Colin's solar powered clocks, radio and fan

Update in March 09
In March 2009 I found that the days are lengthening, and the old car battery voltage after evening use was rising to 12.2V. I now wonder how we shall use all the power in the summer.

In the loft I found my parents old transistor radio. It is a Bush transistor radio TR82D from the late fifties, and I remember it well in our old house when I was still at school 50 years ago. I remembered also that we had seen one in an Edinburgh museum as an ikon of the fifties. Looking inside was such an unfamiliar sight today. There were discrete Mullard OX71 transistors, just two, and big chunky discrete resistors. The "retro" style radio shape is now available in Argus with new digital radio innerds! It seemed with preserving. It did not at first work. The problem was the complicated rotating tone/on/off switch. I replaced it with a simple toggle on/off switch. It then worked fine but was greedy on big expensive 9V batteries. I measured its current and found that with 250 ohm resistors in series the voltage at the radio was just right. So I soldered wires onto an old battery top and wired it into my 12 V bench next to the kitchen. Of course it has no FM but the Long Wave is clear and bright, and will get French radio too!

A second rather frivelous project was a solar clock. In our lounge we have a most beautiful grandfather clock, but it is not always wound up. We have an lovely old French antique clock but it tends to give unreliable times even when wound up. I remembered the rather beautiful quartz clock that my parents had long ago on their mantlepiece and which sat in the loft unused. It was from the London Clock Company with a Japanese movement. It worked fine off a 1.5V battery but to set it up for 12V was not so trivial. The now-so-common quartz movement takes very little current for 1 second then takes about 0.3 amps for a tiny pulse each second as the hands jerk round. I connected the 12 V though a 100K ohm series resister but placed a 500 microFarad condenser across the clock to smooth out the current pulses. The large resistor means that it only takes a milliwatt. The capacitor is probably too large as turning it on, you can see the voltage across the clock slowly rising as the condenser charges up through the resistor. It settled nicely at 1.5 V across the clock. It sits on our woofer conveniently hiding the electric sockets. It has given perfect time ever since.

It worked so well that I thought of a second clock to go outside on our patio using the same power supply as the outdoor lamp. Its design was based on a simple rust-coloured tile that was lying in the loft. I drilled a hole and glued behind it a cheap quartz movement. I also glued a permanent cover over the back as the solar power meant there would be no battery changes. With a touch of vaselene over the hands they keep out the rain without problems.

Some old slabs of marble lying in the shed of our French house set me thinking of a more ambitious outdoor clock. It was to go onto the blank wall in front of our house and rather easily seen from our quite main road. It was to be a "peace" clock. I cut up four pieces of marble slab with my French diamond saw including four diagonal nicks at the centre to allow room for the quartz movement. Again the back of the clock could be glued to be waterproof. The slabs were 50cm wide so that quite large hands were needed. I found a piece of old brass lying on the ground and cut it with tinsnips to make the two hands. The minute hand was nicely balanced using some old brass coins. The 5-minute positions were old German brass deutchmark coins and the quarter hour marks old Canadian dollars. Mo wrote the "Peace on earth" caption with brass-coloured paint. Below the clock I made from soldered brass and copper wire a little dove that seems to nest in the plants below. It all fitted together fine, but timekeeping has been a slight problem. It seems to lose just a minute every few days, possibly because of the rather large angular momentum of the hands.

But it did not use much current so I bought a 120mm diameter 12V fan from Maplin for those hot days to come. It cost £7.08. It takes 0.4 amps which has yet to be achieved by my solar panel. It works very smoothly and gives a nice draught. To stop the air "short-circuiting" around the fan and to hide the rather ugly plastic works, I encased in a heavy case of 20mm thick Belleme oak, stained dark like the bookcase on which it stands.