Members might recall that the Joggers last year bought a large digital clock.
Just what was advertised about the chosen clock, what was read into the advert, and whether the clock lived up to its advert is no longer of any interest. But it has taken Mark Skilton and Chris Bradfield some while to try to put it into service, for our normal requirement of service on a race finish line.
First, the clock certainly isn’t waterproof. We now know that, having drenched it at last year’s Seven Stiles. Fortunately it recovers after being left for the circuit board to dry out. A small gazebo at the finish line is likely to solve this problem.
Secondly, a minor matter, it came with no provision for support, so with Mark’s help, we have added a bracket to allow mounting on a camera tripod. It remains easily blown over by strong gusts of wind.
Thirdly, finding a small rechargeable battery to make outdoor use simple is still in progress. The supplied mains adapter marked ‘for indoor use only’ is scarcely helpful for use on the Kings Field.
Most importantly, there has been some difficulty getting it to respond to the remote control supplied. We haven’t taken the clock to a race start line, not least due to battery difficulties, so we usually start a race with two stopwatches, return to the Kings Field and load a transfer time onto the clock, and start the clock when the stopwatches show the same transfer time. Unfortunately the clock hasn’t started reliably, and for a year had been set on one side. After all, with race timekeeping live, if the clock fails to start despite two attempts, all one can do is to put it aside and focus on the race.
Eventually, some thought identified a common pattern. The clock remote control works reliably on test, at home and indoors, near a mains power source, but had failed consistently outdoors on the Kings Field. Perhaps it didn’t work outdoors. Transferring the test outdoors, both with mains and battery power, confirmed the failure to work outdoors. Thinking further, a possible cause emerged. The remote control uses an infra-red link, much as TV and other remote controls do. Perhaps the receiver was exposed to too much infra-red as part of the daylight outdoors, and so saturated and could not recognise the smaller additional illumination from the remote control. Tests seemed to show that shielding the receiver photo-transistor to cut out much of the ambient lighting did allow the remote control to work.
For the present, the simple solution is shown in the photograph. 
The plywood plate registers on the bottom right inside corner of the clock bezel, and holds an offcut of 15mm copper pipe in line with the phototransistor. This now ensures that the receiver only receives light from a reasonably small angle of view, and so cuts out much of the background lighting, just as a lens hood does in photography. Of course we now have to point the remote control fairly accurately, and squarely on to the clock, but this is a small price to pay. Still to come is a clip to hold the plate whilst setting the clock, and avoid a need for a third hand.
We look forward to further opportunities to improve
Chris Bradfield
You must be logged in to post a comment.