Posts Tagged ‘PIC’

Designing for cool

July 14, 2010

I have not posted any little technical tips lately, so here is a tip to make your micro-controller based projects suitable for the cool shelf and not the nerdy shelf.

Just as low voltage micro-controllers appeared that can be run on a 3V power supply which is easily attainable from a couple of AA batteries, so appeared blue and white LEDs at affordable prices, with their inherent forward voltage of more than 3V.

Blue LED tyre light on a car wheel

Cool gadget

Society has now decided that white LEDs are cool, blue LEDs are super cool, and violet LEDs are really mega cool. It has become very easy to visually identify how cool your gadget is by what colour it lights up when you turn it on. Clearly anything that has an orange, yellow, green, or dare I suggest red LED is just old fashioned and nerdy.

Designer clock with red light emitting diode display

Less cool gadget

This has resulted in a design choice with not always the coolest outcome. Your choices are:-

– You can increase the supply voltage by adding an extra couple of AA cells, probably making it a bit heavier, but getting enough voltage for a cool coloured LED.

– You can use an unfashionable coloured LED.

– You can play the green card and not use an indicator at all.

Here is an alternative, a way to run your voltage hungry cool coloured LED from 3V using little more than software and ten pennies worth of components:-

Circuit diagram showing how to connect a blue LED to a three volt microcontroller

How to drive a blue led from a three volt micro-controller

All you need to do is provide an anti-phase square wave output on the two port pins. This can be done as an interrupt routine or as part of a polling routine in software quite easily.

With careful selection of which pins you use you may even be able to use an on board peripheral like a PWM generator or timer to generate the signal.

Careful selection of the capacitor values and adjustment of the mark/space ratio of the output square wave will allow you to adjust the brightness of the LED in software for added kudos to take you up another level on the cool shelf.

Suzie x


Not the only geek in the village

March 4, 2010

Seeing this thread at UK Angels brought back some nostalgic memories. From the olden days of the 1970s when owning a computer was a dream through to having a Commodore Pet at school which I got to borrow for the summer holidays (only posh schools had a Research Machines – not mine), then to owning a Spectrum until I got my hands on an XT clone with the wonder of a hard disk.

Then there were the others. The broken Dragon32 that I never managed to fix, The Newbrain AD with it’s integrated 16 character union jack vacuum flourescent display and two RS232 ports which could be run on batteries which is still around somewhere.

The coming of the PC really made the early computers redundant as a tool since interoperability is key. There is no fun in reinventing the wheel for a niche machine when the PC can already do it.

Bring on the embedded system. Lots of fun in developing systems that can enhance the functionality of otherwise simple objects at minimal cost because they only contain a couple of chips – not the big computer of old.

First it was the Intel 8051 series. Lovely little processors but not quite little enough for every application.

Now we have PICs so that I can put a computer in pretty much anything – and even the awesome SX processors for those little applications that need an embedded RISC processor running at 150 MIPS! Processing power that would not dare be dreamed of a few years ago.

Parallax SX28 processor

Suzie x