how can i make a timer which is triggered for 1 sec in a min

[pateljayam]

hey guys
i want to make an application in which i can trigger a buzzer only for a sec in a min.
rest of 59 sec the circuit has to be in sleep mode.
please help me out!

can i do it with any kind of PWM ic or may be some sort of 555 circuit
cause i tried making it with 555 but as we know that in astable state the on/off cycle are equal which i dont want!


thank you

 

[jpanhalt]

Actually, the duty cycle of the original 555 astable circuit is greater than 50%. It requires some modification to get exactly 50% (See: **broken link removed**). One approach to your question would be is to have the duty cycle 59/60%, then invert the signal.

A simpler way is to insert a diode in the astable circuit to separate the charging and discharging paths. That approach is described on page 5 of this application note, which is no longer available from Philips:

https://www.electro-tech-online.com/attachments/555an-pdf.52952/

One can do the same thing with a relaxation oscillator made from a Schmidt inverter as done here by Dekker (scroll to Inductor Test bench):

https://www.dos4ever.com/flyback/flyback.html#ind2

Both diode-based methods can give you a very low duty cycle.

John

 

[dr pepper]

2 555's, one in a 1 pulse a min astable, and the other a monostable 1 sec triggered by the 1 min astable.

If you need precision for the 1 minute duration you might be able to use a xtal oscillator in conjunction with a 4060 or other binary counter.

If you use a 7555 or tlc555 you'd be operating at very low power during the off cycle.

A pic micro would be the professionals choice, assuming you have the means.

 

[laurenrodriguez]

The 8-pin 555 timer must be one of the most useful ICs ever made and it is used in many projects. With just a few external components it can be used to build many circuits, not all of them involve timing!A popular version is the NE555 and this is suitable in most cases where a '555 timer' is specified. The 556 is a dual version of the 555 housed in a 14-pin package, the two timers (A and B) share the same power supply pins.

The circuit symbol for a 555 (and 556) is a box with the pins arranged to suit the circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output on the right. Usually just the pin numbers are used and they are not labelled with their function.

Standard 555 and 556 ICs create a significant 'glitch' on the supply when their output changes state. This is rarely a problem in simple circuits with no other ICs, but in more complex circuits a smoothing capacitor (eg 100µF) should be connected across the +Vs and 0V supply near the 555 or 556.

 

[colin55]

Use a 74c14 as it takes almost no current when sitting around for 59 seconds.

 

[ChrisP58]

The standard 555 can sink as much current as it can source, so I would suggest tying the buzzer between the positive supply rail and the 555 output. So the buzzer is off during the output high time. Just use a regular astable 555 set for the period and duty cycle.

 

[pateljayam]

thank you guys really helped a lot!!!
was successful in making it
just a bit of precision is needed but i guess i will make it
thanks a loads