555 timer

Wendy

Joined Mar 24, 2008
23,415
That works, it is a monostable that triggers on power up, U1 powers the U2 circuit.

It might be better to use the output of U1 (pin 3) to reset on U2 (pin 4), and digitally control the second circuit instead.
 

Thread Starter

umer0314

Joined Jul 29, 2009
29
This is the circuit I designed on multisim you gave me. Can you please check If I did this right? Again it didn't do anything it just gave me a straight line. Its not giving voltage for the first 20 seconds and then 1 pulse every 60 seconds.
 

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Wendy

Joined Mar 24, 2008
23,415
That's what you've designed for. The second oscillator has a duty cycle of 99.18% and a freq of .02Hz, or a ½ sec pulse every 59 seconds. The 1st monostable is set for 44 seconds delay. What are you trying to do?

Here is a datasheet I use. Something I made up.
 

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Thread Starter

umer0314

Joined Jul 29, 2009
29
I am trying to make a 555 timer circuit that produces about 3 to 5 volts. The first timer would give voltage for 20 seconds continuous for example 1 pulse every second for 20 seconds or continuous as long as it gives voltage for 20 seconds. After those 20 seconds it also produces same voltage but this time it is 1 pulse every 60 seconds and stays 1 pulse every 60 seconds until power off. I want my power source to be AC.
 

Wendy

Joined Mar 24, 2008
23,415
I'm missing something. You want the first timer to turn on for 20 seconds, then turn off?

Let's talk waveforms. You want a 20 second pulse, then a ½ second pulse ever 60 seconds after the 20 second pulse from then on. Correct?
 

Thread Starter

umer0314

Joined Jul 29, 2009
29
Yes, I want the first timer to be on for 20 seconds producing 3 to 5 volts and then the second timer to produce 1 pulse every 60 seconds with same voltage, so a delay of 59 seconds and keep on doing this until power turned off. Not 1/2 a pulse but 1 pulse every 60 seconds. This controller needs to produce voltage and thats it but with that timing. The first timer will only be on for 20 seconds. I dont know If we can do the whole procedure with one 555 timer or one 556 timer. I am not familiar with 556 timer that well. I just need to design this circuit on multisim.
 

Wendy

Joined Mar 24, 2008
23,415
OK, but I still don't understand. Are you wanting a pulse train something like this?

___________........_..........._.........._
.................\____/.\______/.\_____/.\

A ½ second pulse is still a pulse, it is not ½ a pulse. This is a duration, a length of time. Is 0.5 seconds long enough?
 
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Thread Starter

umer0314

Joined Jul 29, 2009
29
You are right I misunderstood you. I think 1 second duration would be better for me then 1/2 a second duration. You can say it is kind of a pulse train that is not stop until power turned off. The only difference is you can say that when power on it gives 20 pulses in 20 seconds each pulse being 1 second long. Then after those 20 seconds it gives a duration of 1 second pulse but every after 60 seconds.

Example:

/-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\

this is 20 pulses in 20 second, 1 pulse is 1 second long

next step:

/-\_______ 59 seconds delay__________/-\ then keep repeating this step of 1 pulse 1 second long every 60 seconds until power turned off. The first 20 seconds only happens once when it starts.
 

Wendy

Joined Mar 24, 2008
23,415
OK, so I had it backwards,

_....._....._....._....._....._....._....._....._......_........................................._............................................._
.\__/.\__/.\__/.\__/.\__/.\__/.\__/.\__/.\___/.\________________________/.\___________________________/.\

Like this?

for 20 pulses in 20 seconds, 1 second is not an option (otherwise it is a solid high), ½ seconds is 50% duty cycle.
 
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Wendy

Joined Mar 24, 2008
23,415
OK, here's how I would do it...



Output will be approximently 3.2V with a 5V power supply. U3 is a simple inverter, you can replace it with a transistor inverter or CMOS, doesn't matter. U1 turn U3 on, with is a 1 Hz 50% oscillator. When U1 turns off U3 inverts the signal, turning U4 on, which matches your description.

Parts List

C1 - 0.1 µF
C2 - 100 µF
C3 - 10 µF
C4 - 100 µF
R1 - 10 KΩ
R2 - 187 KΩ
R3 - 70 KΩ
R4 - 850 KΩ
R5 - 15 KΩ
R6 - 1 KΩ
CR1,CR2 - Any silicon diode will work.
 

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Thread Starter

umer0314

Joined Jul 29, 2009
29
I designed the circuit you gave me on multisim, can you please check If I did it right. It just gave me a straight line and it was giving 0 volts. This is the oscilloscope settings:

Oscilloscope data: SCP

Time base: 0.010000 seconds per division
Time offset: 0.000000 seconds
Channel A sensitivity : 5.000000 volts per division
Channel A offset: 0.000000 volts
Channel A color: 255
Channel B sensitivity : 5.000000 volts per division
Channel B offset: 0.000000 volts
Channel B color: 6604900
Channel A connected: yes
Channel B connected: no

Column 1 Time (S)
Column 2 Channel_A Voltage(V)
Column 3 Channel_B Voltage(V)
 

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Wendy

Joined Mar 24, 2008
23,415
My bad, R4 and R5 are reversed. I'll correct the original post.

As for multism, not a clue. I know 555 circuits, but don't know squat about mulitism.

My confidence in the revised schematic is pretty high.
 

Thread Starter

umer0314

Joined Jul 29, 2009
29
I corrected R4 and R5 but still It didn't do anything. I think maybe multisim is the problem. Do you know any other software where I can design this circuit because I have to show this to my professor. The circuit you gave me IF that gives me 20 pulses in 20 seconds and then 1 pulse after every 60 seconds and producing 3.2 volts maybe I can just directly build it and get those results, it that ok? I didn't replace U3 with a inverter or anything I just used a 555 timer for that too, is that ok?
 

Wendy

Joined Mar 24, 2008
23,415
Yes, that should be OK. Start from the beginning. What does multism say U1 and U3 is doing? It should say it gives a 20.7 second pulse when power is applied.

I don't know much around SPICE, but it sounds like you may have trouble setting up the initial condition, that of the power supply being 0V, then going to 5V. This may be worth starting a second thread over, and focus (for now) on U1 and U3 producing that pulse. The name of the thread is what gets peoples attention, so focus on the problem you are having. Something like "Setting up MULTISM initial conditions...", then use the U1 circuit and try to show the pulse from it.
 

Thread Starter

umer0314

Joined Jul 29, 2009
29
I am not sure how to check U1 and U3 on multisim to see what it is doing. I just attached an oscilloscope to the output of the circuit you gave me. I used the probe to check for voltage that was coming out from U1 and U3 it was giving me 0 volts.

IF this circuit its not working on multisim, it will work on a bread board right?
The circuit you gave me what If I just built it exactly you gave me and attached with a oscilloscope in school. It will give me 20 pulses in 20 seconds then 1 pulse after every 60 seconds? The same pulse train we talked about.

How can I add a trigger or a push button on this circuit as my input. So when I push it the circuit starts?
 

Thread Starter

umer0314

Joined Jul 29, 2009
29
Can you please explain that? Can you put a switch in your original circuit that will help me better understand?

Thank you!
 
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