The latest doings down on the shore (or up in the burn)

Click on the image to see full-size version, 768 x 568 pixels.

This site is currently under development and may show images from television or a blank blue screen. It is only updated when something interesting happens. At present, the camera used is too sensitive for bright sunlight even when the lens is fully stopped down, so images may appear over-exposed. This camera does not have automatic aperture control, but the final one will. Details of the temporary camera set-up can be found here.

Nov. 6th 2002: the temporary camera has been moved from looking at the shore to looking at the burn behind the house. The amount of water indicates the extent of recent rainfall.

The Sept. 24th image showing two Blackface ewes and one black Jacobs-cross-Blackface was for the benefit of Ron Hilton's WAIS group, some of whom wish to see a black sheep. In view of this interest, I am adding a section on sheep.

Jan. 24th 2003: We got the big batteries up on 29th Dec. with a considerable effort. The Hillcat needed to be winched over a bottomless boggy bit which resulted in a 1 1/4" diameter crowbar being bent at 45 degrees. There is no way of avoiding this place so getting the hill webcam installed will need to wait for a dry spell in the spring. But the batteries are performing very well. With the present 450 mA current drain the batteries discharge for about 200 hours and charge from the wind generator for about 80 hours. When in discharge mode, the generator output is short-circuited by a relay which acts as an electromagnetic brake to prevent unnecessary wear on the bearings. In this state, the generator turns at only about 200 rpm in any wind.

Conventional charge control systems switch in a big resistive load to prevent overcharging, so that the generator is wearing itself out simply to produce waste heat. Eventually, the load resistors burn out, the batteries boil dry, the voltage rises to as much as 100 V and the load electronics are destroyed. The generator then has no load at all, so over-revs and destroys itself.

The present system has been running satisfactorily for over 2 years, though the charge control relay has had to be replaced a couple of times. We experimented with power MOSFETs for shorting the generator, but these have a positive temperature coefficient, i.e. their ON resistance rises with temperature. So when they heat up a bit the generator is progressively unshorted and dissipation increases - thermal runaway.

So we are exercising patience, waiting for the boggy place on the track to dry out, and hope that anybody who looks at this site will do the same.

28 Jan. 2003: During February the temporary webcam may be shut down due to plumbing operations in the house, but it should be back on again in March.

?? Feb. 2003: Chris replaced existing generator with spare one. Later diagnosed worn brushes on slip rings. Charging had occasionally been erratic in relation to wind speed.

19 Mar. 2003: Superb weather. Charge cut in/cut out threshold voltages changed from 24.4 / 27.7 to 26.0 / 29.9, on the advice of battery specialist Dr Stephen Thomas. At that time, cell specific gravities ranged from 1195 to 1240, considerable imbalance. Telemetry transmitter brought down for installation of improved radio link. Chris found the manual for the temporary webcam, from which we learned that some switches on it had been wrongly set. 19th Corollary to Sod's Law: If all else fails, read the instructions! Images now much better in variable light conditions.

23 Mar. 2003: new model telemetry tx and rx from RF Solutions installed. Dried-out light sensor replaced. Temp. webcam fitted with wider-angle lens and trained on road so that Alison can see cars while confined to bed. Some corrosion detected in uphill antennae, replacements needed.

Hits on this site since Sept. 12th 2002:

To give you an idea of the size of the island, the width of this map corresponds to about 32 miles or 52 km.

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History of the system
Local geography
Aviation in Mull: general information
Aviation in Mull: pilot information
Details of South Mull Pubs
Details of North Mull Pubs

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