Hello Everyone,
I want to make a timer from a 555 timer. It should be able to set the timer for max 15 seconds. It should also be able to set times with 2 second intervals until 15 seconds. Monostable 555 timer design. I want the circuit diagram and way of finding the resistances.
Thank you Everyone !!!!!!!!!!
Great Help.

 

Circuit and formula for calculating the time is in the datasheet.

 

I checked the data sheet but I am not comfortable in drawing the circuit on the data sheet using multisim. Is there any way I could find a simpler circuit diagram that is more easier for a beginner.

 

a simpler circuit diagram

You won't find a reliable circuit simpler than Fig 14 in the datasheet.

 

Can You have a look whether this is correct .

 

How do you wish to select the time ? Rotary switch, electronic switch as 4017, 4066 ? Timing is close to just RC . Start with a 1 M pot & 20 uF, adj. to 15 s, measure, replace with fixed value. 2 s will be about 100k .

 

How do you wish to select the time ? Rotary switch, electronic switch as 4017, 4066 ? Timing is close to just RC . Start with a 1 M pot & 20 uF, adj. to 15 s, measure, replace with fixed value. 2 s will be about 100k .

I want to use a rotary switch to set times."Start with a 1 M pot & 20 uF, adj. to 15 s, measure, replace with fixed value. 2 s will be about 100k ." can you explain me this part a bit more. can u label which circuit component should be replaced with 1 M pot and a 20uF capacitor on the picture I sent before.

 

What minimum time interval setting do you want?
The minimum for a 2 second interval to 15 seconds would be 1 second.

 

What minimum time interval setting do you want?
The minimum for a 2 second interval to 15 seconds would be 1 second.

ok I'll have 1 second intervals for now. 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 .
can u tell me the resistor and capacitor values.

 

The equation is in the datasheet. Have you read it?

What does the timer do? What load or device or circuit is the output connected to?

ak

 

The equation is in the datasheet. Have you read it?

What does the timer do? What load or device or circuit is the output connected to?

ak

Yes,
I have attached a screenshot of the calculation but I am not getting these times as the output. I will be connecting the output to a relay.

 

15% of 1.05 MOhm takes around 15 seconds thus. 1.05M Ohm takes minutes but theoritically it should take 15.015 secs . where have I connected the circuit wrong ?

 

Large capacitors generally have a wide tolerance, like +_ 20% so calculations will just get you in the ball park.
I don't have a 20 uF but have a 22 which is really 23.4 uF @ 10 M ohm leakage. Leakage may change with use so soak it ( apply a V ) for awhile before selecting Rs. On your drawing, replace C with 20 uF & R with 1 M pot in series with 1k R.

 

How will you trigger the pulse?
With a pushbutton?

 

Large capacitors generally have a wide tolerance, like +_ 20% so calculations will just get you in the ball park.
I don't have a 20 uF but have a 22 which is really 23.4 uF @ 10 M ohm leakage. Leakage may change with use so soak it ( apply a V ) for awhile before selecting Rs. On your drawing, replace C with 20 uF & R with 1 M pot in series with 1k R.

Ok thanks I'll try it. BTW I want to change the times to 15,10 and 5 minutes.

 

How will you trigger the pulse?
With a pushbutton?

Yes, with a push button.

 

Ok thanks I'll try it. BTW I want to change the times to 15,10 and 5 minutes.

From seconds to minutes?
Those times are too long to reliabily do that with just a 555 by itself.
You could use a higher frequency 555 astable into a counter.
For example a 0.25 minute astable going to two CD4017 decade counters configured to divide by 20, 40, and 60.

 

From seconds to minutes?
Those times are too long to reliabily do that with just a 555 by itself.
You could use a higher frequency 555 astable into a counter.
For example a 0.25 minute astable going to two CD4017 decade counters configured to divide by 20, 40, and 60.

But then you might as well use a CD4060.

 

But then you might as well use a CD4060.

True.
But you need some added decoding logic to get the desired time delays which the CD4017 doesn't need.

 

True.
But you need some added decoding logic to get the desired time delays which the CD4017 doesn't need.

True, but only if accurate timings are required and they aren't going to be all that accurate using an RC oscillator.

[Thinks..]
With the '4060 you could switch different capacitors or resistors (and pots to set the individual times if you wanted) in the oscillator then no extra logic is required.