This is my blog on the development of a Christmas Light dimmer using a design of my own. I am out to build a state of the art dimmer that will out due the current commercial offering in every metric. It will be code named Lynx. I have started with a set of goals to meet with the project and so far I am on track. There has been difficulties but so far I have overcome each of these. The following are the Goals:

Must have a min of 64 channels possible on the board
Must be self contained (no seperate componets on board ssr)
Must have high channel count capabilty per serial port (512) at 25 ms event timing.
Must be scaleable to allow low channel count (16) to start and be able to add later up to 64 to allow the controller to grow.
Must allow multiple boards to daisy chain on a single serial port to the limit(512).
Must have a true 256 usable levels of dimming with even steps all the way from off to full brightness.
Must be serial RS485 to allow usb connection and long distances.
Must be able to drive 600 mini lights per channel as a min and handle Led lights without terminators or changes
Must be easy to assemble and have a profession feel when done.
Must be cost effective per channel cost. (Cheap)
Must be controllable by vixen.

As you can see I have setup very lofty goals for this board and now the choices I have made to meet them.

The protocol:
Since the high channel count and low event timing is difficult I choose to use DMX512 protocol. It helps meet the Vixen and channel count goals as true DMX512 runs 512 channels at 250k baud and vixen already supports it.

The hardware:
Well since a few of my goals are hard to meet with current designed hardware I through it out and did what I always do and started from scratch. I designed my own hardware using a non conventional method of brightness control. Instead of compasating to overcome the issues I removed that which causes the problems to start with from the design. I have the dimmer controller circuit and ssr circuit prototypes working on breadboard currently so I have made good progress I mainly have the communication hardware and firmware to finish. I then can begin layout design of the board. The controller only uses one pic chip as a communication translator so the dimming is not built on firmware just the communications.

Progress :
I have just finished the SSR design durability testing and found the design tough as rocks. I ran 700 mini lights on one channel for 24 hours non stop with the level jumping around and the ssr transistor never exceeded 102 deg F. It is rated up to 300 deg F. I then loaded with 300 more lights with out failure. This is 1000 mini lights on one channel it far exceeds my goal of 600 so I feel good that 600 lights is a lite load for it. A video of the testing can be seen here.

http://media.putfile.com/ssr-test

I also tested the controller and ssr with a single LED 50 light strand and found it to work flawlessly with out modification or Termination of any kind. This meets another goal. This means you could run maybe 4000 - 5000 Leds lights per channel if you wished.

Design:

The board is a challenge as I want it to have a real professional fell and look and yet I have to design it to allow the builder to populate it with different amounts of parts to allow it to be a 16 channel or a 32 channel or a 48 channel or 64 channel board. and to change it at anytime but I am making headway on my rough layout drafts. The cost goal looks like it might not be to bad to meet as it looks like I might come in at around 60% of the cost of a renard so I'm excited about that.

The Plan:
Once finished and tested well I plan to make the design avalible through a kit of all parts, PCB, enclosure, hetasinks, etc done as a coop order. This way you will know exactly what the cost is and you will have exactly the same parts as the prototype has. This goes right down to the weather tight enclosure which I intend to design the board to drop into. You will simple tell me how many channels you want and you will get everything. To add channels you simply add additional parts.

This concludes part one check back for part two in a few weeks to see where I'm at with it.

One of the problems that has hounded me from the start of this project is one of power. How do I feed this monster. If I stay with the design parameters I'm using I will end up with a 64 channel board with a 120 amp max current draw. This is great except most house circuits are fused at 20 amps. This would lead me to one of a number of work arounds to feed it.

#1 multiple power in cords connected to different circuits to supply the needed current.
#2 a dedicated high current outlet installed at my house like what you install for an air conditioner.
#3 abandon the on board ssr's and go remote ssr's like others. (although you still need multiple circuits to feed them)
#4 Abandon the 64 channel limit and go 16 channels like others to prevent the problem all together.

#1 Is possible but I' starting to think 64 output cords & 4 power in cords are going to be a nightmare to fit in the enclosure.

#2 Exspensive but nice way to go but many others would not want to do this.

#3 Would add cost and make it less professional. Some would want this as many already have ssrs built but since the LYNX uses different technology to dim other ssr's wont work.

#4 Might be the way to go but will increase total cost of creating 64 channels as would require 4 of a number of items that a 64 channel board would share. (enclosure, controller chip, voltage regulation,etc)

This is a tough choice but one I need to make soon as I am moving ahead quickly and need to firm up the big picture to go much farther.

I have the SSR design, the controller and the voltage regulation design finished and all I really lack is to finish the communication firmware code to be ready to build the first prototype pcb.

I have decided to put my other design projects on hold temperaraly as I need this controller done for christmas. I plan to run my 64 channel mega tree with it and I do not expect to have the other projects ready for this christmas anyway.

I have decided to move ahead and this is the plan. I am planning to create two different boards. All will be 16 channels with onboard ssr's. One will be a master and will recieve the dmx data as well as be the first 16 channels. The other will be slave 16 channel add ons. The brains will be on the master and it will communicate with the slaves via cat 5 carrying the raw data format and 5 volt feed. This allows the slaves to be smaller and cheaper. I plan to create a dmx512 convertor for the computer that also injects the 5volt for the digital circuits using a wall wart or computer p/s and feeds both over the cat5 to the master. This should create a very neat and scaleable system that can go all the way up to the 512 limit and distribute the system out for both layout and power feed.

Well I have Parts on order and am taking this time to create the schematic and pcb layout. I did some more testing on the ssr design and found that the design can handle 2 amps (600 minis) with no heatsink very easy. This will help with cost and yet if you want to run a few large counts you can add the clip on heatsinks as an option and run 1200 mini's with out concern. I'm looking into two Board layouts. One would require only one pcb for both master and expansion with just a jumper setup to choose which it will be. This would allow board count to stay up for cheaper pcbs. The other would be two different pcbs and the expansion boards might be able to be a little smaller. I will have to see what works out best. I know there might be no one who will build the Lynx but me but after thinking on it I decided to do it my way anyway. If nothing else I created something different and even if we have enough dimmers for the DIY'ers it hurt nothing to have another and I am the only one it cost anything. Beside I had to come up with a cheap dimmer controller and power controller for the LedTriks II and this is what in the long run I have done.

Progress has been good on the board layout and I have decided to go with on board for both. You will build them the same but you wont need to populate some parts on the expansion boards. Just set a couple of jumpers and you are ready to roll. I was going to use three decimal rotary switches as the interface to set the staring channel for the master but the cost for them is too much. It would add about $10 to the cost just to have them so I went with three sets of 4 jumpers. you will set your start channel by jumpering them between 1 and 512. I did everything I could to keep from having to add a Transformer to the board for power but alas I just could not get enough current easily without it. So I am using the smallest step down I can get for pcb on it to drop the voltage down to 8 volts and then I'm using a good old linear regulator to generate the 5v for the digital circuits. I use the 8 volt directly of the transformer to drive the SSR circuits for switching. All this controller will require is a cat5 for data only and plug it in to power. I will go ahead and order the enclosure I designed around do I can check pcb fit before I order the first 5 pcb's. If I spend some more time and feel real confident the layout is good I may order 10 pcb's as the price is not much different and it would give me extras to send out as beta's.

I have finished the layout of the PCB. See it here :

http://www.putfile.com/pic.php?img=5709396

I gave the master boards the ability to have the starting address programmed via dmx. It will come programmed to start on channel 1 but you are able to jumper a pin set and power it up then using vixen or any other dmx system send it the address via the first two channels. First channel is set to level 0 or level 1 and this tells the board what set of 256 you want it in. the second you set it to the number 0 -256 of that bank. So to program it to start at 55 you would send 0,55 and to set 300 you send 1,45. The 1 gets you to 255 and 45 more gives you 300. Then you power off the board and move the jumper to the operate side and when you power it up it is set to that start channel. This keep hardware cost down and yet keep everyone from needing a pic programmer to set it.

The other jumpers you see set the board to either a master or expansion board. The expansion boards will not need a good bit of the hardware on the board to be populated so it will make the first board the more expensive and then it will be much cheaper to add channels. I expect the power supply on this board to power 128 channels so that will be the limit off of one master. The good news is you can run as many masters as you want up to 512 channels on one DMX universe.

I still have a good bit of work to do on the Firmware and the PCB layout need some real good QA checking before I am ready to shell out the $100 to have the first 5 made.

I post asking KC if he could give us the ability to do 256 levels instead of 100 in vixen but no reply as of yet if he will even consider it. The Lynx will still work with the current plug in but it will limit it to the same 100 levels the other dimmers use. I also created a new toy design that needs it but I guess I will wait on it. Its a computer controlled spotlight that uses high powered leds and does full 360 motion while allowing you to change colors. It uses the same circuits as the Lynx and will not cost a lot. It will operate on DMX also and would be helpful to have 256 levels to. We will have to see if we can get true dmx control or not from vixen.

I tried the Lynx on 100 levels and I can say that for those that believe you can't tell a difference I would say what speed are you ramping at. Only at very fast ramps can I not see a big difference. I would post a video for everyone but the camera I have won't let me set the brigness to manual and as the lights ramp up it ramps down so you see it darking sometimes and the lighting and darking. It prevents you from being able to tell anything.

Kc replied and he is given us the choice of 256 true levels of dimming. Way to go KC.. I have added an additional rj45 on the board for DMX out to allow us to daisy chain on to more dmx devices. I was able to drop six devices off the board to reduce the price by about $6 more. This maded more room on the board and allows me to neating up things some also. I can not reduce the board size as it is setup for the enclosure as is so the board will stay this size. For the guys who have to run 24v on there lights I believe I can add a jumper to use the same power to run everything and allow them to not populate the Transformer the rest of us need. This is about $5 less again. Looks like if I am in the ball park the prices will layout like this for the two boards with everything including pcb, parts to populate the pcbs and an enclosure. Just add your power cords as everyone uses different cords and lengths I will leave that up to you:

The master boards 16 ch on board ssr - $80 - $90 complete

Add on expansion to add 16 ch (up to 64 ch) - $60 - $70 complete

This is based on a very small number and could be cheaper with like 50 units or more ordered.

I'm still working on firmware and checking the pcb layout over. I will be leaving for 3 weeks on vacation this weekend so I want be able to get the pcb done and ordered till after I get back.

I got back in town from vacation and finished up the pcb artwork.

here it is http://www.putfile.com/pic.php?img=5848243

I used a pcb print glued to foam to allow me to proto out the boards for componet fit. I'm ordering 5 boards, one I will make as a master the rest as expansion boards yielding me 80 channels of dimming. I'm looking at $4.75 a channel complete with enclosure at this very low volume. This is a good price for ssr, enclosure and all I think at this volume. Price will go down at higher count. If you wish to compare it to other systems make sure to add up every cost. I thought I would review where I am at on my goals:

Must have a min of 64 channels possible on the board
Had to drop to 16 channels to allow managable power requirements.

Must be self contained (no seperate componets on board ssr)
Met this as the units are completely self contained including power.

Must have high channel count capabilty per serial port (512) at 25 ms event timing.
Met by allowing the units to daisy chain out to 128 channels per master and max out at 512 per usb port using DMX

Must be scaleable to allow low channel count (16) to start and be able to add later up to 64 to allow the controller to grow.
Met by allowing min of one master and then less costly expansion units up to 128 channels.

Must allow multiple boards to daisy chain on a single serial port to the limit(512).
Met as above

Must have a true 256 usable levels of dimming with even steps all the way from off to full brightness.
Met by using the new method of handling it I have 256 perfectly even steps with no flicker even on cheaper half wave leds.

Must be serial RS485 to allow usb connection and long distances.
Using dmx at 250k on RS485 using entec usb open dmx unit

Must be able to drive 600 mini lights per channel as a min and handle Led lights without terminators or changes
Leds work plug and play with no flicker. 600 mini's per channel has been tested per board max of 20 amps.

Must be easy to assemble and have a professional feel when done.
Easy to build, custom enclosure and board design makes for a commercial feeling system.

Must be cost effective per channel cost. (Cheap)
with quantitys could be as cheap as under $4 a channel.

Must be controllable by vixen.
using vixen 2.0 and the dmx plugin you have full 256 levels of dimming. On vixen 1.1 you have 100 levels.

Well I finished the Firmware and got a complete Lynx working on the bench. Its really cool to create things and see them work. I was hoping for 25ms event timeing with the system but it looks like the little cheap open dmx units won't keep up with it very well. It handles 50ms just fine at 512 channels but not 25ms. One option is to see if vixen can have the plugin send only the number of channels out that is being used this would increase the refresh and make it possible to handle 25ms at 256 channels I believe. Works good anyway just trying to push it to the max. The Dmx is working well and the dimming with the 256 level capability that KC added to Vixen is so smooth that you can actual make the filiments in the mini's barely glow with no flicker and then fade over a minute to full brightness and you can't see when the levels are changing. The Leds work flawlessly with no flicker. It just seems to like its analog with no steps at all. If you imagine a big variable transformer attached to the lights this is what it acts like. I tried the master I have up out on other dmx software and it has worked on the four that I tried. Three freeware and one demo professional package and they worked with no issues so I feel the dmx firmware is good to go with the exception of a few added goodies like the start channel and channel count programming is not complete but almost. As it turned out by talking about the cost of building a unit and trying to keep the cost down and saying what I expected the cost to be to build a Lynx dimmer, Along with asking a couple of people how cheap a dimmer has to be before people would build them I gave some the impression I was going into bussiness trying to make money off of the DIY community. This was no the plan I thought it was always understood like the other things I had designed I was doing it for others to use as well as myself. And that the cost I spoke of is what the parts would cost in a coop order. I originally intended to design create and then do a coop where everything down to the enclosures would be ordered and then shipped as a kit with instructions so everyone had the correct parts and I would not have people using different parts leading to problems as I would already know that the parts we were using works well. I will be leaving it alone and even thought this make these dimmers the most expensive dimmers anyone ever had due to the time and money I spent developing them for only a few to be built it has given me a great project to work on and I feel the end product has been more than worth it. I will be able this year in my display to have every piece of hardware something I designed and built. I have a grinch to handle the 64 channels of on/off, A Lynx master and four Expamsion units giving me 80 channels of dimming, and then three Ledtriks panels. I hope to have my Remote DMX three axis moving spotlights I'm working on done. This will use high wattage RGB led's to generate any color I want and Servos to point the light where I want it. It looks to be an interesting project. Thanks for taking an interest in my project. When I have the units all pretty and hooked up to lots of lites I will get a good image and post a link here to show them off. RJ

As promised heres a video of a demo for you who have been watching the project. Its a little long sorry trying to give you a feel for how it came out.

http://media.putfile.com/Lynx-Demo

I have started a coop order over at www.doityourselfchristmas.com for the LYNX.

Kiwi over in new zealand has assembled the first prototype built by someone other than I. He has done the mod to test it on low voltage lights and has it working. He will be testing it this week so I should have information on how it works on low voltage lighting soon. He says "over all it was one of the easiest kits i have done, nicely worded manual and the parts just dropped into place. You should be proud of this little project. " So I glad to have one happy builder so far. If all continues to go well for him I will make the changes to the board to allow both normal high voltage lighting and low voltage lighting work on the same LYNX board and I will be ready for the coop order.