Connect with us

Making 100 leds flash?

Discussion in 'LEDs and Optoelectronics' started by Sinpy, Nov 11, 2013.

Scroll to continue with content
  1. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    Im trying to make two sets of 50 leds flash back and forth between each other using a 555 timer chip. I have made two leds flash back and forth between each other so far using these schematics shown at bottom of the page. Sorry its not like most schematics out there. I drew it up best I can so I can understand it.

    *Anyway the 555 timer only has a output of 200mA. The thing I needing help with is understanding how I can make total of 100 of these leds flash. I have small understanding of how I would wire all the leds together and same for transistors. I know transistors going play a big roll in making this work.

    I have few transistors left over from my last project I’ve tried. If they would for this project, it would be nice If I could reuse them. The names of them FQPF13N06L and BC548CTA Came from site called digkey. Here is the links to the things I have.

    http://www.digikey.com/product-search/en?vendor=0&keywords=fqpf13n06l

    http://www.digikey.com/product-detail/en/BC548CTA/BC548CTAFSCT-ND/3478140

    Can anyone please help me out with this?
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,702
    2,717
    Nov 17, 2011
  3. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Easiest would be 1 N-channel MOSFET for 1 set and 1 P-channel MOSFET for the other.

    Bob
     
  4. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    I really don't know anything other than the two transistors I've already have :p Also I took look at the "Got a question about driving LEDs? "and the part about (Image 2.4) "The fourth method is to put multiple strings in paralle" That would be the method I would be using to power all of these leds? Also on that same link you sent Harald Kapp (figure 3.5) is the set up for the transistors I used in my last project but I wasn't fully sure if it was working right. May miss wired it. Would that same set up work for this thing im trying to do?
     
    Last edited: Nov 12, 2013
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    11,702
    2,717
    Nov 17, 2011
    Figure 3.5 is correct. But you also have to think about the implications when putting the LEDs in series. 100 LEDs in series require an operating voltage of at least 100*Vled. Even a simple red LED has Vf~1.6V, thus requiring >= 160V for the string. Other colors incl. white make matters even worse.
    Therefore you should build short strings according to figure 3.5 using only as many LEDs as your supply voltage is able to drive. With the side conmdition that the number of LEDs in one string divides 100 to an integer number. You then put these strings in parallel to add the number of LEDs up to 100.
     
  6. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    Ok, So would this be right then with hooking them all up? (See photo below) and only thing have to do is find out the resistor need for the strings and add up the mA/Amps being pulled by them and see if the transistor will be enough to make it work?
     

    Attached Files:

    • ledp.png
      ledp.png
      File size:
      15.3 KB
      Views:
      127
    Last edited: Nov 13, 2013
  7. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    No. That is exactly figure 2.2 from the tutorial, the one it says "Do Not Connect LEDs in parallel".

    You want either 2.1 or 2.4 depending on your supply voltage and the forward voltage of the LEDs.

    Bob
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    No, you are placing LEDs in parallel without individual resistors. This is EXACTLY what the LED tutorial tells you not to do.

    Either place a resistor in series with every LED in that drawing, or go back to the LED tutorial where it links to sites that allow you to calculate a proper series/parallel arrangement of LEDs. Even once you've done that, you need to make sure that the answer you get is reasonable as these calculators can sometimes give you results that seem OK, but use (typically) very small value resistors.
     
  9. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    Alright, thanks I'll re-read over the tutorial few times and look at them links for the calculations you were talking about steve. But there one problem I have thats going put hold on this whole thing, and thats my power supply. Its going be my car/cigarette lighter because I'm making this thing for use in my car. Doesn't the voltage change for the battery as the battery gets used/recharged as the car is being used?
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    11,702
    2,717
    Nov 17, 2011
    Yes it does. As long as the battery is in good working order, you'll see something between 11V and 14V. You probably can live with the resulting change in light intensity. If not, you need to consider a current source instead of the series resistor. this is also discussed in the LED tutorial.
    Operating an electronic circuit from a car's power supply incorporates the risk of high voltage spikes (due to so called load dump). You should protect you whole circuit by suitable means (suppressor diodes, filter).
     
  11. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    Seem the (Image 2.4) would cost the less to do, and using that calculator shown below that image 2.4 it said I could power 50 of them 12x4 with 47ohm resistors and 2 extra with 270ohm. Now I'm powering 100 leds it shouldn't mater because only one side of the set of 50 leds will be on. Then switch to the other set of 50 leds and keep flashing back and forth between each other?

    Other than that I still need find the "suppressor diodes, filter" to help protect my circuit. Depending on what that does to my voltage I shouldn't have any more problems other than the transistor hook up. I still don't really know how to wire it in to my circuit. That same for my last project I did.


    *Photo below is schematics from my last project. 1st drawing by someone on the site and 2nd one by me trying make it so I could try and understand it better. Still don't think I got it wired right what you think about it? I like to reuse these transistors I have so I don't have order more of them.

    Side note took a Voltage Meter to find out my average voltage for my car. And it was 14.14 volts with out change unless using my hazard lights. And that was 13.90 volts and jumped around between that and 14.15 volts. Car off about 12 volts, but not going use the light with car off.
     

    Attached Files:

  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    I seem to recognise that circuit on the left...

    With that circuit you can drive a single string of LEDs without a resistor If you're using multiple strings with appropriate resistors then you short out R1 (and remove it) and remove Q2.

    The circuit as it is drawn is a linear constant current sink.

    It can be used (with caution) powering the LEDs from a higher voltage than the 555. To make it alternately flash LEDs, you would probably be best inverting the output from the 555 and driving another N channel mosfet.

    This circuit is completely different from your original one and much of the advice given previously does not apply..
     
  13. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    You should recognize it, you were the one that drew it up for me. Sorry about the late reply been in classes all week.
    Anyway I'm bit confused about what you said with adding another N channel mosfet in to the circuit. You talking about just adding another one in there hooked in with the one I already have? The person I get my parts from said it "could" blow up/short out if I power two of these off each other?

    *Side question: Would it be more easy just get a whole new circuit going and with different transistors/mosfet?
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Were you using a different user name? That is a circuit for driving a high power LED, not a string of many (presumably low power) LEDs.

    I think an alternate circuit (certainly an alternate design of the output/driver stage) would be in order.

    How are you planning to wire up the 50 LEDs in each string? From 12V, 25 pairs of LEDs with a resistor all placed in parallel would probably be reasonable.

    What current do you want to run them at?
     
  15. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    Yes I was using another user name but I forgot the password for it and the password for the email used for it. Sorry I didn't point it out sooner

    I know them schematics were for the high power led. I was asking if I could use the transistors/mosfet I used to make that one to make this project work.

    I was looking at that calculator you were talking about on the Got a question about driving LEDs? page. The part about "The fourth method is to put multiple strings in parallel/Image 2.4)" The results I got from using that calculator are shown at bottom of this post.

    I decided drop the total amount of leds down to 80 (two stets of 40) Not much of a difference but yeh Is it going be possible to do the 40x2

    And just be sure on the power supply. I used a voltage meter hooked to my car cigarette lighter, the voltage was 14.14 (Car on) tested over few minutes with out change in the 14.14v unless using my haz-lights and like I said in my other posts this light not going be used unless car is on.
     

    Attached Files:

    Last edited: Nov 23, 2013
  16. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    other than that is there any thing else you can tell me that I could use to search for more information about this stuff?
     
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Here is a method of flashing LEDs alternately.

    Note that Q2 is a P channel mosfet,

    The LEDs and the resistors can be replaced with as many parallel strings of LEDs as you can sensibly drive using the mosfet.

    It may be useful to place a 1k resistor between the output of the 555 and Vcc to ensure that the P channel mosfet turns off completely.

    [​IMG]

    I've not shown the entire circuit, just the output bit. Everything else is the same
     

    Attached Files:

  18. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    Yes. Th easy way to tell is that the arrow points to N (just like in a map). The N channel device has the arrow pointing in to the channel, the P channel device has the arrow pointing away from the channel.

    They look suitable.

    What's your total LED current? My guess is that it will be under 500mA, so these are generously rated.
     
  20. Sinpy

    Sinpy

    12
    0
    Nov 10, 2013
    for whole thing 2.4amp for each set of leds Im wantting to use 1.2 amp each led is 30mA. Is this going be a problem?

    and thanks for the tip about telling the type of channel
     
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

-