For people at FOSDEM 2012 (great event by the way!), you’ve surely seen my name badge around. For others, here is a picture :
As promised to some people there, here are all the details :
I used an MSP430F5171 16-bit ultra low power microcontroller (mcu), and my own arduino port for that platform (that supports nearly all the msp430G, MSP430F2xxxx and msp430F5xxx by the way, with all their ports, and pwm on all the ports if needed).
However, to save some room on the board and to limit the bill of materials, I haven’t used any resistors, playing on the multiplexing effect and praying that the mcu would handle that current (very bad practice for production designs, but for an experimental name badge… ).
Enough chatting, here is the schematic :
And pictures of the badge being built :
If you wonder how I made the pcb, I used the toner transfer method (cheap store catalog paper and laminator), with traces as small as 6 mil, so it works perfectly once you’ve tried all the methods on the web and found the one that is ok for you. I hand soldered all the components using a regular iron.
And, finally, of course,a video of it scrolling :
As you may see, there is a final row on the right that doesn’t light up,
that’s because I tried to put high intensity blue smd leds, that took too much current from the mcu pin, another reason why it’s a bad practice to do what I did without resistors there was just a badly soldered via, now fixed
If I had to to do it again, I’d probably use real led drivers, but trying to find some that are low power (it’s a name badge after all and it runs on battery) and maybe use a bigger resolution, as reading it with a 5×3 font was a bit hard.
If people are interested, I can publish the code here if needed, and I’ll of course post a full version of my arduino lib for msp430 as open source soon don’t worry
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