LED flashing circut at nighttime

Discussion in 'The Projects Forum' started by bushrat, Jun 7, 2016.

  1. bushrat

    Thread Starter Member

    Nov 29, 2014
    97
    22
    A co-worker asked me to build a flashing LED circuit that is powered by solar panel (to charge batteries) and batteries only at night. He asked for minimal parts.
    So far I build this prototype:
    flashing led circuit.jpg
    The only difference on protoboard is that instead of battery, I'm charging 2 x 4700 uF capacitors (I know, short time).
    So far, it works, even on 300 uA.
    Is there anything that any of the advanced users would add or change in this circuit?
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    What type of battery are you planning on, hope it isn't Lithium.
     
  3. bushrat

    Thread Starter Member

    Nov 29, 2014
    97
    22
    For now, i don't know, it's still a prototype on my protoboard.. Any suggestions? Battery should be fairly small in size.
     
  4. dannyf

    Well-Known Member

    Sep 13, 2015
    1,779
    360
    You can think of a battery as a voltage source + a very small serial resistor.
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,910
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    You could use the solar panel as the 'night' detector. With this circuit, the LED's will flash when the panel stops charging the battery.
    upload_2016-6-8_11-27-33.png
     
    bushrat likes this.
  6. dannyf

    Well-Known Member

    Sep 13, 2015
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    What happens when the battery becomes fully charged during the day?
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    There is no regulator to switch of the charging in that event so charging current will continue to flow and so the LED's will stay off.
    This kind of charging is fine for e.g. NiCd and lead-acid batteries as long as the current is not too great.
     
  8. bushrat

    Thread Starter Member

    Nov 29, 2014
    97
    22
    Thank You for the idea, will implement it in my project.

    Battery will be NiCd, 4.8V (3200mAh)
     
    Last edited: Jun 9, 2016
  9. hp1729

    Well-Known Member

    Nov 23, 2015
    1,948
    219
    Design 771 blinking LED.PNG
    One with fewer parts.
    Self blinking LED, one transistor.
    Resistor values may need to be adjusted.
     
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,523
    1,247
    Here is an alternate approach. Fewer parts, fewer soldered connections, a single timing element.

    ak
    Night-Flash-1-c.gif
     
    Bernard likes this.
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