Refurbishing a 48K Rubber Keyed Sinclair ZX Spectrum – Pt.1 Re-Capping

In my last post, I described the steps I took to prepare for refurbishing a 48K Rubber Keyed Sinclair Spectrum. I am now going to describe how I replaced all the electrolytic capacitors, or Re-Capped the board.

Firstly, I extracted the board from the case by removing the five screws on the undereside of the case. I then carefully flipped the entire case over and carefully removed the top. I did this slowly in order to safely unplug the membrane ribbons. If you open the case to enthusiastically, you can damage the membrane ribbons which will probably result in a replacement being needed. I gently disconnected the ribbons from the board and put the top of the case aside, ribbons upwards. It was then a simple case of removing the single silver screw near the center of the board to lift the board clear of the lower half of the case.

Bare Sinclar Spectrum 48K Board

Bare Sinclar Spectrum 48K Board

The kit of capacitors that comes from Retroleum is very comprehensive. There is at least one capacitor for every one in several models of 48K Spectrum. I have re-capped several boards with the same kit and there’s always spares (into my stock they go!).

My technique for replacing the capacitors is to use a hand de-solder pump and to work methodically across the board, doing one capacitor at a time. This gives you time to check and double check which way around the components fit and to make sure you get the correct value from the capacitor kit.

Methodical De-Soldering

Methodical De-Soldering

Check out my ancient Weller TCP-FE soldering iron, still working fine after over 30 years of use! It’s never failed me.

I extracted each capacitor carefully, so as not to damage the traces on the board. These can be damaged easily so I only heated joints when necessary and tried to remove component leads gently. Easier said than done with stubborn leads but patience is king here. If necessary, balance the board on it’s edge, hold the component lead from the top side of the board with a pair of long nose pliers and heat the joint from below the board. Go slowly and pull gently. Only pull the component lead when the joint is adequatly heated otherwise the component will be released too fast. If your de-soldering pump is doing it’s job properly, this should seldom be required.

Soldering In the New Component

Soldering In the New Component

One thing I am a stickler for is neatness in my work. Neat work is good work and makes things easier later on. To this end I bent the components leads at right angles with the help of long nose pliers, a little distance away from the components body. I roughly measured the first couple I did to get an idea of where exactly to bend them. Bending the leads away from the components body affords some strain relief when the component expands and contracts with temperature. Another thing I make sure of is to make sure the components labels are facing upwards. This is not only neat but would help later if any required replacement. Once soldered. I clipped each lead by holding the free end and clipping close to the board. By holding the leads when you do this, it avoids them flying out of control and avoiding potential eye hazards. I have a large coffee tin where I put these off-cuts because they come in very useful for short links and other tasks.

Freshly Re-Capped Spectrum

Freshly Re-Capped Spectrum

When you have completed the re-capping, examine all of the joints even if you have been checking them as you go. It is really easy to miss a’dry’ joint and is difficult to find later. If you see any joints you are not happy with, simply reflow the solder and add some fresh for a good joint.

When finished, I would usually test the board but I was confident I’d done a good job and I was going to move striaght on to replacing the power regulator next in any case. I will describe that process in the next part of this series.

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Refurbishing a 48K Rubber Keyed Sinclair ZX Spectrum – Preparation

Recently, I was lucky enough to ‘win’ a pair of 48K Sinclair Spectrums. The original rubber keyed variety. This model was one of the first I ever owned (the actual first being a Sinclair ZX81).

Rubber Key Sinclair ZX Spectrums

Rubber Key Sinclair ZX Spectrums

Here, I have managed to obtain issue 3 and an issue 3b models. The one with the better case is the 3b so I chose that to refurb first. In preparation for this, I tested both machines. I was surprised to find they both worked, at least to the copyright message, and both the membranes were intact. In fact, the issue 3b seems to have an aftermarket replacement membrane.

The one thing I did notice is the speed at which they both got to the copyright message, it was very fast, a telltale sign of upper RAM issues. This was confirmed when I put a Retroleum Smart Card on the back configured with Brendan Alford’s diagnostic software. Retroleum also supplies diagnostic software with their card but I have grown used to Brandan’s so I use that.

The test revealed that several of the upper RAM ICs on the Spectrum were not reading back correctly. Rather than replace the individual chips which are not the easiest to find, I decided to use a Retroleum Upper RAM module instead. This replaces all the upper RAM with a single module, relieving the old machine of lots of it’s legacy ICs.

Another vital thing to do is a re-cap. The capacitors in old machines often fail and in the Sinclair ZX Spectrum, can lead to faults in other parts of the machine. Again, Retroleum to the rescue! They do a complete re-capping kit that includes a Composite Mod too (although in this instance I will be using my own composite mod solution).

Further to the above, I want to replace the inefficient 7805 5V Regulator. There are two easy solutions; one is the Murata Switch Mode 5V Regulator that can supply 1.5A of power (also available from Retroleum), or the smaller TRACO TSR 1-2450. Since this machine will be seldom used and part of my personal collection, I decided on a TRACO unit.

The last thing to consider is the general look of the machine. The issue 3b’s case is in good condition with only one missing foot. One thing that is dissapointing is the state of the front fascia. It has several dents and a few small scratches. Luckily, all these spares are available nowadays and I chose ZX-Renew to supply a new black fascia.

Sinclair ZX Spectrum - Showing Dents

Sinclair ZX Spectrum – Showing Dents

Once all these spares have arrived, I will post updates in parts to show each step in the process that I take.

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TZXDuino Compact v1.01 and other projects

The TZXDuino Compact v1.01 PCBs arrived today from Hackvana.com I have built one and tested it successfully, so the design files are on the AVR Projects page. Feel free to use the Gerbers with your favourite fabricator (Hackvana are good!). Alternatively, you might like to modify the design to suit your own requirements so I have included the KiCad files and a schematic along with the latest (v1.7b at the time of publishing) arduino code.

TZXDuino Compact v1.01 In Action

TZXDuino Compact v1.01 In Action

For some TZX/TAP files, the output seems a little weak but in conversation with Duncan Edwards, one of the designers of the original device, he told me that later Spectrums do suffer from a less sensitive input. I will look into updating the design with a small amplifier to alleviate this issue. It has also come to my attention that I’m using the wrong display. The code specifies a 128×32 OLED and I have used a 128×64 OLED version. All this does is stretch the characters though so it’s OK to do so. The connections are the same. Admittedly, it does look slightly better in smaller text but the display is rotated 90 degrees. Choose which one you feel works best for your application.

Meanwhile, the composite mod suggested by Andrew Gostling wouldn’t drive the Dell UltraSharp 2007FP monitor. It seems that this particular monitor is really picky with it’s input signal. It also fails to work with my ZX Uno. I have since started using an alternative Dell E173FPf monitor along with a ZX-HD interface, driving a HDMI to VGA adaptor. The ‘2007FP will be pressed into service elsewhere!

I have a few other Spectrum related projects on the go. I have formalised Andrew Gostlings Composite Mod along with two other popular options and designed a PCB to replace the original 48K/128K/+2 modulator internals.

Spectrum 48K Video Mod

Spectrum 48K Video Mod

This I have yet to prove, but once I have had PCBs made and tested them I’ll be publishing the design files on here under Non-AVR Projects.

Another Spectrum related project is a Floppy Drive adaptor board for the Spectrum +3 It is meant to give the facility of easily making a connection cable up from an old PC style floppy cable and giving the facilites of both setting the drive as Drive A or B and also using Side 1 or 2. I have had no end of trouble with this one and development continues.

Yet a another project is an NMI interface, initially for 48K Spectrums. This will hopefully allow interruption of  any program running on the Spectrum and an alternative ROM to be paged in, similar to the Multiface except you can use a custom ROM. I’m hoping to be able to run the Multiface machine code monitor Genie and maybe the Specmate snapshot devices ROM Code.

 

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EPROM Info Table

One of the other things I am involved in is graphics. I have had this table knocking about on my hard drive for a while:

EPROM Table

EPROM Table

It’s avaliable from several sources and I find it very useful. Search as I might, I can’t find out who the original author was. In any case, I have re-drawn it and you can download if from HERE. I have pretty much stuck to the original document, certainly with the information.

New EPROM Table

New EPROM Table

Feel free to download and distribute as you wish but I take no responsibility for the accuracy of the information presented. Although I believe it to be correct, I suggest you verify it all before use.

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Spectrum Composite Mod and Refurb

A short while ago, I became reaquainted with the world of the Sincclair Spectrum. Back in the original Spectrum Heyday, I had many bits and pieces (wish I’d have kept them!) one of which was a composite monitor. In fact, I think it was a Microvitec Cub. Now I have got another Spectrum and I am slowly getting back into machine code programming, I’d really like a better monitor than the 7in Car TV style unit that I’m using.

I found a bargain on eBay, a Dell UltraSharp 2007FP for just under £30. I connected it to the Spectrum on arrival and…. nothing. Well, the screen looks like its about to display and just switches off after briefly displaying a logo in the top left hand corner.

 Dell UltraSharp 2007FP

Dell UltraSharp 2007FP

It’s a lovely monitor with Composite, S-Video, VGA and DVi inputs, as well as a USB Hub built in. The display can even revolve and be used in portrait mode.

I spoke to Andrew Gostling in the Spectrum 4Ever group and he advised me to change the composite mod I had carried out on my Spectrum from the transistor type to the capacitor type. I did so but Dell still did not want to know. Andrew also suggested I try an inverted emitter follower circuit. I didn’t have the chance to do this until now.

Please Note: If you choose to follow these instructions, you are solely responsible for any and all damages and/or injury caused. If you are not confident with a soldering iron and de-soldering equipment, you would be better to find someone with the correct experience. Having said that, it isn’t a hard procedure and, if done properly, it can also be reversed with relative ease. So, in short, these instructions assume a certian level of competence with regard to electronic assembly and it is not meant to be a tutorial as such.

You will need the following components:

  • 1x 100R Resistor
  • 1x 100uF Electrolytic Capacitor
  • 1x PNP BiPolar Transistor (I chose a 2N3906)

Rather than change the Spectrum I had already modded twice, I elected to add the new composite mod to my spare Spectrum Plus board which needed a refurb anyway. Unfortunately, the case for this Issue 6B board has a few screw pillars missing and the keyboard membrane is also shot. This is why I’ve been keeping it as a spare.

The first step was to add the composite mod. I carefully disconnected the +5v and Video Input lines and folded them over the side of the modulator case after removing the friction fit cap. Also, disconnect the resistor from the phono socket on the back of the modulator. Tidy this up since we will be connecting to it in a moment.

+5Volts and Video Disconnected

+5Volts and Video Disconnected

Connections Folded Over

Connections Folded Over

After having disconnecting the original lines, which effectively disconnects the modulator circuit, it was time to add the composite mod itself. First, check the holes that were where the +5v and Video lines were, then clear the hole near the back edge of the board. If you turn the board over, you will see which one is connected to the Ground Plane, that’s the one to clear.

Inverted Emitter Follower Composite Mod

Inverted Emitter Follower Composite Mod

Composite Mod Overview

Composite Mod Overview

I connected the transistors Collector and Base first to provide a foundation to work on. In this instance, I chose a 2N3906. The configuration of the transistors leads means that you should face the flat side towards the modulator case. If you choose a different transistor, fit accordingly. Next, I connected the 100R resistor to the +5V connection on the board and connected the other end to the emitter of the transistor. I put some sleeving on the emitter leg to prevent it shorting against the modulator case, however after adding the capacitor next, it probably was safe enough.

Video Mod Schematic

Video Mod Schematic

I next carefully bent the transistor out of the way and connected the negative lead of the capacitor (which should be clearly marked on it’s body) to the video output center, feeding the lead through the unused plastic port on the modulator. The other end (positive) connects to the junction of the resistor and the transistor’s emitter lead. Hopefully, this is all apparent from the images above.

Before trying the mod out, I felt it was a good time to exchange the LM7805 linear regulator for a TRACO TSR 1-2450 which is a small pin-for-pin substitute. It is a switch-mode unit and is very efficient, far more so than the 7805. It also dispenses with the metal heatsink.

LM7805 Heatsink Removed

LM7805 Heatsink Removed

LM7805 Removed

LM7805 Removed

The TRACO unit is a drop in replacement and is easy to solder in. I used a little blu-tak to hold it in whilst I soldered it in place.

TRACO Regulator Soldered In Place

TRACO Regulator Soldered In Place

I’m very pleased with this particular mod. I ran the board for over an hour afterward and the TRACO unit doesn’t even warm up.

The time had come to try the monitor out but, since it would mean clearing the workbench, I decided that I’d re-cap the board first. This involves getting a re-capping kit from someone like the brilliant Retroleum or sourcing the correct capacitors yourself. I had a spare set from Retroleum so they got used. I carefully removed the old capacitors one by one, noting what value they were and what orientation they were in and replacing them with the new ones. I make it a point to face the values upward to ease future repairs/replacments.

Two Capacitors Replaced

Two Capacitors Replaced

Having finally completed this task, I connected the Spectrum up to the monitor, powered up and… still nothing. Well, I think the monitor is extra picky about it’s composite input. I have spoken again to Andrew and he recommends I try connecting to the S-Video socket. I have ordered a cable that I can modify with a phono connector to provide the correct connection.

Meanwhile, I have a working refurbed Spectrum Issue 6b board and the composite mod does work on my 7 inch car style monitor.

Many thanks to Andrew Gostling for his continued assistance.

 

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Old Skool Tape Loading

As I continue to explore the world of retro-computing, bringing back memories of my late teens and early twenties, I’m constantly amazed at just how big the retro-computing scene is. I’m also amazed that, given all the new interfaces for program storage like the SMART Card and DivMMC, retro-computer users still like the ‘experience’ of loading programs the old way, i.e. from tape. Personally, I am very happy to use a more modern instant loading system but I came across the TZXDuino and that piqued my interest. Mainly because of the tell-tale ‘duino’ part of the name. Further investigation led me to the Tapuino and other such devices.

All these devices allow you to store programs on an SD-Card and send them to the computer, in my case the Sinclair Spectrum, in audio. This basically replaces the tape machines of old with a completely reliable piece of hardware, avoiding the dreaded ‘r Tape Loading Error, 0:1’ from appearing.

What attracted me to the various designs is their simplicity. The main parts are an AVR (be it Arduino Nano, Uno, Mega or bare ATMEGA328), an SD-Card module and an LCD/OLED Display. Also some buttons for control. That’s it! All the magic is in the code. Currently at version 1.7b, written by Andrew Beer & Duncan Edwards.

Having looked at a few of the many designs, I went for one with an OLED display after seeing Davide Barlotti’s amazing internal build.

Davide Barlotti's Internal TZXDuino

Davide Barlotti’s Internal TZXDuino


I prototyped it up with an Arduino Uno clone and breadboard to check all was well. I always like to prove a design for myself.

TZXDuino Prototype

TZXDuino Prototype

I was very pleased when it worked first time, usually I have issues with breadboards! I successfully loaded some of my original games, starting with my favorite Knightlore. The interface is simple; you scroll to the file you want, or into a sub-folder and when you have the file you wish to play highlighted, you simply press play after setting the computer into loading the program from tape as usual. I do understand the attraction of experiencing the original loading procedure. Along with owners of the original Spectrum, I went through this process countless times!

Now I had proved the prototype worked, I moved to design a PCB to house the modules and controls. I’m intending to power the device from the Poundland Power Banks I recently purchased, so I included a mini-USB connector for power input along with the usual DuPont style header. I have also included a polarity protection diode in case the header connections get reversed. The power is routed over to an ATMEGA328 and the OLED Display and Micro-SD Card modules. I have designed the board to accept the modules being the easiest way of construction. There are also four holes for later mounting in a case or for securing feet.

TZXDuino Compact v1.00

TZXDuino Compact v1.00 KiCad 3D Preview

I call this the TZXDuino Compact. I will shortly be ordering PCBs to test the design and, as per usual, once proved the design files will be available on this site.

TZXDuino Compact v1.00 KiCad Preview

TZXDuino Compact v1.00 KiCad Preview

I have been focusing on the TZXDuino, which is primarily for the Sinclair ZX Spectrum but the device can operate with other machines and lots of other filetypes.

  • TZXDuino plays TZX/TAP/CDT/P/O files.
  • CASDuino plays CAS files for MSX and Dragon.
  • Arduitape plays WAV files (up to a max of 22050Hz)

You can find details on the Arduitape Facebook Page.

 

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Spectrum Resurrection

All the excitement around the Spectrum Next Kickstarter, and now the shop opening on the forum got me inspired to get hold of an original machine on eBay. Supposedly in working condition, it arrived with a problem.

Spectrum RAM issue

Spectrum RAM issue

The eBay seller apologised profusely and requested I send the machine back and have a full refund, however, I know my way around a circuit 😉 so I kept it. The eBay seller kindly gave me a partial refund. I was pretty sure what the problem was from how the display was and the exchange I had with the seller. It looked like a RAM issue.

Since I was intending to use the machine for programming and such, I had decided to fix it sooner rather than later. I ordered a ZX SpectROM with Diagnostic software specially supplied to narrow down the problem.

Upon powering the machine up with the ZX SpectROM installed on the rear expansion port, the Spectrum bleeped 8 times and then went on to have it’s RAM checked. All the lower RAM passed, the upper RAM failed every test!

I ordered a couple of upper RAM modules from Phil at Retroleum Whilst I was ordering, I got a couple of re-capping kits too! They duly arrived and I went about fitting the capacitors first. however, before fitting, I gave the board a once over and found a connection un-soldered!

Ooops, someone missed this!

Ooops, someone missed this!

It was completely clean, as if it had been in this state from factory! Needless to say, I rectified the problem before proceeding to replace the capacitors. I made a special effort to face all the values upwards so that they can be read in the future.

After re-capping, I had to remove all the upper RAM chips to make way for sockets. This would be primarily for the new RAM module but it’s nice to have the facility to fit original RAM should I choose to sometime in the future.

Upper RAM removed

Upper RAM removed

Eagle-eyed among you might spot a dodgy track on the lower right-hand pair of chip placements. Careful as I was, I still had that one track lift. However, despite how it looks, it didn’t break. I managed to get it back into place before soldering the sockets over the top.

Sockets installed

Sockets installed

With the sockets installed, it was time to fit the RAM module. This went on very easily. You just have to line up the top left pin with the top left socket and the bottom right pin with the bottom right socket. The module fitted in very firmly. I double checked I’d got it in the right place.

New Upper RAM Module Fitted

New Upper RAM Module Fitted

Since I was in the machine and the components came with the re-capping kit, I chose to perform the composite video modification as well as the re-capping and RAM replacement. This is another simple procedure.

Two options are available and Phil includes components for both with the re-capping kits. The mod can be done with a capacitor or a transistor. I chose the transistor mod because that also provides a buffer for the Spectrum’s video circuitry.

First the internal connection to the output socket is de-soldered and folded out of the way. Then the power and feed lines to the modulator are disconnected and folded over the can’s edge and finally, a transistor is soldered in place and a connection made from the pin nearest the rear of the Spectrum up and through the modulators case to the output socket.

Composite Mod Transistor

Composite Mod Transistor

Composite Mod From Above

Composite Mod From Above

After carrying out all this work (and having a much needed cuppa!) I did a final check around the board, particularly in areas I had worked in. All seemed OK so I replaced the board in the ‘Plus’ case, screwed it up and plugged it into a 7-inch composite monitor. I was greeted with the ‘© 1982 Sinclair Research Ltd’ message. Yay! I’d fixed it.

I really enjoyed the experience too. Buoyed by this, I built a DivIDE interface for storage and convenience. Unfortunately, the board does not didn’t work.

DivIDE 57c

DivIDE 57c

I take great care when I build anything and I double checked the connections. All seemed fine. I checked the ROM and GALs had data programmed into them with a Minipro TL866 but later, loaded EXSDOS since that’s what I will be using when the Spectrum Next arrives. Updating the ROM had no effect. Pressing the NMI button just reset the Spectrum.

I had a chat with some of the guys on the Spectrum 4 Ever group on Facebook and the consensus was that the Z80 chip probably had a weak/faulty M1 line. I reopened the case, de-soldered the Z80 and replaced it with a socket. I then tried 3 other Z80 chips, all of which even failed to react to the NMI button at all. I suspected there is an issue on the DivIDE board or that the Z80’s I substituted all had M1 issues. I continued to work on the issue.

In the meantime, I’d found a couple of cassette tapes of utililties and machine code that I wrote in 1991! I’ve begin to transfer them over to PC so I can re-learn what I knew back then.

[UPDATE]
I dug out the ZAViouR board to see if I’d left a Z80 on it. I had, and one substitution later, I had a working DivIDE! So, this confirms, I have four Z80s with weak or faulty M1 lines. I have marked them clearly and will only use them in projects that don’t require the M1 line!

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Electronic Film Clapper

By way of a break from the Timed Camera Cable Release, I chose to develop the Electronic Film Clapper further and learned a lot in the process. I had the first iteration of the boards fabricated by Hackvana as usual and they arrived in good time.

On the board, I included several options to tailor the design to the builders taste. Provision for both a digispark board or bare ATTiny85 chip, small or large tact switches and a jumper to defeat the LEDs supply resistor for extra brightness.

I chose to build the Digispark version first. It went together easily (bar a hole size issue, more of that later) and I programmed the digispark via it’s own USB socket. And… the board completely failed to start up. It took me some time to realise that I’d got the USB power connections inverted! Lucky I’d added a reverse polarity diode! I de-soldered the USB ‘A’ type plug and re-soldered it on the back side of the board flipping the connections. I don’t have the correct type of USB plugs anyway, so it’s a bit of a kludge at the moment. However, once this was done, the board sprung to life. When powered up, the Digispark’s micronucleus bootloader kicks in for a few seconds and then the Clapper code starts.

The hole size issue was due to my custom tact switch footprint in KiCad being wrong. Although I managed to transfer the dimensions across from the datasheet successfully, I’d used the wrong size drills for the through plated holes and hence, the larger Omron type tact switch will not fit. I have amended the footprint now. At the moment, the switch on the prototype board sits slightly high on the surface.

There was another issue to be resolved; although the board started up fine, the ‘pip’ seemed to be incomplete. It was obvious from the symptoms that there wasn’t enough power to flash the LED and sound the pip at the same time. To sort this problem out, I bridged across the 78L05 part of the circuit. Once I had done this, the board worked perfectly.

So, on to the bare chip version. Having learned of the tact switch problem on the first build, I elected to use the smaller tact switch on this board. It fit perfectly. I had it complete in short order. I programmed the ATTiny85 chip via a technique called ArduinoISP where an Arduino UNO becomes a programmer. Upon powering the board up… Flash but no pip. This frustrated me for several days. I tried many fixes including changing the ATTiny’s fuses, but finally discovered that the bare ATTiny85 doesn’t directly support the Tone() function which is what I used in the code for the pip sound. I can only assume that the Digispark has custom code to account for this.

After a lot of research, I discovered an article on Technoblogy detailing this issue and a pointer to a library that adds the functionality. Once I re-programmed the ATTiny85 all was well!

Film Clapper prototype and v1.2 boards

Film Clapper prototype and v1.2 boards

To finalise the design, I’ll be inverting the USB Type ‘A’ plug, removing the regulator circuit and making provision for a link across the buzzer resistor. I have found that driving both the buzzer and LEDs directly from the ATTiny’s GPIO lines gives a much brighter LED and louder ‘pip’. I would imagine that this stresses the ATTiny slightly but since it’s a brief pulse, and provided it’s not done repeatedly, I believe it will be OK.

Design files are available on the AVR Projects page.

 

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New Project: TB Timer – Timed Camera Cable Release

One of my other pastimes is Photography. I used to be ‘in the trade’, in fact, I have been a photographer and a photographer’s assistant several times. Nowadays, I pursue photography in a hobbyist sense. I still enjoy experimenting with exposures and recently, I was lucky enough to win a Lee Big Stopper Neutral Density Filter. I’d like to do some long exposures with this. The trouble is, I have no cable release to go with my camera. Sure, I could jump onto eBay or another website and order one of the myriad of pre-made cable releases but where’s the fun in that?

I have worked up a design that will hopefully fill all the criteria I need and be expandable too. I have settled on four modes:

  • B – Standard bulb mode where the camera shutter opens as long as you hold down the button
  • T – The shutter opens on the first press and closes on the second press
  • TB – Timed ‘B’ where the cable release is programmed with a time and the shutter opens for this amount of time
  • EX – Provision for an external trigger to connect sound and other sensors

It’s taken some research but I have built a prototype with my trusty ARDX Arduino Uno kit

TB Timer v1.00 Prototype

TB Timer v1.00 Prototype

Currently, the device changes mode with a press of the mode button which will later be incorporated in a suitable rotary encoder. I modified the prototype’s rotary encoder to remove the detents and therefore, have continuous motion rather than be stepped. When stepped, the value hops by two at a time. The ‘B’ and ‘T’ modes both operate as expected and at the moment, the rotary encoder changes a value in ‘TB’ mode and is displayed on the OLED display. the outputs are opto-isolated so will appear as switches to the camera. Although I’ll be using the cable release with a Canon DSLR, it should be very easy to make it work with other DSLR makes.

It’s early days yet and still to do are moving the rotary encoder code into the ‘TB’ function so that the time is only changed whilst in this mode. I’d also like to be able to change the value of minutes and seconds independently.

As with all ProjectAVR designs, the design files of the final boards will be available on this site as Open Source in due course.

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minDUINO Next

Whilst the Spectrum Next Kickstarter goes from strength to strength (1st stretch goal reached already at £350,000), I have been redrawing the minDUINO in KiCad. Today, I received the first batch of PCBs from the ever brilliant Hackvana and they are great.

minDUINO v1.6k Front and Back

minDUINO v1.6k Front and Back

I have since built one and tested it so I’ve also added the files to the minDUINO page for download.

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