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Tuesday, 22 December 2015

Beach Huts

These parts

plus some more colourful parts

Once welded together with a soldering iron and painted

create a set of beach huts. Of course you have to make sure that the colour combinations are acceptable with some sorting:

More to follow when I have the full set of parts...

Commodore SR4148R Calculator

In order to get a charger for a Commodore S60 that I recently bought, I purchased an SR4148R which came with the same model of charger as the S60 uses. The S60 had old leaky NiCds in it which I replaced, and a faulty VFD display with bad ghosting that I fixed with a pull down resistor.

Anyway, the charger for the SR4148R worked fine, so I have that for the S60. It didn't turn on the SR4148 though. From the outside it looks like this:

From the inside it was apparent why it didn't work on the charger:

There were no batteries and the charger socket wasn't wired to the main board. The PCBs were covered in battery leakage mess. After a bit more disassembly wwe get this:

Taking the keyboard apart led to a nice surprise. the keys are individually mounted and each one has it's own metal spring. A quality design that simply wouldn't be done these days.

Very unfortunately, you can see that the battery leakage has reached the LED display, as there is green behind the bubbles, on the left.

I cleaned the mess with baking soda and it all cleaned up a bit. I then disassembled the LED display, removing the bubbles to see if I could dissolve the mess off the display. After some cleaning I managed to do this and got a mess free display.

Very very unfortunately, the mess seems to have completely dissolved two of the seven segment digits. They just aren't there any more. Oh well, that isn't going to be repairable at all, I suspect. I will now have to find a broken calculator of the same model, or a replacement display. Interestingly I noticed that the small 0.96 inch OLED displays that I am fiddling with at the moment are an interesting size relative to the LED display:

It looks like two displays would cover the same area as the original display. Adding a PIC micro and some code to demultiplex the drive signals and we could display the seven segments on the OLED display. Hmm, a project for another day, but it probably isn't too tricky.

Monday, 14 December 2015

Printing Station

Having bought another printer (the Fisher) I needed to accomodate the two printers in the workroom. I had already built a plywood container for the Mendel that I used to store the printer and also transport it about before I had a permanent home for it. As I wanted to keep this case in case I wanted to move the Mendel again (and also protect it against dirt when it wasn't in use) I decided to fit it with legs and put the Fisher underneath the Mendel. This gives me a printing station with two printers one on top of each other and an area for filament reels below.

The small coloured filament is being used (I store it in bags when not in use) and is hanging on the frame for some wall mounted IKEA CD holders.

Here's a video of both printers running simultaneously:

The base for the mendel is fixed to the wall using the type of bracket that I print out quite often:

Creating a bracket like this is really quick and easy (in OpenSCAD) and while it is being printed I can do something else...

Small Box

In the olden days when yoiu wanted a small box for a couple of audio jacks attached to a ribbon cable, you'd have to send a pretty large cheque through the post to a mail order firm, then wait, then it arrives and you'd have drilled some holes, and there you go...

These days you print one.

Faberdashery Filament Storage

i have bought quite a lot of filamanet from Faberdashery in the UK. It's very good quality, but it doesn't come on a rell, which can be a pain. I have made reels in the past, but the coil of filament needed to be wound onto the reel, which was time consuming.

So, I made a reel out of cardboard and printed blocks:

The advantage of this reel is that you can unscrew one of the cardboard sides, slip a coil of filament in and screw the side back on. This makes it much easier to fit the coil to a reel.

Once the reel is screwed together I slip it on a filament bar that I fitted to the printing bench.

There's a couple of cardboard reels on the filament bar, the one on the far left is a wooden version I made, which is a lot more robust, but the cardboard ones have been pretty good so far. They also have the advantage that the corrugated cardboard is perfectly formed to act as a filaement end holder, as you can see on the black filament reel in the middle. You can tuck the end of the filament into the cardboard corrugation hole to stop the reel unwinding.

Surface Mount Component Storage
 I've bought some surface mount components as they seem to be the way ahead. They make it easier to make PCBs as you can skip most or all of the process of drilling holes in the PCB, at least if you stick to single sided PCBs. The problem with SM components when compred to the old through hole components is storage. I ordered a bundle of resistors and a bundle of capacitors from ebay as a starter set. They are quite compact, but awkward to store in an orderly fashion.

One common way to store these components is in plastic wallets which are then held in a ring binder. The pockets are designed to hold components, either on a strip like these, or in a small envelope. i need to store strips, and having to delve around in an envelope seems a bit fiddly, so I looked for plastic pockets. Unfortunately they seem to be pretty tricky to buy and are expensive. Some people on the web have tried making their own pockets out of standard A4 plastic ring binder holders. This involves a soldering iron or a hot wire system to melt the plastic and build up smaller pockets. This looks a bit hit and miss and also quite a lot of work. So, I gave up on the pockets and stored the components in a drawer.

Until I saw this in a charity shop this weekend:

It's a (very old) photo album. It is a binder with card pages that have a plastic page on each side. The plastic sticks in a temporary fashion some tacky strips on the cardboard pages.

The idea is that you peel back the plastic and tuck your photos inside, under the clear plastic sheet. The tacky strips then hold the sheet down and stop the photos sliding about.

This is also ideal for holding the strips of surface mount components:

You can get quite a lot of strips on each page, I suspect too many would reduce the number of tacky strips that are available to hold the plastic, but 6 strips is no problem at all.

As the binders were designed to hold photos they have been designed to expand as items are put into the binder, which also means thst they can accomodate quite a few strips of components.

I managed to buy two binder of different exterior design but with the same tacky strip arrangement and I'll definitely be looking for more as I suspect they can be used to store things other than SM components.


I've had an old BT phone for a while now, and recently bought a cheap one in a market. I finally decided to put some time into converting it to stand-alone use, using an arduino. The result is in the video below.

The internals comprise an Arduino Uno and a 'Music Player' shield. There's also a prototyping shield with some custom circuitry on it.

The original dialler mechanism has two GPIO lines on the Uno attached to it, the code uses these to decode the numbers that are dialled. The 'on hook' switch is also attached to a GPIO line, this is used to detect 'on hook' or 'off hook' and put the code into one of two modes.

The bell solenoids have been rewired from their original series configuration and have been attached to a GPIO line each via some power transistors. 

The music shield is wired to the earpiece in the handset, this is used to play various tracks on an SD card inserted in the shield.

The two modes of operation are either 'on hook' which is when the phone delays and rings, and the 'off hook' mode which is when it waits for dialled numbers. 

Dialled numbers are commands to the phone:

112 moves to the next track on the SD card
2DR is a command that delays for D seconds in 'on hook' mode and then rings the bells for R cycles.
3DR is the same as 2DR except that the delay is in minutes not seconds.

The music player shield is frankly rubbish. It is  an MP3 player chip with GPIO lines wired to all the manual controls. There's no detection of the track being played and all you can do is turn it on and off and move to the next track. And adjust the volume. It barely works for the Arduphone. I have a long recording of a dialtone as the first track, so that is what you hear when you pick up the handset after turning the phone on. It does run out after a while, though, and will then move to the next track.

The ringing circuit was tricky as it is driven from a high voltage in the real phone environment. I had to drive a power transistor with four GPIO lines to get enough current to provide a kick to the clanger which would actually ring the bell. This area could be improved.

I think if I get round to doing a second version then I'll have to update the music shield, but this version is quite a lot of fun eveb with it's problems.


Wednesday, 9 December 2015

Microscope Reflector

A few months ago I bought a couple of old microscopes from a junk shop. They were pretty cheap, but the carriages were seized. I managed to free them up and they work nicely, but on one of them the mirror used to reflect light onto the sample was missing. It was a simple disc shaped mount, so I turned one up on the lathe:

The metal is shiny enough for this to be good enough to use without a mirror. i may cut a piece of mirror to fit, or, more likely, I will add some form of LED illumination. Messing about with a mirror is a bit of a pain anyway.

Woodrat Things

I'm still working on a template routing attachment for the wwodrat. The latest part I'm trying to make is a clamp for holding work to be morticed. The latest version of the part is here:

the idea is that this is screwed to the template holder plate and the bolts hold the workpiece. This is 3d printed in PLA, and unfortunately it isn't rigid enough, I need to reprint with a different design.
It takes about 2 hours to print this, so I have to pick a window where I can allow this much time to print the part, so it's taking a while to get this done.

Thursday, 3 December 2015

Shredder Pushstick

We have to cut a fair amount of hedge down and bought a shredder to mash up the cuttings, as otherwise they take up a lot of space. The shredder came with a plastic pushstick for pushing stuff into the shredder. It was a bit delicate, though, and started to tear in half after about 8 hours of shredding. So I made a wooden one:

I've yet to try it out, we'll see how well it works...