Replace double click with single

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
There's an old machine in my shop. When you work on it you have to double-tap a certain button a lot. It gets annoying considering the design of the button (long with a single pole in a middle). I wanted to install a new button (soldering it to the board in parallel to the old one), but so that you only have to tap it once. I tried looking for a push-button that would implement it mechanically, but didn't find anything. Anyone help me to design a schematics that would simulate that electronically?
 

MaxHeadRoom

Joined Jul 18, 2013
20,463
If the button is mounted on a PCB, then it could be a form of keypad contact, not the traditional, metalic contacts, if so it seems a poor choice for a machine shop equipment.
You could look at soldering a couple of conductors to the board at the old switch position and install a normal panel mount control version.
The other simple option is to use contact cleaner on the existing one.
A photo would help.
Max.
 

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
It moves a backstop of a paper cutter. Single click acts as a "=", when you use manual position input. To engage movement you have to double-tap it. Its not a safety feature, just a lazy design. On all other cutters there's a dedicated "move" button, since that's a button operator has to use the most.
 

MaxHeadRoom

Joined Jul 18, 2013
20,463
In that case, it may not be a feature of the PB, but a software feature, if so it precludes fitting any other kind of switch.
Max.
 

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
If the button is mounted on a PCB, then it could be a form of keypad contact, not the traditional, metalic contacts, if so it seems a poor choice for a machine shop equipment.
You could look at soldering a couple of conductors to the board at the old switch position and install a normal panel mount control version.
The other simple option is to use contact cleaner on the existing one.
A photo would help.
Max.
It's not a poor function issue. The switch itself works fine. I just want to add a separate button, that would simulate a double-click on the same circuit board contacts.
 

Yaakov

Joined Jan 27, 2019
1,612
My first impulse would be to find a similarly sized ON-OFF-ON momentary switch and wire the two ON sides in parallel. It would still require operating the switch all the way, but you could push one way, then pull all the way the other in one movement which might be less bothersome.
 

LesJones

Joined Jan 8, 2017
2,607
An electronic solution might be to use an exclusive OR gate. Feed the output of the switch directly to one of it's inputs and feed it to the other input via a delay network (A series resistor and a capacitor to ground from the gate input.) The output would be one pulse when the switch contacts made and another pulse when the switch contacts opened. This assumes that it is not a keyboard matrix system. If it was you could try adding a CMOS switch such as a CD4066.

Les.
 

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
My first impulse would be to find a similarly sized ON-OFF-ON momentary switch and wire the two ON sides in parallel. It would still require operating the switch all the way, but you could push one way, then pull all the way the other in one movement which might be less bothersome.
That's just replacing one inconvenience to another. I thought maybe there's a way to simulate a double click. For example, pressing a button creates two pulses that close a relay. I'm not good at electronics design myself, but i'm sure there should be an easy solution for that.
 

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
An electronic solution might be to use an exclusive OR gate. Feed the output of the switch directly to one of it's inputs and feed it to the other input via a delay network (A series resistor and a capacitor to ground from the gate input.) The output would be one pulse when the switch contacts made and another pulse when the switch contacts opened.

Les.
That's, more like it
 

MaxHeadRoom

Joined Jul 18, 2013
20,463
It's not a poor function issue. The switch itself works fine. I just want to add a separate button, that would simulate a double-click on the same circuit board contacts.
One option may be to fabricate a two miniature micro switches wired in parallel, with a suitable notched operator.
Max.

upload_2019-7-18_8-54-29.png
 

MaxHeadRoom

Joined Jul 18, 2013
20,463
Or come to think of it, you may be able to use one micro switch, when pushed in it will operate the switch and then go far enough to go off the sw, on release, spring action return will activate the switch again.
Max.
 

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
Or come to think of it, you may be able to use one micro switch, when pushed in it will operate the switch and then go far enough to go off the sw, on release, spring action return will activate the switch again.
Max.
I was actually surprised to find that there are no "double-action" push-buttons on the market. You'd think someone would make them already.
 

Alec_t

Joined Sep 17, 2013
11,165
The schematic is not quite right. The cap should connect to ground, and B should connect instead to the junction of the R and C.
 

MrChips

Joined Oct 2, 2009
20,915
I was actually surprised to find that there are no "double-action" push-buttons on the market. You'd think someone would make them already.
There is no double-action switch on the market as far as I am aware. This is a software feature invented for the mouse.

For your application I believe a solution can be emulated in three different ways.

1) Use a bunch of RC circuits to detect rising and falling transitions of the button.

2) Use a series of monostable multivibrators to generate a pulse-delay-pulse.

3) Use a tiny microcontroller to do the same.
 

Thread Starter

Vikt0r

Joined Apr 23, 2019
18
Updated version. Couple questions:
1. When calculating RC, is there a preference between high R - low C or low R - high C.
2. Which type of capacitors is better for RC circuits?
 

Attachments

MaxHeadRoom

Joined Jul 18, 2013
20,463
I was actually surprised to find that there are no "double-action" push-buttons on the market. You'd think someone would make them already.
In the double action condition, does it close the same contact twice for the 'engage' action, if so the single micro would be simple, but even so, if double contact, it should be easy to make up a double switch arrangement, particularly as there is a single actuator through the middle.
Is it possible to post a pic of the switch?
Max.
 

MrSoftware

Joined Oct 29, 2013
1,746
>>> Edited to remove wireless suggestion:

You mentioned the "=" key, is it a standard keyboard and mouse? If yes, will the machine accept a USB keyboard? If yes again, consider configuring a basic arduino as a USB keyboard with a simple program that sends your favorite key twice when you push a button once. Put it in a pretty box and wire up your button of choice, now you have a dedicated button. Start here: http://mitchtech.net/arduino-usb-hid-keyboard/
 
Last edited:

LesJones

Joined Jan 8, 2017
2,607
I see Alec has beat me to correcting your circuit in post #13. You will probably have to play round with the C/R time constant to get the pulse length right. I like Max's idea of the micro switch once when the button is pressed and once when it is released. It is so simple to implement.

Les.
 
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