Steve's wireless shed alarm

I once had the privilege of working alongside a delightful chap named Steve

Say hello Steve

Okay, that's actually his sock.
Moving on, Steve is a man with sheds, and like any man with sheds he wishes to protect them.
But rather than standing guard 24 hours a day with a handy flamthrower, he built a wireless alarm system.

The system uses IR rangefinders to detect would be shed raiders, as pointed out by the man himself.

On the inside of the door there's the innards of the detector, a PIC12F675 and a PMR radio with added wires.









The detectors (3 of, one per shed) have analogue outputs which the PIC reads and compares to it's stored values.
If the reading on any input go over it's stored value for more that 10 readings, the PIC "presses" the call button on the radio, causing an annoying bleepy noise to come from the receiving bedside radio. This in turn causes an angry Steve to come running into the garden, chainsaw in hand.
Or something like that...








AH yes! the code!
Tis in assembler, as mister Steve doesn't believe in brackets

webby makes a ground loop isolator

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

(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?

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

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

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

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..