Hi All,

I am trying to automate an existing board with push buttons/tactile switch. I want to create a circuit that closes the circuit twice when powered on simulating push button was pressed twice when powered on.
But once the push button is bypassed and closed twice by the circuit it remains open till next power up.

I don't want to use any microcontroller.
I want this to be a cheap solution.

Thanks in advance for your help.

Regards
Susanta

 

it remains open till next power up

What is the interval between successive power-ups?

 

Sounds like something a CD4060 counter/timer could do.
What's the voltage.
Do you need relay contacts to simulate the push-button closure, or do you know what the switch does?

 

What is the interval between successive power-ups?

Thank you for replying.
It will be long enough may be once a day.

 

Sounds like something a CD4060 counter/timer could do.
What's the voltage.
Do you need relay contacts to simulate the push-button closure, or do you know what the switch does?

Thanks for the suggestion.
Grateful for your reply.
I will definitely look into it.
I was thinking if it can be done just with transistor and capacitor/resistors.

 

Do you have any particular reason for not using a processor?
I don't quite understand why you would not. A processor like an Arduino would make it easy, and enable the timings to be adjusted as required.
And the price can be very low if you Ebay it all.
I can get an Arduino Pro Mini Atmega168 for $2.34AU. It requires a programming lead for an extra $5 or so, but that is uesed for others too.
Or an Arduino Nano for $4.30AU.
That is pretty hard to beat.

 

I was thinking if it can be done just with transistor and capacitor/resistors.

It could be but it would take quite a few of all those components to generate the two sequential pulses you want.
Generating those two pulses is not a trivial problem, and is most easily done with a micro, as dendad suggested.

 

Do you have any particular reason for not using a processor?
I don't quite understand why you would not. A processor like an Arduino would make it easy, and enable the timings to be adjusted as required.
And the price can be very low if you Ebay it all.
I can get an Arduino Pro Mini Atmega168 for $2.34AU. It requires a programming lead for an extra $5 or so, but that is uesed for others too.
Or an Arduino Nano for $4.30AU.
That is pretty hard to beat.

Thank you.
I will take the wise man's word on this.

 

Consider using block language to program.

https://forum.allaboutcircuits.com/threads/pulse-sequence-generation.161138/#post-1408557

Block languages like mBlock, Scratch for Arduino, Ardublock, Snap4Arduino ......

Youtube has videos on these.


Regards,m Dana.

 

uP is best for your purpose, but if you must use non-uP, here is a circuit. Many years ago I made this to pulse the third brake light on my car. When you apply the brakes, it pulses a selected number of times, then remains on. It goes off when you step off the brake. You can set the pulse rate and the number for pulses with the pots.

 

The period between the successive closing, how much has to last? How precise needs to be?

 

Consider using block language to program.

https://forum.allaboutcircuits.com/threads/pulse-sequence-generation.161138/#post-1408557

Block languages like mBlock, Scratch for Arduino, Ardublock, Snap4Arduino ......

Youtube has videos on these.


Regards,m Dana.

Thank you for your kind suggestion.
Definitely I will look into it.

 

uP is best for your purpose, but if you must use non-uP, here is a circuit. Many years ago I made this to pulse the third brake light on my car. When you apply the brakes, it pulses a selected number of times, then remains on. It goes off when you step off the brake. You can set the pulse rate and the number for pulses with the pots.

View attachment 186292

Really grateful for putting up this diagram.
Thank you for your help.
I will let you know after I have given it a try.

 

The period between the successive closing, how much has to last? How precise needs to be?

Thank you for trying to help me here.
The period can be a few milliseconds even if within half a second should be fine.
It need not be very precise.

 

I have an old CD4060 circuit for this, but ...

Assuming the switch-simulating output can be an open-drain MOSFET,

1 - Inverter (1/6 hex inverter or equivalent)
1 - 2-input NAND gate (1/4 package)
R's, C's, etc.

1 chip, 24 soldered pins, no 555's, no development system, no code programming, no device programming, $1.00.

This can be done with two sections of a CD4093 Schmitt trigger quad NAND gate, or four sections of the same gate all acting as inverters, or four sections of a CD40106 Schmitt trigger hex inverter.

ak

 

Here is a circuit from 2017 that puts out a double pulse when powered up. You can ignore U1C and D (but their inputs must be connected to something), and delete X1 and the connection between U1 pins 10 and 11. A 2N7000 MOSFET gate connects directly to U1B pin 4, source to GND, and the drain is the output.

R1-C1 and R3-C3 set the widths of the two pulses, and R2-C2 sets the time delay between them. On powerup, C2 holds the U1A inputs low, so the output is high. The other end of C3 is pulled high by R3, so U1B is acting as an inverter. Pin 6 is held low for approx one R-C time constant, forming the first output pulse. After that pulse, pin 6 stays high so any activity on pin 5 is simply inverted at the output.

After one R2-C2 time constant the output of U1A goes low, pulling both sides of C3 low. C3 then starts charging through R3. U1B pin 5 sees this as a low pulse, inverts it, and this is the second output pulse.

ak

 

Double pulses at each power up, adj RC tc's as needed to change period and/or duty. Probably could use any ole cheapy fet on hand, total cost perhaps a few dollars. Suggest driving a SPST relay as I'm not sure of you circuit requires sinking and/or sourcing current .

 

Below is the LTspice simulation of the timer portion of AK's circuit in post #16.

If you need a relay to provide the contact closure, you can add a transistor and relay at the output.
Don't forget the diode across the relay coil for inductive spike suppression.
Also connect all unused inputs to ground.

 

The initial statement of requirements was rather lacking in quite a few details, such as supply voltage and also the actual output. Was the need for contacts, or a logic level, or mains voltage?
Why do some tout the use of a micro, with it's programming requirements, total lack of repairability, fragile structure, and invisible operation?

 

Why do some tout the use of a micro, with it's programming requirements, total lack of repairability, fragile structure, and invisible operation?

I could not resist
Over the years I have designed and built many circuits for industrial control applications.
And, yes, some did not have a micro.
But, as the thread starter was going to build this himself, it could well be a good project for learning a micro. So he would have the code to reveal the "invisible operation". Assuming that is what you are referring to.
The circuits above may well work ok, there is no argument against that. But I would suspect they will be prone to noise and component aging.

Recently, I had a batch of my boards returned for repair after being in the field for around 25 years. These were PIC based controllers. The "fragile structure" that had failed were the electrolytic caps. The micros were still going strong.

I tout the use of a micro as it is often easier and cheaper. A "discrete" design is good too as it shows the logic of the circuit, but I rarely use that now.