Press-n-peel alternative

Press and peel is that great blue powdery paper used for printing circuits onto, to transfer onto copper clad board (either with a domestic iron or, in our case, a heavy-duty laminator).
It's easy to use, creates a sharp, clean image and is a tried-and-tested way of making circuit boards the world over. The only downside is that it's pretty expensive!

At nearly £20 for 5 sheets from Maplin it's nearly four quid a sheet! That's an expensive way to make your own PCB boards - per square inch, it works out nearly twice the cost of the actual copper clad board you're pressing the design onto!

Jason at BuildBrighton recently bought some alternative "toner transfer" paper from eBay. At £15 for 50 sheets (£20 with delivery), it's much cheaper than "regular" press-n-peel. Jason uses a household iron for his toner transfer PCBs and gets pretty good results (we have always found some smudging with an iron ,which is why we use the laminator approach)  But Matt has also used the same stuff and hasn't a good word to say about it!

There's only one thing to do - try it and see!
Jason gave us a couple of sheets to try out, so were' going to print and make up our multi-pedal circuit and see how it goes. We printed the PCB layout onto a carrier sheet, affixed the press-n-peel replacement and re-printed the circuit. Here's the result:

The first thing we noticed is that the image is very delicate to the touch. In places, the black toner is already flaking away. While this is probably good news for the transfer part, it's not great for making a stable image on the paper. This was printed using the usual settings - a Xerox Phaser 7400 printer with commercial press settings, full black with the fuser set to "thick card stock" (we use 360gsm card as the carrier sheet).
(the photo above was taken as the image came straight out of the printer and before we poked and prodded it to see what the effect would be!)

The image was transferred onto the copper board using three passes of our laminator, as we usually do with Press-n-Peel:

The final image was quite stable - rubbing a finger over the copper removed no further flakes of toner - the image looked pretty much the same as it did on the paper before transferring. The flaked parts of the solid plan can easily be filled in with a Sharpie (permanent marker) before etching, but the important thing is that all the traces are solid and there were no immediately obvious trace breaks or blurring which would result in a badly etched board.

We're waiting for our ferric chloride to be delivered following a last-minute eBay order, so we'll have to etch the board as soon as it arrives, to complete the comparison between this "cheap alternative". But to date, it looks like it could be a suitable alternative.

Press n Peel blue = £18 for 5 x A4 sheets from Maplin = £3.60 per sheet
Press n Peel blue from eBay = £11 for 5 sheets (including delivery) = £2.20 per sheet
Alternative = £19 for 50 sheets (including delivery) = 38p per sheet

At almost a tenth of the cost of Press-n-Peel blue from Maplin and nearly a sixth of the price from the cheapest alternative supplier on eBay, we're really hoping that the final etch is as good as the transferred image! It's all well and good getting a transfer as good as press-n-peel blue, but it's the etch resistance that we need to be sure of.

Hopefully we'll have an answer tomorrow.....

MIDI saxophone

This rather tongue-in-cheek article (http://www.mindworkshop.com/saxophone.html) explains how I feel about learning saxophone. I bought one a few years ago, even took a few lessons, learned a few songs, but then put it back in it's case, where it's stayed ever since.

Why? I guess I'm just too considerate!
I didn't like the idea of my neighbours having to listen to the squeaks and farts that came out of the shiny bendy bit day and night, and the cost of going to someone else's house to learn and practice become prohibitive quite quickly. So I figured that one day I'd build a practice sax, that would let me learn the fingerings and notes without having to blow the thing too loudly.

That was four or five years ago.
My lovely saxophone was too nice (and too expensive) to hack, so every now and again I'd check eBay for a cheap instrument. Well, this morning, all that waiting finally paid off

Here's my new sax, ready to be fitted with a load of wires to be converted into a midi instrument. My first idea was to run some CAT5 cable through the body, then separate the wires afterwards. This very quickly proved too difficult

So I separated the cable into individual strands and placed a small weight (capacitor) at one end of each wire.

I then pushed the capacitor through an open, erm, valve? pad? hole? and wiggled it round, while feeding the wire into the body of the sax.

Eventually it appeared at the neck end of the instrument (I started feeding the wire into the larger holes in the curved bit at the bottom of the bell and worked up the instrument)

Sometimes - especially once a few wires were in place - the cap got caught up with other wires or fell into the hole of another note. If it couldn't be shaken free, a bent bit of solid-core wire was easily pushed down the next to hook it free and retrieve the other end of the wire.

After about an hour of wire-wiggling, I managed to get twelve wires from the lower 12 holes, through the instrument body and secured out of the top of the neck. Once all 24 are in place (the body has 23 holes and a 24th on the crook of the mouthpiece) then can be soldered to a PCB and hooked up to a PIC microcontroller for the MIDI fun to begin!

Multi-effect pedal

We had a great time at BuildBrighton with our working fuzzface guitar pedal. New member Patrick even brought along a VOX wah pedal to get some Voodoo Chile type riffs going!

Which got us thinking about embedding our effect pedal inside a guitar, and how to simplify the circuit. So we came up with this idea - it's an effect pedal combining a fuzz face and a wah pedal. Either or both can be by-passed (so you can have clean, just fuzz, just wah, or fuzz going into wah).

In a future version, we're planning replacing the potentiometer on the wah (labelled VR3) with a digital pot. This will allow us to hook the wah effect up to a PIC micro-controller and use a 3-axis accelerometer to change the wah sound. Tip the headstock towards the ground to simulate rocking the pedal back, then move it upwards to rock the pedal forward.

The introduction of an accelerometer on the guitar opens up all kinds of possibilities (imagine hooking it up to the volume control: tip your guitar skyward, a la Slash, for a volume boost while solo-ing!) Any way, here's the first version of our multi-pedal:

Multi Pedal schematic

Multi Pedal PCB

Parts list:


C1 2.2uf  capacitor
C2 0.01uF capacitor
C3 22uF capacitor
C4 0.01uF capacitor
C5 0.22uF capacitor
C6 4.7uF capacitor
C7 0.01uF capacitor
C8 0.22uF capacitor
L1 500mH inductor
Q1 BC108 NPN transistor
Q2 BC108 NPN transistor
Q3 BC108 NPN transistor
Q4 BC108 NPN transistor
R1 33K resistor
R2 330 resistor
R3 8K2 resistor
R4 100K resistor
R5 68K resistor
R6 1.5K resistor
R7 470 resistor
R8 470K resistor
R9 22K resistor
R10 33K resistor
R11 82K resistor
R12 470K resistor
R13 10K resistor
R14 1K resistor
SW1 = DPDT switch
SW2 = DPDT switch
VR1 = 1KB potentiometer
VR2 = 1KB potentiometer
VR3 = 100K potentiometer

Working fuzz face pedal

Here's a video showing the fuzz face effect "pedal" working with a Peavy Raptor guitar and miniature Marshall amp.

There's a definite difference between "clean" and "distorted" sounds and we're keen to say that the whole thing works well. The only thing is, after trying out our board, Jason from BuildBrighton turned up and asked us to try out his design - and his works even better!

So we've ended up with two types of effects pedal. Our latest design is more of an "overdrive" distortion effect, whereas Jason's is very much more "fuzzy" - more reminiscent of the original FuzzFace.

(check out the video jump at about 0:44 where the video was paused while we swapped out "our" pedal for Jason's)

Guitar effects pedals

In preparation for the Mini Maker Faire in Brighton in September, we're busy designing and prototyping tiny guitar effects pedals which can be embedded behind a scratchplate.

As this involves hacking an actual instrument, it seems only sensible to keep track of where we've started from (if only so we go back to it, in the event of something going really wrong!)

The ideal starting point is not necessarily the wiring we start with - even really expensive guitars (for us, anything over about fifty quid is a really expensive guitar) can sometimes have quite shoddy wiring. So we're going to start with shielded wiring, to keep any hum and noise introduced by our effects "pedals" to a minimum.

Here's a typical three-pickup setup with shielding - note that the ground plane should be extended to the underside of the scratchplate, the tone and volume pot bodies and, if possible, the entire inside of the electrics cavity:

Shielded Wiring for Stratocaster guitar

Basic Wah Pedal

As part of a series of up-and-coming BuildBrighton workshops, and in preparation for this year's Mini Maker Faire we're busy putting together some simple effects "pedals" that can be put together inside a guitar, to provide onboard electronics.

We've already started work on a number of fuzz-face (distortion pedal) variants.

This time it's the original Cry-Baby Wah effect that we're looking to emulate. In fact, this circuit design is quite a bit simpler than the Dunlop version, but is perfect for what we're trying to acheive - a simple, workable circuit to act as an introduction to gutiar electronics. Here's the circuit schematic:

Wah Pedal Schematic

And the PCB layout:

Wah Pedal PCB
(as ever, print onto A4 at 100% no scaling for a press-n-peel/toner-transfer-ready image for etching your own)

This is how the final PCB should be assembled:

The beauty of this simple design is that it uses a single 500K linear potentiometer to achieve the wah-wah sound. Which means we can do a lot with this design when it comes to "hacking" up our guitars later. For example, it could be replaced with a digital pot and hooked up to a microcontroller (such as a PIC or Arduino) for all kinds of funky fun!

Basic4Android

One thing we've been keen on over the last 12 months or more, is making our own USB devices. These can be anything - we've made miniature instruments and servo controllers amongst other things, but the idea that you can create a device, plug it into a PC and it just works has been really exciting.

Out in the real world - not Nerdland - the rest of the world is busy getting on with mobile phones and tablets and cool things like that. And leaving us PC lovers behind as we look so archaic, sitting hunched over a notebook/laptop in the local coffee shop. The cool kids are too busy swooshing and swishing on their touch screens to worry too much about a few motors chained to piece of rapidly-becoming-obsolete piece of technology!

So we've had a bit of a change of heart here at Nerd Towers recently.
Rather than trying to continue denying mobiles and mobile computing, we're slowly learning to love it. By which, of course we mean, slowly learning to love Android (installing iTunes on a PC is akin to pouring cold tea down the back of the air vents, shudder, Apple, shudder). But developing for Android means getting messy with Java.

Unless you're already quite proficient with Actionscript (AS3) - then haXe is probably a great place to start. But haXe libraries are pretty limiting. We've not found anything that, for example, allows you to communicate with the USB port. So once again we set off looking for a development suite that would compile for Android, and give us access to the USB stack.

Step forward Basic4Android.

Not only is this a brilliant IDE, offering VB-style syntax and a familiar looking environment (you even hit F5 to compile and run your code for goodness sake!) it also compiles to native Android code - so no pesky AIR runtimes and making your apps incompatible with a large share of the market (AIR only runs on devices with ARM7 or better processors - most mid-range phones are still shipping with ARM6 in them).

And the best thing? USB support!
So far, we've only got a simple "hello world" app working, but it's a start.
But already Basic4Android is looking to be quite a powerful bit of kit that could really kit-start some interesting ideas (a bit like Oshonsoft Basic did for our PIC microcontrollers). It's so great, in fact, that the author is offering a special deal for all of us:

If you like the Basic4Android software, you can buy it from http://www.basic4ppc.com/

Put in the voucher code - coxvau - and you'll get a massive 50% off!

And we'll get a year's worth of free support and upgrades. So everyone benefits! But no-one more than you - when you've compiled and released your first app, who knows where it could lead.......