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solar cell how to measure output current

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Guest

Mon Oct 22, 2018 1:45 am   



Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

George Herold
Guest

Mon Oct 22, 2018 2:45 pm   



On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Quote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.


Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.

default
Guest

Mon Oct 22, 2018 4:45 pm   



On Sun, 21 Oct 2018 16:50:20 -0700 (PDT), sebastiasebas_at_gmail.com
wrote:

Quote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.


Use a voltage comparator - basically an op-amp with an open-collector
output for driving a little bit more current.

The 18-21 volts could be easily discriminated (down to a few
millivolts) but you'd need something like a precisian reference that
doesn't fluctuate with the panel's voltage output. That could be as
simple as a zener diode or just use a 3 terminal regulator to power
the indicator circuit and reference against a voltage divider.

(bearing in mind that if you have a 5 volt regulator, for instance,
the comparator may be destroyed if you try to plug 18 volts into one
of the comparator inputs, the voltage divider takes care of that but
another diode to clamp the voltage at a safe level would also be nice)

George Herold
Guest

Tue Oct 23, 2018 12:45 am   



On Monday, October 22, 2018 at 9:44:54 AM UTC-4, George Herold wrote:
Quote:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.


If your'e getting power from it, then measure I-V
along the 'diode' curve... modulate something a little bit.

George H.
(are solar panels at all close to 'ideal diodes'?)

Sebastia RodaMon
Guest

Tue Oct 23, 2018 9:45 am   



El dilluns, 22 octubre de 2018 16:48:23 UTC+2, default va escriure:
Quote:
On Sun, 21 Oct 2018 16:50:20 -0700 (PDT), sebastiasebas_at_gmail.com
wrote:

Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Use a voltage comparator - basically an op-amp with an open-collector
output for driving a little bit more current.

The 18-21 volts could be easily discriminated (down to a few
millivolts) but you'd need something like a precisian reference that
doesn't fluctuate with the panel's voltage output. That could be as
simple as a zener diode or just use a 3 terminal regulator to power
the indicator circuit and reference against a voltage divider.

(bearing in mind that if you have a 5 volt regulator, for instance,
the comparator may be destroyed if you try to plug 18 volts into one
of the comparator inputs, the voltage divider takes care of that but
another diode to clamp the voltage at a safe level would also be nice)


mr Default : there must NOT be a 5 Vcc regulator : the circuit has to get voltage from the solar cell, which is the only power available on site.

Thanks. Ceba.

Sebastia RodaMon
Guest

Tue Oct 23, 2018 9:45 am   



El dimarts, 23 octubre de 2018 1:35:47 UTC+2, George Herold va escriure:
Quote:
On Monday, October 22, 2018 at 9:44:54 AM UTC-4, George Herold wrote:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.

If your'e getting power from it, then measure I-V
along the 'diode' curve... modulate something a little bit.

George H.
(are solar panels at all close to 'ideal diodes'?)


mr George : the solar cell is not a "working" one,
but a small one (30 cm x 30 cm, max 10 W) to be used as "monitor" of sun light.

Anyway, of course I want to measure I/V along the diode curve.

My problem is I know no circuit to do that.

Thanks. Ceba.

George Herold
Guest

Tue Oct 23, 2018 3:45 pm   



On Tuesday, October 23, 2018 at 4:03:05 AM UTC-4, Sebastia RodaMon wrote:
Quote:
El dimarts, 23 octubre de 2018 1:35:47 UTC+2, George Herold va escriure:
On Monday, October 22, 2018 at 9:44:54 AM UTC-4, George Herold wrote:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.

If your'e getting power from it, then measure I-V
along the 'diode' curve... modulate something a little bit.

George H.
(are solar panels at all close to 'ideal diodes'?)

mr George : the solar cell is not a "working" one,
but a small one (30 cm x 30 cm, max 10 W) to be used as "monitor" of sun light.

Anyway, of course I want to measure I/V along the diode curve.

My problem is I know no circuit to do that.

Thanks. Ceba.


30 cm x 30 cm is pretty big compared to things I use.
But still measure Voltage OC or current SC... Or along the way
Assuming you have a few millamps to power things you could make
an opamp-Fet-R current sink and measure the voltage as a function
of current. 10W you'd need a heat sink. How about a smaller solar cell?

George H.

default
Guest

Tue Oct 23, 2018 4:26 pm   



On Tue, 23 Oct 2018 00:59:54 -0700 (PDT), Sebastia RodaMon
<sebastiasebas_at_gmail.com> wrote:

Quote:
El dilluns, 22 octubre de 2018 16:48:23 UTC+2, default va escriure:
On Sun, 21 Oct 2018 16:50:20 -0700 (PDT), sebastiasebas_at_gmail.com
wrote:

Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Use a voltage comparator - basically an op-amp with an open-collector
output for driving a little bit more current.

The 18-21 volts could be easily discriminated (down to a few
millivolts) but you'd need something like a precisian reference that
doesn't fluctuate with the panel's voltage output. That could be as
simple as a zener diode or just use a 3 terminal regulator to power
the indicator circuit and reference against a voltage divider.

(bearing in mind that if you have a 5 volt regulator, for instance,
the comparator may be destroyed if you try to plug 18 volts into one
of the comparator inputs, the voltage divider takes care of that but
another diode to clamp the voltage at a safe level would also be nice)

mr Default : there must NOT be a 5 Vcc regulator : the circuit has to get voltage from the solar cell, which is the only power available on site.

Thanks. Ceba.


The five volt regulator would work off the 18+ the solar array puts
out. You can also shop around for one that uses miniscule amounts of
standby current. An ordinary 7805 eats something like 3 milliamps,
but they make others that go into the low microamp ranges too.

Or a zener diode to provide the reference voltage for the comparator,
and operate the comparator on unregulated power.

Sebastia RodaMon
Guest

Thu Oct 25, 2018 1:45 pm   



mr George : can you clarify a bit ?

1) open circuit voltage is ? ... the measure of voltage without any load on the cell ?

2) short circuit current is ? ... the measure of intensity with only the Fluke, so R = 0 ?

Case (2) is not dangerous for the cell ??

Thanks.

Sebastia RodaMon
Guest

Thu Oct 25, 2018 2:45 pm   



El dilluns, 22 octubre de 2018 15:44:54 UTC+2, George Herold va escriure:
Quote:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.


Ok, mr George : I did the test.
At a given moment, with a given sun, I read
Voc = 4,2 volts, Isc = 107 mA.

Whay now ?
Thanks for your patience ... Ceba.

George Herold
Guest

Thu Oct 25, 2018 4:45 pm   



On Thursday, October 25, 2018 at 8:51:48 AM UTC-4, Sebastia RodaMon wrote:
Quote:
El dilluns, 22 octubre de 2018 15:44:54 UTC+2, George Herold va escriure:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.


Ok, mr George : I did the test.
At a given moment, with a given sun, I read
Voc = 4,2 volts, Isc = 107 mA.

Whay now ?
Thanks for your patience ... Ceba.


Just George.. no Mr. please..it just makes me feel old.

So for a photodiode I made the following setup on my bench.
Adjustable light, photodiode, measure I and V.
See pics here.
https://www.dropbox.com/sh/a4nn4682xwtkjsq/AACk-wWtsOA4ynm8c1qb6SFua?dl=0

Data,
I(uA) V(mV)
15 275
150 349
1590 440
3700 490

The last was with the incandescent light right above the PD.
I went back to repeat the lower current numbers.. and V_oc was
smaller. I then remembered that the open circuit voltage depends on
temperature.. so that's not going to be the best thing for you
to measure.

Anyway the SC current will tell you how much sunlight is
hitting your cell.

George H.

Sebastia RodaMon
Guest

Thu Oct 25, 2018 4:45 pm   



El dijous, 25 octubre de 2018 17:10:52 UTC+2, George Herold va escriure:
Quote:
On Thursday, October 25, 2018 at 8:51:48 AM UTC-4, Sebastia RodaMon wrote:
El dilluns, 22 octubre de 2018 15:44:54 UTC+2, George Herold va escriure:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.


Ok, mr George : I did the test.
At a given moment, with a given sun, I read
Voc = 4,2 volts, Isc = 107 mA.

Whay now ?
Thanks for your patience ... Ceba.

Just George.. no Mr. please..it just makes me feel old.

So for a photodiode I made the following setup on my bench.
Adjustable light, photodiode, measure I and V.
See pics here.
https://www.dropbox.com/sh/a4nn4682xwtkjsq/AACk-wWtsOA4ynm8c1qb6SFua?dl=0

Data,
I(uA) V(mV)
15 275
150 349
1590 440
3700 490

The last was with the incandescent light right above the PD.
I went back to repeat the lower current numbers.. and V_oc was
smaller. I then remembered that the open circuit voltage depends on
temperature.. so that's not going to be the best thing for you
to measure.

Anyway the SC current will tell you how much sunlight is
hitting your cell.

George H.


Hi, George - I am 63, so no reason to feel ... old

I can mesure the SC current, but .. is it correct to have the cell always in Short Circuit ?

If if is is providing me 10 W ... lets say 15 volts ... it means 0,6 amperes.
Or 30 ohms.

George Herold
Guest

Thu Oct 25, 2018 8:45 pm   



On Thursday, October 25, 2018 at 11:33:19 AM UTC-4, Sebastia RodaMon wrote:
Quote:
El dijous, 25 octubre de 2018 17:10:52 UTC+2, George Herold va escriure:
On Thursday, October 25, 2018 at 8:51:48 AM UTC-4, Sebastia RodaMon wrote:
El dilluns, 22 octubre de 2018 15:44:54 UTC+2, George Herold va escriure:
On Sunday, October 21, 2018 at 7:50:24 PM UTC-4, Sebastia RodaMon wrote:
Hi - I got a brand new solar cell "Eco Line ES10M36".

In my garden, under full sun it provides 21 volts and 500 mA,
and under big shadow it gives 18 volts and 30 mA.

Load is a 24 volt bulb lamp in series with the Fluke.

As the voltage margin is small, I want to detect the intensity
to determine if there is sun or not.

What electronic circuit would you recommend to do it ?

If I place 2 resistors conected in serial,
the voltage drop will have the same small margin the cell has ...

Thanks.

Sounds like you have some circuit working already.
I don't know (big) solar cells. For little photodiodes and
things you can either measure the open circuit voltage
(V~log (Intensity)) or the short circuit current,
(I~ Intensity)

George h.


Ok, mr George : I did the test.
At a given moment, with a given sun, I read
Voc = 4,2 volts, Isc = 107 mA.

Whay now ?
Thanks for your patience ... Ceba.

Just George.. no Mr. please..it just makes me feel old.

So for a photodiode I made the following setup on my bench.
Adjustable light, photodiode, measure I and V.
See pics here.
https://www.dropbox.com/sh/a4nn4682xwtkjsq/AACk-wWtsOA4ynm8c1qb6SFua?dl=0

Data,
I(uA) V(mV)
15 275
150 349
1590 440
3700 490

The last was with the incandescent light right above the PD.
I went back to repeat the lower current numbers.. and V_oc was
smaller. I then remembered that the open circuit voltage depends on
temperature.. so that's not going to be the best thing for you
to measure.

Anyway the SC current will tell you how much sunlight is
hitting your cell.

George H.


Hi, George - I am 63, so no reason to feel ... old

I can mesure the SC current, but .. is it correct to have the cell always in Short Circuit ?

If if is is providing me 10 W ... lets say 15 volts ... it means 0,6 amperes.
Or 30 ohms.


Are you worried that the short circuit will damage the solar cell?
I don't think that is a problem. Just put a small value resistor across
it, (say 0.1 to 1 ohm.) to measure current. (0.1 if you think the max
current is an amp.)

George H.

+++ATH0
Guest

Sun Oct 28, 2018 8:45 pm   



On 2018-10-21 16:50, sebastiasebas_at_gmail.com wrote:
> What electronic circuit would you recommend to do it ?

Google for MPPT (Maximum Power Point Transfer). There are ICs that do
all this including DC-DC converter functionality so you can get whatever
power is available out at the voltage you need.

e.g.
https://www.analog.com/en/technical-articles/high-efficiency-solar-mppt-battery-charger-using-lt8611-and-ad5245.html

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