I need a Blinking Led to be Solid.

Discussion in 'General Electronics Chat' started by Yoe777, Jul 21, 2013.

  1. Yoe777

    Thread Starter New Member

    Jul 21, 2013
    Sorry if this is to simple for you guys but I couldn't find any Schematics on the internet on how to do this.

    I have a battery charger that has a blinking Led to signify when a charge is complete but I need it to be a solid Led or solid source of DC voltage. This is so I can connect it to my CBA Charger and it will detect when a charge is complete so my West Mountain Radio software can react accordingly.

    I cannot modify my charger because I don't want to void the warranty. I just ran a parallel wire from the led outside of the charger in order to create the circuit there.

    Could someone tell me a circuit that I could create to cause this effect?

  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Some form of electrical isolation might be needed between LED & remote. A small isolated DC supply might be helpfull. What color is the LED?, might be able to borrow a little LED current to power a IR LED isolator. After isolated signal is available it can be amplified, integrated & detected to give a V level output.
  3. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    I'll bet your attempt to modify the circuitry voided the warranty as well.
  4. Evil Lurker


    Aug 25, 2011
    Run a couple wires off the anode and cathode of the LED to a simple sub-circuit on perfboard. Use a diode such as a 1n4148 to rectify part of the voltage going into the LED and feed that into a small value electrolytic cap. A current limiting resistor after the rectifier diode probably will be needed as well as you don't want to accidently smoke any transistors controlling the LED. Attach a bleed down resistor in between the terminals of the capacitor so that when the LED stops flashing the cap will discharge. Then run a wire to whatever voltage sensing circuit you need. Which values of caps and resistors you will need, you will just have to do the math on your own.
  5. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    Could you run the LED leads to a latch, so that upon receiving the first blink, the output will change. This change can then be used to drive your external circuit. It would require a manual reset before the next charging operation. I'd create a schematic, but I'm on my phone.
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
    You could place a light activated transistor where it will receive the light from the charger LED, and then use the pulsating signal from the transistor to activate a retriggerable monostable that outputs steady DC to your CBA Charger. This would not require any electrical connect between the new circuit and the battery charger, but would require a close physical connection. Such a connection could be nothing more complex than duct tape holding the photo transistor to the front panel of the battery charger.
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
    If the led is normally off, and flashes when charged, then use a photo transistor covered to trigger a 555 timer monostable , that will give you your steady voltage,
  8. Yoe777

    Thread Starter New Member

    Jul 21, 2013
    It is a Green Led. It pulses and off 1v DC.

    I need a higher level output from 3v - 50v constant.
  9. wayneh


    Sep 9, 2010
    Operate the LED of an optoisolator in parallel to the green LED and use the monostable as mentioned to convert the pulses to a steady signal.
  10. WBahn


    Mar 31, 2012
    If you haven't already voided your warranty -- and it sounds like you probably have -- then use the chain of suggestions above.

    1) Mount a phototransistor against the LED so as to couple it as much as possible optically to the LED.

    2) Use this to tigger a retriggerable one-shot (monostable multivibrator) that has a period longer than the time between flashes (the time for several flashes to occur would probably be best). A 555 would be well suited for this.

    3) Use the output of one-shot to activate a relay or a MOSFET or some other suitable device that can be operated from the output of the 555 and that is compatible with your 3V to 50V requirement.