author
15Instructables42,041Views26CommentsSouth 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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  • How to Run a Battery Clock on Solar Power

    Some further thoughts. . .The battery electric clock consumes power in 30 mS pulses every second and virtually zero for the rest of the cycle and this makes an average power consumption extremely difficult to measure.The picture shows my attempt at this. A wooden dowel with a small piece of printed circuit board stuck to each end is inserted into the clock in place of the battery and it allows the clock power connections to be brought out and plugged into a solderless breadboard. Connected to the breadboard you can see a battery which feeds a 10 Ohm resistor in parallel with a 3 Farad super capacitor in series with the clock. To measure the clock current connect up and measure the voltage across the 10 Ohm resistor--it may take a little time for the system to equilibrate. You will nee...

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    Some further thoughts. . .The battery electric clock consumes power in 30 mS pulses every second and virtually zero for the rest of the cycle and this makes an average power consumption extremely difficult to measure.The picture shows my attempt at this. A wooden dowel with a small piece of printed circuit board stuck to each end is inserted into the clock in place of the battery and it allows the clock power connections to be brought out and plugged into a solderless breadboard. Connected to the breadboard you can see a battery which feeds a 10 Ohm resistor in parallel with a 3 Farad super capacitor in series with the clock. To measure the clock current connect up and measure the voltage across the 10 Ohm resistor--it may take a little time for the system to equilibrate. You will need a voltmeter able to measure in the milli-Volt range. The use of a super capacitor might seem extreme but normal large electrolytics could not begin to touch it.I tried the circuit on four house clocks. I started with a cheap one mounted on a flattened beer bottle and equipped with a second hand and this yields 4 milli-Volts denoting a current of 400 micro-Amps. The three remaining clocks had no second hands fitted, were of better quality and these yielded current consumptions int the 270 to 390 micro-Amp range.Thus I found some but not a massive improvement when no second hand was on the clock but the experimenter would be advised to make his/her own measurements especially if dealing with larger clocks with bigger hands.This crude experiment does give an indication of the power you are going to have to find to run a clock 24/7/365.

    Thanks for that GregW171, It's really great when someone picks up one of your ideas and makes a success of it.

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    • How to Switch Off a Joule Thief During Daylight
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  • Lionel Sear's instructable How to Run a Battery Clock on Solar Power's weekly stats: 22 days ago
    • How to Run a Battery Clock on Solar Power
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  • How to Run a Battery Clock on Solar Power

    Thanks for the query!You may be making things unnecessarily complicated and in view of the fortunate latitude of your location I think that there may be a very easy solution. A 2 volt solar cell placed in your kitchen window could charge a super capacitor up to around 1.4 Volts using the circuit shown. (They don't come much simpler than this one!)The solar cell can be a salvaged item from a garden light and you could use two in parallel. The diode is necessary to prevent the power from leaking back through the solar cell but there is a cost due to the forward voltage drop of the diode. By replacing the Schottky diode with a germanium one you could gain another very useful 0.2 Volts or so.This circuit works well in the summer at my latitude but runs out of steam around October. With your...

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    Thanks for the query!You may be making things unnecessarily complicated and in view of the fortunate latitude of your location I think that there may be a very easy solution. A 2 volt solar cell placed in your kitchen window could charge a super capacitor up to around 1.4 Volts using the circuit shown. (They don't come much simpler than this one!)The solar cell can be a salvaged item from a garden light and you could use two in parallel. The diode is necessary to prevent the power from leaking back through the solar cell but there is a cost due to the forward voltage drop of the diode. By replacing the Schottky diode with a germanium one you could gain another very useful 0.2 Volts or so.This circuit works well in the summer at my latitude but runs out of steam around October. With your location you stand a much better chance especially if your kitchen window gets some direct sunlight on a regular basis.Note that the super capacitor is an automotive one of 500 Farad capacity.Note also that this simple circuit charges quickly when the capacitor is 'empty' but the charge rate slows down as you head towards the upper voltage limit.

    I have hacked single solar lights for parts and to modify but not a string. It seems to me that the circuitry is similar with the solar panel charging a 1.2V Ni/MH rechargeable cell which then powers the LED or LED string via a step up circuit. Voltage from the solar cell turns off the circuit during daylight. Two possibilities come to mind:1. Disconnect a string from the solar unit and try it on a well tempered Joule Thief. If the LED's are bright enough then simply run each string from its own Joule Thief and power them all from the super capacitor.2. Take out the Ni/MH cell from a unit and feed power in to this point from an external source. Although the step up circuit normally runs on a steady 1.2 Volts it would be interesting to know if the circuit will run, say, from 1.5 Volts ...

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    I have hacked single solar lights for parts and to modify but not a string. It seems to me that the circuitry is similar with the solar panel charging a 1.2V Ni/MH rechargeable cell which then powers the LED or LED string via a step up circuit. Voltage from the solar cell turns off the circuit during daylight. Two possibilities come to mind:1. Disconnect a string from the solar unit and try it on a well tempered Joule Thief. If the LED's are bright enough then simply run each string from its own Joule Thief and power them all from the super capacitor.2. Take out the Ni/MH cell from a unit and feed power in to this point from an external source. Although the step up circuit normally runs on a steady 1.2 Volts it would be interesting to know if the circuit will run, say, from 1.5 Volts down to 0.8 Volts. If it does then feed in power from your super capacitor to a number of units in parallel.Regarding option 1 the simple Joule Thief does not have the facility for switching off during daylight but I have found a very cheap and simple way to do it and this is to be the subject of my next Instructable.Thanks for possibly stimulating some ideas!

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  • How to Run a Battery Clock on Solar Power

    One great thing about capacitors is that you can put them in parallel by the boxful if you want!I suspect that the best approach will be to put two 500 Farad super capacitors in series to produce a 5.5 Volt 250 Farad unit and then put numbers of these units in parallel.There are cheap efficient step up voltage converters that would enable you to extract the powerefficiently as the capacitor voltage drops from 5 to 2 Volts.You can place the solar cell in a remote position and the lead length could be large since the current levels are relatively modest.I have had some success just simply propping the cell up against a favourable window pane inside the house.

    Thanks for your interest (and to everyone else who has commented.)Yes and a good point although I do rather like to see the second hand going round--it shows that the clock is still going :-) In the case of a radio controlled clock I would see it as important to have the second hand since a selling point of the device is that it really is accurate to the second.Interesting though and I will do some measurements as it could help bring the ability to run a solar powered clock into the dimmer regions of the the modern house.

    This is true but it does take you out of the realm of what you already have in the junk box or can get through simple eBay suppliers and up to professional suppliers like, (in the UK,) RS and Farnell with associated minimum order sizes. There must surely be a vast potential in super capacitors and efficient ways of using them as in what you suggest will be very important.

    That's a good idea. Taking into account the inherent drop of 0.6 Volt in the regulator then the supercapacitor would give useful power as it drops from 2.5 to 1.6 Volt whereas with what I have done we use the power of the super capacitor from 1.5 down to just over a Volt. This at the price of a slight extra complication.From my previous work I know that what I have done works at my latitude all the year round with a super capacitor of 50 farad so 500 should enable it to work much farther north. Your idea could take it even farther north.

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  • An Improved Joule Thief--An Unruly Beast Tamed?

    Hello samtani2013 - Apologies for my late reply but I have had problems recently logging on to Instructables.1. You can never produce more output power than that supplied by the batteries--we must live our lives by basic physical laws :-) I think that the spiky waveform produced by this circuit makes current measurement extremely difficult and this is where false hopes are generated. Proper measurement of the efficiency of a Joule Thief circuit is therefore vital for serious experimentation and this is the way that I do it.Make sure that the power input is well decoupled using a high value electrolytic capacitor e.g. 1000 microfarad connected between the supply rail and ground. This will ensure that the supply current and voltage can be properly measured and then the power into the ci...

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    Hello samtani2013 - Apologies for my late reply but I have had problems recently logging on to Instructables.1. You can never produce more output power than that supplied by the batteries--we must live our lives by basic physical laws :-) I think that the spiky waveform produced by this circuit makes current measurement extremely difficult and this is where false hopes are generated. Proper measurement of the efficiency of a Joule Thief circuit is therefore vital for serious experimentation and this is the way that I do it.Make sure that the power input is well decoupled using a high value electrolytic capacitor e.g. 1000 microfarad connected between the supply rail and ground. This will ensure that the supply current and voltage can be properly measured and then the power into the circuit is given by:Supply voltage multiplied by supply current (V * I)To calculate the output power I place a 10 microfarad electrolytic capacitor in parallel with a 10 Ohm resistor between the LED and ground and then measure the voltage developed across the resistor/capacitor combination. You will need a quality digital voltmeter to do this as a 1 milliamp LED current will generate only 10 millivolts across 10 Ohms. Hence you will see that the output LED current is given by :Voltage across the 10 Ohm resistor multipled by 10 (the value of the resistor)To calculate the output power in the case of this 1 milliamp: we know that the voltage across a working white LED is 2.5 Volts, (you may like to measure it accurately and separately with a power supply and resistor in series,) and then the LED power is 2.5 X 0.001 = 2.5 milliWatt.The circuit efficiency is given by (LED power / power in) times 100.In practice I am finding that a well tempered Joule Thief can have an efficiency of 50 to 70% with a supply battery voltage of over 1 Volt but this efficiency drops away as the supply voltage drops down even though the circuit is still producing light.2. Mains transformers can be used to make transistor inverters but they are not designed for this duty and the efficiency will not be very high especially with a small transformer.

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  • How to Give a Wall Clock Luminous Hands and Time Interval Markers

    Thanks for your interest.The key here is how long does it glow and will it glow all night?I think that the products based on zinc sulphide without radioisotope activation will not and I think many products fall into this category. They are very impressive to start with especially if you expose them to a bright light but fail to deliver after an hour or so.Read the reviews from those who have purchased the luminous alarm clocks that are widely and cheaply available and you will detect an underlying theme of disappointment with the luminosity.The green variety of rare earth doped strontium aluminate really does glow all night after activation and perhaps it is the coarse nature of the product that stops its wider application--fundamentally it is not based on expensive materials.Regarding...

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    Thanks for your interest.The key here is how long does it glow and will it glow all night?I think that the products based on zinc sulphide without radioisotope activation will not and I think many products fall into this category. They are very impressive to start with especially if you expose them to a bright light but fail to deliver after an hour or so.Read the reviews from those who have purchased the luminous alarm clocks that are widely and cheaply available and you will detect an underlying theme of disappointment with the luminosity.The green variety of rare earth doped strontium aluminate really does glow all night after activation and perhaps it is the coarse nature of the product that stops its wider application--fundamentally it is not based on expensive materials.Regarding your point regarding duct tape I see that clear duct tape is available although I have never used it. As a suggestion it might be an idea to lay some out on a surface from which it can be peeled and then carefully spread some 'glow in the dark' powder in the central area. Then place another tape layer on top sealing your powder in. You can now peel off your combined product sandwich and deploy elsewhere.

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    • How to Give a Wall Clock Luminous Hands and Time Interval Markers
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  • How to Run a Battery Electric Clock on Solar Power--Part II

    Thanks for your interest. I don't think that there will be problems in the latitude of South Florida--plenty of sun!The radio controlled clock here is still where it was placed in March 2016 and has run faultlessly ever since. Importantly, it has coped with the 'spring forward/fall back' adjustment where the clock has to have the power to wind back eleven hours in October. The clock can stay there now and it should carry on running so long as there is a long wave radio signal and daylight!Even now, there may be ways of deploying the solar cells in a more efficient way and thus cope with poor light levels or maybe take advantage of artificial light. If I come up with anything I will tag it on to this article.

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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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