Solar cell sensor BPW34 for tracking device with stepper motor

Hey. I want to connect multiple small solar cells in a circular shaped array and place on a tripod and then have a stepper motor orient itself to the same position as the solar cell which is producing the most electricity at any given moment.

Since I’m still very new to Arduino I’m a bit unsure how to do this, but I found a candidate sensor use which is the “Miniature Solar Cell - BPW34“, but I’ve read people say about similar cells that they max out their current/voltage production very quickly so what I’m afraid of is that if I put an array of these in sunlight they will all produce the same amount of electricity and it won’t be possible to orient motors with them. Does anyone know if this is the case or should this strategy work with these sensors?

What I want is a nice gradual difference in the outputs of all the sensors. Preferably I would also like to log the output from each one so I can analyse exactly what happened afterwards.

Here is a link for the sensor I’m talking about:

Even if they max out, you can use the values of the sensors further around by looking for two that are close and chose the position mid way.

Weedpharma

You can reduce the field of view of the photodiode by putting it in a tube or a well. Depending on the depth of the tube/well, only one or a few will be illuminated at any one time.

It is much better to use the photodiode in reverse-bias mode, rather than "solar cell" mode, and monitor the current flow instead of the voltage. The current flow will be linearly proportional to light intensity over a large range.

weedpharma:
Even if they max out, you can use the values of the sensors further around by looking for two that are close and chose the position mid way.

Weedpharma

I’m not sure I understand, if several sensors max out then the best position should be in one of them, so why would I want to change position to a mid-value between a maxed out one and a not maxed out one?

jremington:
You can reduce the field of view of the photodiode by putting it in a tube or a well. Depending on the depth of the tube/well, only one or a few will be illuminated at any one time.

It is much better to use the photodiode in reverse-bias mode, rather than "solar cell" mode, and monitor the current flow instead of the voltage. The current flow will be linearly proportional to light intensity over a large range.

I’m afraid I cant have that. I need all the sensors to receive light and be able to monitor the differences between them. Do you think there is a real possibility of several of them maxing out and therefore it becomes impossible to get anything useful from them on a sunny day?

And I don’t know how to make reverse-bias mode happen, is it a matter of how it is connected? So it’s possible with the BPW34 I suggested?

Hi,
you only need two sensors, mount them on the PV array, the software then moves the array to get the light even in both sensors.
You don't need an array of sensors at different angles.

Tom.... :slight_smile:

Hi,
two sensors like attached image.

Tom… :slight_smile:

TomGeorge:
Hi,
you only need two sensors, mount them on the PV array, the software then moves the array to get the light even in both sensors.
You don't need an array of sensors at different angles.

Tom.... :slight_smile:

Yes, thank you I am aware of this method but it’s not what I’m after. I need to have the array so I can measure what’s going on with the irradiation at different angles.

petters:
I’m not sure I understand, if several sensors max out then the best position should be in one of them, so why would I want to change position to a mid-value between a maxed out one and a not maxed out one?

If several sensors max out they are obviously pointing at the light but you do not know which has the most light.

If you look either side +/- 1 then +/- 2 (of the maxed out block) until you find a pair that is not maxed out, you can deduce that the highest light is half way between. That is where you point.

Weedpharma

If the purpose of the solar cell sensor is simply to get direction (rather than produce useful energy) why not use an array of Light Dependent Resistors. I don’t think they will max-out. If it was my project I think I would LDRs for direction even if I did also need the solar cells.

…R

Robin2:
If the purpose of the solar cell sensor is simply to get direction (rather than produce useful energy) why not use an array of Light Dependent Resistors. I don't think they will max-out. If it was my project I think I would LDRs for direction even if I did also need the solar cells.

...R

I think resistors like that usually have a much narrower spectral sensitivity, I need my sensors to respond in the same way that a real full size PV-panel would. These can be made of different materials that behave differently ofc but from what I could see in the BPW34 datasheet it looks like it responds similarly to a normal silicone cell. My biggest worry is that it maxes out immediately and becomes useless.

Hi,
I assume this is an assignment project of some sort, and you need the off angle readings to prove the efficiency of the tracking system?

Tom...... :slight_smile:

TomGeorge:
Hi,
I assume this is an assignment project of some sort, and you need the off angle readings to prove the efficiency of the tracking system?

Tom...... :slight_smile:

No. I’m studying spectral effects on PV-panels in tracking situations and some of my simulations suggests that certain semiconductor materials prefers the wavelength distribution of sunlight that has reflected off a surface (grass, roof material etc.) compared to direct irradiation, so if I manage to build this it’s just to prove/disprove if there can ever be situations in real life where it’s better to have a higher tilt on the panel than what normal tracking methods usually have.

petters:
certain semiconductor materials prefers the wavelength distribution of sunlight

I imagine the important thing is the orientation that produces the most energy - regardless of the path it takes to get to the panel. That would probably require a separate MPPT device for each panel.

I wonder would the experiment be easier to manage using a single solar cell that is panned and tilted (relative to the sun) while measurements are taken?

...R

so if I manage to build this it's just to prove/disprove if there can ever be situations in real life where it's better to have a higher tilt on the panel than what normal tracking methods usually have

I'm surprised that this is even a question. Reflections from building windows have been well documented to inflict burns on people and melt the plastic on parked automobiles. Perfect place for PV panels!