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I have a Brookstone rover 1.0. In the app, you can trigger an IR LED to go on. I have also installed lights in the front and back of the rover in a simple LED series driven by a resistor connected directly to the battery.

I was thinking it would be possible to use discrete components such as a few transistors to trigger the LEDs to go on when the IR is off. The IR LED is connected to GND (this much I know), and when the microprocessor sets the pin to high the led goes on as the circuit is completed (this I am assuming). I have no way of accessing the code, and changing the procedures.

Is there a way to trigger a transistor as a switch so to speak to make the LEDs go on, when the IR is off (i.e. when there is no (+) going to the IR) and vice-versa?

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  • \$\begingroup\$ A picture of the board is needed to help. \$\endgroup\$
    – Passerby
    Commented May 17, 2014 at 1:17
  • \$\begingroup\$ That really wouldn't yield anything, but heres some: openipcam.com/forum/index.php?topic=261.0 \$\endgroup\$
    – Alex
    Commented May 18, 2014 at 1:01
  • \$\begingroup\$ Assuming that's your exact model and same board revision, Q1 near the camera/ir connector controls the IR. It might be PNP, or NPN, 3v or 5v. Some testing with a multimeter is needed and a schematic needs to be drawn. At that point, it's simple enough to add an inverse controlling transistor. Keep in mind, a simple connection will leave the leds on until the batteries drain, unless you also add a control to keep it off if the board is off. \$\endgroup\$
    – Passerby
    Commented May 18, 2014 at 1:53

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A relay would be a very simple way to do what you want. Connect it in series with the IR led and set it up so that when electricity flows through the LED + relay, the relay disconnects the other LED's from power, and when the IR LED is off, the relay contact is released and completes the other LED circuit, allowing power to flow and turning on the other lights.
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  • \$\begingroup\$ Interesting, can't believe I didn't think about that. Although I am looking if there is a way of doing with this w/ transistors, if that proves to be too complicated I can always go this route. Another issue is the relay will draw power? The IR led receives a very moderate amount of current, and when connected to the relay it would probably prevent the IR led from functioning at full power... \$\endgroup\$
    – Alex
    Commented May 17, 2014 at 1:02
  • \$\begingroup\$ @Alex You can always connect the relay in parallel with the IR led, as long as they are controlled by the same switch. \$\endgroup\$
    – Delta1X
    Commented May 17, 2014 at 1:08

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