Binary-Coded-Decimal rotary switch replaced with Potentiometer

Thread Starter

PaulKruse

Joined Nov 9, 2023
5
Hi everyone.

I am new to this site and thought I might find some helpful info here, I have a machine that uses BCD rotary switches for feed, rpm and axis selection and override percentages, I can not find these switches anywhere only pcb mount ones that will not work in this environment.
Maybe someone here recognizes the attached picture of the switch I am looking for.
Anyway, the main reason for this post.
I understand that a BCD switch has a common input and say 5 other wires connected to it that would be the outputs and when turning/switch the knob to the next position some of those output wires would be "HIGH" and some "LOW" and the sequence will then create a binary code that the machine interoperates. This from what I understand is to have more selection with less wires.
I have a 5 and a 13 position switch on my machine that I would like to replace with maybe a Potentiometer or rotary encoder without interfering with the machines current wiring(PLUG AND PLAY) I thing that the common wire is 24v not sure if AC or DC, but I will check that.
Is there a way that I could use say an Arduino to read a potentiometer, output a code to some kind of IC and switch selected outputs for the 24v signal to the wires?
2 of the switches are working and I was thinking that I could map the outputs with a multimeter and then just use that to sequence / emulate the original switches. obviously a bank of relays are not going to work so a IC with 24v output and 5v control capability would be ideal.
I am sure that there is many ways to solve this problem but I am more mechanical than electrical and could really use the help to try and solve this problem.

Hope I gave enough info.

Thanks in advance
PaulWhatsApp Image 2023-11-08 at 09.04.21.jpegWhatsApp Image 2023-11-08 at 09.07.26.jpeg









WhatsApp Image 2023-11-08 at 09.08.20.jpegWhatsApp Image 2023-11-08 at 09.07.44.jpeg
 

panic mode

Joined Oct 10, 2011
2,670
rather than reinventing the wheel (and adding arduino, relays or driver ICs etc.) why not check in comparable products already on the market?
GrayHill is one of makers of many similar products including
https://www.mouser.ca/datasheet/2/626/grhl_s_a0002921684_1-2289353.pdf
https://www.mouser.ca/datasheet/2/626/grhls01175_1-2289301.pdf
https://www.mouser.ca/c/electromechanical/switches/coded-rotary-switches/

one possibility is to use standard rotary selector switch with multiple decks (one per bit)
or single deck and encode it with handful of diodes.
 
Last edited:

Thread Starter

PaulKruse

Joined Nov 9, 2023
5
rather than reinventing the wheel (and adding arduino, relays or driver ICs etc.) why not check in comparable products already on the market?
GrayHill is one of makers of many similar products including
https://www.mouser.ca/datasheet/2/626/grhl_s_a0002921684_1-2289353.pdf
https://www.mouser.ca/datasheet/2/626/grhls01175_1-2289301.pdf
https://www.mouser.ca/c/electromechanical/switches/coded-rotary-switches/

one possibility is to use standard rotary selector switch with multiple decks (one per bit)
or single deck and encode it with handful of diodes.
Thanks for the quick reply and the info!
I thought this might be a case of re inventing the wheel but i do not have that much knowledge of circuits, to know what would work for the applications. Do you think the switches are proprietary that I can not find something to replace them with? I also do not know what to look for. BCD, coded switch and rotary dip switch is all that I could find but nothing matches or even looks similar.
I will look into the switches you recommended!
thanks again
 

MisterBill2

Joined Jan 23, 2018
17,796
If you could replace the switches with a variable resistor you would discover a different speed every time. Probably that is not what you want.
 

djsfantasi

Joined Apr 11, 2010
9,151
BCD switches use 4 bits to encode one decimal digit from 0-9. You mention 5 and 15 positions, so I don’t think they’re BCD switches. They could be binary coded; just not binary coded decimsl (BCD). You’d need three bits or three outputs to encode 0-5 in binary. Or four bits or outputs to encode 0-15 in binary. 0 could be an off position. But it really doesn’t matter because you’d still need 3/4 bits regardless.
With 1 bit you can encode two values (0 & 1). With 2 bits you can encode up to four values (0,1,2,3). With 3 bits you can encode up to eight values (0,1,2,3,4,5,6,7). And with 4 bits you can encode up to 15 values (*taking a deep breath* 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15).
Or the encoding may not be easily organized in a sequential manner. Each control may control a variety of sub-circuits. In this case, a proprietary switch with internal circuitry (such as a diode matrix) might be what you have.
You can’t tell without more testing and research.
 

Thread Starter

PaulKruse

Joined Nov 9, 2023
5
BCD switches use 4 bits to encode one decimal digit from 0-9. You mention 5 and 15 positions, so I don’t think they’re BCD switches. They could be binary coded; just not binary coded decimsl (BCD). You’d need three bits or three outputs to encode 0-5 in binary. Or four bits or outputs to encode 0-15 in binary. 0 could be an off position. But it really doesn’t matter because you’d still need 3/4 bits regardless.
With 1 bit you can encode two values (0 & 1). With 2 bits you can encode up to four values (0,1,2,3). With 3 bits you can encode up to eight values (0,1,2,3,4,5,6,7). And with 4 bits you can encode up to 15 values (*taking a deep breath* 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15).
Or the encoding may not be easily organized in a sequential manner. Each control may control a variety of sub-circuits. In this case, a proprietary switch with internal circuitry (such as a diode matrix) might be what you have.
You can’t tell without more testing and research.
Hi ,
I mapped the 13pos switch, it is not in the order that the pins are on the switch, numbers are correct though they are just staggered , but the positions are in order from 1-13, if you dont mind, could you please have a look and see if you could make out what type it is. I assumed that pin 1 is common, could be wrong.
 

Attachments

dendad

Joined Feb 20, 2016
4,426
1699594196077.png
It looks to me to just be a binary coded switch.
Pins 1 and 5 may be commons.
Pin 2 = 1
pin 4 = 2
pin 6 = 4
pin 3 = 8.

Just a thought, have you tried to use any contact cleaner/lubricant spray on one of the faulty switches to see if that helps?

It may be worth your while to contact the factory...
https://www.electro-nc.com/contact-us
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
28,513
Hi everyone.
I understand that a BCD switch has a common input and say 5 other wires connected to it that would be the outputs and when turning/switch the knob to the next position some of those output wires would be "HIGH" and some "LOW" and the sequence will then create a binary code that the machine interoperates.
Typically BCD switch only requires 5 connections, four for the digits and one for common?
You may have something else going on there!?
Did you check the logic with a meter?

1699630020381.png
 

djsfantasi

Joined Apr 11, 2010
9,151
Hi ,
I mapped the 13pos switch, it is not in the order that the pins are on the switch, numbers are correct though they are just staggered , but the positions are in order from 1-13, if you dont mind, could you please have a look and see if you could make out what type it is. I assumed that pin 1 is common, could be wrong.
How did you map the pins? With a FVM I assume. Where did d you place ess as ch of the leads?
 
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