with a single resistor to the power supply. We have a bit of a problem in that you're not likely to have a useful low voltage power supply lower than 5V so let's go for 5V. You can basically get these anywhere, although you're going to need one that does 5V at an amp per RGB LED.
2.4v red - we need to 'burn off' 5-2.4v or 2.6v. Ohms law gives us r = v/i or r = 2.6v/.35A. We need about 7.4 ohms. If we had that exact resistor it would dissipating fractionally under a watt. You can make things easier by using half watt resistors in parallel or use those big wire wound ones. I'd use a wire wound one, you know they're good for 5W or so.
3.5v green and blue - you want a 4.3 ohm resistor or so for this. It's only going to dissipate a bit more than half a watt.
Additionally I would modify this to go up a bit in resistance values to drop the current. The reason is that LED forward voltages drop as they heat up so the current will increase, this is the entire reason for constant current power sources. It's better to play it save, the LEDs will be pretty bright.
Logistically you're going to end up building a little circuit with your mosfets or ULN2003 and resistors for each jeenode and you're going to need a 5V supply at an amp per light.
This would be much more pleasant with the current source plugs but they're 19 euros each and you will need TWO per light. That could get pretty expensive fast. On the other hand... you could maybe, drive two lights from one jeenode using those, so you save a bit of money on a jeenode and you could use one common power supply of 6v-9v (which will be easier to get in 2A) and save a bit of money there. So maybe that would make sense.
The cheapest way to do it would be using a jeenode to control a number of lights and use the resistor method.
A better way of doing it would be to buy individual colour LEDs, buy a few more reds than the green and the blues (the 2.4v vs 3.5v thing). Wire them up in series and use the LM317 regulator idea which comes into its own if you're using a number of LEDs in a string.
That may be more wiring and a bit of breadboarding more than you want, but you'll get a lot more light, proper current regulation and you wont be burning away more power than you're using in the LEDs.

Posted 01/03/2011 05:02:54
kafka82

Hey endless thanks for your advice!! following your suggestions and links I found this interesting kit http://www.sparkfun.com/products/10111 . It seems to have all specs I need for my little prototype and it is reasonably cheap. It also sold from a local reseller here in UK. HAve a look also at this http://dawes.wordpress.com/2011/01/08/computer-controlled-rgb-led-mixer/ .
In general If I have 3 leds to plug on a jeenode do I need to use the three different ports if I want to use PWM? From the schematics and logice of the above board, if I want to control/fade each led then they cannot be connected in series, so each led needs a proper PWM pin as I would it on an arduino board.
What about the power connection from the jeenode to the board then?

Posted 01/03/2011 12:04:15
lurks

That LED board looks nice but I would put it firmly in the category of 'indication' rather than lighting.
I'm not sure what you mean, if you have three different coloured LEDs, you want a different port for each so you can make different colours right? Do you mean three of those boards on on Arduino? Nothing to stop you hooking them up in parallel if you want. Eg all the reds to one port, all the greens etc...
Basically if you have one control point/brightness etc, you need a port for it. It's not absolutely required to use the hardware PWM, but it gives a great result and it's easy as pie to set the levels, you don't need the SoftPWM library. (Not that this is difficult) Jeenodes are a bit weird in the PWM ports, you'd be well advised to look at the schematic for the Jeenode and see which pins are PWM capable, they're labelled.

Posted 04/03/2011 02:14:16
kafka82

Yeah - true they are more useful for "indicating" - but this in part fits the scope of my project at moment. I dont really want to go in lighting design while I am more interested to output with different colors the current temperature+humidity state of each lamp.
So do you think that with the dimmer plug the brightness control would be easier than with just software? I had a look at the dimmer sketch demo and I find it very complicated - very few comments :-( . Moreover the dimmer class documentation seems offline at moment http://jeelabs.net/projects/cafe/wiki/ClassDimmerPlug .
As I want to control the brightness according to current temperature+humidity level I will need to sort out also how to combine these value in a single one.
I will have a series of IF statements I guess - but how do I controll each single led value with the dimmer class? IOW how do I make each value go from 0 to 255? Do you have an example?

Posted 04/03/2011 03:04:16
lurks

Ah jcw's sketches are often not the easiest to work out what's going on. No, it wont be easier to use the dimmer plug, because 'just software' is super super easy if you're using the pwm ports, it's basically pinmode(something,OUTPUT) then just analogWrite(something,value) to set the PWM, you can see how it's done on the Arduino playground.
Temp and humidity. Hmm. Well I'm not sure what I'd do for humidity but personally I'd do something like define colour range and sort of map the temperature to it. So cold was blue, hot was red, and anything in between was some sort of smooth blend. Doing that would be much more complicated than anything to do with controlling pins. I could do this easily in Python but I'd find it tricky in C. Course there's probably just some code you can steal online somewhere.
The dimmer plug convention looks like this: dimmer.setReg(DimmerPlug::PWM0, brightness level); That said, I did find the setup() stuff tricky for the dimmer plug, I ended up needing to read the data sheet.
You should probably just go for the regular ports if you're not sure about this stuff, it'd be a better place to start really. There's enough PWM pins for what you want anyway by the sounds of it and even if there isn't, the SoftPWM library is really really easy to use. I just find it flickers a bit.

Posted 04/03/2011 07:21:25