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Urgent Help Please Circuit Design 555 Cd4017

Discussion in 'General Electronics Chat' started by Keshin, Dec 17, 2015.

  1. Keshin

    Keshin Member

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    Hey everyone im completely new here, and very little experience in circuitry, That aside iv retouched home with my passion for this kind of stuff and will be scouring the forums to learn what i can. right now i don't have the time and need some help

    i have 24 hours to finish my nephews present i decided to make. Its a led name plate 6 letters.
    I had this brilliant idea at first that i wanted it to light up each letter starting from left to right until all letters where lit up
    Then i wanted it to fade or turn off left to right or something simple
    That idea was almost impossible for me to find a design on,

    Then i decided okay, we can go a chaser circuit that does 10 leds individually from left to right.

    That lead me to this schematic, http://www.eleccircuit.com/led-chaser-by-ic-4017-ic-555/ (sorry if im not allowed to link i just need to show what i found)
    That page was fine until i noticed components change from figure to figure and i cannot understand it.
    This leads me to my need for help im willing to go buy more components immediately if someone can help design a very simple circuit to help me get this done in the next 24 hrs

    (please note this circuit is going to run on 6v) Also note. Each letter of the 6 letter name has approx 14 leds (each led is wired up with a 200 resistor and are wired to a common positive for each letter..... so 6 positives for 6 letters allowing me to activate each letter individually and 1 common ground for all letters)

    Below is a list of components i have on hand i have already purchased.
    *ne555p (1 pc)
    *cd4017 decade counter(1 pc)
    *16v 10uf capacitor (2 pc)
    *suntan 3296 trimmer pot (1 pc)
    *0.5w 1K resistor (8 pc)
    *0.5w 2K7 resistor (8 pc)
    *0.5w 430R resistor (8 pc)
    *0.5w 470 ohm resistor (2 pc) can't get anymore unless i try salvaging
    *0.5w 200r resistor (8 pc)
     
  2. Mosaic

    Mosaic Well-Known Member

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    Ok...

    I gather u have configured the 6 LED characters to spell the name already and you just want to sequence the characters illumination in some way.

    A microcontroller is the approach I'd recommend...but....you need it done...like now so...moving on from that:

    What u have will do this to the LED digits:


    Which won't light them all at once!

    Now for something a bit better:

    Go get an LM3914, 10 LED linear display. It can sequentially light the letters from left to right and back based on the level of the voltage it sees.
    How to get the voltage to ramp up and down? Use the 555 chip u have to charge/discharge : say 1 sec on, 1 sec off pulses; feeding the 10uF cap via a largish resistor, perhaps a 100K to get a time constant of about 1 second. This Capacitor anode feeds the LM3914 input which you can calibrate to how it responds to the input voltage range.

    Note here:
    https://en.wikipedia.org/wiki/RC_time_constant

    Presuming your 14 segment LEDs are common cathode:

    Here's the Lm3914 circuit u need, use bar mode:
    https://learn.sparkfun.com/tutorials/dotbar-display-driver-hookup-guide


    Driving the 14 seg LED digits common cathode line with just the LM3914 can heat it up a bit....so if that happens you can alter the duty cycle of the 555 (like 1 sec on 2 secs off etc) so as to reduce the 'on' time of the LEDs.

    If your LEDs digits are common anode...you're gonna need to drive 6 PNP (2n3906) transistors ( say 220Ω base resistors) with the output of the LM3914, this does 2 things. Reduce the heating on the LM3914 a LOT and makes it Com. Anode compatible.

    Since it's almost 5AM here and I am tired..I am sure others can come up with something better for u to try.


    good luck.

    PS...with the LM3914..u can use dot mode...and when the 7th LED output 'lights' you can cause it to drive pin 9 high to BAR mode via a 2n3906 PNP pulling pin9 high when its base goes low (from pin 13 signal) ....so u get each letter lighting sequentially...and after the last one they all light,then it all reverses as the 555 pulses low and the 10uF cap. discharges and then.repeat, automatically.
     
    Last edited: Dec 18, 2015
  3. spec

    spec Well-Known Member Most Helpful Member

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    Hi Keshin,

    Welcome to ETO

    Mosaic's approach in post #2 is the easiest, but if you would like to build yourself using your current parts, I can probably post a circuit quite soon.

    Some information is needed though:

    (1) What is the Ohm resistance of your trimmer resistor?

    (2) When one of the LEDs (with 200R series resistor) is connected to 6V how much current does it take?

    (3) What colour are the LEDs?

    (4) Are all the LEDs the same type and the same colour?

    At the moment it looks like you will need an additional 10 transistors (small low cost).
     
    Last edited: Dec 18, 2015
  4. dave

    Dave New Member

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  5. Keshin

    Keshin Member

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    ok guys sorry i didnt see this i had an attempt this is what i did, i know iv made a mistake, Also thank yous heaps for getting back to me so quick thats awesome.

    ok to start ill share what i have done

    555 chip
    16v 10UF capacitor to between pin 1 and pin 2 (negative side to pin 1)
    pin 2 connected to pin 6
    pin 4 connected to pin 8
    pin 6 connected to pin 7 via 2.7k resistor (instructions said 10k but i dont have one)
    trim pot (using middle leg and one of the outter legs) connecting pin 7 to pin 8 (instead of 4.7k resistor as suggested in instructions)
    pin 8 to positive
    pin 1 to negative
    Pin 3 to 4017 chips pin 14

    CD4017 Chip
    Pin 14 to pin 3 on 555
    pin 16 to positive
    pin 13 and 8 to negative
    pin 15 to output pin 5 (changed this from negative as i only want to run 6 outputs not 10)
    pins, 3,2,4,7,10,1 output to leds

    here is a video of it turned on and what its doing hopefully that might shed some light or just show i messed up bad haha


    In answer to your questions
    The leds are all blue and where purchased as a bulk 100 lot i believe they are 3mm
    i am not sure on current but i can get my tester out and work out how to test that
    The trimmer is 10Ω - 5MΩ
    resistance tolerance +10% (+20% only for 10 ohm)
    According to the websites information
    http://www.suntan.com.hk/pdf/Trimming-Potentiometers/TSR-3296.pdf
     
  6. spec

    spec Well-Known Member Most Helpful Member

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    Hi again Keshin,

    Thanks for information. That is a big help.

    Circuit posting imminent :)

    spec
     
  7. Keshin

    Keshin Member

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    thank you Spec
    and thanks Mosaic i did see that video but i need to make this circuit tonight/tomorrow
    (i know i leave everything till the last minute haha)

    i am however very much enjoying learning this stuff
     
  8. spec

    spec Well-Known Member Most Helpful Member

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    No probs Keshin,

    Circuit attached below.
    It functions by turning on each LED Bank in turn.
    Q1 can be any of the types shown in the note. If you would like to use a different type and need to know if it is OK, please post.
    Also if you need any help/info, just ask
    In case you are wondering abut the Q and Discharge connections on N1 (LM555), it is correct as shown on the schematic.
    The period is set by RV1
    I would recommend that you modify your existing circuit to be like the attached schematic. Best not to run the existing circuit because I think it is overcurrenting the counter chip.
    If you do build the circuit below, be nice to know how it all turns out

    spec

    OBSOLETE SEE LATER SCHEMATIC

    ETO_2015_12_18_LED_Sequencer_Iss01_01.png
    ERRATA

    (1)
     
    Last edited: Dec 18, 2015
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  9. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A CD4017 with a 6V supply can light only one LED dimly. A transistor is needed at each output to drive 14 LEDs.
    The CD4017 circuit will not light each letter until they are all lighted. Instead it will light each letter one at a time. It will not fade each letter, instead it abruptly turns off a letter and abruptly turns on the next letter. It needs to have its reset wire connected to its 7th output so it does not continue counting up to 10 and it stops after turning off the 6th letter.
    A much more complicated LM3914 circuit will do what you want.
     
  10. Keshin

    Keshin Member

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    thanks heaps that is awesome, im going to start remaking the circuit now
    couple of questions,
    1: next to the led resistors you have "r5" "r2" etc, what does that mean?
    2: if i understand correctly each bank (6 in total) will need a "560 ohm resistor" is this correct?
    3: on the 4017 it has the 10 outputs, as i only want to sequence through 6 of them can i run the 7th output back to pin 15 to reset (this isnt a major concern to me however)
    4: lastly im still trying to understand the terms on most components. im assuming q1 is a transistor, and if i understand correctly those are all part numbers listed below that will work?
     
  11. Keshin

    Keshin Member

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    yes i gathered this and from what i understand the circuit spec has drawn up intergrates transistors. i thought i needed something along those lines but wasn't sure as this is honestly the first circuit board iv ever done. as for fading etc, after starting this project i realized the 4017 and 555 timer wouldn't perform those features and i settled with each letter turning on and then off, however if i adjust the pot i could get them moving fairly fast.
    all in all this is just a step i decided to take as a learning curve to get back into electronics and so far am enjoying it and this forum :) will definitely post up results tomorrow

    Edit: also interested in learning more about the LM3914 chip
     
  12. spec

    spec Well-Known Member Most Helpful Member

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    That's why there is a transistor at each output


    That is what the circuit is designed to do, as stated

    Nobody said it would

    Mised that. I had assumed 10 LED banks

    Didn't you read the original post- Keshin HAS NO TIME
     
    Last edited: Dec 19, 2015
  13. spec

    spec Well-Known Member Most Helpful Member

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    Hi

    No worry. It was touch-and-go if I would finish the schematic in time :D

    (1) That is just the way that the schematic package I am using does it- every component must have a name. It means nothing,
    (2) Yes, each LED bank is competely independant from the others, so you would need to assemble 7 LED banks, complete with transistor and input resistor. Each LED bank then connects to its respective point on the counter output
    (3) Yes, that will be exactly the right thing to do- I had missed the reset thing in the rush
    (4) Q1= transistor. N= integrated circuit (chip), C= capacitor, RV= variable resistor (potentiometer or just pot). That is right, on a schematic you put the name (R1 for example) then the value 1K (1000 Ohms for example). If you are mystified by something like, 2K7, it is quite simple. The multiplier, in this case K (1000), replaces the decimal point- the reason. It's because a decimal point can easily be missed or, on a print-out fade, and cause errors.

    Resistors less than 1K are written with an R at the end. So 10R is just 10 Ohms. Things can get complicated: 0R1 means o.1 Ohms or more correctly 100 mili Ohms. High value capacitors can also cause confusion: 10,000µF (ten thousan micro Farads). should be written as 10mF (mili Farads), but the touble is this then gets confused with µ, especially as many people, me included, use u instead of µ because we can't be botherd to get the special character.

    I hope that you get your circuit working in time.
    Also I hope the counter outputs have not blown- they were having a hard time with the original circuit.

    Dont be discouraged if you get some slights from certain members on ETO- some of them like to throw their weight around and show off, especially to newbees. Apart from them, they are a pretty good bunch, and very helpful too. :happy:

    PS: I didnt include it on the shematic, because I didn't think you would have a spare one, but, if possible fit a capacitor fron the Contrl input of N1 to the 0V line, 1nF to 100nF would be fine. This is not essential, but just good practice to stop any interference getting at the multivibrator timing.
     
    Last edited: Dec 18, 2015
  14. Mosaic

    Mosaic Well-Known Member

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    It isn't 'much' more complicated, just 1 555 and 1 lm3914 and perhaps a few 'switching' transistors. The analog ramp/dc% concept may be more complex for a newcomer to electronics though, but there are many LM3914 examples to literally just copy within the time frame described.

    Looking at the OP's video, he's made letters using discrete LEDS with different numbers of LEDS per letter. Up to 14 it seems MUST be lit to get the letter. This will require considerable current to drive per letter (perhaps 70mA minimum) unless series LED configurations and higher voltage is used with a current limiting resistor per string.

    A parallel drive approach is going to require a dropping resistor for each LED or some LEDs will be bright and others may be dim or not light at all based on LED Vf variations. Driver transistors or one of these driver IC's looks mandatory.
    http://www.ti.com/lit/ds/symlink/uln2003a.pdf

    I used a current mirror approach for this project to manage LED brightness. jump to near the end to see the PCB etc.
     
    Last edited: Dec 18, 2015
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  15. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I don't think reset at 8 is important anyway. So, you get 3 character times (delay) before it repeats which I don't think is a big deal.

    When you have time, you can read about component designations: https://en.wikipedia.org/wiki/Reference_designator

    The decimal point gets blurred in real drawings, prior to the laser printer anyway, so vales can be
    100R2 (100 ohms) or 101 for 100 ohms. K is also used for x1000, M for xe6, m (milli) and M (Meg) are different.

    Some capacitors are marked 101 which actually means 10 with 1 zero pf or 100 pf or 100E-12 Farads. Many calculations use the Farad as the unit.
    Basic units are Amps, Volts, Farads, Watts. Prefixes like umMKpn are used to modify the values. e.g. uW for microwatts,

    Some of this stuff goes out the window with SMT components. Old schematics used MFD for uF, The u technically being μF.

    Not bad spec.

    Good luck.
     
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  16. Mosaic

    Mosaic Well-Known Member

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    I don't think I've seen an SMD ceramic capacitor or ferrite bead with a marking at all.
    Recently I discovered that for RF work, soldering smd resistors upside down reduces their ESL...! So on the PCB, you can't see their marked values.
     
  17. spec

    spec Well-Known Member Most Helpful Member

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    Keshin, revised schematic below. You will need 1 extra transistor as show. I have included the decoupling capacitor too.

    OBSOLETE SEE LATER SCHEMATIC


    ETO_2015_12_18_LED_Sequencer_Iss02_00.png
     
    Last edited: Dec 18, 2015
  18. Mosaic

    Mosaic Well-Known Member

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    R11 at 560 ohms drops a max of 5.2V or so for 9mA base drive. But you are asking for 14 x 0.03A (if LED Vf =3V), or 420mA. 9mA is not enough base drive. For full saturation switching you need 40mA or the transistors will overheat in their linear region.

    For simpler construction.I'd suggest a 12V supply , and string 3 LEDs together at a time (2 minimum) with a 200R resistor to make up the letters. That should make the wiring a lot simpler and cut the number of dropping resistors down significantly. Current loads drop by around 2/3rs toperhaps 120mA per transistor (12mA base drive) and R11 can then be (12-.65)/.012 or about 1K.
     
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    What is the transistor for "LBIP#7" for? The name has 6 letters and the 7th output resets the counter to light the first letter LEDs again. The 7th output will occur for such a short duration that if it drives an LED then that LED would not be visible. Instead of resetting the counter it would be nice if the 1st to 6th CD4017 outputs have series diodes feeding the 560 ohm resistors then the 7th to 9th outputs can drive a transistor to turn on all six transistors that drive the letters. The 10th output would be a pause without any LEDs lighted before the counter begins again.
     
  20. spec

    spec Well-Known Member Most Helpful Member

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    Great minds think alike:cool:

    ETO_2015_12_18_LED_SEQUENCER_Iss03_00.png
    ERRATA
    (1) Trace missing LED3 & LED4 cathodes
     
    Last edited: Dec 18, 2015
  21. spec

    spec Well-Known Member Most Helpful Member

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    Hello Keshin,

    Here is LED SEQUENCER2.
    This version will prgressively turn the LED Banks on, then pause off and then start over again.
    Perhaps get issue 03 of LED SEQUENCER working OK and then fit the extra transistors, resistors and capacitors later.
    It is possible that the extra capacitors will not be required, so try LED SEQUENCER2 without them first.

    ETO_2015_12_18_LED_SEQUENCER2_Iss01_00.png
    ERRATA
    (1) Q3, R10, & C5 are not fitted to LED BANK #1
    (2) FEEDBACK HOLD OUTPUT LB2 connects to FEEDBACK HOLD INPUT LB1 and so on
    (3) Verticle trace across across counter output lines delete.
     
    Last edited: Dec 19, 2015

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