Turn on relay by default, turn off when push button press

Thread Starter

sforsandeep

Joined Feb 6, 2020
1
Hi Friends,
Myself a very beginner in electronics and I'd like to build a design to control an AC device.
When activating a momentary push button, it should turn on the device. When pressing another button, it should turn off the device. But I'd like to make this without Arduino or any MCU.
I've a 40A SSR for the purpose. But not getting an idea how to implement it
 

dendad

Joined Feb 20, 2016
3,591
Without showing you how to actually do it, maybe read...
https://en.wikipedia.org/wiki/Flip-flop_(electronics)
Or here is one using the famous 555 IC....
https://www.eleinmec.com/article.asp?5

Drive the LED of the SSR from an output, and add a couple of push buttons to set and reset.
A hint, put a small capacitor across the reset button to ensure it starts in the reset condition.

Make one up on breadboard just running a couple of LEDs for a start.
 

danadak

Joined Mar 10, 2018
4,057
Just out of curiosity why not an Arduino or ATYTNY85 ? Is it the coding
you would find difficult ?


Regards, Dana.
 

vu2nan

Joined Sep 11, 2014
161
Hi Friends,
Myself a very beginner in electronics and I'd like to build a design to control an AC device.
When activating a momentary push button, it should turn on the device. When pressing another button, it should turn off the device. But I'd like to make this without Arduino or any MCU.
I've a 40A SSR for the purpose. But not getting an idea how to implement it
Hi Sandeep,

Why not just use an electromagnetic relay/contactor?

laching-circuits1.gif

The remaining 'NO' contacts of relay/contactor 'K' may be used to control the load.

Regards,

Nandu.
 
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MisterBill2

Joined Jan 23, 2018
6,720
I have created that circuit at least a hundred times in designing machines, and it is simple and reliable,. But if you are determined to ONLY use that 40 amp rated SSR things get a bit more complex.
The standard arrangement uses one normally open contact on a relay to hold the coil energized, and a normally closed pushbutton to momentarily open the circuit to release the relay. I am guessing that the 40 Amp SSE requires 5 or 12 volts to tun it on, since most of them do not have a mains voltage control input. In that case you can use a quite cheap single pole relay for the logic and not need to use mains-insuklated wire for the controls wiring. The circuit would be similar, but not identical, to the one shown in post #5
 

danadak

Joined Mar 10, 2018
4,057
I would think that a self-declared beginner in electronics would know very little about how computers work, much less how to code them.
This can be done w/o coding......is partly the point of my asking. All micro users started knowing very little.....including me.
Its why we are the techs and EEs and hobbyists we are, we explore, learn, try, fail, try again......

And unless the TS has been in a box his/her life they have been programming, using a calculator, in their collective heads.
He/she just need an explanation there is another view behind what happens when operating a 4 function calculator.


Regards, Dana.
 

MisterBill2

Joined Jan 23, 2018
6,720
Observe with the circuit shown here in post #10 that there is fairly serious problem if the load current is other than very little. The problem is that every bit of the load current passes through the start button until such time as the relay starts conducting. With a mechanical relay that may be from 20 to possibly as much as 100 milliseconds. And even worse, every bit of the load current also passes through the off button as long as the circuit is on.
Certainly there are inferior quality appliances that use this arrangement but I would not want one of them. You will not find a direct connection scheme like this in any equipment where reliability is important.
And is it likely that the 40 amp rated SSR has a 240 volt control input?
Remove the load from in parallel with the coil and instead control it with the main contacts on a contactor, with the latching on done by the extra contact and you have a valid circuit concept.

But since we have no other information about the SSR other that it has a 40 amp rating, we do not know, and so it is guesses.
 

Reloadron

Joined Jan 15, 2015
5,609
Hi Friends,
Myself a very beginner in electronics and I'd like to build a design to control an AC device.
When activating a momentary push button, it should turn on the device. When pressing another button, it should turn off the device. But I'd like to make this without Arduino or any MCU.
I've a 40A SSR for the purpose. But not getting an idea how to implement it
There are several ways to do what you wish to do. Keeping it simple I would consider a latching relay circuit using a DPDT or even a DPST NO (Normally Open) relay. A circuit similar to this:
Latching Relay Ckt..gif

Just focus on the upper part of the drawing. Any relay with a 5 volt coil or 12 volt coil will do fine. The idea is when the momentary switch push button which is N/O (Normally Open) is momentarily pressed RY1 coil is powered through the N/C push button, the N/O contacts will close and this creates a latching action. When the N/C (Normally Closed) push button is pressed it opens the circuit, the RY1 coil field drops out and that's it the Start / Stop process is repeated. A Google of latching relay circuits will bring up a few dozen circuits like this and those already posted.

Then using another set of N/O contacts on RY1 power your SSR control lines. Generally 3 - 32 VDC but you didn't mention that.

Ron
 

MisterBill2

Joined Jan 23, 2018
6,720
There are several ways to do what you wish to do. Keeping it simple I would consider a latching relay circuit using a DPDT or even a DPST NO (Normally Open) relay. A circuit similar to this:
View attachment 198571

Just focus on the upper part of the drawing. Any relay with a 5 volt coil or 12 volt coil will do fine. The idea is when the momentary switch push button which is N/O (Normally Open) is momentarily pressed RY1 coil is powered through the N/C push button, the N/O contacts will close and this creates a latching action. When the N/C (Normally Closed) push button is pressed it opens the circuit, the RY1 coil field drops out and that's it the Start / Stop process is repeated. A Google of latching relay circuits will bring up a few dozen circuits like this and those already posted.

Then using another set of N/O contacts on RY1 power your SSR control lines. Generally 3 - 32 VDC but you didn't mention that.

Ron
Thanks, Ron, this indeed is the circuitI was describing., even drawn with standard symbols. And all of your comments are exactly on target. Doing this with an arduino would be a whole lot more complex, more expensive, and much less reliable.
 

danadak

Joined Mar 10, 2018
4,057
An advantage of using Arduino/ATTINY85 is ability to debounce buttons
for glitch free load control. Also establish min button press time to
screen out false turn on of SSR.

This would have to be checked but I believe the Arduino/ATTIN85 GPIO
are glitch free during power up of Arduino/ATTINY85.

Disadvantage is one needs a power supply for the ATINY85/Arduino.

Programming can be done in mBlock or similar block language where you
drag and drop functional blocks, config them, and tool converts the visual
environment to Arduino code. The code you see in right hand window was
generated from user block coding window immediately to its left.

Note this example implements button debounce, so would have to be
expanded to handle second button and the on off functionality. There is a
learning curve doing all this, but very rewarding for future project creation
and capabilities. Example of a talking voltmeter, a very complex problem
turned into a simple program as you can see. https://forum.allaboutcircuits.com/threads/talking-arduino.161537/


1581160638239.png




1581158748782.png

Regards, Dana.
 

Attachments

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MisterBill2

Joined Jan 23, 2018
6,720
An advantage of using Arduino/ATTINY85 is ability to debounce buttons
for glitch free load control. Also establish min button press time to
screen out false turn on of SSR.

This would have to be checked but I believe the Arduino/ATTIN85 GPIO
are glitch free during power up of Arduino/ATTINY85.

Disadvantage is one needs a power supply for the ATINY85/Arduino.

Programming can be done in mBlock or similar block language where you
drag and drop functional blocks, config them, and tool converts the visual
environment to Arduino code. The code you see in right hand window was
generated from user block coding window immediately to its left.

Note this example implements button debounce, so would have to be
expanded to handle second button and the on off functionality. There is a
learning curve doing all this, but very rewarding for future project creation
and capabilities. Example of a talking voltmeter, a very complex problem
turned into a simple program as you can see. https://forum.allaboutcircuits.com/threads/talking-arduino.161537/


View attachment 198592




View attachment 198588

Regards, Dana.
Relay logic does not need contact debouncing. Why junkify a well proven very reliable arrangement with a toy processor?
IN ADDITION, the TS mentioned in their fourth sentence that they did NOT want to use an arduino. That alone is a good reason to not consider it.
 
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