Archive for the Hardware Category

The 6809 machine

Posted in Electronics, Hardware on 29/11/2019 by imekon8

The first machine I had was a CompuKit UK101, a 6502 based machine. I wanted to build my own machine, and went for a 6809 based system.

I had a metal case in which I put a toroidal transformer, a rectifier and four voltage regulators: -12V, -5V, +5V and +12V.

I used double sized Euro cards and built a backplane that could support four of these cards.

THE FIRST BOARD

This consisted of the 6809 processor, 4kBytes EPROM, 4kBytes static RAM, an ACIA, a VIA chip and an AY-3-xxxx speech synthesiser chip. This was hooked up to an 8 digit 7 segment display and a keypad to enter hex values. I hand wrote the monitor software and used a friends machine to burn the EPROM.

THE SECOND BOARD

I built a 6545 video controller card with 4kBytes of dual ported static RAM. The 6809 has a symetric clock, so one half could be the video controller, the other the CPU. I initial had problems with the static RAM being too fast, as it picked up addresses that weren’t read on the video side resulting in the first character being displayed as a rapidly changing character. I solved this by shifting the clock until it loaded the address 250ns after the video bus supplied it and the issue went away.

I created my own character generator, 128 characters in the first part and blocky graphics in the second part.

THE THIRD BOARD

I designed a dynamic RAM board with 8 1 bit chips that gave me 64kBytes, and did the essential refresh in TTL counters. The 6809 had no support for dynamic RAM (unlike the Z80), so I had to design my own. It surprised me when it worked first time and was rock solid.

THE FOURTH BOARD

I got hold of data on a Western Digital chipset – two chips. I bought a double side 5ΒΌ” floppy disk drive and built the electronics around the chipset. I used hardware to drive the timing for the heads, motors etc. I eventually got it working and got 1.8MBytes out of a standard floppy and started running FLEX with it.

All these boards were wire wrapped. It did not last and the main CPU board died. By then, I’d moved on, and got interested in the BBC range of machines. I went from Acorn Electron, to BBC Master and finally the Acorn Archimes A410/1. I still have that in my garage… rotting away…

printed a Netduino 2 box

Posted in 3D Printing, Arduino, Gadgets, Hardware with tags , , on 05/07/2014 by imekon8

Now it’s getting MUCH better!

empty netduino box

…and the Netduino fits… almost!

netduino 2 plus in box

I think the USB slot needs a little enlarging!

It took about two hours to print. I wasn’t sure how well it would work, but it’s pretty good.

See here for the source: http://www.thingiverse.com/make:84036

Getting better…

Posted in 3D Printing, Arduino, Gadgets, Hardware with tags , , on 21/06/2014 by imekon8

Learning to set Z0 correctly!

Image

y belt clamps

Posted in 3D Printing, Arduino, Gadgets, Hardware with tags , , on 14/06/2014 by imekon8

Had a go at printing some Y belt clamps. Almost works but one side is too tight to fit the belt.

y belt clamps

The design came from here: http://www.thingiverse.com/thing:263720

more test prints

Posted in 3D Printing, Arduino, Gadgets, Hardware with tags , , on 14/06/2014 by imekon8

Worked out I hadn’t put a final jumper on the Duet board, so it was drawing power from USB. Once that was done, I plugged in a network cable and can see the printer on my home network.

Getting better at printing. I adjusted the Z height to 1mm above what I measured and things are much better. I also switched on the bed levelling compensation. Now my 20x20x20 cube is correct. My next problem is the print lifting off the bed, it doesn’t seem to stick too well.

Here are some hollow test cubes:

cube prints

The left hand one had too low Z height and no bed compensation – hence the squashed look! The second from the left had the Z height raised by 1mm, but no bed compensation. The last two had the Z height raised and bed compensation, and they do come out as 20x20x20 cubes.

Here are some more test prints:

more prints

The flange on the left started lifting off the front left edge, as did both of the other objects. The ring in the center is worst affected.

You can find the designs for these objects here: https://www.tinkercad.com/users/0nFtFdXwbGz-pete-goodwin

first prints

Posted in 3D Printing, Arduino, Gadgets, Hardware with tags , , on 11/06/2014 by imekon8

oh dear…

first prints

slight issue with Z height

finally finished putting together the 3d printer

Posted in 3D Printing, Arduino, Gadgets, Hardware with tags , , on 11/06/2014 by imekon8

finished

the finished printer with filament