555 Timer Help

Discussion in 'The Projects Forum' started by umer0314, Sep 1, 2009.

  1. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    Hey GUYS!

    I am working on a 555 timer controller on a software called Multisim. The objective of my controller is to produce voltage from about 3 to 5 volts.
    What I need this controller to do is to produce pulses with the timing that I want.

    First Step:

    Produce 20 pulses in 20 seconds. Each pulse can be either 1/2 second or 1 second long it doesnt matter but it only lasts 20 seconds.

    ex: /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\

    These are 20 pulses in 20 seconds

    Second Step:

    After the first step is done which is only 20 seconds long the next step is to create a pulse but with a delay. This pulse should only be produce once every 60 seconds and keep on repeating this second step until power turned off.

    ex: /-\ ________________________/-\________________________
    pulse 59 sec delay pulse 59 sec delay

    The first step only happens once and second step keeps on repeating until power off.

    Can someone help me create this circuit.

    Thank you!
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
  3. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Its your multisim giving the problems. There ain't a better circuit than what you have.
     
  4. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    I was thinking maybe I can just built it directly on the bread board and tell my professor its the multisim that is giving me the problem.

    If I build this, It will give me 20 pulses in 20 seconds in the beginning and 1 pulse after every 60 seconds and keep repeating the seconds step and produce 3 volts at least? Do you know how much current it will produce?

    If you guys are sure it will do this and I should just build it?

    What would it look like on a bread board?
     
  5. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    The Output depends on your supply voltage. It will give nearly the same voltage as your Vcc.

    At 5V Vcc, High output = 3.3V, Low output = 0.05
    At 15V Vcc, High output = 13.3, low output = 0.3

    You can reduce it if you want with resistors and zenners. Current will be 200mA maximum. If your need more current, use transistors on the output.

    It will work for sure, but after you build it, double check it to make sure you have made no mistakes in connection to fry anything.

    If you use 555's, It will be 4 555's arranged in a staright line. If it is 556, will be just 2 chips.

    You can also try a simulation on another program if you need to. There are lots of them available including free versions. Just check out the Electronics chat thread.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Try breaking it down. U1 should turn on for the requeset 20 seconds in your SPICE. When U2 is on it will oscillate around 1 Hz. Do each one separately, then move on.

    Most jobs can be broken into smaller more managable pieces.
     
  7. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    You mean when U2 is on it will oscillate around 1 Hz meaning it produce 1 pulse after every 60 seconds right? And each pulse is 1/2 a second long right?

    I want to put two leds in this circuit and I can try to show the simulation that way to, where should the leds go. The green led can show the frist 20 pulses lighting up fast 20 times and after that it will show one green led lighting up for about 1 second and the other red led lighting up meaning waiting 59 seconds.
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    U1 is a power up monostable that stays on 20.6 seconds. You should be getting this. The button will allow you to manually trigger that, but I put a button (without a signal conditioner) to test this. You can find the details here.

    The other circuit around U2 is equally basic, it's details are here.
     
  9. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    I kind of got confused about what you just said can you please explain it to me.

    In this circuit after the output is high for 20.6 seconds in monostable mode it automatically goes to 1 pulse after every 60 seconds right which would be astable mode?

    Can you please tell me where I can put the leds in the original circuit to show the output?
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    U1 is a monostable. It is on for 20.6 seconds when powered up. When it is high the U2 1Hz oscillator works. When U1 goes low u2 is disabled and U3 (a simple logic inverter) goes high, turning U4 on. U4 is the once every minute oscillator. The diodes combine the two signals.

    Study the articles I referred you to with the links. They explain how these circuits work.

    Try each circuit separately.

    555 Monostable
    555 Hysteretic Oscillator
     
  11. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    How would I build each part of the circuit separately? For monostable I would just build U1 and U2 together then for the hysteretic oscillator I would build U3 and U4 together? Can you please show me each one separately?
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Try using the datasheet I attached previous. Shows each basic 555 circuit as a block.

    The power up 555 (U1) gets it signal from the resistor capacitor not shown in the datasheets diagram.

    Here is the power up schematic shown driving a relay.

    [​IMG]

    I've also shown you these links, which come with a theory of operation.

    The 555 Projects

    555 Monostable

    555 Hysteretic Oscillator

    You need to try reading these. They really do explain a lot.
     
    Last edited: Sep 7, 2009
  13. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    So I should build this circuit you just gave me with a relay to see the monostable stage?

    What If I just build the whole circuit together the original one with 4 555 timers on a bread board? That would just work?
     
  14. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    At this point it is up to you, I can advise, but I can't do the work.

    I was thinking this was a problem in multism, in which case I would wire each circuit individually in multism to get them to work separately, then build on that.

    I am extremely confident that these work on a protoboard. Have you looked at any of the links I recommended? I show how I did it on a protoboard. These are all verified experiments.

    The relay was left over from a drawing I made for another thread, another OP. It is not needed, nor is the transistor. It does illustrate what a circuit like this might end up driving however.
     
  15. umer0314

    Thread Starter Member

    Jul 29, 2009
    29
    0
    I tired each circuit separately on multisim and it did work. Now I want to build the whole thing together on bread board. Not separately but do the whole circuit together and give me that 20 pulse in 20 seconds and 1 pulse after every 60 seconds after that. I am sure too if will work but I hope when the pulse goes high for 20 seconds and then automatically goes to 1 pulse after every 60 seconds and there on. I hope no disturbance there in that step in the middle.

    Is radioshack the best place to get the equipment?

    Thank you!
     
  16. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Radio Shack has it, but you can get it a lot cheaper elsewhere. What part of the world are you? I'm guessing USA since you mentioned Radio Shack. Parts houses like Digikey, BG Micro, and others are generally less than half the cost, if you can find a local store even better.

    I use Radio Shack myself, but that is more because I put them on the parts lists of my articles. If I am in a hurry I'll got there, but in this case time savings cost money.
     
  17. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
Loading...