Can 555 Timer work for two minutes and then pause for ten seconds? How is that

Thread Starter

Omar551

Joined May 29, 2021
4
Hi.. Notice, I'm not an electronics professional, and the question might sound silly.
Can the ICTime like 555 Timer or ne555 be set in an oscillation or rotation manner, so that the working period is two minutes and the pause is ten seconds and continue like this?
The most important thing is whether the setting is by code or by the method of Conduction or what?
witchcined of these mode i have to use:
"if I want it to work for two minutes and pause for 10 seconds ... and continue like this"
555 Timer as Astable Multivibrator
555 Timer as Monostable Multivibrator
555 Timer as Bi-Stable Mode
 
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BobTPH

Joined Jun 5, 2013
3,316
The '555 does not have code.

You would use astable mode. The 2 minute period can be done, but it will not be accurate. The timing is controlled by a capacitor and 2 resistors.


Bob
 

Tonyr1084

Joined Sep 24, 2015
5,990
Welcome to AAC.

Capacitors and resistors react to temperature and cause their value to drift. Cheaper made parts have greater variances. That's why achieving a 2 minute on and 10 second off (pause) period is not considered accurate. If you can live with a lack of accuracy then you would use a 555 timer chip.

If accuracy is required then you're better off with a microprocessor. You control the timing with code. You could achieve very accurate and stable time periods that way.

So the questions to you is "How accurate do you want it" and "How much variance in timing can you tolerate"?

EDIT: What are you wanting to control? What amperage?
 

Ian0

Joined Aug 7, 2020
2,252
Firstly, look at the capacitor tolerance. You might not get better than ±20% for the size of capacitor you need, that will tell you the best accuracy you are likely to achieve. Then there's capacitor leakage current which will spoil it even further.

If you want accuracy without a microprocessor you could start with a higher frequency. You could probably get a 555 (or at least a CMOS version) to do 5 seconds off/ 5 seconds on reasonably accurately, then divide by 13.
 

Tonyr1084

Joined Sep 24, 2015
5,990
In this schematic "Ra" and "Rb" control the longer charging time of the capacitor. Discharging the cap is through "Rb". That is where you get your timing for how long the output is high (pin 3) and how long it takes to go low. The 555 timer chip is just a voltage divider with a built in switch. When 2/3 of the voltage is reached then pin 7 becomes active and drains the capacitor. When 1/3 of the voltage is reached pin 7 becomes inactive (does nothing) and the capacitor starts charging up again. The cycle continues until you turn it off.

1622302326916.png
 

Tonyr1084

Joined Sep 24, 2015
5,990
You could probably get a 555 (or at least a CMOS version) to do 5 seconds off/ 5 seconds on reasonably accurately, then divide by 13.
Good approach for accuracy.

Questions still remaining: Accuracy? Can you tolerate variance in performance? What are you driving (circuit wise - I don't care about your car)?
 

Thread Starter

Omar551

Joined May 29, 2021
4
Firstly, look at the capacitor tolerance. You might not get better than ±20% for the size of capacitor you need, that will tell you the best accuracy you are likely to achieve. Then there's capacitor leakage current which will spoil it even further.

If you want accuracy without a microprocessor you could start with a higher frequency. You could probably get a 555 (or at least a CMOS version) to do 5 seconds off/ 5 seconds on reasonably accurately, then divide by 13.
thank you for that but my need it 2 minute on/ 10 seconds off .. continuously
 

Thread Starter

Omar551

Joined May 29, 2021
4
So the questions to you is "How accurate do you want it" and "How much variance in timing can you tolerate"?

EDIT: What are you wanting to control? What amperage?
thank u so much for your clarification and questions
-accurate Not that important even if the difference 3 or 4 seconds
- variance in timing 5% Acceptable
- The circuit is for a battery-powered ignition device, very similar to an electric cigarette lighter
-amperage will be 12v or 3.7 (I am first of all, and I will determine the type of current based on the advice I receive from the experts)


thank u again
 

Ian0

Joined Aug 7, 2020
2,252
thank you for that but my need it 2 minute on/ 10 seconds off .. continuously
Yes - that's what it would do.
5 seconds on 5 seconds off gives you a 10 second period. Divide by 13, gives a total of 130 seconds repeat time.
Use something like a 74HC161. Invert TC and connect to PL.
Set the preset inputs to 3.
So it will count 3-4-5-6-7-8-9-10-11-12-13-14-15-3-4-5-6 etc, and the TC output will be high for 1 period (10 seconds) and low for 12 periods (2 minutes)
 

DickCappels

Joined Aug 21, 2008
7,442
The NE555 is not the only chip that does timing. If you need precision, we can probably show you better ways to do it if you tell us the precision you desire.
 

crutschow

Joined Mar 14, 2008
27,229
As suggested by Ion0, below is the LTspice simulation of a 555 astable generating a 0.1Hz clock, driving a divide by 13 counter to get the 10s output pulse with a 120s period.
This should be more accurate than trying to do it with just a 555 (which likely would have a problem getting a 120s time)

1622314757331.png
 

Papabravo

Joined Feb 24, 2006
16,160
Yes - that's what it would do.
5 seconds on 5 seconds off gives you a 10 second period. Divide by 13, gives a total of 130 seconds repeat time.
Use something like a 74HC161. Invert TC and connect to PL.
Set the preset inputs to 3.
So it will count 3-4-5-6-7-8-9-10-11-12-13-14-15-3-4-5-6 etc, and the TC output will be high for 1 period (10 seconds) and low for 12 periods (2 minutes)
Works pretty well IMHO
 

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AnalogKid

Joined Aug 1, 2013
9,257
If you need any kind of decent repeatability / stability / accuracy, 2 minutes is a loooong time for an R-C timer circuit. Consider a CD4060 oscillator/divider with much smaller (hence more accurate/stable) timing components. Keeping things to a single chip solution, the cycle gating is 2 diodes and 2 resistors.

ak
 
I would vote IanO’s suggestion as the one which has the best chance of a successful implementation. Which is a higher frequency astable followed by a counter.

Many moons ago I attempted something similar with a 555, and the required large electrolytic caps will simply have too much leakage current to work consistently.
 
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