pulsing led

Discussion in 'The Projects Forum' started by wahoomy, Dec 25, 2012.

  1. wahoomy

    Thread Starter New Member

    Dec 25, 2012
    I need to build pulsating LED light,between 6 and 12 volt powersource,but pulse frequency MUST go higher with voltage raise,so if its one blink a second with 6 volts ,it should be like 0.5 sec with 9 volt and so on.i was looking for something like that ,just cant find it on market.thnx ahead for any reply.Btw I`m not a pro in electrics so something more simple would appreciate higher .Thanks
  2. absf

    Senior Member

    Dec 29, 2010
    Have not look deep into it but I think it should be possible with some comparators and a VCO like NE566 or 74LS624. But a simple 12F675 with ADC should be able to do it easily. Wait till all the experts are back from X'mas. May be they have simpler solutions.

  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Might try the VCO section of a CD4046. R1 around 1m, C1 around .1μf, & from bertus, Fmin = 1/ R2 C1; Fmax = 1/ R1C1
    Or a 555 with timing R, [ CdS- LED analog photo coupler ], from pin3 to 2&6. Range adjusted with LED current limiting R & LDR series/parallel R.
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    This circuit works in simulation. Frequency vs voltage was as follows:

    Code ( (Unknown Language)):
    1. 6V      .85Hz
    2. 7V      2.1Hz
    3. 8V      3.5Hz
    4. 9V      5.0Hz
    5. 10V     6.4hz
    6. 11V     7.7Hz
    7. 12V     9.0Hz
    The toggle flip-flop on the output is used to maintain 50% duty cycle of the LED, independent of frequency.
    The LP2950 is a 5 volt low-dropout regulator, and is available from Jameco and other distributors.
    absf likes this.
  5. DickCappels


    Aug 21, 2008

    Ron H likes this.
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    I'm on the road with no tools but I did something very similar once,customer required a LED replacement for an incandescent bulb to have very similar brightness when runover 10 to 28VDC range.

    Needs: 1 PIC12HV615, 1 resistor for voltage regulator (PIC has onboard current shunt regulator), bypass cap, 2 resistors for A2D ranging, and transistor & resistor for switched (PWM) LED driver. Oh, and the LED.

    4 R's, 1 C, 1 Q, 1 IC.

    And a little firmware too.
  7. wahoomy

    Thread Starter New Member

    Dec 25, 2012
    I`m impressed with quick ,nomerous response ! Thank you all.I now realize,Ishould have mentioned at first ,I want to install this on my pc, and conect it to PCU cooling fan,so when PCU is loaded,it goes hotter ,automaticlly voltage on PCU fan rises,and voltage rise should accelerate speed of blinking,wich would make the machine look lifelike.However can not power some complicated circuit from PCU cooling fan source. Was hoping for something simple , like resistor/cap, some zenner diode maybe...Anyway thank you ALL for botherin on my trouble.I`ll just keep looking further...