New poker card design

After spending hours last night updating and re-writing their printing routines, Nick from Custom Stuff emailed over some print previews of playing cards with coloured boxes in each corner, according to our latest ideas.
In short, some of them looked horrible.

With the correct photo, with the correct border, on the correct coloured background, sometimes it doesn't look ghastly (Queen of spades in the example photo) but mostly, the garish coloured blocks just distract from the images on the card and look awful (9 of spades).
Yes, we could make playing cards with "regular" card faces, pips and spades and diamonds and the like. But even then, each suit would have three picture cards with a jack, queen and king on them. So they'll still look terrible!

This morning, Nick showed us some left-over offcuts from a deck made overnight.
The customer had asked for a different coloured border around each of the cards, to signify which suit the card was (they were for teaching games to adults with learning difficulties). Apparently, thanks to the rise in internet poker and in particular, tiny graphics in mobile poker games, it's not uncommon for poker cards to use different colours for different suits - black = spades, red = hearts, blue = diamonds, green = clubs. This makes identifying your cards easier on a small-screen device (apparently).

My guess is that the programmers chose "primary" colours (let's not get into yellow being a primary colour and green a mixture of blue and yellow - we're dealing with lights, not pigments here!) to make each suit easily distinguishable from the others. Whatever the reasoning, this is quite fortuitous for us!

Having explained our card-reading idea, Nick suggested an alternative card layout:

The entire border of the card could be coloured to match the suit on the card (this was a quick mock-up, my guess is that clubs would probably be green, not blue). The numerical value of the card could be shown via a series of 4 black and white dots. Nick explained that these dots are much less conspicuous than large multi-coloured blocks, and we have to agree!

Of course, a 4-bit value gives us a range of values 0-15 (or 1-16 if you prefer).
Which is perfect: we can determine the suit of the card by detecting the colour of border, then read off the black/white dots to get the value. It does mean that we'll need 5 LDRs instead of four (the fifth will be under the border of the card, immediately to the outer edge of the dots) but the symmetrical layout of a playing card means we can just put all five in a line and the orientation of the card will make no difference.

We're quite excited by this new development.
The cards look great (we've yet to see a physical card, as Nick has a lot of work to do getting her programmer(s) to re-code their website for us!) and how it works should be quite simple.

By using black and white dots, our LDRs should be able to read a white dot value, irrespective of the colour being reflected off the face of the card - we can use this as a double-check; if we flash a red light and read back two white dots, we would expect the same response when we flash it blue and green.

Exciting stuff. We're already building prototype boards (using black tubes over the LDRs like we did with our invisible instrument last year) for reading the black/white dots, and we're pretty confident we'll have this working quite quickly. The only bit we haven't yet tried is the colour detection. More posts coming soon!

Miniature instruments make a return

Using the invisible instrument idea, and the early DeskJam prototypes (originally developed for a concept for Mattel in Sept 2010) we're soon to launch a range of miniature, playable instruments.
After being turned down by Mattel - their target audience was 7-10 years olds, and the instruments had to be dumbed right down to the point of losing their impact - they were also presented to Ravensburger in Germany. They too loved the idea, but couldn't get the cost of production down to less than $4/unit (apparently this was to be able to sell them for $40 each!). So we've decided to hang the expense, and make the little instruments here at Nerd Towers.

The original DeskJam range included guitar and bass (both worked in the same way) a miniature synth and the original instrument that kicked it all off - some miniature usb drums. As we're no longer going ahead with DeskJam - there were two other companies involved in the original project, but all the electronics, firmware and software development was strictly our own work - we're building the entire range again from scratch.

The first instrument in our new range of instruments is the guitar.
We're working on a range of guitar shapes and styles, but each will basically consist of the same set of components: a touch-sensitive neck for selecting the chord/riff to play, and a set of touch-sensitive strings, which the user can strum to trigger the sound(s). For anyone reading the blog a few weeks back and wondering why the topics had jumped around to include multiple touch sensitive inputs, things should become clearer from hereon in...

The first thing we did was create a multi-layered guitar shape.
For the main guitar body, we're working with two layers of 5mm acrylic - into which we've cut a void to give a 10mm deep space for the electronics:



The front and back are cut from 3mm coloured opaque acrylic (this laser cutter has been soooo handy!) and a scratchplate made from some 1mm HIPS. This super-thin material is just right for the scratchplate (3mm acrylic is far too thick) and means that when we introduce some 3mm thick pickups, they stand proud by just the right amount - just like a real guitar!



Finally the layers are all assembled and the final guitar is starting to take shape:



The channel along the neck is for the touch-sensitive board. PCB pins will be inserted onto the "back" (non-copper) side of some copper clad board, and soldered to the etched front. To allow space for the soldered pins, we needed to keep a channel running along the length of the neck.

So it's off to the cupboard to dig out some Ferric Chloride and to get etching. Finally, it feels great to be making PCBs again - and this time, the end product is ready and waiting to be populated with some tried-and-tested electronics. This is one project that might actually get finished within a reasonable timeframe....

Simplified Invisible Instrument kit contents

It seems that we've had a massive amount of interest in the Invisible Instrument Kits already, so if you're not able to get your hands on one (either at the event, or through the BuildBrighton website) here's a list of what you need.

All the components are available through Farnell.
They've just launched a hacker/maker community called element 14 and are really helpful towards the design/prototyping community. And you can order stuff today and get it by 10am the next morning!

As well as the PCB (you can etch this yourself) you'll need:
1 x PIC 18F2455
2 x 14-pin MCU socket (optional, or replace with 1x28 pin socket)
1 x USB B-type socket
1 x 470nF capacitor
1 x 20Mhz crystal
4 x LDRs (light dependent resistors)
4 x 1M linear potentiometers

And of course, some firmware for the PIC microcontroller.
Here's a pre-compiled hex file you can burn to the chip using any PIC programmer:
http://www.nerdclub.co.uk/files/invisible_instrument_simplified.rar

That's it for the simplified kit. If you want to use the LED indicators (which light up as each input detects and triggers a sound) you might want to use

4 x 5v LEDs

Alternatively, you can use the invisible instrument to play up to 4 sounds per input, and instead of LED outputs, use the same sets of pins to connect pushbuttons to, in order to turn the extra sounds on or off. In which case, you'll need:

4 x push button switches

Happy shopping!

Invisible instrument - simplified details

As the Brighton Fringe Festival draws to a close, BuildBrighton are hosting a drop-in "Noise Toys" workshop at Hectors House (strictly speaking, it's not Hectors House anymore, since it was recently taken over by a community arts/maker group, but everyone still knows it as that).

We've submitted a simplified version of our invisible instrument that has been made into kit form, so people can make one up and try it out in just a few hours. We've removed the LCD, LEDs and buttons and MIDI output, making it much more like the original prototype.

Build Bright On Invisible Instrument

A datasheet and instructional guide is available here on Scribd. Schematics (printable at 100% to make your own) are below:

Invisible Instrument Simpified

Invisible instrument - simplified

As part of the Brighton Fringe (and partly why there's been little blog activity of late) the BuildBrighton group are hosting a daytime workshop followed by an evening gig filled with 8-bit bleeps and electronic music.

I've made a simplified version of the invisible instrument - removed the character LCD and buttons and LEDs, so it's just a voltage divider going into a microcontroller. The idea is to have up to twenty people making their own (from kits) at the workshop, then having a go playing them together! So I've been busy etching PCBs all afternoon.

Here's a shot of what 20 home-made invisible instrument PCBs look like:



They still need drilling (28 pin mcu + 4x2 legs on LDRs + 4x3 legs on potentiometers + crystal + cap + vias) over 50 holes per board. I think that's a job for the power tools at the Skiff this evening.

Now with just a few hours left, I need to write some simplified firmware (with the new pin input mapping) and software for the PC to make it play tunes...

Invisible instrument - different modes

click to view larger image with readable text!

With the introduction of a 16x2 character based LCD display, and a dial (ok, in this instance a slider, but it should be a rotary dial) and some buttons, we can set the device into a number of different modes.

when tuning the input channels, the LEDs light up to show when a channel has detected a shadow and raised a "hit" value. In this case, because the LDRs were not inside their black tubes and the light is coming from behind, the camera actually cast a shadow onto the device, triggering two inputs!

Here we've set the device into "tuning" mode. It basically reads the input value from each channel/LDR and displays a message telling the user which way to "tune" the device. In an ideal world, each input should be around the half-way mark (reading a single-byte value of 128) so that changes in ambient light can be easily detected.
In this example, the display is showing that the "at rest" value is greater than 128 and so the user should adjust the pot on the first LDR. When the ideal value is reached (120-140) the LCD display will read "OK" and the user can use the slider to choose another channel to "tune".

It is important to use linear (not log) potentiometers for the tuners.
In fact, I didn't have linear pots to spare, and used log pots, but tuning is difficult because there is very little movement between too high and too low. A linear pot would be preferable here!

Assembling the invisible instrument

Here are some shots of the invisible instrument undergoing assembly.
It took a number of failed boards before we settled on this design (and even this is a bit messy - we still need to move a few 5v and ground pins to stop the cables for the LCD display getting everywhere) After a couple of failed boards, we finally managed to get one working that we were happy with! The main problem with the original PCB layout was the LDRs were mounted with the legs running east-to-west. No big deal? Not until we put the black tube covers over them and tried to bend them into position.
Because of the way the legs were facing, there was no give in them, to allow them to bend - they happily moved backwards and forwards, but not left-to-right.

This has been corrected in the latest PCB layout.
See photo (below) for the correct way to mount the LDRs:



Note also that the LDRs are unlike other components - they are not mounted flush to the board, but a few millimetres left on each leg. This allows the LDRs to be bent into the correct position once the black tubes are put into place.

Here's the board with all the cables for the LCD screen in place too.
We added the screen to allow the user to interact with the device (set ambient light levels, change chord sequences/scale modes etc) without having to refer back to the PC. The idea behind this was to allow the device to be converted into a MIDI instrument in future.

Note: the green LED does nothing special - I just ran out of 5v red ones!

We're off to BuildBrighton tonight and hope to spend a bit of time on the laser cutter there, making up a cool enclosure from 3mm acrylic. Then it's just a case of a few firmware updates, and another project will be officially complete!

Shadow Harp/Invisible instrument

With the USB servo controller board pretty well complete (well, the hardware and firmware at least - there's some software to do, making animation creation simpler, but for now, anyone with Notepad can create a simple animation script) thoughts are turning to the BuildBrighton music gig at the end of May, as part of the Brighton Fringe Festival.

With a working prototype already in the bag, and an enclosure design already planned, if not drawn out yet, it's time to put the whole thing together onto a PCB and get soldering!

Here's the first version of a PCB. It's not been tested yet, but has been built with reference to the schematics posted earlier.


Shadow Harp v1 Pcb
As always, print at 100% landscape orientation for press-n-peel toner transfer to make your own version of the invisible instrument

Refer to the schematics and follow the silkscreen layout below for help placing components on the border before soldering:

This layout has been updated, to include the USB socket on the board but more importantly, the orientation of the LDRs has changed. On this board, the LDRs will not bend easily side-to-side, which is important for setting up the device to play! An updated layout will be posted shortly!

Enclosure design

Proposed enclosure design - inside the main body are four black tubes (actually drinking straws covered in black crepe paper but only because I couldn't find any black straws anywhere!)

It still needs four buttons (to turn each of four different channels on and off) and somewhere to put the "tuning pegs" for the potentiometers (which adjust the light sensitivity levels on each input pin) but this is the initial design idea for the enclosure.

The 16x2 character display allows users to tune the inputs and select different keys/sample sets without having to refer back to the PC the device is connected to. The LEDs show which channels are currently on and off. Of course a lot of this information could be display onscreen (on the PC) when used as a USB/HID device, but keeping it off-screen allows us to modify the firmware to create a midi version of the instrument in future.

The invisible instrument - schematics

Here's the latest schematics for our invisible instrument.
This version hasn't even been built yet (not even on a breadboard) but is an idea for improving on the current version.
We're acutely aware that four inputs isn't a massive number for an instrument - we could use "doubling-up" to create up to seven inputs (e.g. accept 1000 as the left-most position, 1100 as the next position towards the right, 0100 as the next, 0110, then 0010, 0011, 0001) but this would stop the instrument being poly-phonic (since 0110 would mean "play sound four" rather than "play sounds 2 and 3 together"). It's swings and roundabouts really.



Despite only four inputs, this does allow a large number of pop (and rock) songs to be played - 90% of popular music consists of three chords, four if you include a relative minor for the middle eight (if none of this means anything to you, don't panic!). Changing the sequence or overplaying chords with different lead lines is what gives most pop music depth. After all, too many chord changes and the song becomes unpredictable: and it's the predictability of music that gives it its "hook" (or, easy-to-recall melody).


Triggering riffs/chord samples with a single input allows songs to be built up from simple, repetitive sequences

This new instrument includes a dial (for selecting the current key/chord/scale if we ever get around to midi output) as well as some buttons and LEDs. The buttons are used during playback to "layer" multiple sounds from a single input:

The idea is to allow the user to load up to four different sounds to be played back whenever an input is trigger. It's a bit like having up to four channels, which can be muted/unmuted. It could be a bassline, guitar chord(s), synth parts and a melody line. When an input is triggered, all four sounds can be played at once. The user can turn off which of these are played by pressing the buttons which latch the sounds on and off. The LEDs show which "channels" are selected for playing when an input signal is detected.

So players can start with just the guitar part playing (for example, channel one active) - playing up to four different chords/riffs/patterns either in sequence or together - then turn on the bassline (channel two) and whenever a single input is triggered, both the guitar and bass parts play. The key to the success of this approach of course is that sound1 on channel 1 and sound1 on channel 2 are in the same key or at least sound harmonious when played together.

By combining these simple channels, it should be possible for someone (with a little practice) to create some rather complex sounding tunes.

I guess the only way we'll ever know, is to build one of these things and try it out!

What does the invisible man play? An invisible instrument

To date, we've been calling our instrument a "shadow harp".
While this is accurate - the instrument detects the presence of shadows in order to play notes - we've been undecided about the name for a while. Really, because Peter DeSimone has already created an instrument he calls a shadow harp (albeit one that was abandoned and replaced with his "pocket harp") and although this instrument was inspired by his, it really is a different project (more in-line with his original pin-hole light harp than his final shadow harp solution).

After a bit of debate and a few beers (ok, a few cups of tea) we decided to call our version the "invisible instrument". It's a specific enough name to convey what the instrument does (it's an instrument but the playing surface is invisible) but vague enough to allow for modifications and changes to the design and behaviour in future revisions!

So from now on, any references to a "shadow harp" are purely accidental - we mean, of course, "the invisible instrument".