Motor control for solar tracker

[Y.Y]

Hi,

I am an undergraduate student embarking on a project to build a solar tracker. What I have planned for the system right now is to use a pair LED's as a sensor(for one axis), and have the voltages from the sensor fed into the computer through an RS-232 + ADC. Here is where Labview comes into the picture. I plan to design a VI that can detect the voltage output from the sensors, detect the difference and finally have the VI capable of automatically controlling a stepper motor to move in the direction where a higher voltage reading is obtained.

I am totally new to LV, and will be starting everything from scratch. What I would like to enquire here is :

1. Is it possible for me to interface the input from the sensors without using any DAQ, just direct from the sensors through RS-232 to the software.

2. How and if possible some links with resources on designing a VI that will be able to sense this voltage, and automatically generate a response to control the motor.

3. I will be using a stepper motor( either from scrapped printers or if I am unable to find one, purchase one from the electronics stores),  so what do I need for the setup. 

 4. By using just a single RS-232 port, is it possible to first of all obtain input from the LED's and from the same RS-232 port control the stepper motor movement.

5. From what I understand, I need a driver circuit to control the stepper. So, what I should do is just obtain the suitable chip, wire it up with the rs-232, connect the stepper to the outputs of the chip, and from there leave the rest to Labview. Did I get it right, or did i miss something out?

Really appreciate any resources, guidance and advice. Thanks!  

[Napoleon_Buonaparte]

Hi,


1. If your sensor provides a serial interface, it can hook up to serial port and read data. However, I've not heard about that for light detector. You normally use LDR for a light detector and since ldr is a resistor, you must build a circuit to detect its resistance change which probably use voltage divider or op-amp circuit to give voltage output that can detect by DAQ. In conclusion, I recommend using LDR and some circuit with DAQ card to detect light change.

2. Please try http://zone.ni.com/devzone/cda/tut/p/id/7466 and http://zone.ni.com/devzone/cda/tut/p/id/3536.

3. Please see #5

4. Not possible.

5. There is stepper driver circuit interface with RS-232 available in market. You may try finding it from the internet.


Regards, Kate

[Buechsenschuetz]

I do not think that it is a very good idea to use a stepper motor cannibalized from a printer or one from a bargain store. It will be hard, if not impossible, to find precise data about such motors, i.e. stepping angle and current. There are several manufacturers making motor drivers (amplifiers) controlled by RS232, I think Intelligent Motion Systems Inc makes such devices (we use their drivers without RS232 interface). 

[Y.Y]

Hi Kate. Thanks for your reply. Well, actually from what I have found over the net, and also tried, LED's will put out a small voltage, around 1-1.5 volts under sunlight. Their structure is much like that of a solar panel ( a p-n junction), so the LED's give out light when voltage is supplied, and also work the other way around. I understand that there are some chips specially for the RS-232, that can convert an analog voltage to a digital input. So I will use that as my sensor. It eliminates the need for a separate circuit for the LDR.

For #4 , if I cant control the motor and also obtain the input from just the 1 single rs-232 port, what other options do I have for the interfacing? I would prefer not to use a DAQ card, since it is quite costly to purchase one, and it is also my goal to complete the project on as low a cost as possible.

For #3 and #5, is it possible to build the circuit myself?

________________________________________________________________________________________________________________________________________

So long as I can get a stepper motor with data sheet and proper specs, I should be good?

[Napoleon_Buonaparte]

Hi,


I don't know about an LED, but this is for sure is not specified in LED specification, and therefore, you've to try it on your own.

For #4, you definitely need analog input for voltage read, and I've no idea how could you achieve that without DAQ card.

For #3 and #5, it's possible, but you've to work a lot on your own, and another thing is that stepper drive interfacing with serial port normally provide a protocol to interface with PC, but if you build on your own, you've to study on your own a lot more on this.


Regards, Kate

[BMac]

I recently developed a sun tracking application for NI CompactRIO that includes a LabVIEW function for calculating the sun azimuth and elevation based on latitude/longitude and time. The 2-axis sun tracking control system application uses a Bushnell NorthStar 525 x 3" Reflector Telescope (around $200), modified with solar panels mounted instead of the telescope.Two NI 9505 motor drive modules are used to control the motors, and a special algorithm for LabVIEW FPGA is used to decode the sine-cosine sensor feedback signals for precise positioning. The Sun Angle Calculator VI is based on the "SunAngle for Palm" open source project by Greg Bell (v 1.5 2003/06/23). I also have some examples that draw sun charts, and plot/track the current sun position. The system could also be extended for mirror tracking (heliostat control, i.e. for "power tower" type solar thermal generators) with additional algorithms. We are in the process of publishing the LabVIEW code, documentation and assembly instructions online but feel free to email me (brian.maccleery@ni.com) if you would like a copy of the material.

[BMac]

 The CompactRIO sun tracking reference design example code is now available online. Follow the link below for an application note and to download the code and assembly instructions.

Solar Tracking Reference Design

[jacksons]

Hi

Can I have a look into your LABView program if you have build it please. I am doing a similiar project and need some help. I am new to it aswell. Thanks!