Connect with us

Adding to existing circuit

Discussion in 'General Electronics Discussion' started by edinc90, Sep 1, 2013.

Scroll to continue with content
  1. edinc90

    edinc90

    3
    0
    Sep 1, 2013
    I have an LED circuit (a tally system for television cameras) that I need to add on to. My add-on works fine stand-alone, but when I plug in both the existing system and mine, the existing system seems to get all the power, and my LEDs go out.

    The system is fed 5 volts from the video switcher when the LEDs should go on (when the camera is live.) I'm simply splitting the cable and feeding the same voltage to both the existing circuit and my new one.

    The system has both red (on-air) and green (next up), but red and green will never be on at the same time. We also don't have the green tally implemented yet, so I don't know if I have the same problem with green as I do with red.

    To sum up: existing circuit works, my circuit works, both together and the existing circuit takes over. Thanks for any help.
     

    Attached Files:

  2. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    There are two possibilities.

    1. The power supply or cable can not provide the current necessary.

    2. The new circuit uses two leds in series. If the voltage drops there may not be enough to turn them on.
     
  3. edinc90

    edinc90

    3
    0
    Sep 1, 2013
    My sneaking suspicion is that there's not enough current. I'm thinking of building a circuit with a bunch of transistors to switch a higher amperage power supply to feed the LEDs. Double check my work, I know very little about electronics design.
     

    Attached Files:

  4. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    I do not know where this array will be connected. Without extra power, it is unlikely to work.

    The base of each transistor should have a current limiting resistor. Depending on the load it could be 1k to 10k. Each led should retain its current limiting resistor.
     
  5. edinc90

    edinc90

    3
    0
    Sep 1, 2013
    Sorry, I should have explained. Since the switcher doesn't supply enough amps, I would use this array to switch a higher amperage 5 volt supply to drive the LEDs (upper left, +5 volt supply). If I understand transistors right, the base connected to the weak 5 volts of the switcher (through Red Tally and GN tally, left of schematic) should allow the higher amperage 5 volts from an external power supply to flow from the collector to the emitter, and on to the LEDs (through the XLR plugs on the right.)
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-