Sunday, 19 December 2010

A Christmas Ghost Story

Christmas is traditionally a time for ghost stories - I never really understood why.

We are home at the moment - the boat is iced in and under several inches of snow - she's not going anywhere in a hurry.

Ever since our cats were kittens, they have enjoyed climbing up inside our business desk in our lounge.

They climb up past the printer and get behind the three drawers that we have.

They then usually push out one or two of the smaller letter drawers from behind as they pass down or for a big finale, push the larger bottom drawer out, with them sitting in the bottom of it as it extends.
This then then enables them to go round for a second go.

As they have grown and got physically larger, it has become more difficult for them to do this, although not impossible as they are keen to prove occasionally.

Last night, we were watching TV (well the first mate was; I was watching the inside of my eyelids).

Suddenly, the first mate observed the top drawer nudge and then slowly come out about 6". The second draw nudged a bit and also came out.

The drawer slides are quite stiff - they don't run on bearings or runners and use wood to wood contact.

It looked just like a bit of "cat on drawer" action.

The male cat was asleep on his beanbag on the opposite side of the lounge.

The female cat was nowhere to be seen.

She waited for the big drawer to open, expecting to see the smug looking she-feline sitting there.

Nothing more happened. The big drawer stayed firmly shut.
She verbally encouraged the cat to get herself out of there, otherwise she would have to get up out of her seat and rescue her.

Nothing happened.

Irritated, she got up, walked across the room and opened the big drawer to get the cat out.

Our Tomcat even went across with her and curiously sniffed at the open drawers.

You guessed it - there was no cat inside - the desk was empty - all she saw were the usual letters, books, letter opener, pencils, etc.

After a quick search, she found our queen asleep in the bedroom upstairs.

I missed the whole thing, but it doesn't surprise me. We've had other instances over the years, usually around the first mate.

Just out of interest, the drawers were no more than 2-3m away from the first mate and in clear visual sight at all times.

Saturday, 11 December 2010

LineWatch - It Works !!

I've been struggling with the LineWatch.
It works fine in terms of the local alarm on board the boat, but I've been having problems getting it to text me when I'm not on the boat.

Firstly, the LineWatch was pulsing the SMS unit and triggering a text every five seconds.
Apart from my mobile vibrating like crazy, it quickly used the credit on the PAYG SIM in the unit.

So, I modified the circuit. Partial success, it would just send one text, but the system stayed locked on in the alarm condition.

Finally, today, I sorted it.

It now sends just one text. If the alarm condition persists (i.e. boat stays adrift and at distance from the sender), it will repeat the text about 45-60 minutes later.

I've now got all the various independent systems that I've designed and built, working together.

There are basically two modes:

Marina mode:

I receive a text on my mobile if:

- There is more than 5mm water in the engine bilge (also generates a local alarm on the boat)
- Somebody trips the shore breaker, so that my battery charger and anti-frost heaters go off

I can then choose whether I want to drive to the boat to check it out or just give one of the marina staff a call.

Towpath mode:

I receive a text on my mobile if:

- There is more than 5mm water in the engine bilge
- The boat drifts more than 5m from the sender unit (e.g. pins forced out by passing boats or boat set adrift by vandals, etc)

These events also activate different tone alarms onboard to wake occupants up.

The text message wording enables you to identify the different causes, so if you're sitting in the pub and can't see the boat, you will know what problem is being reported.

I don't think we are going to drift very far with this ice at present though !!!

Thursday, 2 December 2010

Cut Adrift - LineWatch

Well I've been busy working on a prototype and I'm pleased to say that it works.
The black unit is the receiver, which mounts on the boat. It operates from the boats 12-15V DC battery supply.
The white unit is the Wireless Sender Unit. Its splashproof and can be attached to a tent peg in the bank, hung from a low branch etc.
When the boat is moored safely, the Wireless Sender Unit is attached to a fixed point on the towpath or bank and is switched on. It runs from a CR2032 Lithium battery and will last for 160 hours on one battery.
The Receiver Unit is switched on with the little toggle switch and the red light flashes to confirm that it is operating.
The Receiver Unit will chirp a couple of times to confirm that it is communcating with the sender and then it will fall quiet.
If the boat is set adrift, accidently by a passing boat or deliberately, by a towpath yob, intent on cutting you adrift as you sleep, the two units will continue to communicate silently.
Once the boat has started to drift away and reaches a certain distance from the Wireless Sender Unit, the Receiver Unit will start to alarm.
An annoying integral buzzer will wake you up from your slumber, before you drift too far.
You can make your boat secure again. Once the original distance is achieved again, the alarm will stop and the system can continue on watch or you can recover the Wireless Sender Unit and move on to a safer berth.
If you are not on the boat e.g. down the pub enjoying a dinner or at home, the Receiver Unit will output a 12V alarm pulse which can be used to trigger a SMS Messaging Unit, which will text your mobile to tell you that the "boat is adrift".
I've called the system LineWatch and am not really interested in producing the unit commercially - not enough demand, I feel.
It was an interesting technical challenge though and I plan to fit it on my boat to test the system in real life conditions.