author
11Instructables27,902Views15CommentsSouth west EnglandJoined February 16th, 2016
I am a retired analytical chemist living with my wife Cynthia in Cornwall, south west England. I have held the UK radio amateur call sign G3PPT since 1961. I have been interested in computing since the days of the Commodore PET and have written some (very bad) programs associated with amateur radio in C and C++. Another hobby which we both share is the chasing up and photographing of film locations for the website www.reelstreets.com.

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Solar Contest 2016
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    • How to Make Glow in the Dark Adhesive Stickers and Magnets
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  • How to Make Glow in the Dark Adhesive Stickers and Magnets

    Hi Skistler and thanks for the interest.The powder that I purchased came in 10 gram bags and, since I had one unopened, I scattered the contents over a 4 inch square of black card and I have attached a picture. From this I would suggest that 20 grams would do the job.That said, I think that scaling up will present challenges. I have been very generous with the applications shown in the article and the resulting surface has tended to be a little uneven physically although this does not degrade the visual effect.For large areas I would imagine that the even application of the nail varnish will be important and maybe thinning with pure acetone may help. Also applying the powder from a height from a vessel such as a free running salt cellar might be a good thing.Do bear in mind that nail v...

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    Hi Skistler and thanks for the interest.The powder that I purchased came in 10 gram bags and, since I had one unopened, I scattered the contents over a 4 inch square of black card and I have attached a picture. From this I would suggest that 20 grams would do the job.That said, I think that scaling up will present challenges. I have been very generous with the applications shown in the article and the resulting surface has tended to be a little uneven physically although this does not degrade the visual effect.For large areas I would imagine that the even application of the nail varnish will be important and maybe thinning with pure acetone may help. Also applying the powder from a height from a vessel such as a free running salt cellar might be a good thing.Do bear in mind that nail varnish and acetone are highly inflammable and as you scale up in size the vapours become quite narcotic so good ventilation is vital.I hope you are successful.

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    • How to Add ' Glow in the Dark' LED Eyes to a Plaster of Paris Ornament
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    • Adding an LED Back Light to an ACCTIM BENTIMA  LCD Alarm Clock
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  • Adding an LED Back Light to an ACCTIM BENTIMA  LCD Alarm Clock

    One side of our aforementioned partnership agrees with you! I, in the other hand will own up to 'dubious dongle' :-)My plan B is indeed to go the Joule Thief route with the circuit powered by the clock's own battery. This would allow a completely sealed solution with no further access to the interior required. But. . . there are things to consider. Space is tight! I think it reasonable to allow a budget of 0.2 mA continuous power consumption for the Joule Thief so as not to cause frequent battery changes; this is quite a big ask but possible. The circuit needs to be stable, you do not want to be adjusting the circuit or even having to have a hole in the casing to access a trimming pot. Watch this space.

    Thanks for your interest.We have had the same experience with garish green alarm clock displays and had to resort to coloured films and cloths but it was never right and the offending clock went to the charity shop in the end. We got a red one which was much better being in a visible region that is kinder to the eyes but all of them need a facility whereby you can turn the display intensity right down to almost zero. With the LED battery being external in this case it might, in principle, be possible to turn off the LED during daylight. Semiconductor photocells work in the wrong sense in that they are high resistance in the dark so you would have use one to turn off a series transistor but it might be tricky to control the starvation current of a few micro-amps that we are using. Th...

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    Thanks for your interest.We have had the same experience with garish green alarm clock displays and had to resort to coloured films and cloths but it was never right and the offending clock went to the charity shop in the end. We got a red one which was much better being in a visible region that is kinder to the eyes but all of them need a facility whereby you can turn the display intensity right down to almost zero. With the LED battery being external in this case it might, in principle, be possible to turn off the LED during daylight. Semiconductor photocells work in the wrong sense in that they are high resistance in the dark so you would have use one to turn off a series transistor but it might be tricky to control the starvation current of a few micro-amps that we are using. The hope is that our battery will last a very long time.

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  • Joule Thief With Ultra Simple Control of Light Output

    Thank you for your interest and sorry for the delay in my reply.I have an ongoing interest in applying the Joule Thief circuit and I have built a number of them over the last year or so. My feeling is the the single most important factor in the construction of the transformer is the use of bifilar winding i.e. the wires must be tightly twisted together before winding on to the toroid. If you are adding a third winding for some reason the use trifilar. I general I think it is a good idea to keep the number of windings up to bring the oscillator frequency down to reduce capacitive losses and maybe even radio frequency interference.It is tempting to do the winding in two stages bringing the centre tap out for connection to the positive rail but my experience is that this can cause diffi...

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    Thank you for your interest and sorry for the delay in my reply.I have an ongoing interest in applying the Joule Thief circuit and I have built a number of them over the last year or so. My feeling is the the single most important factor in the construction of the transformer is the use of bifilar winding i.e. the wires must be tightly twisted together before winding on to the toroid. If you are adding a third winding for some reason the use trifilar. I general I think it is a good idea to keep the number of windings up to bring the oscillator frequency down to reduce capacitive losses and maybe even radio frequency interference.It is tempting to do the winding in two stages bringing the centre tap out for connection to the positive rail but my experience is that this can cause difficulties in the starting of the circuit even if the windings are very close on the toroid. (A Joule Thief that does not start reliably is a disaster as there is a near short circuit from the positive rail through the transformer to the transistor collector and then from the transistor emitter to ground.)Considering the use of different turns ratios for the transformer I cannot comment as I have always successfully used 1:1 but I will have a go on the breadboard at varying the ratio to see if there is any improvement in efficiency to be had--the LED does present a very strange load to the circuit.

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  • A Simple Solar Charger for Nickel/Metal Hydride and Alkaline AA Cells

    Thanks for your interest Mark.The critical factor is that each cell has its own diode and resistor in series. The diode isolates each cell from the others and the resistor drops the voltage and limits the current to that cell. Hence although you may have six volts applies to the diode and resistor the voltage across the cell itself will only be up to 1.4 Volts with the voltage difference being dissipated in the resistor. If you insert a totally flat Ni/MH cell and monitor the voltage across it as it charges over time you will see it come up fairly rapidly to around 1.2 Volts where it will stay while the battery absorbs charge and then, when the battery is charged, the voltage will rise to 1.3 to 1.4 Volts. At this point the battery is 'float charging' and the energy is converted in...

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    Thanks for your interest Mark.The critical factor is that each cell has its own diode and resistor in series. The diode isolates each cell from the others and the resistor drops the voltage and limits the current to that cell. Hence although you may have six volts applies to the diode and resistor the voltage across the cell itself will only be up to 1.4 Volts with the voltage difference being dissipated in the resistor. If you insert a totally flat Ni/MH cell and monitor the voltage across it as it charges over time you will see it come up fairly rapidly to around 1.2 Volts where it will stay while the battery absorbs charge and then, when the battery is charged, the voltage will rise to 1.3 to 1.4 Volts. At this point the battery is 'float charging' and the energy is converted into oxygen and hydrogen gas by electrolysis and then the gases recombine to form water.The resistor limits the charge current to just a few mA so the charging is slow and the charging and float charging is at a very gentle small current. When time is not too important this doesn't matter. Note that I gave a wide range for the series resistors--with low value resistors you will get a faster charge especially in good quality sunlight but then the subsequent float charging will be higher and you may be happier taking the cells off charge when full . With higher value resistors the charging will be slower but the float charging will be less aggressive and you can leave the cells in the device ready for use in tiptop condition.Note that your 6V 150 mA solar panel will only give this power in full sunlight. In dull conditions this will drop drastically but our charger will continue to put at least a little something into each of the cells.This overall concept may seem a bit wasteful but we do get the energy for free!

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  • Joule Thief With Ultra Simple Control of Light Output

    Hello and thanks for the interest.Yes indeed. The method of control relies on the output being rectified to produce a positive voltage which is fed back to the transistor which is connected to the oscillator transistor base turning it on and turning down the oscillation. So to answer your question, the positive voltage can also come from an external source and a 2 Volt solar cell salvaged from a defunct garden light is perfect this being shown in the final stages of the article.The Joule Thief is perfect for a newbie. It will work on a solderless breadboard and you can learn much putting one together and it actually does something i.e. lights up. Be prepared to write off the odd LED or transistor but that is all part of the fun!

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  • Joule Thief With Ultra Simple Control of Light Output

    Thanks enormously for that and I will now do some editing. On the first point I will add the LED in to the schematics.Regarding the second point I admit to being a little unclear. The circuit is correct but the solar cell is being used as a very cheap (scavenged) component to control a circuit rather than be a source of solar power. Inside a house there is very little energy left in the daylight once it gets through the windows and not enough in general to yield very much from a solar cell--you might source some energy by positioning the cell on a window sill, up against a window or perhaps catching a transient shaft of sunlight. However there is more than enough to provide the few microwatts of power required to switch off the Joule Thief when not required in daylight and thus prev...

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    Thanks enormously for that and I will now do some editing. On the first point I will add the LED in to the schematics.Regarding the second point I admit to being a little unclear. The circuit is correct but the solar cell is being used as a very cheap (scavenged) component to control a circuit rather than be a source of solar power. Inside a house there is very little energy left in the daylight once it gets through the windows and not enough in general to yield very much from a solar cell--you might source some energy by positioning the cell on a window sill, up against a window or perhaps catching a transient shaft of sunlight. However there is more than enough to provide the few microwatts of power required to switch off the Joule Thief when not required in daylight and thus prevent waste of battery power. I will go back and emphasise this point in the text.This does raise the interesting point regarding the possibility of a solar powered night light. I think that it is a viable project but such a device must work 24/7, winter/summer and ideally in as many parts of the world as possible and it certainly is not as simple as it sounds. It will need more effort than modifying a solar garden light!Thank you again for your help.

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  • A Simple Solar Charger for Nickel/Metal Hydride and Alkaline AA Cells

    Thanks for your interest.The diodes isolate each individual cell from all of the others. This is necessary otherwise cells with more charge would discharge into other cells possessing lower charge especially when the solar cell is not illuminated. This will happen for instance when you have three cells fully charged or well on their way to being charged and you put on one flat cell. Conventional wisdom is that it is not a good idea to charge nickel cells in parallel as their individual characteristics vary and they cannot be relied upon to properly share the current.

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