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momentary pcb switch question

john2k

Jun 13, 2012
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Jun 13, 2012
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I have a small PCB with 4 momentary pcb small switches the ones that when you press it, it briefly completes the circuit until you let go. There are also some back light LEDs. There is a 6 pin connector on the PCB. Two of the pins on the connector are for the + and - of the LEDs. I've tested those two and I am able to power the LEDs from those. Now I have 4 pins left and 4 switches. Now my question is exactly how is 4 switches likely to be switched in context to the 4 pins? The reason I ask is because I want to swap around the function of two buttons. The buttons need to remain in the same place but the unit processing the signal from the connector I just want to flip the pins by de-pinning the connector if possible. But just not sure how 4 switches are connected to 4 pins.
 

john2k

Jun 13, 2012
188
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Jun 13, 2012
Messages
188
Here's a picture below of the PCB. the two pins for the LED backlights i have indicated. The remaining 4 pins can only be related to the buttons that i've labelled. Because the PCB has no other function. When a button is pressed some sort of connection is made on the connector which the receiving controlling unit interprets and activates the function related to that press.

68DseKN.png
 

john2k

Jun 13, 2012
188
Joined
Jun 13, 2012
Messages
188
Actually I just had a look at the wiring harness that connects to this and it appears the two led pins and the middle column is used. The column at the end isn't actually used. Which means all 4 switches are switch via the two pins.
 

73's de Edd

Aug 21, 2015
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Sir john2k . . . . .

DAMN you Charlie Brown . . .for having left so many variables unanswered .

Joe Blow is going to come up with 4 or so possibilities/ answers . . . . . . my brain HURTS ! as it is is coming up with 1478 answers, all in accordance to un supplied / specified variables .
Initially lets confirm if the LEDs are just . . . ALL . . . .being constantly on power presence / illumination indicators . . .OR . . . . is one lighting up as its associated key is being depressed ?
Are the inter connecting foil paths on the other side of the keyboard visible or do we have an UN-viewable sealed sandwich construction ?
Tell us what keys Roman I thru IV function is being . . . . . I Open Door . . .II Feed Dog . . . . .III FIRE . . . . . .IV SPELL CHECK . . .etc . . .etc . . . .

KEYBOARD REFERENCE IDENTIFICATION ASSIGNMENTS . . . . .

upload_2022-6-14_14-47-8.png

If the LEDs are just for illumination, I would expect the a and d pin connectors to terminate to 1-3-5-7 and 2-4-6-8.
If key activated we would have to "ohm out" that possibility of connections.

Sir Bertus referencing of normal pin connections being in duplicate, on the MAJORITY of tact switches, do not seem to be the case here, with only two contacts used on your switches.
Now if you pull out ohmmeter and put in lowest ohms scale and then short meter probes together to see what meter reading you then get.
That will be a direct shorted connection indication.
If you now move to the A thru H connections in OHMs metering, I would suspect direct connections being between A-C-E-G or the other possibility of B-D-F-H connections.
Whichever combination which you do not find interconnected, leaves the other options individual contacts to be connected to b-c-e and f pin connections
Also check to meter out and see if the string of A-C-E-G or B-D-F-H connections might also directly connect to a or d.

Next tell us which of the I - IV switches needs to have function reversals on ?
It would just be a simple matter of a small gauge "wire wrap" reversing jumper from each of those switches to their respective pins on the 6 pin connectors and then breaking the original foil connect path.
UNLESS you have an earlier mentioned . . . . .un viewable / and un accessible sandwiched board.
BUT . . .I can even give you a workaround for that . . .if so being encountered.

HOWDOITBE WORKINGS ? ? ? ? . . . . .

MULTIPLEXING . . . . .


Those pin connections to those 4 monitored pins are being constantly and sequentially scanned between . . .typically, upwards to 5 times a second . . . to see if a switch has been pressed at that moment in time, the units u/Processor can then determine which switch was depressed and respond in that functions activation. accordingly.

Thaaaaaaaaaaaaaaaaaaasit



My thoughts are . . . . . . . . The farther away the future is . . . . . the better it looks.

tenor.gif



.
 
Last edited:

John Canon

Jun 1, 2022
81
Joined
Jun 1, 2022
Messages
81
Sir john2k . . . . .

DAMN you Charlie Brown . . .for having left so many variables unanswered .

Joe Blow is going to come up with 4 or so possibilities/ answers . . . . . . my brain HURTS ! as it is is coming up with 1478 answers, all in accordance to un supplied / specified variables .
Initially lets confirm if the LEDs are just . . . ALL . . . .being constantly on power presence / illumination indicators . . .OR . . . . is one lighting up as its associated key is being depressed ?
Are the inter connecting foil paths on the other side of the keyboard visible or do we have an UN-viewable sealed sandwich construction ?
Tell us what keys Roman I thru IV function is being . . . . . I Open Door . . .II Feed Dog . . . . .III FIRE . . . . . .IV SPELL CHECK . . .etc . . .etc . . . .

KEYBOARD REFERENCE IDENTIFICATION ASSIGNMENTS . . . . .

View attachment 55418

If the LEDs are just for illumination, I would expect the a and d pin connectors to terminate to 1-3-5-7 and 2-4-6-8.
If key activated we would have to "ohm out" that possibility of connections.

Sir Bertus referencing of normal pin connections being in duplicate, on the MAJORITY of tact switches, do not seem to be the case here, with only two contacts used on your switches.
Now if you pull out ohmmeter and put in lowest ohms scale and then short meter probes together to see what meter reading you then get.
That will be a direct shorted connection indication.
If you now move to the A thru H connections in OHMs metering, I would suspect direct connections being between A-C-E-G or the other possibility of B-D-F-H connections.
Whichever combination which you do not find interconnected, leaves the other options individual contacts to be connected to b-c-e and f pin connections
Also check to meter out and see if the string of A-C-E-G or B-D-F-H connections might also directly connect to a or d.

Next tell us which of the I - IV switches needs to have function reversals on ?
It would just be a simple matter of a small gauge "wire wrap" reversing jumper from each of those switches to their respective pins on the 6 pin connectors and then breaking the original foil connect path.
UNLESS you have an earlier mentioned . . . . .un viewable / and un accessible sandwiched board.
BUT . . .I can even give you a workaround for that . . .if so being encountered.

HOWDOITBE WORKINGS ? ? ? ? . . . . .

MULTIPLEXING . . . . .


Those pin connections to those 4 monitored pins are being constantly and sequentially scanned between . . .typically, upwards to 5 times a second . . . to see if a switch has been pressed at that moment in time, the units u/Processor can then determine which switch was depressed and respond in that functions activation. accordingly.

Thaaaaaaaaaaaaaaaaaaasit



My thoughts are . . . . . . . . The farther away the future is . . . . . the better it looks.

tenor.gif



.
I got the Dopeler Effect while reading this ...the faster it approaches, the smarter it seems.
 
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