Converting Polaroid Land Cameras: Step 1

After the first part of the operation

We had a lot of fun today drilling and sawing. We’re following these instructions to convert some Polaroid Land cameras from very old Polaroid film which is no longer made to 5x4 and Fuji Instax. The procedure is simple enough, although you do need to be careful when using the drill (and it is best if you have sharp drills). You have to remove the back of the camera, along with a pressure plate assembly which used to squeeze the chemicals onto the photographs. You then add a 3D printed back plate along with a film holder.

We need to tidy up the tape we added to make the camera light tight against the 3D printed back.

We’ve got the back off the camera, adjusted the camera focus and fitted the new back. The next step is to change the “infinity stop” on the front of the camera so that it will focus at the correct place for the Instax Film holder we are using.

Rule 1: Point the camera in the right direction..

This is actually of a group of people

Photography is hard. First you have to set the lens aperture and shutter speed. Then finally, you have to point the camera in the right direction. Took some pictures today using a camera which uses a “sports viewfinder” which is just a wire frame you look through in the right direction. I looked in the wrong direction and we now have a bunch of tree pictures we weren’t expecting….

May the Fourth be with you

You can even see me in this picture if you look carefully enough….

Up town today to take some pictures at a local “May the Fourth” Star Wars event. It was great fun. Lots of bits and bobs for sale and loads of people in character. I was using Ilford HP5 film which is fast and gives a really nice grainy effect.

You talking to me?

Hull CS50 looking good

Warren asked me for some words about the upcoming Hull Computer Science 50th Anniversary.

The celebration runs over Friday 11th October and Saturday 12th and takes place on the Hull University campus. We start with a welcome event on Friday evening, but the main celebration event is on Saturday 12th. We'll have robot rugby for the kids, research talks, campus tours, Hull Stories, Retro video games, embed you in carbonite with our 3D printers, slot car racing, and a 'Computer Science Welcome Party Redux' in the evening where you can relive your first departmental social engagement at Hull, complete with a dodgy quiz.

If you fancy a doing a bit of coding while you’re here, we'll also be running a Three Thing Game hackathon. Get your three 'game things' at our online event on the evening of Wednesday 9th of October and then spend as much time as you like building something impressive in our lab. We’ll be judging the games on Saturday afternoon and then presenting the winners that during the welcome party.

Ticket holders will get lunch and dinner on the Saturday, and those awfully nice folks at Visr (visr-vr.com) have put some money behind the bar for the evening celebrations. Why not come for the weekend and spend Sunday exploring the city or revisiting old haunts.

The event will formally start on Friday 11th of October at 6:00pm with a meetup on campus. A good place to meet up and unwind after your journey up to Hull. We'll be around to chat about the old times.

On Saturday morning our day of celebration starts at 11:00am with tours around the campus, or a coffee in the Bronte Brasserie. We'll have a memory board for pictures from the past (send us some if you want to be famous-ish) plus retro consoles to play on. After lunch we'll have a sequence of micro-talks, starting with an overview of current research activities and then moving onto stories from Hull past and present. If you've got something to tell we'd love to hear from you.

At 4:30 we'll award the prizes for the Three Thing Game competition and serve out the food. Then, at 7:00pm we start the evening's entertainments with a 'Welcome Party Redux'. If you've got fond memories of your first social gathering here this is your chance to relive them.

We're going to have a Welcome Quiz with fiendish questions, retro games, slot car racing we'll even 3D scan you and create an image of you in carbonite.

(this programme is slightly provisional and may be subject to change - especially if we can't find any carbonite)

You can find out more (and maybe even register) here.

Making a box for my Telephone Exchange

This was much easeir than I expected

I’m making a telephone exchange for my Red Telephone. I’ve found a nice looking box design that has space for the ssd underneath the Pi. But I wanted to add some text to make it more interesting. The slicer made this really rather easy, which was nice. Next thing I have to do is print it.

Big Car Rob

I took my little car into the dealers for its MOT test yesterday. This is an annual British ritual where you find out just how dangerous that thing is you’ve been driving around in all year. My car passed (which is nice) although it did need two new tyres. They gave me a loaner car to play with which was huge (and according to the form I signed worth about 60,000 pounds). This was deeply scary but also great fun. I’m almost looking forward to the test next year…

Chatting with Bob

Which one is me?

Today I did some more work on the Large Language Model I’m connecting to my Red Telephone. Turns out to be quite fun.

Yet more Canon Dial mending

New dial and its inspiration

Over the weekend I bought yet another Canon Dial from those lovely folks at West Yorkshire Cameras. It was sold as “broken” from their outlet store. They handed it to me and then gave me a plastic bag holding the side rubbers which had been removed as part of an attempted repair.

I’ve been playing with it and It now works fine. All I had to do was remove the winder and free off the gears inside and add the tiniest amount of oil. Then I stuck the rubbers back on. Joy of joys, the meter works! I’m not sure what it is about these cameras that I like so much, but I’ve now got a couple that I can use which is nice.

Typewriters for kids

Now, where is P?

Bought a typewriter yesterday for number one granddaughter. It was in a charity shop calling for me. After I’d walked past it twice I decided that it was actually for me. Kind of nostalgic. Just like the one I used when I was a student nearly fifty years ago. And of course it still works. Number one granddaughter was fascinated. The idea that you can directly make marks on paper with something mechanical was quite new to her. Within a few minutes she was happily bashing out letters and learning that there is no delete key……..

Great fun.

Got my first ever tattoo

It’s starting to wear off a bit I’m afraid

Perks of being a grandad number 101: Got my first tattoo today. I don’t think it will stick around but it was expertly applied with plenty of glue…

Robots in HackSpace

My domination of the publishing world continues. In this month’s HackSpace magazine you can find episode 2 of my series about the Robot Operating System.

It was great fun to write. There’s a complete walkthrough of setting up ROS 2 on a Raspberry Pi using Docker in the lab part of the article. This makes it comparatively easy (if you use my scripts) to run ROS on a Raspberry Pi 5 running the latest Bookworm OS. It runs rather nicely on that platform, including the graphical tools.

Pixelbot PCBs at the May 1st Hardware Meetup

The coloured pins make it much easier to see what each connection does

The Hull Pixelbot is going from strength to strength. The original device was powered by an Arduino Uno running a thing we call HullOS. Late last year we ported HullOS to the Raspberry Pi Pico. To make it easier to connect (and to add some interesting new options) Brian has designed a PCB that provides a proper power supply for the PICO and exposes all the connectors for motors and sensors. We’ve also got space for an OLED screen and a couple of push buttons.

This is a major development for Pixelbot. It means that we can expand Python-Ish (or maybe even replace it with “real” Python). It certainly gives us a lot more options when building robots.

Brian used a tiny hotplate to install all the surface mount components. We’ll have the hotplate and some components at the next Hardware Meetup so you can actually watch a circuit board being soldered.

Connected Little Boxes Direct Commands

YOu need to add the “direct” tag to your device for direct commands

Making stuff by yourself is all very well, but I find that projects really catch fire (in a good way) when you get other people involved. I’ve been working on Connected Little Boxes for ages and I think it is now almost useful. You can make little devices that can send messages to each other and you can control from the web. There’s a web interface you can use to manage your devices and create control pages for them. It’s all underpinned by MQTT (Message Queue Transport Protocol).

Ross took a look and he reckoned it would be nice to be able to just hit a url and send an arbitrary message over MQTT to a device. So I’ve added it. If you take a look the device edit page above you will see that the cosylight device has a Device URL. If perform a GET from that url with a query string which contains a “text” value the contents of the value are sent over MQTT to the box.

There is no validation or security, so I wouldn’t use it to control my front door. But if you want something very lightweight it provides a neat way of sending commands. If a device is being abused you either disable direct commands or change the url to a contain a different GUID.

If you want to have a go with Connected Little Boxes get in touch and I’ll set you up with a username and a password on the portal.

Fun with colour film

Local Blossom

Took a colour film in to be processed today. I like doing this. It is a bit pricy I suppose, but it is my hobby, so there. And apparently you can spend an awful lot of money on golf clubs (not to mention course fees) - so there’s that. Anyhoo, they came out pretty well.

Just some trees

Hull University Wilberforce building artwork

University library looking good in the rain

These pictures are from scans that I got when the film was processed. I think they look pretty good, although the physical prints look even nicer. They aren’t particularly high resolution but I’ve found it pretty much impossible to make better ones with my own scanner.

Bought an Olympus Pen EES from Japan

Not bad for a fifty year old camera

It’s number one son’s fault. He told me about the Buyee site which lets you bid in Japanese auctions. I’ve been after an Olympus Pen EES (with manual focus) for a while and so I took a look. They had one on there priced at 27 quids. Very good condition and with a “working” exposure meter. So I bought it. The price is impressive for a camera like this; although I did have to pay another 27 quids for postage and packing.

The service is very good. The Japanese seller of the camera sends it to the Buyee warehouse in Japan where it can be stored for up to a month. If I bought any other bits and bobs they could have been sent there too and then all combined for shipping. As I was just buying the one camera I had it shipped out as soon as possible. It took four or five days to arrive and the whole process was very smooth. I’ve had orders from ebay which have taken longer. The order didn’t attract any import duty and I was able to use the Japan Post website to track the package all the way to being out for deliver by Royal Mail Parcelforce.

The camera arrived today and (of course) doesn’t quite work properly. The exposure meter isn’t working and the aperture is stuck at F22. But I don’t mind. It will take pictures (although I’ve yet to develop them). Even if I have to spend a few quids to get it fixed or brave going inside and fixing it myself I’ve still got a camera in extremely good condition. The site sells a huge variety of stuff, some of it at very interesting prices. I don’t think I’ll be buying things every week, but it is nice to have the option if I want to get something which is a bit out of the ordinary.

Making Working Microphones

I’m quite proud of the above circuit. This is not because it is especially well designed, or that it is definitely the best way to do it. I like the circuit because it does what I want. I connect the phone handset to the left hand connection and the microphone to the right and I can speak into the handset and record the resulting audio on the Raspberry Pi.

The circuit contains a “potential divider” which is a posh name for two resistors wired in series. In the above case the two resistors are R1 (the 1K resistor) and the handset carbon microphone (which measures around 500 ohms or so). One of the magical features of electricity is that a voltage “spreads itself out” across the resistors in a circuit. If the handset microphone has a resistance of 500 ohms, we put it in series with a 1K resistor and we put 5 volts across the pair of them we find that the 5 volts is spread across this circuit in a manner proportional to the resistance values. Total resistance 1,500 ohms (1K + 500). The 1K resistor is two thirds of this total, so two thirds of the voltage goes across this resistor. The point where the 1K resistor and the handset microphone are connected should therefore be at a voltage of one third of 5 volts, the other two thirds having been dropped across the 1K resistor.

If this is confusing to you consider how, back in the day, we used to make Christmas tree lights using bulbs that were powered by 12 volts. You might think that putting a 12 volt bulb across the 240 volts mains supply would cause that bulb to explode. And you’d be right. But if we connect 20 of the bulbs in series, one after another, each bulb only drops a 20th of the 240 volt supply (12 volts), so all works well. This is also horribly dangerous though. You might think that 12 volts is a safe voltage to work with, but in the case of mains powered Christmas tree lights people were regularly electrocuted. This is because a human being has a high resistance, much higher than a 12 volt light bulb. So, according to the laws of the potential divider, if I insert myself into the tree light circuit in place of a bulb, the fact that I have a much higher resistance than a bulb causes most of the 240 volts in the circuit to go into me. Ouch. Nowadays we don’t wire lights this way. A set of lights will contain a transformer which converts 240 volts into something much less tingly.

So, we have a potential divider which contains two resistors, the 1K one and the carbon microphone. Consider what happens when I speak into the microphone. The carbon granules vibrate and the resistance of the microphone changes. This changes the voltage at the point where the two resistors are connected. This change is an audio signal that represents the sound. The signal goes through a resistor (R2) to reduce its level a bit and then into a capacitor which only lets through the alternating current (the sound signal). This goes into the microphone and hay-presto, we have a sound signal.

This is the third version, which is small enough to fit in the phone

Above you can see my realisation of the circuit on stripboard. I’ll spare you the sight of the soldering underneath. The circuit is now in the phone and working. Next I have to work on the software.

Making Microphones

It is a surprisingly good microphone

When I’m attacking a problem I sometimes like to have several fronts open at the same time. I’m presently trying to get speech input into my Red Telephone. The phone has a carbon granule microphone which changes in resistance in response to sound. This won’t work with the microphone input in the phone. I could either build a circuit to make the carbon microphone work with a “normal” microphone input or I could find a different microphone to put in the phone. I decided to do both. Starting with microphone replacement.

I got the microphone above with a stereo system from way back. It helps the amplifier adjust itself to the acoustics of the room its working in. The stereo is long gone, but I kept the microphone because well, you never know when you might need one. It works fine with the USB audio input I’m using with the Pi and it even fits inside the handset of the phone. But there is a problem. The handset is connected to the phone using a lovely red curly cable. This cable is not screened at all because old phone cables don’t need screening. Unfortunately, microphone cables do. So although I got an audio signal from the microphone I also got an awful lot of hum caused by the cable picking up mains radiation from the devices in the house. Oh well, on to tomorrow.

Making Spanners with ChatGPT

Close but no cigar

As part of the fixing of the Canon Dial camera I needed a spanner to remove the dial spring winder. The spanner is a bit special because it needs to fit between the winder and the camera body. Ivan was kind enough to make me one out of brass, but it turned out to be a little bit too thick. So I thought I’d 3D print one. I’ve been impressed with how tough PETG prints have turned out, and the spanner doesn’t have to be particularly strong, so I was hopeful this might work.

And, since I’m lazy I thought I’d ask ChatGPT to produce the spanner design as a Python program I can run inside FreeCAD. I asked the question and out popped some Python. Which didn’t work. There then followed around fifteen minutes of me explaining why the supplied design was wrong, followed by ChatGPT then producing a differently wrong result along with an explanation of how it had fixed the faults that were still there.

Eventually I gave up and wrote the design in about five minutes or so. These things are very clever, but if they get it wrong it seems that sometimes it stays wrong whatever you do.

The spanners worked a treat, although I had to make a really thin one

Canon Dial 35 Cleaning

Those tiny little dots in the plastic bag in the middle are the screws that hold the winder in place

I’m not sure if people really want to know the saga of my Canon Dial 35. But it’s my blog. So there.

Anyhoo, today I thought I’d get to the bottom of the the sluggish way that the camera was winding on after each photograph. I was able to take the winder off the bottom of the camera and use a whole bunch of cotton buds to clean muck off the inside. I then added a tiny bit of oil (too much oil is a really bad thing in cameras like this) and then put it all together.

And it works. Go me. The wind on is now very smooth and positive.

Distance Sensing at the Hardware Meetup

Brian has built a pixelbot test rig which is very impressive It was even playing music

We had our hardware meetup at Hull Library Makerspace today. Folks are building robots and they are starting to move around and do stuff (the robots that is, not the folks). Today we added some distance sensors and had them reacting to their environment a bit, which was rather nice.

Richard had his robot making noises which were definitely not music

If you want to take part, and maybe build a robot of your own, you are welcome to come along. We meet on Wednesday afternoon, starting around 5:00pm and then going on until 7:00pm. We tend to meet up every two weeks, the next meetup is on Wednesday 1st of May (apologies - an earlier version of this blog post said 24th April which is wrong). The robot we are building is the Hull Pixelbot. You can find out more about it here.