Z80 Stuff
The Zilog Z80 was one of the most successful 8 bit proccessors of all time, with speeds upto 20MHz. Used in many home computers of the 80's and still used in Alarm and Control systems today. It has 158 instructions, maskable & non-maskable interupts, its own I/O adressing system, which unlike some processors at that time did'ent use up its own memory space for I/O use.

sorry no image This photo shows a Z80 SBC that's a single board controller or computer with upto 32Kb of Eprom for the control program and data and 32Kb of RAM, two 8255 I/O chips each giving 24 control lines in 3 8 bit ports A, B and C. It measures 8"x4.5" and has been used to control home-made robots, stepper motors, a data logger for a weather-station, etc. It is produced by the same company that produced the Interak computer, and indeed can be used in that computer as a general purpose input/output interfacing card...
This photo shows a home made version, built on a standard Euro-card (6"x4") with only one 8255 chip, But the low power RAM has battery back-up which will hold the program and/or data in memory for a good year or more, when not in use.. In fact it replaced 3 such cards in an older system. This was used along with a Hex keyboard and 6 digit LED display as a Z80 machine code trainer, and it allowed me and friends to learn a lot about low level programmmimg. sorry no image
sorrry no image yet A typical controller board needs! a CPU Z80 or otherwise, an Eprom chip to hold the controlling program or code, RAM memory chip(s) for data storage and progam variables, an I/O chip for interfacing to the outside world, and a few TTL logic chips for address decoding, etc. Not forgetting resistors, capacitors and the odd diode to glue it all together
Visit the website of Alan Paton for more pictures and information about the Z80
A PIC, what's a PIC? or a PicAxe! Arduino?
A microcontroller, in a conventional controller system using a CPU (Z80,6502, etc) the CPU would also require extra devices to provide memory, timing, I/O ports etc. In a microcontroller CPU, memory, timers, I/O ports and sometimes even A/D converters are all brought together in one device, a microcontroller. The Arizona-Microchip PIC series are so easy to program, and need very few components to make a working system.....
Here is a small (2"x2.5") home-made controller based on Microchip's PIC-16F84 (or 16C84) microcontroller while this is not so powerful in some ways as a Z80, it has many benifits, size, low power, low component count, a timer and pre-scaler. it's own built-in system clock can run at upto 10MHz. It has both programmable EEprom and data memory, and includes 68 general purpose registers, Interupts, 13 I/O lines consisting of port A D0-D4, port B D0-D7 all capable of sourcing or sinking 25mA to directly drive LED's etc.. There are only 35 istructions, so much easier to learn and remember than 158. Will go to sleep (save power) when not active, wake-up on a key press, interupt, etc... This and some other PIC's can be reprogrammed over and over again! sorry no image
sorry no image yet So just what do you need to build a microcontroller?? not much a PIC 16F84 chip, a PCB or piece of Vero board, 2x39pF capacitors, 1x10-100uF cap, 1x 0.1uF cap. A crystal upto 10MHz, 4MHz seems very popular! or this can be replaced by a small cap and resistor if a precise clock is not required, this is also useful if you need a slow clock speed. Power-on reset may be required this will need a 1-2.2uF cap and a 10k resistor. You now have a working controller, you can now program it to read switches, light up LEDS, drive relays and LCD displays, etc and generally control and time things. And all of this will still give you change from £10, building a simple programmer will cost you about the same.

The controller shown has two sets of pin headers, the larger for all I/O, power, and control signals. The smaller is a direct pin compatable connector for intelligent LCD modules, allowing direct plug-in or ribbon connection to these. Want to know more about PIC microcontrollers. you can call Microchip on 0118-9215858 or e-mail Dr Mac at Drmac@microchip.com or visit their website at www.microchip.com Don't forget to mention you read it on Mel's page

The Buggy, Robot or whatever!!
These shots show my first Picaxe Buggy-bot. The chassis and all circuits are built on Vero board! Picaxe are normal Pic chips, but pre-loaded with a bootloader, this makes programming very easy using simple but powerful basic programming. At the start we have LEDS for lights, and micro-switches on the front for bump sensors..and sound for beeps and bangs! Now we add IR leds and sensors to detect obstacles. All boards are held together with pin headers and sockets, making expansion and a brain transplant easy.
This is my first round bot, using a Tamiya twin motor/gearbox unit, and an Ultrasonic range-finder, to avoid bumping in to objects.
A Tank or tracked bot again using more Tamiya parts, like the wheel and track set and base plates. An Ultra-sonic detector, on a servo so it can "look" left and right, then decide which way to turn. etc...
This was my last Picaxe controlled robot. At this point I changed over to the Arduino's, much more powerful. Based on the well known Pololu RP-5 tracked chassis, again an Ultra-sonic detector to avoid objects and walls, etc. A good climber with a tilt switch just in case it tries too hard.. and is in danger of turning over
This is the Pololu Zumo chassis, small and compact. But speedy and fun. Still working on it, adding opto detectors to count wheel turns for better control, as below. This is driven by an Arduino UNO and a dedicated robot shield. The LCD gives feedback to the user.
This bot, uses two clear acrylic disk! and Micro motors. I hopt to add wheel encloders for better control of turning and speed. Also opto sensors for line following and edge detection. Just for fun a bright RGB Led flashing and colour changing... This is also the first time I used 14500/AA rechargable lithium batteries at 3.7V each, so only two are required, not the usual 4.
This is my DrawingBot, using 2 x 200 step, stepper motors, with MicroStepping you get 1600 steps per rev. But it took a spreadsheet to work it all out, depends on wheel size, spacing, etc. The drawing? is all one bit of code to draw half circle, full cirle, squares (Not quite true squares) and what I like to call a feather!! Note: the Nano fitted in a socket, also 2 motor driver modules piggy-backed together.
If you have an interest the Arduino controllers at hobby level, electronics in general, building gadgets, mechanics!! anything to do with a soldering iron Then please e-mail me for a chat or to share our resouces etc..

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