Microdot - wrist watch LED pattern timepiece

Another RGB Sunset Productions production!

This project is a circuit board for making a wrist watch size version of my minidot clock:
http://www.instructables.com/id/EEGLXQCSKIEP2876EE/
with a few more functions more applicable to a portable device. A lot of help and suggestions came from ians 01/\/atch binary watch:
http://www.instructables.com/id/EYNTHEN1WUEP287APH/
Eaglecad schematic and PCB are available below from the original design, and an updated version with a few corrections is also included. The project is aimed to more experienced electronics hobbyiests as it involves small SMD components, and special programming methods. I'll be going through some of the problems and solutions that arose from making this device. This will hopefully help anyone else attempting to make a small microcontroller device. It might get a bit wordy, if you want action in a hurry....just download the project files and build.
Battery and case construction will be handled in another instructable. This one is just for the board itself.
Downloadable files:
- microdotfw.zip ...the sourcecode for the Soureboost compiler, includes a .HEX file
- microdotv1.zip ...the original PCB, with a couple of mistakes as mentioned in the text regarding missing resistors
- microdot2.zip ...a slightly modified PCB design, with all the proper components. Note I haven't tested this PCB, but it isn't too different from the original. The software should work on both.
Update 3 August 2007!:
From my other two instructables:
The holoclock - http://www.instructables.com/id/E11GKKELKAEZ7BFZAK/
Charliplexing tutorial - http://www.instructables.com/id/ERHG974F1ZM4KIR/
I've updated the microdot code to incoorporate cross fading between patterns and some better battery management. See attached file "microdot with crossfade and autotimeout.zip" below.

Step 1 The idea

As in the mini dotclock the idea came from a pattern clock found at Thinkgeek. Basically the time is shown by a random distribution of different coloured LEDs. The number of LEDs in each colour corresponds to the time. The opening picture of the microdot show the time 3:45pm (1 red, 5 yellow, 4 green, 5 blue -> 15:45 or 3:45pm)
Having done the mini-dotclock I wanted to do a much smaller design. This was mocked up in Eaglecad and visualised in Povray using the Eagle3d user language program for Eaglecad. See ians \/atch project for more details.
This pic sort of set the basic scene, and by printing out the board layout and pasting onto little pieces of paper I could start to visualise the final design. One thing obviously missing from this early design was a way to set the time.....so I thought,and thought.
Then I added SMD switches for input which can be seen in the intro picture.

Comments

[moemoneysouth]

Do you have an exact parts list ? values of the resistors to drive the leds and the capacitor values ? i would just save time that's all

[binnie]

WOW I GOTTA MAKE ME ONE OF THESE WHERE THE HELL IS THE SCHEMATIC uh yea sure oh really the schematics at the bottom sure this is 100% awesome make a little bit bigger verion and i can put it on my bike for a clock for fun i recon this rgbphil guy must have a great job/ alot of free time to be able to make this lol just one problem in australia i cant find anyone who i can buy smd pics off of i dont want overseas or internet order so its either mail order or i walk in

[rgbphil]

thanks for the comments. The schematics are in the zip files and are in EagleCad format, which is a great free schematic capture and PCB design program. You can download a size limited version at www.cadsoft.de. There are two zip files, v1 is an old one with a few errors (as detailed in the article) and v2 has the errors corrected. As for SMD PICs....you're right, there are no retail outlets for these devices, but you can get samples from Microchip. If you want a bigger clock, have a look at my dotclock project, or if you get EagleCad going you can use the schematic as a base, then re-layout the board however you wish. As a start though I'd suggest using the same positioning of the LEDs, so the software doesn't need changing. Load up the schematic and board in EagleCad, then use the 'rip up' function to undo the tracks. You'll have a ratsnest showing the schematic connectivity, you can then expand out the LEDs out to a more managable size and re-layout the board, possibly moving the components on the bottom side back to the top.....a lot of work, though it would be a good intro to PCB layout. The other parts get be gotten retail from Jaycar or Altronics. I'll have the PCBs available eventually for a small price, probably with the PIC already soldered and programmed....though you'll have to assemble the rest of the parts yourself.....it's too fiddly to be cost effective ready made. Phil

[binnie]

you can get smd picaxes for 5-20$ at microzed, and remove picaxes bootloader but thats too expensive as for samples from microchip, how many is a sample considered, or if i pay for them i can get as many as i would wish

[binnie]

i can only find the pic16f88 i/so with 18 leads for sample will this work without modifacations to the code or like

[rgbphil]

Yep the 16f88 will be OK, that's whats actually used in the prototype. However I used the 20pin version. You'd have to re-layout the cct, and ignore the AVdd/AVss connections for the 18pin (as they don't exist, they are used in the 20pin version for more control over the A/D converter in the chip, for the microdot they are tied to Vdd/GND as the A/D converter isn't used). See Step 2 for some discussion on the AVdd/AVss pins. The code will work in any version of the 16xx88. The only difference is that the usable battery life will be lower, because as the battery voltage drops below about 4.8V the 16F88 PIC will start to reset, the 16LF88 can go much lower. If you were to make a larger version, I would add a power regulator and higher capacity batteries (I recommend the MCP1252 5V charge pump also from microchip, although a plain old 7805 will do). If you didn't want to stuff about with EagleCad, a cct using veroboard and 5mm LEDs will work just as well. Probably a lot easier using veroboard to implement because you can take advantage of the up/down positioning of the LEDs, and use wire links. The layout was a nightmare for me. You may wish to re-arrange the LEDs in this case to be a bit more logical, if so then some changes to the code might be necessary to the arrays in display.c. In the case of the microdot, the main exercise was in making everything as small as possible, so some corners (as mentioned in the article) were cut with regards to proper power management. If you do make a bigger version, I'd recommend using a DIP version of the chip, and you can use an external programmer rather than fiddling about with ICSP. In any case I haven't implemented power saving code in the published zip files yet....I do have a bit of spare time, but not a whole lot!

[moemoneysouth]

Are any of these chips good for the build ?

PIC16LF88-I/ML
http://ww1.microchip.com/downloads/en/DeviceDoc/30487c.pdf

PIC16LF88-I/P
http://ww1.microchip.com/downloads/en/DeviceDoc/30487c.pdf

PIC16LF88-I/SO
http://ww1.microchip.com/downloads/en/DeviceDoc/30487c.pdf

[binnie]

where did you get the blue smd leds jaycar do not seem to hove them ( except for the long strips )and altronics dont stock them either

[puffyfluff]

Not really pertaining to the PIC, but can you give me links or part numbers to every component there is?

[rgbphil]

mmmm....that's a bit of a task. However if you install EagleCad and go to the EagleCad web site you can download a number of User Language Programs (ULPs) that do a bill of materials BOM.

[puffyfluff]

Thanks. But I still have one problem. Where can I get the ICSP Programmer?

[rgbphil]

Hi...I got mine from www.dontronics.com and am using the MeLabs usb programmer.

[stickeater]

do you still have spare boards

[TieDyedPie]

Thanks for the fantastic project. You took something way over my head and broke it down beautifully. I just fired it up tonight - blinking lights never pleased me so much.

[rgbphil]

Congratulations thats great news, I think you might be the first person to actually make one of these yourself. Please feel free to post pics or any questions and improvements you make.

[TieDyedPie]

Thanks, I'll get some pics up soon. Here's a question: I used a 16LF88 and I'm having trouble below about 4v. Does that seem right; am I optimistic to hope for lower?

[rgbphil]

A 16LF88 should work down to around 2.5V, however you might have trouble getting the green and blue LEDs working at this voltage. In hindsight I should have added a charge pump to regulate the voltage to the LEDs and processor...oh well.

[TieDyedPie]

hrm, all my LEDs say they're good at 2.1 (I went with one color and just spaced the sections apart, I really should get a picture up). I'm new at this, is the PIC dropping the voltage any extra?

[TieDyedPie]

I wanted to have the LEDs wrap around my wrist, and flexible PCBs seemed hard to etch.
http://www.flickr.com/photos/11834044@N04/3613369498/

[rgbphil]

Hi TieDyedPie, The flex microdot looks like a great idea...I'm amazed and admire your patience for soldering free air components. As for the PIC dropping the voltage a bit...it will, but not much. The PIC has mosfet outputs, so you can consider them basically outputting 0, Vcc or open circuit. I've seen SMD LEDs red, yellow and green with the same forward voltage, and blue slightly higher, but less than a 5mm blue LED forward voltage. It's good you're testing your own. Back to the flex idea....If you can get your hands on some really thin copper sheet, and some heat resistant plastic and glue(presumably epoxy based), you might be able to make your own flexible PCB blanks and etch the normal way. Bond the copper top and bottom to the plastic and compress. When the glue is dry you should have a double sided flexible PCB. Should make a good instructable. Flex PCBs are not any different from normal PCBs except that they are thinner and flexible. Commercial stuff has two types of copper, one for multiple flexing and the other for once only. Presumably the former is a more ductile alloy. If you can get your hands on flex blanks your halfway there.

[freerunnin1]

sweet animation software:)

[madbeing]

I've really enjoyed reading this article and the related ones on charlieplexing. Did you ever have a batch of boards made up? I'd be interested in buying a couple of boards if possible.

[rgbphil]

hi, check your messages....

[elliot.green]

hey really cool watch. can u now buy them as i have no programmer and don't know how to make the board

[pyrocop1]

Hey check out this website has some simular for those us who can not build it our selves

Tokyo Flash

[triplebirch]

I got a watch from them.

[twenglish1]

those are some pretty sweet watches

[yourcat]

I REALLY want one, but that was all more than a little over my head...

[puffyfluff]

Anywhere you can get PCBs made?

[rgbphil]

I had a batch of PCBs made a while back. I have a paypal account....give a few days to sort out the whats and wherefores of the details (I haven't used it for a while) and I can send one to you for $10. Phil Note....there's a few issues you need to be aware of, basically the power needs to be regulated as there is no regulation on the board apart from a dropping diode. Putting 6V from a couple of coin cells works OK, but not for extended periods of time as eventually the 6V drops too low. Something like a capacitor charge pump regulator is preferred which can drain every last drop from the battery even when the battery voltage drops below the regulation voltage.

[Ankush]

Wow, amazing. But could you just tell me what type of LEDs have you used?These look a different from the standard bulb shaped LEDs.

[rgbphil]

Hi, These are R1206 sized surface mount LEDs. About the size of a SMD resistor. Phil

[mattruck92]

Hi Im a teen that realy does not understand electronics enough to try one of these projects. So how much does it cost to make one of these and could assemble it and il'l pay you thanks.

[rgbphil]

Sorry but I'm a bit too busy to make projects for people. I'd be happy to help answer any questions though. First read the comments on this instructable and I've updated this instructable with some links to other instructables with more info. Any other questions ....fire away. If you're not experienced in electronics I wouldn't recommend this project first go, it is an advanced one due to the small size of everything, try the holoclock first.

[mattruck92]

thanks ill try that

[Maxaxle88]

Um.....I can't read it or understand how the heck it works. Plz explain those two things a little better, maybe with a diagram.

[rgbphil]

Hi,
Which two things are you referring to? I'd be happy to explain, but don't quite know what you're after? The charlieplexing? RTC?....
I'm thinking of putting up a charliplexing instructable guide there have been quite a few questions on this.
I've recently put up another instructable:
http://www.instructables.com/id/E11GKKELKAEZ7BFZAK/
with an extension to this sort of idea.....don't know if it will help.
Anyway, if you can give an idea what sort of diagram you're after then that'd be good.
Phil

[smaugus]

rgbphil, this really looks nice... I am thinking about a simmilar project - do you know what is power consumption ratio with charliegrid vs. normal matrix ? How long does your watch work with one pair of batteries ?

[rgbphil]

Sorry about the delay in response. As for power consumption, because only one LED is on at any particular time, it wouldn't be more than one LEDs worth of current, ie about 10mA. I haven't checked the runtime with batteries yet.

[prosser]

great instructable, any news on wether you'll be selling "ready made" items or how much they'll go for?