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Solar Tracker Circuit Is Giving Me Issues - Appreciate Anyone's Help

Discussion in 'General Electronics Chat' started by rs14smith, Feb 7, 2010.

  1. Dragon Tamer

    Dragon Tamer Member

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    True the circuit has some underlying issues, it was just something I threw together in a hurry. The CdS can be replced with a photo transistor. I only used the 741 because it's cheap and easy to obtain. I had a 3rd circuit that I chose not to post (in other words, I couldn't find it). That circuit had major problems with stopping when the sun had passed (it couldn't see).

    I'm sorry, but I'm not that good with modifying an existing circuit unless I made it. Meaning that I'm just going to start from scratch and we can work on a solution.
     
  2. mneary

    mneary New Member

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    I don't intend to be unnecessarily judgmental, but the "issues" with the circuits you just threw together are the same issues (with more added) we have addressed, and solved, in the past 120 messages and nine pages.

    The circuit that Robert is currently breadboarding was not thrown together in a hurry.
     
  3. mneary

    mneary New Member

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    I hope you don't expect us to start over.
     
  4. dave

    Dave New Member

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  5. Dragon Tamer

    Dragon Tamer Member

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    Of coarse not, I'm going to start over. I'm going to make the exact same circuit you made. I can understand how it works better if I make the circuit myself.
    Although, I have to ask, what was the logic behind photocells instead of something like photo-diodes?
     
  6. mneary

    mneary New Member

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    Photocells are usually more sensitive to light than photo diodes, which some designers prefer. Photodiodes require a more sensitive circuit. Not a problem when we're dealing with sunlight.
     
  7. marktinkerman

    marktinkerman New Member

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  8. Dragon Tamer

    Dragon Tamer Member

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    I've been looking at the circuit and I'm afraid that I can't work in the return to east function without my own circuit. I may be able to use it in this circuit if someone will sum up the circuit for me. I don't get why you used 4 comparators instead of 2.

    If you don't mind I'm going to post my circuit of a solar tracker. It has a variable voltage on the motor so that as the sun moves, it will modify the voltage by either sinking or sourcing more current to the motor.
     
  9. Dragon Tamer

    Dragon Tamer Member

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    Here is the circuit that I have come up with, I tried to work out some of the design flaws, however there are likely to still be some more issues. I haven't had the chance to test it yet, I'm working on my own thread. If you find any issues, the just correct them as needed (by the way, this one has a return to east function built in).
     

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  10. rs14smith

    rs14smith Member

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    Is there anything more beginner-friendly that we can use to replace the BAT54, as I just got 20 of them in the mail today and was amazed at how small they were?

    What I did to allow me to use it on the breadboard is just solder wires to the 3 leads (only needed to do it for 2 leads), but that was a huge hassle because of the size of the BAT54S. Currently I've wired the entire circuit on the breadboard but I left out the BAT54S as I knew the circuit would still work without it, but it helps protect the motor, so that's just temporary, but so far the circuit works fine. I will be installing the BAT54S in the circuit in a moment to see how it does and get back with you, but it would still be great if we can find a larger component that gives the same effect the BAT54 gives so it's easier to work with.
     
    Last edited: Mar 17, 2010
  11. mneary

    mneary New Member

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    Although the 1N4148/1N914 isn't a Schottky, it should work in this circuit in place of the BAT54.
     
  12. rs14smith

    rs14smith Member

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    Great, and it appears RadioShack carries these (Silicon Switching Diodes (50-Pack) - RadioShack.com), so I'll just stop by there tomorrow sometime.

    I'm currently uploading a test/rough video of the current circuit without the BAT54.
     
  13. rs14smith

    rs14smith Member

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    Video Solar Test #1

    [video=vimeo;10249938]http://vimeo.com/10249938[/video]

    For a test run I decided to just use a 12v (rated at 6,9, and 12v) hobby motor, but it rotates so fast it's hard to film that the motor is actually turning left and right depending on where the lamp (light source) is. And since I didn't include the BAT54 I didn't want to take a chance messing up my $136 linear actuator lol!

    As far as the distance to place the photo transistors, they seem to do fine from the distance in the video, but I have seen other solar trackers have them even closer, so that's another idea to test. I checked with a voltage meter and I was receiving the correct voltages as well, so all looks well so far.

    I do plan on implementing a low power consuming LED somewhere just for the sake of knowing that the solar tracker is receiving power or not.
     
  14. mneary

    mneary New Member

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    It's always nice to see something working.

    No need to worry about the actuator. BAT54 is to protect the transistors, and is only needed if the comparators aren't hooked up right.
     
  15. rs14smith

    rs14smith Member

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    Okay I ran into an issue somewhere but at this moment it is totally unknown what is causing it.

    I purchased the diodes from RadioShack today, and placed it in the correct spot in the circuit and the "hobby motor" was rotating fine, both left and right, and the temp on the FETs were still doing fine as well.

    Later I hooked up my linear actuator, it was working decent for the first run through test, however, I did notice that on my variable power supply, as the left and right switching was occurring, the power supply had a slight short circuit effect happen to it. It didn't completely cut out the entire circuit's power, but there was a noticeable power loss for a split second as it was switching directions or polarities I should say.

    So afterwards I decided to swap the photo-transistors with the clear photo-transistors which are more sensitive to light than the tanned one's you see in the first video. So after using those for a few seconds, again the circuit worked fine, really, the circuit worked "better" with the clear photo-transistors.

    Anyway, soon I noticed I couldn't get the linear actuator to pull in it's stroke, it would only push out the stroke, or in other words, only 1 polarity would work. I then notice something smoking, which was my Q4 FET, and that was the only one to appear as to getting extremely hot whenever I shined the light source to the photo-transistor that activates that side of the H-Bridge (Q1 & Q4).

    So I tried re-checking my wiring, swapping the diode, as well as both FETs (Q1 & Q4), but still only 1 polarity works. So I'm still puzzled at the moment what exactly went wrong here, but as I stated before, while using the linear actuator you can really notice the polaritiy switch from the minor short circuit that seems to occur, something that I believe I didn't notice using the hobby motor. I'll have to run more test tomorrow though as it's getting late. Let me know if you guys think you know what exactly may be causing this issue or what I should re-check based on the info I gave, or if you need more info let me know.
     
    Last edited: Mar 18, 2010
  16. rs14smith

    rs14smith Member

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    Ok, so I found out it wasn't Q1 or Q4 that was bad, but Q2 that needed replacing, so I'm still yet to figure out what caused this, but I'm surely going to do a long drawn out test tomorrow with the hobby motor and the linear actuator by making it switch polarities for a good 4-5min non stop to see if the circuit breaks down again. Guess I need to go ahead and put in another order for some extra FETs :)

    At the moment, the circuit is working fine, and this is without the diode, but I'll be putting that back into the circuit later today when I do the long drawn out test since you said it is what protects the FETs and whatnot.
    I'm also still using the clear photo-transistors (i'll get the right name of those tomorrow lol) as well, which again are so much better.
     
  17. Dragon Tamer

    Dragon Tamer Member

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    I have an idea for your circuit, if you want a return to east function, tilt your photocells about 45 degrees away from each other, and your circuit will return to east in the morning once there is enough light for the circuit to work properly.

    You could also add a resistor to your compartor that senses the light for the east solar cell to make it think that it is lighter on that part of the circuit.

    If someone would please explain the schematic for me, then I can understand it and help you a little more.
     
  18. nickelflippr

    nickelflippr Member

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    rs14smith said:
    Unless the diode pulls the logic to ground, it can be a hindrance?, so something to check.

    I am just lighting up leds at the moment, but have previously seen both output leds on at the same time. Can't seem to duplicate it with current setup though.

    Random Notes:

    Accidentally smoked my only photo diode (needed two anyways), so have been playing with the ldr's** (photocells). Going this route, a voltage divider buffers the LM393 comparator input with the ldr and 10KΩ resistor topside and 50kΩ pot bottom side. The pot setting of approx. 30kΩ seems to be the best setting for sensitivity.

    Still being stubborn, and using 4081 AND logic. The comparator outputs are anded with the ldr/comparator inputs, so as to turn off at dark. It took a bit to understand what Mneary was talking about here. One problem is that one output seems to be stuck on prior extinguishing at dark. May have to introduce a low level limit here per official schematic, or let the limit switches do their thing on the signal transistors.

    Because of the ldr sensitivity, will most likely be using a #10 welding lens in full sunlight conditions. Electrical tape might work also.

    ** These smaller Radio Shack ldr's are real sensitive, with about 30Ω full light resistance, and upwards to 1MegΩ dark.
     
    Last edited: Mar 19, 2010
  19. rs14smith

    rs14smith Member

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    Well I performed a really rough test on the circuit yesterday using the diode and the hobby motor, and the circuit did well. Basically what I'm doing in these test is to see if I can break the circuit by doing things like switching the polarities extremely fast, leaving 1 polarity active for a long time etc.

    I planned on making another video with me doing that for record purposes, but was way to busy the other day. I'll have it done probably today sometime hopefully, as I still need to do the same test for the linear actuator.
     
  20. marktinkerman

    marktinkerman New Member

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    friend of mine suggested using 12v powered widow winder from car as actuator?? mark
     
  21. rs14smith

    rs14smith Member

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    Well what most people (DIYers) use for their solar trackers is some type of combination of 2 linear actuators to move the array of panels in a dual axis motion. However, there are many types of ways of constructing the solar tracker, but that seems to be what most use.

    A window winder could probably work as well. It's up to you, but if the circuit test can handle what I'm going to throw at it, most general motors should do fine.

    By the looks of things, I should have time to go ahead and perform these quick test now and video record it.
     
    Last edited: Mar 20, 2010

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