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Solar Charging Night Light not working

Started by Alberto May 25, 2020
Hi all,

I am trying to implement a very simple solar charged night garden light.
Schematics is here: https://www.jameco.com/Jameco/workshop/JamecoFavorites/solarled.html
Basically a solar panel charges a battery. When the solar panel output is low (at night), a joule thief circuit lights a led.

The joule thief part works just fine, the problem is that the dark detector (2n3906 + 4.7K resistor) never triggers the joule thief and I cannot understand why.

Here are the pictures of the breadboard:
https://ibb.co/khNBjft
https://ibb.co/SKsSMxJ

If I bypass the dark detector connecting the positive wire from the battery to the center of the transformer (moving the yellow wire from row 16 to raw 14) the led lights up. 

Thanks a lot for your time.
On 26/05/2020 4:50 am, Alberto wrote:
> Hi all, > > I am trying to implement a very simple solar charged night garden light. > Schematics is here: https://www.jameco.com/Jameco/workshop/JamecoFavorites/solarled.html > Basically a solar panel charges a battery. When the solar panel output is low (at night), a joule thief circuit lights a led. > > The joule thief part works just fine, the problem is that the dark detector (2n3906 + 4.7K resistor) never triggers the joule thief and I cannot understand why. > > Here are the pictures of the breadboard: > https://ibb.co/khNBjft > https://ibb.co/SKsSMxJ > > If I bypass the dark detector connecting the positive wire from the battery to the center of the transformer (moving the yellow wire from row 16 to raw 14) the led lights up. > > Thanks a lot for your time. >
It would seem to me that the 5K resistor is not going low enough when the solar panel is covered. Try covering or disconnecting the panel and putting the 5k resistor to battery neg ( the end that was connected to the diode). That should enrgise the led, if not test the transistor.
Hi, thanks for your reply.
I tried without the panel connected and covering it with black tape, nothing happened. 
I did not try connecting the 5k resistor to the battery negative as I cannot do it now, but I will give it a try in the next week and I will update you.

Thank you very much!
On Tue, 26 May 2020 00:56:56 -0700 (PDT), alberto.m.scattolo@gmail.com
wrote:

>Hi, thanks for your reply. >I tried without the panel connected and covering it with black tape, nothing happened. >I did not try connecting the 5k resistor to the battery negative as I cannot do it now, but I will give it a try in the next week and I will update you. > >Thank you very much!
When you say the blocking oscillator works are you saying the light works as long as the battery is charged, and the cell has full sunlight on it? So the light stays on all the time and doesn't turn off when there is light on the cell? It would be better to think of it as a light detector that stops the oscillator while the cell has light on it. (the "famous" joule thief, is ancient technology from the days of vacuum toobes) https://en.wikipedia.org/wiki/Blocking_oscillator
On Tuesday, May 26, 2020 at 2:36:40 PM UTC+2, default wrote:
> When you say the blocking oscillator works are you saying the light > works as long as the battery is charged, and the cell has full > sunlight on it? So the light stays on all the time and doesn't turn > off when there is light on the cell? >=20 > It would be better to think of it as a light detector that stops the > oscillator while the cell has light on it. >=20 > (the "famous" joule thief, is ancient technology from the days of > vacuum toobes) > https://en.wikipedia.org/wiki/Blocking_oscillator
Hi! When I say "The joule thief part works just fine" I mean that, with a charg= ed 1.2 AA battery, and bypassing the light detector, a 5mm blue led lights = up very bright. So, the oscillator works, otherwise the led would not switc= h on at all. "Bypassing the light detector" means that I connect the battery positive to= the center of the transformer directly, without going through the first tr= ansistor so that the transformer is always powered by the battery as far as= it is charged. This works with or without the solar panel, with or without= light on it. I am interested in making the light detector work, to switch on the light o= nly when meaningful and to maintain the battery charged. Eventually, I would also try to replace the battery with a capacitor but I = am not 100% sure this is a good idea. And I would like to know the frequenc= y of oscillation, I don't know if there is a practical way to calculate it,= I do not an oscilloscope.=20 Thanks link too!
On Tue, 26 May 2020 07:28:37 -0700 (PDT), alberto.m.scattolo@gmail.com
wrote:

>On Tuesday, May 26, 2020 at 2:36:40 PM UTC+2, default wrote: >> When you say the blocking oscillator works are you saying the light >> works as long as the battery is charged, and the cell has full >> sunlight on it? So the light stays on all the time and doesn't turn >> off when there is light on the cell? >> >> It would be better to think of it as a light detector that stops the >> oscillator while the cell has light on it. >> >> (the "famous" joule thief, is ancient technology from the days of >> vacuum toobes) >> https://en.wikipedia.org/wiki/Blocking_oscillator > > >Hi! > >When I say "The joule thief part works just fine" I mean that, with a charged 1.2 AA battery, and bypassing the light detector, a 5mm blue led lights up very bright. So, the oscillator works, otherwise the led would not switch on at all. >"Bypassing the light detector" means that I connect the battery positive to the center of the transformer directly, without going through the first transistor so that the transformer is always powered by the battery as far as it is charged. This works with or without the solar panel, with or without light on it. > >I am interested in making the light detector work, to switch on the light only when meaningful and to maintain the battery charged. > >Eventually, I would also try to replace the battery with a capacitor but I am not 100% sure this is a good idea. And I would like to know the frequency of oscillation, I don't know if there is a practical way to calculate it, I do not an oscilloscope. > >Thanks link too!
OK now I think I get it. It appears as if the solar panel is part of the bias circuit for the PNP transistor. Solar panels normally supply power when the sun shines, but when the sun is absent they turn into resistors and allow power to flow backwards. Which biases the PNP transistor "on" allowing power to go to the oscillator circuit etc.. The light presumably turns ON and all is happy with the world.... got it? If you were to use a panel that doesn't "leak" or has a built-in diode to prevent reverse flow, that circuit would not work. So what are you using for a solar cell? I'm assuming you are using the specified panel and your battery is two cells just like the schematic shows, the 1N914 diode has the right polarity, etc.. Right? Try connecting a 5-10K resistor between the base of the PNP to ground, that should get it conducting and turn the light on, and that will provide a clue to why it isn't working. (solar cell dark during the experiment) It must have a resistor to protect the base from drawing too much current and killing the PNP transistor. The idea is to provide a leakage path that may be lacking in your solar cell.
On 2020-05-26, alberto.m.scattolo@gmail.com <alberto.m.scattolo@gmail.com> wrote:
> On Tuesday, May 26, 2020 at 2:36:40 PM UTC+2, default wrote: >> When you say the blocking oscillator works are you saying the light >> works as long as the battery is charged, and the cell has full >> sunlight on it? So the light stays on all the time and doesn't turn >> off when there is light on the cell? >> >> It would be better to think of it as a light detector that stops the >> oscillator while the cell has light on it. >> >> (the "famous" joule thief, is ancient technology from the days of >> vacuum toobes) >> https://en.wikipedia.org/wiki/Blocking_oscillator > > > Hi! > > When I say "The joule thief part works just fine" I mean that, with a charged 1.2 AA battery, and bypassing the light detector, a 5mm blue led lights up very bright. So, the oscillator works, otherwise the led would not switch on at all. > "Bypassing the light detector" means that I connect the battery positive to the center of the transformer directly, without going through the first transistor so that the transformer is always powered by the battery as far as it is charged. This works with or without the solar panel, with or without light on it. > > I am interested in making the light detector work, to switch on the light only when meaningful and to maintain the battery charged. > > Eventually, I would also try to replace the battery with a capacitor but I am not 100% sure this is a good idea. And I would like to know the frequency of oscillation, I don't know if there is a practical way to calculate it, I do not an oscilloscope. > > Thanks link too!
Switching the main current to the Joule Theif is probably the wrong approach, switch the current to the base instead, that is only switch the current that flows through the transformer branch that goes to the base. this is a much smaller current, and so it takes less energy to run the switch. (you can use a smaller base current to the switch) A second problem is that the joule thief may not start automatically when power is gradually applied. Some sort of positive feedback to ensure that the power snaps on should help there. -- Jasen.
On Thu, 28 May 2020 10:13:52 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

>On 2020-05-26, alberto.m.scattolo@gmail.com <alberto.m.scattolo@gmail.com> wrote: >> On Tuesday, May 26, 2020 at 2:36:40 PM UTC+2, default wrote: >>> When you say the blocking oscillator works are you saying the light >>> works as long as the battery is charged, and the cell has full >>> sunlight on it? So the light stays on all the time and doesn't turn >>> off when there is light on the cell? >>> >>> It would be better to think of it as a light detector that stops the >>> oscillator while the cell has light on it. >>> >>> (the "famous" joule thief, is ancient technology from the days of >>> vacuum toobes) >>> https://en.wikipedia.org/wiki/Blocking_oscillator >> >> >> Hi! >> >> When I say "The joule thief part works just fine" I mean that, with a charged 1.2 AA battery, and bypassing the light detector, a 5mm blue led lights up very bright. So, the oscillator works, otherwise the led would not switch on at all. >> "Bypassing the light detector" means that I connect the battery positive to the center of the transformer directly, without going through the first transistor so that the transformer is always powered by the battery as far as it is charged. This works with or without the solar panel, with or without light on it. >> >> I am interested in making the light detector work, to switch on the light only when meaningful and to maintain the battery charged. >> >> Eventually, I would also try to replace the battery with a capacitor but I am not 100% sure this is a good idea. And I would like to know the frequency of oscillation, I don't know if there is a practical way to calculate it, I do not an oscilloscope. >> >> Thanks link too! > >Switching the main current to the Joule Theif is probably the wrong >approach, switch the current to the base instead, that is only switch >the current that flows through the transformer branch that goes to the >base. this is a much smaller current, and so it takes less energy to >run the switch. (you can use a smaller base current to the switch) > >A second problem is that the joule thief may not start automatically >when power is gradually applied. Some sort of positive feedback to >ensure that the power snaps on should help there.
How do you plan to switch only the base of the oscillator transistor? https://www.jameco.com/Jameco/workshop/JamecoFavorites/solarled.html
On 2020-05-28, default <default@defaulter.net> wrote:
> On Thu, 28 May 2020 10:13:52 -0000 (UTC), Jasen Betts ><jasen@xnet.co.nz> wrote: > >>On 2020-05-26, alberto.m.scattolo@gmail.com <alberto.m.scattolo@gmail.com> wrote: >>> On Tuesday, May 26, 2020 at 2:36:40 PM UTC+2, default wrote: >>>> When you say the blocking oscillator works are you saying the light >>>> works as long as the battery is charged, and the cell has full >>>> sunlight on it? So the light stays on all the time and doesn't turn >>>> off when there is light on the cell? >>>> >>>> It would be better to think of it as a light detector that stops the >>>> oscillator while the cell has light on it. >>>> >>>> (the "famous" joule thief, is ancient technology from the days of >>>> vacuum toobes) >>>> https://en.wikipedia.org/wiki/Blocking_oscillator >>> >>> >>> Hi! >>> >>> When I say "The joule thief part works just fine" I mean that, with a charged 1.2 AA battery, and bypassing the light detector, a 5mm blue led lights up very bright. So, the oscillator works, otherwise the led would not switch on at all. >>> "Bypassing the light detector" means that I connect the battery positive to the center of the transformer directly, without going through the first transistor so that the transformer is always powered by the battery as far as it is charged. This works with or without the solar panel, with or without light on it. >>> >>> I am interested in making the light detector work, to switch on the light only when meaningful and to maintain the battery charged. >>> >>> Eventually, I would also try to replace the battery with a capacitor but I am not 100% sure this is a good idea. And I would like to know the frequency of oscillation, I don't know if there is a practical way to calculate it, I do not an oscilloscope. >>> >>> Thanks link too! >> >>Switching the main current to the Joule Theif is probably the wrong >>approach, switch the current to the base instead, that is only switch >>the current that flows through the transformer branch that goes to the >>base. this is a much smaller current, and so it takes less energy to >>run the switch. (you can use a smaller base current to the switch) >> >>A second problem is that the joule thief may not start automatically >>when power is gradually applied. Some sort of positive feedback to >>ensure that the power snaps on should help there. > > How do you plan to switch only the base of the oscillator transistor?
> https://www.jameco.com/Jameco/workshop/JamecoFavorites/solarled.html
the transformer has two windings, connect the other one to the supply. -- Jasen.
On Thu, 28 May 2020 19:29:11 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

>On 2020-05-28, default <default@defaulter.net> wrote: >> On Thu, 28 May 2020 10:13:52 -0000 (UTC), Jasen Betts >><jasen@xnet.co.nz> wrote: >> >>>On 2020-05-26, alberto.m.scattolo@gmail.com <alberto.m.scattolo@gmail.com> wrote: >>>> On Tuesday, May 26, 2020 at 2:36:40 PM UTC+2, default wrote: >>>>> When you say the blocking oscillator works are you saying the light >>>>> works as long as the battery is charged, and the cell has full >>>>> sunlight on it? So the light stays on all the time and doesn't turn >>>>> off when there is light on the cell? >>>>> >>>>> It would be better to think of it as a light detector that stops the >>>>> oscillator while the cell has light on it. >>>>> >>>>> (the "famous" joule thief, is ancient technology from the days of >>>>> vacuum toobes) >>>>> https://en.wikipedia.org/wiki/Blocking_oscillator >>>> >>>> >>>> Hi! >>>> >>>> When I say "The joule thief part works just fine" I mean that, with a charged 1.2 AA battery, and bypassing the light detector, a 5mm blue led lights up very bright. So, the oscillator works, otherwise the led would not switch on at all. >>>> "Bypassing the light detector" means that I connect the battery positive to the center of the transformer directly, without going through the first transistor so that the transformer is always powered by the battery as far as it is charged. This works with or without the solar panel, with or without light on it. >>>> >>>> I am interested in making the light detector work, to switch on the light only when meaningful and to maintain the battery charged. >>>> >>>> Eventually, I would also try to replace the battery with a capacitor but I am not 100% sure this is a good idea. And I would like to know the frequency of oscillation, I don't know if there is a practical way to calculate it, I do not an oscilloscope. >>>> >>>> Thanks link too! >>> >>>Switching the main current to the Joule Theif is probably the wrong >>>approach, switch the current to the base instead, that is only switch >>>the current that flows through the transformer branch that goes to the >>>base. this is a much smaller current, and so it takes less energy to >>>run the switch. (you can use a smaller base current to the switch) >>> >>>A second problem is that the joule thief may not start automatically >>>when power is gradually applied. Some sort of positive feedback to >>>ensure that the power snaps on should help there. >> >> How do you plan to switch only the base of the oscillator transistor? > >> https://www.jameco.com/Jameco/workshop/JamecoFavorites/solarled.html > >the transformer has two windings, connect the other one to the supply.
The windiings have the turn on bias a well as the inductive feedback and turn-off riding on them. The center-tap is integral to the operation.. There should be a way to do it: pass the AC feedback while isolating the DC bias, but it is a little more complicated than separating the center tap and it would take a few more components.