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Solar Charging Night Light not working...

A

Alberto

Guest
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.
 
R

RheillyPhoull

Guest
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.
 
R

RheillyPhoull

Guest
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.
 
S

server

Guest
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!
 
S

server

Guest
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!
 
D

default

Guest
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
 
R

RheillyPhoull

Guest
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.
 
S

server

Guest
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!
 
S

server

Guest
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!
 
D

default

Guest
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
 
D

default

Guest
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.
 
D

default

Guest
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.
 
J

Jasen Betts

Guest
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.
 
J

Jasen Betts

Guest
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.
 
D

default

Guest
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
 
D

default

Guest
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
 
J

Jasen Betts

Guest
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.
 
J

Jasen Betts

Guest
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.
 
D

default

Guest
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.
 
D

default

Guest
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.
 
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