Norlin

Hi All,
Not really any questions, just a little writeup on what I'm working on. Feedback or advice definitely welcome as I'm flying blind for the most part just looking stuff up through google when I run into problems.

Started working on a small project yesterday making my own electronic scoreboard. This came about because while playing volleyball, everyone asks me what the score is before every score. Sometimes I make mistakes and people argue for a bit over the score, so I figured it'd be pretty trivial to create an electronic display and then have a wireless "clicker" in my pocket to increment the score for each team.
For the clicker, I'm figuring on having 5 buttons:
Increment Left team score
Decrement Left team score
Increment Right team score
Decrement Right team score
Reset scoreboard (to 00:00)

For the scoreboard, I cut some shapes out of some foam board to put LEDs into to form digits, using as an example: Sparkfun's GPS clock http://www.sparkfun.com/commerce/pre...p?p=GPSClock-1
but doing so on a much smaller scale and with only 4 digits.

So far, I've written up code for the receiver/display microcontroller, using a PIC16F628A. I figured using infrared for communication would be easy, but don't want to have to aim at the scoreboard each time I update the score, would rather just keep the clicker in my pocket. So I figured I'd use an ASK KLP RF module (http://www.sparkfun.com/commerce/pro...ducts_id=7815). Would a different frequency or baud rate be recommended? They seem to be offered at 2400 and 4800 baud using 315MHz or 434MHz. Once I get the transmitter side programmed I guess I can do some real life testing to see what works best and figure out if I need antennas (easy for the receiver side, harder for the transmitter side due to size requirements needing to be small).

For the physical scoreboard, I have a bunch of cheap high intensity LEDs with a narrow viewing angle. Basically what I'm doing is cutting my digits into two seperate pieces of foamboard, putting a piece of tracing paper between the two and also on top of the top foamboard. The LEDs go under the bottom piece of tracing paper and the light seems to get diffused very nicely, don't see bright spots just a clean segment. (will have to post some pics when I'm home to explain this part better)

I'll try to post some pics of my progress or once I'm done.

Norlin

Oh, quick question. I've always run my PICs off of a 5V linear regulator, but looking at my spec sheet for the 16F628A it says maximum ratings for VDD with respect to VSS is -0.3 to 6.5V
Would I be being risky if I ran my PIC off 4xAA batteries providing 6V theoretically? Or should I stick to using a regulator (I'm considering battery life, perhaps the regulator shouldn't be much fo a concern and I should just use it?)

Cry_Wolf

I think its ok to use 4 AA batteries for pic. But there are other factors you should take care of when working with high frequencies like decoupling etc. Wish you good luck, waiting to see it work..

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Norlin

Here are some pictures of assembly so far:
Demonstrating the layering

Order from top to bottom:
Transparent paper
cutout foamboard
Transparent paper
cutout foamboard
Foamboard with LEDs


Back of LED board pre-wiring


Assembled, pre-wiring




Next, once I get it wired up I'll post some pictures of how the LEDs diffuse through the transparent paper. They're narrow angle LEDs but the space between the two layers of transparent paper diffuse the light nicely. Also, I painted the thin areas between segments with black paint to reduce light bleeding through from one segment to another.

kchriste

Remember that fresh alkaline AA's will output around 1.6V, as will freshly charged NIMHs, so you'll get close to 6.4V. Put a diode in series with the battery supply to drop 0.7V which will also help if someone puts the batteries in backwards.
Nice work on the giant 7 segments! Gotta see them lit up!

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Cry_Wolf

excellent work. I really like it.....
I am waiting for the seven segments toooo...

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Norlin

Yeah, I was thinking about using a diode instead of a linear regulator and it seems like a better and better idea the more I think about it. Now just to figure out which kind of diode to use, have so many! Time to browse some datasheets

Pommie

It looks like you are doing an excellent job. Keep us posted.

Piggy.Rep++;

Mike.

Norlin

Today I finished up the receiving and displaying end of the circuit and wired up the LEDs in back to a test breadboard, here are some lighted pics:

Testing a single digit


Wiring side of single digit test


Testing all digits with code running


Wiring side of all digit test


Noticed I have a problem with my code, it outputs hex values, but I'm going to need to output packed BCD values, so now to write a function to convert the output unless PICC has a library function built in for this. After that the next steps are to build and code the transmitter, make a PCB for the receiver/display (eventually a PCB for the transmitter as well and housing).

Edit: Noticed in the pictures the LEDs show up as spots, to the naked eye the diffusion is much more seemless, seems the camera picks the light up differently.

Cry_Wolf

really tasty..

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Hero999

Also note that the voltage will drop down to 1V per cell which won't give you any head room if the LEDs are wired in series and have a drop of 2V per diode.

A diode might not be needed, it depends on the absolute maximum voltage rating of the PIC, for example the 12F509 can stand 6.5V. I know it's bad practise to operate ICs at their absolute maximum ratings but the batteries won't stay at 6.4V for long, they'll quickly drop down to much less than 6V with all those LEDs turned on.

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blueroomelectronics

Nice job, looks very nice.

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Mike, K8LH

Nice work.

One comment about the light diffusion. When I helped my daughter build a 2 foot high 7-segment display as a "demonstration" type science fair project we discovered that we got much better and more even lighting of each segment by mounting the light bulbs to the side of each segment and bouncing the light off a piece of shiny bright white cardboard mounted at a 45 degree angle on the back of each segment. The display was built into standard 1/4 inch thick paper covered foam project/display board.

blueroomelectronics

Did that affect the viewing angle?

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Norlin

I've been working on this on and off over the past few weeks and I'm stuck on getting the wireless working. I'm using an ASK RF module (A434) and was using serial communication at first using the PIC built in USART module, I would send a single character to increment/decrement/clear the scores for the two sides. This worked, however there was so much noise in the air that the scoreboard would constantly change on its own. So I changed this to a four letter string, when wired this would work fine, however once wireless I couldn't get the score to change as I couldn't get a complete 4-letter string across, again due to noise. I tried adding some encoder ICs I got from reynold's electronics (www.rentron.com) however I couldn't get these to work properly even when directly wired to each other (was using HT-12E and HT-12D, also have R-8PE and R-8PD on hand, but didn't try them). So I decided to scrap USART and switch to a manchester encoding scheme. However I cannot get this working wired and it seems much to complex for my project in which I'm looking to just send one of six codes once every few seconds. Would anyone have any suggestions perhaps to a cheap, easy to use alternative to the ASK RF modules? Would have to be small in side for the transmitter end, since it's going to be similar to a car key fob. In the meantime I've been working on getting i2c working with a PCF8583 I picked up to add a clock functionality to the scoreboard.