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absorb trickle voltage w/out proportional impact on voltage increase

Discussion in 'General Electronics Discussion' started by Bob39157, Oct 1, 2010.

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  1. Bob39157

    Bob39157

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    Oct 1, 2010
    My solar charge controller uses the current input from the solar panel to sense ambient light. When the sun goes down and the panel stops producing current, the controller switches on a light circuit. The problem is, the light is causing the solar panel to generate a small amount of current and the charge controller doesn't have a low current limit to the light switch. This causes the charge controller to think it's daytime and switch off the light. There is a reset delay so the system switches on and off every few minutes. Is there any way to absorb the trickle voltage before it gets to the charge controller without significantly impacting the battery charging current to the charge controller by the panels when the sun is up.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Place the light where it cannot illuminate the panel (or the panel where it cannot be illuminated by the light), or shade the panel from the light.
     
  3. Bob39157

    Bob39157

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    Oct 1, 2010
    Thanks Steve. Unfortunately, the process of shielding the panels from all sources of appreciable light at night is impractical for this application and can only be assured at night through trial and error. Some type of switch was suggested today at work, which would only allow current to pass through after achieving a critical point, which would be slightly more than is produced by non solar light exposure to the panels at night. The switch could be placed "in line" on the panel feed to the charge controller. The critical voltage blocked by the component must remain constant and cannot increase as panel current increases during the day or the system charge efficiency will be compromised. I don't mind a little voltage drop through the switch, but it can't be proportional to the load current. The idea sounds good in theory, but I don't know what to use as a switch.
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    HUH????

    you said it was a light , not lots of ambient light....
    so going on the info you originally gave.... Steve's response was totally valid

    Dave
     
  5. Bob39157

    Bob39157

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    Oct 1, 2010
    Daven,
    Yes, I said light generated from the system, then ambient night light because the solar panels are being affected by the LED powered by the battery system, but also by other light sources, such as parking lot lights and headlights. I understand that Steven's suggestion is valid, but still not practical. If I have to be on location at night to monitor for ambient light sources and also monitor the LED direction to prevent solar panel activation, the system becomes too labor intensive to be practical. It must be mobile and able to assemble in daylight without having to worry if it will work when the sun goes down. That being said, Does anyone know of a switch that would stay in the off position until the load current reached some low critical value, then would switch on to pass the current without too much resistance? Would a relay work? I'm not sure what the measure of the power being generated by night light contamination is, or whether it is more practical to measure voltage or amperage or current to control switch activation. I'm assuming amperes or current. I think voltage rises appreciably, even though there's little power being generated. Please assume the solution isn't with controlling the light source or panel location. I need a hardware solution.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you play about with the sensor which determines when it is dark enough, the likely side effect is that the lights will come on earlier (before it is dark) and stay on longer.

    Using the solar panel as a light sensor is going to save a few cents on an LDR but cause these problems is a way that's real hard to fix.
     
  7. Bob39157

    Bob39157

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    Oct 1, 2010
    Steve,
    The charge controller has the panel voltage sensor for light activation feature built in. It is not adjustable. An LDR would be redundant because I cannot disable the light activation feature built into the charge controller. The only way to circumvent the trigger is to stop current flow until actual daylight current generation overrides the trickle voltage blocking switch that I am looking for. I need a hardware solution. Is there such a component?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    your best option is to leave the charge controller to charge the battery and build a new light controller that will turn the lights on and off as desired, using (perhaps) an LDR with a shade that can be adjusted to point to open sky and nothing else.
     
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