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  • blink led
Related

Flashing Led's

commanderkelly
commanderkelly over 6 years ago

Hello, I am new to this site and loving it. I did a bit of Electronics in 1995 where I made a flashing led circuit with 2 led's and it was cool. My other hobby is model trains and I would like to put 2 small led's in buffer stops and make them flash and run it off a DC train controller. Does anyone have a simple circuit that would do the job for this? I am basically a noob at electronics but I can follow a simple circuit.

 

Thank you.

 

Gary.

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  • 14rhb
    14rhb over 6 years ago +12 suggested
    Hi Gary, Welcome to Element 14 Community. Although a long time ago, you have already completed the first step on the world of modern electronics - the famous 'blinky' experiment . I'm assuming you want…
  • beacon_dave
    beacon_dave over 6 years ago +8 suggested
    Probably can't get much simpler than a flashing LED: https://uk.farnell.com/c/optoelectronics-displays/led-products/flashing-blinking-leds Size may be an issue however. 3mm is the smallest listed.
  • fmilburn
    fmilburn over 6 years ago in reply to 14rhb +7 suggested
    Hi Rod and Gary, I am more of a digital guy but I saw this and had to build it. The circuit is close to the first link that Rod gave above. The voltage source is 4 AAA, R1 and R4 are 330 ohm, R2 and R3…
Parents
  • 14rhb
    0 14rhb over 6 years ago

    Hi Gary,

     

    Welcome to Element 14 Community. Although a long time ago, you have already completed the first step on the world of modern electronics - the famous 'blinky' experiment image.

     

    I'm assuming you want your LEDs to alternate. There are many ways of doing this from relays, microcontrollers, 555 timers etc but what will be easiest is probably to search for "Astable Multivibrator + transistor". One good link I have just found is this https://www.build-electronic-circuits.com/blinking-led-circuit/  (however I apologise to other E14 members as in my own comments I have stated that I don't like posting links off site). A little way down that linked-page is a circuit titled Astable Multivibrator using transistors.

     

    If you are in the UK you can get the parts from somewhere like CPC Farnell (nice and low cost delivery), Farnell UK or in America use Newark. The transistors are nothing special, so 2N3904 would be fine; there are many other suitable ones. Again a quick Google and you will likely find a full parts list. You need to adjust the values of R1 and R4 to suit the Power Supply you are using - for 12v I would increase them to something like 750 ohms.

     

    Keep asking if you are unsure of anything, and I'd really like to know how you get on (eg a photo of the finished buffer stop lights in action image )

     

    Rod

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  • 14rhb
    0 14rhb over 6 years ago

    Hi Gary,

     

    Welcome to Element 14 Community. Although a long time ago, you have already completed the first step on the world of modern electronics - the famous 'blinky' experiment image.

     

    I'm assuming you want your LEDs to alternate. There are many ways of doing this from relays, microcontrollers, 555 timers etc but what will be easiest is probably to search for "Astable Multivibrator + transistor". One good link I have just found is this https://www.build-electronic-circuits.com/blinking-led-circuit/  (however I apologise to other E14 members as in my own comments I have stated that I don't like posting links off site). A little way down that linked-page is a circuit titled Astable Multivibrator using transistors.

     

    If you are in the UK you can get the parts from somewhere like CPC Farnell (nice and low cost delivery), Farnell UK or in America use Newark. The transistors are nothing special, so 2N3904 would be fine; there are many other suitable ones. Again a quick Google and you will likely find a full parts list. You need to adjust the values of R1 and R4 to suit the Power Supply you are using - for 12v I would increase them to something like 750 ohms.

     

    Keep asking if you are unsure of anything, and I'd really like to know how you get on (eg a photo of the finished buffer stop lights in action image )

     

    Rod

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  • commanderkelly
    0 commanderkelly over 6 years ago in reply to 14rhb

    Thank you for the info you have given me, I will do a photo for sure and let you know how it went. I will have to wait 2 weeks to get the stuff as I do not work so not got money right now. I do live in the UK so I will check the places you have told me to check.

     

    Gary.

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  • fmilburn
    0 fmilburn over 6 years ago in reply to 14rhb

    Hi Rod and Gary,

    I am more of a digital guy but I saw this and had to build it.  The circuit is close to the first link that Rod gave above.  The voltage source is 4 AAA, R1 and R4 are 330 ohm, R2 and R3 are 47k, the caps are 22 uF, and the transistors are 2N3904.

     

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  • commanderkelly
    0 commanderkelly over 6 years ago in reply to fmilburn

    Thank you for the video and for the info given, I will be using a DC train controller for the power. The output power of the controller I am using is 14.2V now I did try a led on it hooked up to a 1k resistor as that is all I got at the moment are 100x 1K Ohm and it worked great did not get to bright.

     

    Gary.

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  • 14rhb
    0 14rhb over 6 years ago in reply to fmilburn

    Hi Frank,

     

    That is really great to see, well done, I'm sure it has really helped commanderkelly to see what the finished project will look like before spending any money image

     

    Ro

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  • 14rhb
    0 14rhb over 6 years ago in reply to commanderkelly

    If you have loads of 1k resistors and don't mind using several of them up you could parallel two to get 500 ohms. Put three in parallel to get 330 ohms. Then put the double bundle in series with the triple bundle to get 830 ohms....probably about right for your 14v supply.

     

    If you are buying a resistor for R1 and R4 I would choose something around 680 ohms for a 14.2v supply (14.2 v - 0.2 v drop in transistor, 20mA design current for LED ) and they should be a good brightness. That assumes a fairly standard LED current, if you know the part numbers of the LEDs you have then you could look up the If (the forward current they recommend). Again, if you are unsure, just ask.

     

    Rod

     

    [editted: see calculation below that included the voltage drop of the LED]

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