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Introducing the seven-a-side PICAXE FUN WITH THE NEW Picaxe PICAXE 14-M! by Stan Swan There’s a new kid on the block! He’s from the rapidly-growing PICAXE family (now with 11 siblings!) and goes by the name of 14-M. If you’re a PICAXE fan, Stan wants you to meet him ’cos he’s really friendly – especially if you already know his younger brother, 08-M! I t could come as a suprise to readers who were only aware of the ever popular baby 08(M), but the PIXAXE family now in fact has 11 members – titled by their number of IC legs (8,14,18,28,40). Revolution Education’s new PIXAXE 14-M, based around the well-thought-of MicroChip PIC16F684, is billed as an 08-M “big brother” but in fact looks best suited to simplify introductory work for students and hobbyists. The “M” refers to the musical capabilies of both PIXAXEs” – but don’t expect MP3 quality! The 14-M offers a lot more than the 08-M. Indeed, the 14-M may become the entry-level PIXAXE microcontroller, overtaking the 08-M in time. The pricing is attractive and its increased and more logically positioned I/O pins serve to make the 14M even easier to work with than the 08. Old PIXAXE hands may scoff at the thought of something that’s even easier than the 08 they’re used to and now know almost like the back of their hands. But it’s important to consider new learners and the fresh crop of PIXAXErs continually emerging – through magazine articles such as this and now, thankfully, a large number of schools and colleges who have introduced their students to electronics and micros through the mighty PIXAXE. This protoboard layout photo fairly closely matches the “3V” version (the left-hand layout overleaf). Stan has used multicolour LEDs in his version – you can do the same as long as you don’t try to use white or blue LEDs, because these often aren’t reliable on a 3V supply. siliconchip.com.au June 2007  75 It’s because the PIXAXE is so easy to understand and use that it has achieved such popularity. You may recall that when we first introduced SILICON CHIP readers to the PIXAXE (in a series of articles starting in February 2003), We commented at the time that the PIXAXE could become the “555” of the nineties simply because it was/is so simple yet so versatile. It’s opportune that such a PIXAXEas the 14-M has been developed, especially since the five inputs (including two ADC) and six outputs offer many educational applications normally beyond the limited I/O PIXAXE-08(M). Also, the “top” eight pins of the 14-M are pin-for-pin compatible with the eight-pinned 08-M, so all those breadboarded PIXAXE circuits can use exactly the same layout and much the same code. Who let the smoke out? A word of precautionary housekeeping: the 14-M’s DIP14 (Dual In-line Plastic 14-pin) packaging makes the chip a look-alike to numerous cheap logic ICs, so it is essential to clearly label them before turning them loose on beginners! It’s sometimes difficult to get across the concept that even though chips might look the same, they’re different. To some, a chip is a chip is a chip! Many young students (and even weary-eyed academics!) may innocently consider all such 14-pin ICs as interchangeable – the same problem periodically arises with DIP8-style PIXAXE-08s being mistaken for 555s and 741s, with frustrating (and occasionally explosive) outcomes. Initial 14-M circuits In pondering initial ‘icebreaker” educational circuitry that the 14-M suits, the in-line nature of the six outputs struck me as being particularly well suited for ever-popular LED chaser and level displays. Such circuits are simple to wire up but are most entrancing, while cheap and various-colour LEDs allow all manner of colourful effects to be explored. The looping algorithms required may also focus and stretch young minds, with the instant feedback provided to the validity of a program effect encouraging both V+ CON2 DB9 2 3 5 10k IN4 IN3 PROGRAM EDITOR (TO PC SERIAL PORT) K A IN2 IN1 K LEDS A IN0 PICAXE 14M 14 SC 2007 7 1 2 1 3 EQUIVALENT PICAXE 08M 12 FOOTPRINT 4 11 5 PICAXE 10 14M 6 9 7 13 OUT0 OUT1 OUT2 OUT3 OUT4 14 8 330Ω∗ λ 330Ω∗ λ 330Ω∗ λ 330Ω∗ λ 330Ω∗ λ 330Ω∗ λ 6x LEDS OUT5 * WITH RED, GREEN OR YELLOW LEDS SUPPLY CAN BE 3V AND 330 Ω RESISTORS CAN BE OMITTED new Picaxe 14m – led chaser Take one PIXAXE 14-M, six LEDs, two programming resistors . . . and you have yourself a chaser! We’ve superimposed the 08-M on the 14-M in the circuit to show how it is pin-for-pin compatible – at least that much is! the talented and lethargic. A teachers dream! As it’s apparent that the 14M can be considered at several levels – both introductory and advanced – “power” users may even be able to redefine some of the 14-M’s nominal inputs and outputs, potentially allowing up to nine outputs under “portc” commands. Normally even handling eight LEDs on such chasers requires a more involved and costly PIXAXE 18 (see www. picaxe.orcon.net.nz/18leds.jpg). Indeed, the first electronic chaser we ever saw (after the motor-driven mechanical monstrosities before the solidstate era) consisted of two 14-pin IC flip-flops connected as a twisted ring counter, along with a significant number of components to pulse them and to decode the output to drive lamps. And now you can do it with one PIXAXE and six LEDs! V+ 3V (2x “AA” ALKALINE) * PICAXE-14M 22kΩ 5 3 2 4.5V (3x “AA” ALKALINE) * 22kΩ PICAXE-14M 6 x 330Ω PROGRAMMING A 5 3 2 PROGRAMMING A 10kΩ K 0V 22k RXD +4.5V* IO CHANNELS PROGRAMMING RESISTORS 6 x LEDs 10kΩ K 0V 6 x LEDs * OR 4.8V (4x NiCd OR NiMH) On the left is the protoboard wiring for the chaser circuit with a 3V supply. We’ve shown rectangular LEDs because (as the photo shows) these can fit together better on the standard 0.1” protoboard spacing. With our more usual 4.5V (or 4.8V) supply the wiring is slightly more complicated, as shown at right, because series resistors need to be added to ensure the LEDs aren’t destroyed by too much current. But either way, you could hardly get a much simpler circuit! 76  Silicon Chip siliconchip.com.au Save Up To 60% On Electronic Components PICAXE 14-M BASIC LISTINGS – 14CHASE.BAS AND 14WIPER.BAS ‘14CHASE.BAS PICAXE 14M demo LED follow me chase April 2007 ‘Ensure latest editor used with 14M option selected ‘Uses 6 LEDs at output pins 0-5 for a ‘follow me’ L-R effect ‘b1=LED number chase: for b1=0 to 5 ‘starts follow me chase high b1:pause 100:low b1:pause 100:next b1 ‘sequentually wink LEDs wait 1 ‘1 second rest goto chase ‘repeat entire effect ‑‘14WIPER.BAS PICAXE 14M demo LED ‘wiper’ April 2007 ‘Ensure latest editor used & 14M option selected ‘Uses 6 LEDs at output pins 0-5 for accelerating L-R-L wiper action ‘b0=delay b1=LED number wiper: for b0=250 to 0 step -5 ‘decreasing chase delays(msecs) for b1=0 to 5 ‘loop for outward LED chase high b1:pause b0:low b1:pause b0:next b1 ‘briefly flash LED for b1=4 to 1 step -1 ‘loop for return LED chase high b1:pause b0:low b1:pause b0:next b1 ‘briefly flash return LED next b0 ‘decrease delay between flashes wait 1 ‘1 second rest goto wiper ‘repeat entire effect You can download from www.picaxe.orcon.net.nz/14chase.bas and www.picaxe.orcon.net.nz/14wiper.bas Construction Although purpose-designed PC boards are already available, the small breadboard layout we’ve used since we introduced PIXAXE circuits perfectly suits many 14-M designs, especially (as we mentioned earlier) 08-M/14-M program pins are identically placed. And this layout is so simple even a raw beginner shouldn’t run into any problems (just watch chip and LED polarities!) To further ease constructional woes, the 14-M can be run from two “AA” batteries (3V) thus removing the need for the usual 330W dropping resistors on the LEDs. A 50mm screw or nail can replace a cell in the popular PIXAXE 3 x AA (4.5V) battery box as a simple way to lower the supply voltage, or a less common 2 x AA switched box can be used. The reduced (3V) voltage will normally still program and run the PIXAXE with LEDs, although blue and white LEDs may no longer illuminate, as these more recent (and costly) LEDs normally need a supply higher than 3V. Of course, there’s nothing to stop you running the 14-M from the more usual 4.5V supply but in this case 330W current-limiting resistors will be required to ensure you don’t burn out the LEDs. Therefore we have shown these on the circuit diagram and one of the breadboard layouts. Also, it is possible that some serial ports may become unreliable at lower supply voltages, so a 4.5V supply is better from that point of view. But once you’ve programmed the 14-M and you wish to make your chaser “portable”, a SC 3V supply should be perfectly OK. Programs, references and labels: Hosted for download, along with other 14M material, at www.picaxe.orcon.net.nz/14m.htm siliconchip.com.au Great New ET-AVR Stamp Only $26.47 * Includes ATMega128 Microcontroller * Up to 53 I/O Points * 8-Channel 10-bit A/D * Direct In-Circuit Programming * Ideal as a Removable Controller Exciting New ET-ARM Stamp * Includes LPC2119 Microcontroller * High-Speed Operation * Heaps of I/O plus CAN, UART, I2C * In-Circuit Programming * Supporting Board Also Available Only $33.12 Save Heaps on Components Only $7.85 We carry a wide range of Integrated Circuits, Microcontrollers, Capacitors, LEDs and LCDs. All at very competitive prices. We are your one-stop shop for Microcontroller Boards, PCB Manufacture and Electronic Components. www.futurlec.com.au Radio, Television & Hobbies: ONLY the COMPLETE 00 $ 62 archive on DVD &P +$7 P • Every issue individually archived, by month and year • Complete with index for each year • A must-have for everyone interested in electronics This remarkable collection of PDFs covers every issue of R & H, as it was known from the beginning (April 1939 – price sixpence!) right through to the final edition of R, TV & H in March 1965, before it disappeared forever with the change of name to Electronics Australia. For the first time ever, complete and in one handy DVD, every article and every issue is covered. If you're an old timer (or even young timer!) into vintage radio, it doesn't get much more vintage than this. If you're a student of history, this archive gives an extraordinary insight into the amazing breakthroughs made in radio and electronics technology following the war years. And speaking of the war years, R & H had some of the best propaganda imaginable! Even if you're just an electronics dabbler, there's something here to interest you. NB: Requires a computer with DVD reader to view – will not work on a standard audio/video DVD player Use the handy order form on page 81 of this issue. June 2007  77