Another 4017 thread *sigh*

Discussion in 'The Projects Forum' started by luvv, Feb 25, 2012.

  1. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    Honestly i have searched for a thread that covered this....

    I SWEAR i did....

    And as much as i hate to ask you guys to read yet another thread w/ the words LED and 4017 in it..

    So yea.. ive been through piles of threads here and across googlverse.

    And none have fully covered my questions to my satisfaction..

    So here it is, i want to use.

    9 outputs, all 9 outputs have r/g bi color leds

    All 9 outputs stay red until the output goes high at which time it goes green.
    When the output returns low the led returns to red.

    That is simple enough and covered in a few threads here and elsewhere..

    Here is where im not so sure, i also want the same outputs to drive a relay..

    So when the led is lit green the corresponding relay is closed, and when output goes low led goes red and relay opens.

    All the methods ive seen of controlling the leds would make it hard to energize the relay coil.

    Or perhaps im over complicating it and missing the obvious..not uncommon for me.

    The relay(s) i have picked out are 5v 500 ohm coils, i had intended to just use these little TO-92 mosfets i have to drive the coils..

    But that was before i decided i wanted some bi-color led bling ..

    Thanks,

    -luvv-
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Hmm, I thing we have that circuit, almost, complete with PCB design. It was a 3 LED circuit though.

    Led fading circuit

    It is a long read, but like I said, a PCB design at the end.
     
    luvv likes this.
  3. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    Wow thanks Bill.M,

    That was quite a project there,and one i hadn't seen yet.

    It's not quite what i had in mind tho, think more of runway lights.
    *see attachment*

    And yes, Ive seen a few threads here related to such.

    The effect i need appears to be covered in this thread http://forum.allaboutcircuits.com/showthread.php?t=35333&page=2

    Particularly by the emitter follower schematic AG posted.

    My issue is two fold, one how best to energize a relay from the same output.
    Two how to do the same job w/ IC(s) other wise it's 18 transistor for 9 outputs:(
    Is there no way to use logic gates?

    Or npn/pnp paired transistors in a dip package at least?

    Love IC sockets,saves me a lot of desoldering which my cheap proto boards do not like.


    Thanks,

    -luvv-
     
    • Seq.PNG
      Seq.PNG
      File size:
      13.8 KB
      Views:
      23
  4. nerdegutta

    Moderator

    Dec 15, 2009
    2,517
    785
    Didn't you and Magnet18 make a circuit like that with some transistors and a 4017 IC?

    Some ting like this?
    http://youtu.be/epNF5Bv1Ld0
     
  5. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    @ nerdegutta: that is indeed the function im after,tho much slower clock no pic involved and a relay for each of the 9 outs.

    -looked closer and realized he was using dif color leds ..im wanted bi color r/g -
     
    Last edited: Feb 25, 2012
  6. nerdegutta

    Moderator

    Dec 15, 2009
    2,517
    785
    Last edited: Feb 25, 2012
    luvv likes this.
  7. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    So it's clear what im looking for i made a GIf animation, i did'nt put relays on there but yea you get the picture.
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    How much LED current?
     
  9. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    Nothing set in stone, but this is what i was looking @http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_34673_-1

    Ive bout come to the conclusion it will be simpler to try to synchronize two 4017(s).
    Have one drive the R/G led(s) via the totem pole circuit AG made in the link in post 1.

    Have the other drive the relays via TO-92 mosfets..

    I have never tried to sync two 4017(s) but i assume i can just split the clock?

    That is unless someone has another way to drive r/g/led(s) and the relay on same output.
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    I don't see how that's going to save on parts. That requires 27 transistors, and another IC. You can use AG's circuit. Drive the relay off the NPN emitter. Connect the other end of the relay coil to ground. Protect the transistor with a reverse-biased diode across the coil.
     
    luvv likes this.
  11. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    Thanks,

    I'll go ahead and order the leds and give it a whirl.

    This is but one part of a larger contraption i have rolling around in my head.

    I'll be working through each part and ill try to get a schematic put together for you guys to laugh at next week sometime.



    -luvv-
     
  12. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    I just realized that what I suggested might cause reverse breakdown in the LED that is connected to the NPN. You can avoid this by using two resistors - one in series with each LED, instead of a common one. This has the advantage of allowing you to set each LED current to be independent of other.
     
    luvv likes this.
  13. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Actually it should not be that hard to do. How much current do you want through the LEDs.

    You are going to need a simple inverter, either transistor or IC, that can handle current. It is a classic case of H bridge, simplified.
     
  14. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    It works, and here is the vid http://www.youtube.com/watch?v=0TiJ7uPLU-4

    The switching is flawless and does exactly what i was looking for.

    Ignore the led meter and button pushing those are for a different thread :D

    Thanks to AG for the original schematic and to Ron H for altering it to better suit my needs.

    No relays on the board as the are SIP type and not bread board friendly.

    Thanks again,

    -luvv-
     
    Bernard likes this.
  15. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    Found a issue today..

    One i can't believe slipped past me for this long:rolleyes:

    My supply voltage is 5-6 v..my relay is 5v.@500ohm w/ a minimum on of 3.75v.

    I'm getting 3.6v at the emitter of the npn which will turn on the relay but just barely.

    With a 700ma load on the relay i just know its toasting the relay's contacts and severely hampering the switching speed.

    So my question is other then upping my supply is there a way reduce the losses or drive these relays w/ a full 4.5-5v ?

    Thanks,
    -luvv-
     
  16. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    With vcc=5V, you should be getting 4.2 to 4.3V on the emitter. Do you have a resistor in series with the base or the collector?
     
    luvv likes this.
  17. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    Thanks for the reply Ron H

    Just went and rechecked turns out my psu is a little off..4.84 not 5v as i assumed.
    It's a converted PC PSU and was at one time dead on..i must have hurt it at some point.
    I'm getting 3.42-3.63 at the emitter, before the resistor to the led.

    No other resistors beyond the the pnp base resistor.

    My original plan when all is said and done is to power it from a 6.4v SLA bat.
    so this may not be a issue at all,just wanted it to work all the way down to 4.5-5v.
     
  18. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    What is the voltage on the base?
    How much current are you giving the LED?
     
  19. luvv

    Thread Starter Member

    May 26, 2011
    186
    31
    4.239v. to base of npn from 4017 out.

    8 ma through green side of common cathode led.

    I didn't end up using the linked jameco led(s) they wanted 10$ to ship 12$ of merchandise..

    So i got these http://www.goldmine-elec-products.com/prodinfo.asp?number=GP55

    They test out in the neighborhood of 1.6-1.7 forward voltage.
     
  20. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    You're losing 0.6V at the 4017 output due to transistor base current. Your base current should be less than 160uA with a minimum beta of 100. Cd4017 can source at least 510uA with only 400mV drop from vcc.
    What kind of transistor is your emitter follower? Are you sure you don't have the base and emitter swapped? That will result in a low beta transistor that still works, just well enough to baffle you.
     
    luvv likes this.
Loading...