Solar guider

Thread Starter

rsfoto

Joined May 14, 2013
134
As usual after investigating I answer my questions by myself :D

I am going to work now on this circuit

http://solartracker.greenwatts.info/solar_tracker_LM339_schematic.htm

as I have a spare power source from a salvaged PC and there I have -12V, 0V and +12V. From former experimenting I know how to start this power sources.

After much thinking the inverted LED solution makes it possible to switch 2 outputs alternatively and simplifies my switching and when both LEDs are balanced I have no switching.

... and the sun is shining ... :rolleyes:

Let me see what comes out ...
 
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Thread Starter

rsfoto

Joined May 14, 2013
134
OK, I am a step further. Taking off both pot and replacing them by LED the comparator works great.

Changing the angle of the 2 LEDs there comes a moment where the Output goes High (opens) and the test LED does no shine. It is quite sensitive.

I think the exact orientation of the leds on the axis is going to be the key that this Sol guider works or not.

OK, now I have to move to the next step using 2 comparator for one axis.

Will keep you informed.
 

Thread Starter

rsfoto

Joined May 14, 2013
134
OK, another step forward but working only halfways :confused: as it does not what I fully expected.

Attached the schematic and my Breadboard set up.

OK, the problem is that instead of not letting the current thorugh when they should they both close and the LED are ON.

Also they do not react as I expect that means when the Sun is shining on one side of the active sensor LED the other LED is also aktiv.

In full Sun I get ~ 1.6V out of each green LED. Taking 2 sensor LED and conecting them parallel inverse I can see how moving them they go from -1.6V to +1.6V passing through 0V as it is described in this message by

Mike Mladejovsky, PhD EE

in this forum

http://www.electro-tech-online.com/renewable-energy/106625-simple-solar-tracking-circuit.html

Based on my positive experience of my single comparator circuit I thought I could use at both outputs a LED and see the switching action. It shows up but does not work as expected like shutting down when the conditions are given.

1. Sun shining on both sensor LEDs NO LED should be ON
2. Sun shining on one LED corresponding output should close eg. switch

It does it partially correct but when the turn is to switch off the LED on the side where the Sun shines it does not shut off.

I measured the current the sensor LEDs deliver and we are talking about less then 1μA. I especially went to buy a better multimeter in order to be able to measure that.

I am thinking what could the problem be but so far no clue.

Any hints to what is happening are welcome ...

Thanks

I did some reading about using LEDs as photo-detectors, and got motivated to try an experiment. I tried some moderately bright red LEDs that I have laying around, similar to these. They are in a water-clear T1 3/4 lens. I do not know their viewing angle; i'm guessing they are the 30 degree variety, because they were bought for indicators.

Shunting an unbiased LED with a 1megΩ resistor, under outdoor illumination on a sunny day, I get about +1.5V anode to cathode, using a Fluke 73 DMM (>10meg input impedance). The LED is directive, consistent with the "viewing angle" shown on the referenced data sheet.

I then connected two LEDs in parallel, which approximately doubled the output voltage, indicating that the current produced by the LED (into the 1megΩ resistor) also doubled. I then reversed one of the LEDs so that the pair is connected in inverse parallel with the 1megΩ resistor, and bent their leads so that their optical axes diverged by about 45 degrees.

The inverse-parallel 2 LED array produces +- 1400mV as the array is panned across the sun, with zero volts out when the optical axes of the two LEDs roughly bisects the angle formed by the two diverging LEDs. Seems like this could be used to drive a Sun Seeker, because the 2 LED array puts out a signal which goes from +1400mV to zero to -1400mV as the sun angle changes.

To construct a Sun Seeker using the inverse-connected two LED array, you may have to put a small baffle that splits the angle between the two LEDs, orthogonal to the sun's path. In the morning, when the array is parked looking at the wrong horizon, the baffle would cast a shadow onto the west LED, allowing the East LED to dominate to drive the seeker toward the East horizon. After the seeker locks on, the baffle would be edge-on to the sun, so the differential mode of the array would not be effected by the presence of the baffle.

Using this idea, I modified your circuit to include a deadband near the balance point, and made it so that the motor switching transistors use a Darlington connection to minimize power dissipation while the motor is running.

Attached is a schematic and a running LTSpice simulation. The Solar Flux is simulated using a current source, which produces a voltage across the LEDs similar to what I measured outside. I use two comparators to implement the deadband region near the balance point, so the motor is switched off cleanly once the seeker centers itself. The transistors dissipate less than 1/2W when switching 1A. Substituting a PFET and NFET for the transistors lowers the part count, if you have the FETs.
 

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Thread Starter

rsfoto

Joined May 14, 2013
134
One more thought about this ...

Could it be that it does not work as it should, as I am not feeding a negative voltage into the GND PIN of the LM339 ?

If that is the case I will hack a PC Powersource :D
 

Thread Starter

rsfoto

Joined May 14, 2013
134

Thread Starter

rsfoto

Joined May 14, 2013
134
Hi,

Still working on this project. Latest news is that I have now 2 axis and making sensitivity tests. See below the latest prototype. For each hole in the front I have 2 sensor LEDs at the end of the tube arranged in a 90° angle. Works nice just need to get a better change at a smaller angle. This is a question of designing parts in the CAD program, make them and test them.

regards Rainer
 

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wayneh

Joined Sep 9, 2010
17,496
Cool pictures. Looks like a nice location, by the way.

So what circuit are you using now?

This will make a nice entry for the "completed projects" section, when you're happy with the results.
 

Thread Starter

rsfoto

Joined May 14, 2013
134
Hi Wayneh,

Thanks. Below look at the circuit.

On the left side where you see CON East-West there I connect 2 LED cross connected eg. A1 to C2 and A2 to C1 and parallel to it a 1MΩ resistor and a 10nF capacitor as sensor assembly.

Now on the right side for the tests just imagine away the TLP521-2 and instead a little red test led one on Out1 adn 1 on Out2 and so I see when the sensor assembly is balanced or not. When both LEDs are off then it is balanced and the sun is shining in equal portions onto the 2 leds.

Now more work has to be invested in making a reasonable light trap.

Got it ?

Just added the LED sensor circuit
 

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Thread Starter

rsfoto

Joined May 14, 2013
134
Hi,

It is me again and my solar guider. Since 3 days I am stuck with how to make a electronic DPDT switch in order to change the polarity of 2 cables.

An equatorial mount needs in the morning a different input then in the afternoon and so I have to change the polarity of 2 wires only.

I have been reading since 4 days in the internet, here and everywhere about digital switches bust somehow I am banging my head on to a wall.

I have read a lot about the LM555 which seems to be a solution for my project but for gods sake I am just not able to fiddle out how to wire the circuit.

As far as I have read the LM555 has a TRIGGER and RESET input and I guess with these I could change and leave the polarity as long as I need it to be actuated.

I also see there 3 other Pins with DISCHARGE, THRESHOLD and CONTROL. I have no idea for what those are used.

Again of course I would drive optocouplers for this outputs because of ground loops :D I know I am neurotic about optocouplers and ground loops :eek:

I have also found some ICs like the 4016 or the AS17XX, BU4066BC, etc and still studying how to drive them.

I just want to use to push buttons for sending a signal.

Any tips are welcome.

Thanks in advance.
 
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wayneh

Joined Sep 9, 2010
17,496
The conventional way to reverse polarity to a motor is an H-bridge. Just look here for "h-bridge motor controller" and you'll find lots of examples.

If you don't mind throwing the switch manually, I'm sure someone here can show us how to wire a DPDT to accomplish the same thing. I thought you just put the load at the center pole and the power to the sides.
 

Thread Starter

rsfoto

Joined May 14, 2013
134
The conventional way to reverse polarity to a motor is an H-bridge. Just look here for "h-bridge motor controller" and you'll find lots of examples.

If you don't mind throwing the switch manually, I'm sure someone here can show us how to wire a DPDT to accomplish the same thing. I thought you just put the load at the center pole and the power to the sides.
Hi,

Thanks. The electronic area makes us lazier. I know how to wire a DPDT switch for polarity reversing but I would like to have a more fancy and elegant electronic solution and thought that by using an AM and a PM push button and with these, switch between morning and afternoon operation :D



I thought I could activate an output of the LM555 to work indefinitively until I push the other button to activate the other operation method.

Morning operation at start up and if it is afternoon pushbutton pressed short time and afternoon mode is active ¿? Now that I am writing this I think I just need one push button as I guess if I power down the LM555 then it resets for the next day ¿?

Will keep looking what is out there ...
 
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Thread Starter

rsfoto

Joined May 14, 2013
134
I think I solved my problem with using 2 push buttons, a LM555 and a DPDT relay.

The LM555 is going to be used in Bistable mode which activates or deactivates the coil of the DPDT relay.

The buttons will be on Trigger and Reset.

¿ What do you think ?
 

Thread Starter

rsfoto

Joined May 14, 2013
134
OK, a while later I have got this circuit.

The DPDT relay is 12V with a 720Ω coil that means it draws 17mA. I think the LM555N does support it.

On the right side the TDS-1202L as a DPDT switch inverting the polarity of the cables. As far as I see from the datesheet the PINS 6 and 11 are NC and if I energize the coil PINS 8 and 9 close (being in no energized state NO).

http://www.cika.com/soporte/Information/Varios/Relays/SunHold/TDS-1202L.pdf

¿ Where is the bug ?
 

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wayneh

Joined Sep 9, 2010
17,496
I'd add an LED to indicate which state the timer is in. And it probably doesn't matter but I think pin 5 should still have the capacitor in series to ground, for stability.

I've never used a 555 in this mode, and it wouldn't have occurred to me. But it look like a handy trick. Learn something every day.
 

Thread Starter

rsfoto

Joined May 14, 2013
134
Hi,

Well I found a few pages where they have this Bistable driving of the 555 so the idea of using the 555 did not mature on my manure :D. I was just reading like crazy everything I found about the 555.

In one there is no connection from PIN 6 to ground but as you say there is a tiny capacitor between PIN 5 and ground. There are several different layouts of this Bistable mode of the 555.

Also another one uses 2 diodes to protect the 555 from the eventuell spikes when shutting down a coil. One diode in serie with the coil and one reverse parallel to the coil. Maybe I will add those two diodes too.

There is a lot of info in the web but the most dificult thing is what I have learned so fdar doing this is how to put the search phrases to find one what wants.

Using the 555 in Bistable mode looks like to be too little (it is like transporting a cube of chicken broth with a 40 ton truck ) :D for the capacities for the 555 so there is not much mentioning about it, perhaps.

Will get some 555, DPDT relays and play with them to see their behaviour. Good idea about adding a little LED so I know if I am in AM or PM mode :)

I have seen that one LED can be used betweeen Out and +V (this is in reset mode) and the other can then then placed parallel to the coil for the other mode (eg, Set or triggered mode)

I am still astonished about what one can do with a bit of electricity and those 6, 8 or more legged bugs or even centipedes :eek:
 
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Thread Starter

rsfoto

Joined May 14, 2013
134
Another polarity switch using this circuit

http://forum.allaboutcircuits.com/showthread.php?t=40717

and, of course being a fanatic of optocouplers :D , I used 4 of them for making a DPDT switch.

INstead of using a 1μF Tantalum capacitor I used a 0.1μF and with a quick push on the toggle button it switches over.

Just breadboarded the above circuit and played with it. Now I will add 4x 4N25 with some load resistors and see what comes out of the optocouplers.

When applying power the red LED goes on first which I will use for AM modus (Telescope on the WEST side of the mount) and then with the toogle switch go to the green LED as PM modus (Telescope on the EAST side of the mount).

As I am not sirching more then 0.2mA coming from the Inputs for reversing polarity why use a huge DPDT realy with a coil.

So in total I have now 3 separate circuit blocks for my Solar guider.

The guider itself using an LM339, an automatic ON-OFF circuit using a LM393 in case of clouds and this one for changing AM-PM modus with the NE555N as Bistable Multivibrator.

Next step will be to get some hardware for the Sun ray projecting onto the sensor LEDS as accurate as possible and then solder the first prototype on a pre drilled plate. I hope to finish before August first because then I have one week time in the Observatory for making the real tests with a Sun imaging set up. :eek:

Thanks for reading and looking and if you find a bug please report and THANKS A LOT for the support I have got here :D
 

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wayneh

Joined Sep 9, 2010
17,496
Since you chose to use pushbuttons and a 555 instead of a simple switch, I'm wondering why you didn't go a step farther to eliminate the buttons altogether by incorporating a clock of some kind to push the buttons for you.
 
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