I´m currently working on a project that is basically a solar tracker. It has two LDRs (one on the left and the other on the right of the servo) that read the amount of light comming from one direction. The idea is that the arduino reads the values on the LDRs and then turns left if the amount of light is greater than on the right and right if the amount of light comming from the right is greater than the one that comes from the left. In the end, it should be tracking the movement of the sun. And right now it is working well.
The next step of my project is to put a solar panel between the two LDR, so that the arduino could be powered by the solar panel, in order to make the arduino work where there is no PC or AC plug available.
But my questions are: I have a 5V panel, but I don´t know if it will provide the amount of power the arduino needs to work. And what kind of voltage the panel should output to make the arduino work? How do I install the panel, in order to make it power the microcontroller?
I´ve searched the forum but I haven´t found the answers to my questions. Can you help me with this?
It would be nice.
You have not given the specs for the panel. Nor have you indicated what Arduino model you plan to use.
THe arduino itself will not consume too much, perhaps 50 ma. The main power consumer will be the motor or motors turning the panel. How big is the panel, etc ?
In my opinion you should use a battery (charged by the solar panel) to even out the inevitable fluctuations in solar output. If the motors require a short term burst of power occasionally that can come from the batter and be replaced by the solar panel before the next burst of power is required. Actually I would size the battery so it could keep the thing working for a few hours (perhaps even overnight) on its own.
The battery will determine the solar panel minimum voltage. Unfortunately a 6v lead-acid battery would be too much for the 5v Arduino pin and too low for the power input socket. You could try some NiMh batteries to make up, say 4.8v (and many other variations), but lead-acid batteries are pretty much foolproof.
I´m sorry I didn´t reply to your advices but I didn´t have much time these days to work in the project.
I´m using an Arduino Uno board and as you know I´m trying to power the Arduino (it is working merely as a sun tracker; I do not want to create a kilowatt generator, at least not yet). My panel is about 13,5 cm by 8.5 cm and outputs about 5V (which is not stable, depends on the sun). But i searched and found out that the Arduino works well when powered by voltages between 7V and 12V. Therefore the panel won´t be able to power the Arduino. I guess i will use a battery. That way the panel would be used to charge the battery and then the battery would power the Arduino. It would also be able to charge during the day and power the Arduino by the night.
What about a NiMH 9,6V 800MAH AA battery? However, don´t you think that a lead-acid battery is too much? . Where can I find one lead-acid battery? I can just think about those found in the cars. But I still don´t know how to install the power source into the Arduino.
Thank you for all the help you´ve been gaving me. And sorry for not having replied lately.
PS: The 5V pin will be powering the motor, so I cannot use a 6V panel. Anyway I don´t want to buy another one.
The solar panel will power the Arduino directly. As the light level falls the Arduino will eventually stop but does that really matter? You can also run a regulated 3.3v Arduino from your 5v panel. See the 2nd vendor (and many others) for the 3.3v alternative.
A bigger issue is the motor to turn the panel. How much power does it need?
I would use a 6V sealed lead-acid battery (google for "6v SLA battery") and power the motor directly from that. If your Arduino does not already have a low dropout regulator on board (you can look up the part number), use an external 5V low dropout regulator. Note that when powering the Arduino from 6V, you need to apply power to the Vin pin and not the barrel jack, because the barrel jack has a series diode that drops around 0.7V.
Powering the motor from the Arduino 5V pin is not a good idea, because the 5V regulator in the Arduino is not designed to supply that amount of current.
You should regulate the solar cell output so that the battery voltage does not exceed the value specified by the manufacturer when the battery is on charge. You can use either a series or a shunt regulator for this.
About that, i´m using a simple stepper motor that is working fine, when plugged to the 5V pin. I thought I could use the 5V pin with a motor. Which pin should I use? Don´t worry I´ll use the Vin pin to power the Arduino using the 5V panel and a lead acid battery.
gamerblarg:
About that, i´m using a simple stepper motor that is working fine, when plugged to the 5V pin. I thought I could use the 5V pin with a motor. Which pin should I use? Don´t worry I´ll use the Vin pin to power the Arduino using the 5V panel and a lead acid battery.
Unless your stepper motor is a very small, low-current device, then it probably takes more current that you ought to draw from the 5V pin. If you use a 6V SLA battery as the power source, then I suggest you power the stepper direct from 6V. You can add small resistors in series with the stepper motor windings if you are worried about the extra 1V.
