elektrickery!

webby makes a ground loop isolator

2012-02-11T18:25:00.000Z

This is a follow on from my previous post in which I made a vague effort to stop my mp3 player/phone making noise when it was connected to my car radio while charging.

While the linear regulator helped reduce the noise, it was still audible.
Time for a ground loop isolator!

For the uninitiated, a ground loop is where the ground/shielding/0v connections form a loop (hence the name). In theory this wouldn't be a problem, except that devices within a ground loop usually want to be at different potentials and throw tantrums if they can't have it their way. Or something like that... See wikipedia for a real explanation.
In my case the phone, radio and charger form a loop and I end up with lots of whiney noise coming from the speakers.

To the ~~workshop~~ ~~shed~~ ~~basement~~ desk that I use for everything!
Step 1: order parts
2x 1:1 audio transformers

1x box (optional, but only if you like police bomb squads)

1x shielded audio cable (I used the leftovers from the previous phone bodgery)

Step 2: Tea
Tea is the most important part of engineering, closely followed by hotglue and shiny things.

Step 3: Draw really easy to interpret diagrams
This should really be the first step, but it's a really basic project.

Normal audio cable:

From carphone2

Ground loop isolator cable:

See! dead simple! From carphone2

Step 4 make it happen:

note: 2 of the 4 cores on the 4 core cable are connected to
ground. From carphone2

Should have made the wires longer... From carphone2

From carphone2

No more noise!

I think I'll order some longer wire for it so I can hide it under the dash a bit more at some point. There's no degradation in audio quality (none that you'd notice over the MP3 compression and weedy speakers anyway...)

All in all, I'm quite pleased with the result

car notphone

2012-02-05T21:19:00.002Z

(Rant)
Have you heard the radio recently?
Does anyone actually listen to that rubbish?
...
What do you mean "Yes"?

Fine, be like that then, but I find the content broadcast from payola land to be poor at best and one can only take so much radio four before the need to kill a politician takes hold.
(/Rant)

Solution:
Old mobile phone to in car mp3 player conversion!
"But that's easy" I hear you say. Well yes, it is easy, but it's a Sunday and my soldering iron needs some exercise.

So we take one of these:

From carphone

Do this to it:

mmmm.... hot glue... From carphone

And this:
(so I can find the buttons without looking)

more hotglue!! From carphone

then do this:

yet more hotglue! xD From carphone

To keep it running forever I threw together a charger:

12V through a USB port backwards.. nice one guys..
From carphone

no such thing at too much hotglue From carphone

Hopefully this one wont put an annoying buzz onto the audio output like the switch mode ones do. Either that or next week will be "webby makes a ground loop isolator"

In addition to the hardware, I've put sypftp on the phone so I can upload music to wirelessly and light control to keep the backlight lit while the phone is unlocked.

I'll give it a test on the way to work tomorrow. :)

Still there?

2012-01-30T22:52:00.000Z

I'm a bad blogger. I blame my lack of workspace, tools*, the phase of the moon and various politicians for the lack of posting.
*a good workman always blames his lack of tools

Anyway, here's what I'm currently working on:

note: correct quantity of tea.
This isn't just any keyboard. This is a Dell RT7D50 USB keyboard,

with it's internals thoroughly hacked about,

and made slightly less internal.

then bunged into a teensy++ 2.0
This isn't just any keyboard. This is a spiderwebby keyboard**
**functionality not guaranteed, may cause major economic disruption, fires and permanent damage to shatners bassoon.

And for a little side project I decided to have a go at one of these silly clocks that seem rather popular at the moment:

It kinda needs a video to do it justice, but let it be said that random ticking, backwards, swapped handed clocks are quite fun*** :)
***especially at the company office with Twitchy McTwitchingtons.

Aaand that's about it for the moment, more postings next week (hopefully...)

Farnell Stuff Review

2011-09-20T08:55:00.001+01:00

So I was stumbling around on the internet in a semi-drunken state one Wednesday afternoon (as you do when visiting your sister's pub..) and I discovered I had an email from a nice chap at Farnell asking me to review some stuff for him. My initial thoughts were the result of a head on collision between "it's a phishing attempt/spam" and "FREE STUFF!"
fast-forward a week or two and I now have in my possession some 3 watt LEDs some AA battery holders and some ATMega328s.

Starting with the LEDs, I basically went for the best brightness to price ratio while not being SMT. I chose amber because I have plans for a future project involving these.

Fluff not included. From LEDs

Mouse Repair

2011-09-05T23:07:00.001+01:00

Here's an example of getting stuff done and a justification for the heap of potentially useful stuff (lovingly referred to as "crap" by friends and family :P)
Today my boyfriend's 5 year old mouse developed a ~~slight cough~~ dodgy left click switch. While it was amusing listening to the increasing levels of frustration as single clicks turned into quadruple clicks and drag selection turned into time wasting, it needed fixing.

Here's the vintage rodent in question, a Logitech mx3200 series. From mouse

To the ~~crap~~ useful stuff heap!

keyboard circuit diagram

2011-08-05T14:06:00.000+01:00

This is more or less the current circuit layout:

From keyboard

Current problems: LCD stays lit and powered while the PC is turned off, possibly due to wake on keyboard/mouse being enabled..

I'm planning to add:

a rotary encoder for navigating menus
keeping track of stats like words per minute
switching backlight power
arduino reset button
morse code input?

Long term i'm aiming to have the arduino connected directly to USB, but i'm not sure if it'll cope with the extra load..

keyboard code

2011-07-23T19:17:00.000+01:00

I've fixed most of the major issues with the keyboard, so without further ado here be code:

and header file:

There's probably far better ways of doing most of it, the status lights still do nothing and I had to do a rather annoying workaround so that rightctrl+z works properly (and other key combinations that start with 0xE0)

Advice/suggestions would be brilliant :)

Keyboards 4: The LCD of Awesome!!!

2011-07-20T21:59:00.000+01:00

The LCD screen arrived today, it was remarkably easy to wire up and get running. I ended up using a couple of the analogue inputs as digital outputs and I've still got 4 pins left over..

I also plumbed in the LED which turned out to be very bright green and tweaked the code to make it flash while the keyboard is sending data. This is almost the most annoying thing on the planet, only second to the American pronunciation of the word "solder".

pictures!!

From keyboard

Cheers to ByVac Electronics for the LCD of awesome :)

Keyboards 3: The Tidying of USB

2011-07-18T20:22:00.000+01:00

I finally got round to replacing the usb ports on the keyboard yesterday
I've gone for a standard socket for the spare port on the hub and a mini-b connector for the host connection (i figure there should be plenty kicking around now that mobiles have switched to micro usb)

also: hotglue.

From keyboard

Naturally they're somewhat wonky, I might straighten them at a later date..

Stay tuned for the next instalment: Keyboards 4: The LCD of Awesome
(coming in 2.5+((effort*lazy)/awesome) days)

Drill Battery Charger

2011-07-13T13:44:00.003+01:00

A few months before I moved to sunny Scotland my dad passed on his nice bosch drill set, which kicked around for a while and now that I want to use it, I discover the charger's dead!

AL 60 DV 1411 charger From drill charger

To the workshop, Batman!

Read more »

toasty modem!

2011-07-12T11:10:00.000+01:00

BT business broadband modems run hot (at least the 2Wire ones do). They also have no heatsinks or fans, but then at "room temperature" this isn't a problem.
The problem arises when you put said modem in a smallish room with about 800w of computing equipment and two people. On a warm day the room hit's between 25 and 27°C and the modem gets a little flakey.

Enter: the big fan!

From modem

I chose this one because it runs quite happily on 5v and is nice and quiet, screwed it onto the lid of a spare modem and swapped the lids over this morning. (hopefully) problem solved!

Noisiest. O-scope. EVER!

2011-06-05T03:12:00.001+01:00

I have the world's noisiest o-scope! It's an old ADC-200 computer based parallel interface box. harmless enough.
However, once it's plugged in it emits the most infuriating squeak I've ever heard. It's like it's full of really tiny rape alarms or something.
While it may be a bit low spec compared to a modern scope (20MHz, 10 in dual channel mode), it's a whole 5MHz faster than my vintage farnell DTC12 (wooo...) and it's PC based therefore a storage scope (YAY!!!!)

I'm going to do a bit of poking around and see if this is normal or fixable. Or I might just wrap it in foam and operate it from a draw...

switches!

2011-05-31T11:41:00.001+01:00

I've added some switches for turning the peripherals on and off. Mainly because I got fed up with having to unplug the whole thing every time something threw a wobbly, the memorystick got unmounted/ejected or if the USB port it was plugged into wasn't providing enough power.

Aren't they beautiful! (erm.. no)

from left to right: nothing* Program protect*, Storage, Keyboard

*this was going to be the FDTI but the TX, RX and DTR lines where enough to keep it powered :(
*isolates the DTR line

code

2011-05-25T18:38:00.000+01:00

I'm not entirely sure how to release the code for this, maybe on Google code under the GPLv3?
Anyway, the last useful version is linked here.

keyboard!!

2011-05-25T12:46:00.001+01:00

Take one Dvorak using engineer, an unhelpful IT admin, a vintage keyboard and an arduino.
Mix well for 2 weeks and bake for three years at 9000°F

Okay, maybe I didn't bake it (I'm no good at cooking anyway..)

The initial plan was to read the scancodes from the keyboard and re-shuffle them so that I could use a Dvorak layout while the operating system was set to qwerty. This turned out to be pretty simple to do once I got my head round the PS/2 system. I never got round to allowing PC -> keyboard communication, mostly because I can't be bothered (who needs status LEDs anyway?)

Having Dvorak-ifyed it I decided to have some fun and add a random expletive button.

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