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I've DESTROYED 3 piezo buttons :((((

gubavac111

New Member
So, I've damaged 3 piezo buttons...

This is the piezo button: https://uk.rs-online.com/web/p/piezo-switches/1241087

Datasheet: https://docs.rs-online.com/9e69/0900766b8152fb83.pdf

Quick explanation on what MPZI019/F/BL/24 is:

MPZI - Illuminated piezo switch
019 - 19mm diamater
F - Flat head
BL - color of illumination, in this case it is blue
24V - illuminating LED voltage

Also, it is a momentary switch, not latching.

This is the pinout:


1.JPG




This is how I connected it:

2.JPG



If you look at the datasheet, the switching contact is rated at 24VACDC 1 A.

1656667043247.png




It seems that I have destroyed 3 buttons.

There is a short between brown and yellow.


What did I do wrong???
 
Solution
That series of switches includes ones without LEDs; they do not require power to work (other than the "latching toggle" one).

The LED is a totally separate indicator lamp in the momentary type.

The switching device is triggered by voltage from a piezo transducer & also possibly powered by stored energy - they probably draw a few microamps when open circuit & charge a small capacitor to hold the switch on for a short time when pressed.

Once you have found the LED wires, ignore them for now.

Just use the other two. Connect to power with a simple load in series - eg. a 24V led & resistor combination.
Try both polarities in case it only works one way.

JimB

Super Moderator
Most Helpful Member
Am I missing something here?

I cannot see any pin-out or connection information in the product datasheet.

How did you determine where to connect the supply, as shown in your annotated picture?

JimB
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Am I missing something here?

I cannot see any pin-out or connection information in the product datasheet.

How did you determine where to connect the supply, as shown in your annotated picture?

JimB

Interesting point - and have you seen the price of them!!

Just been looking more closely at the datasheet - it appears to (very poorly) show the colours drawn in the connection diagrams, green and yellow for the switch, and brown and grey for the LED.

However, I suspect there may be supposed to be a connection between brown and yellow, it'd be a good idea for the OP to try one before connecting it up.

It would also be a good idea if he mentions EXACTLY how he's connecting it, and EXACTLY what to.
 
Last edited:

Les Jones

Well-Known Member
Most Helpful Member
I agree with JimB. The colour coding SEEMS to suggest that the contact wires are grey and the supply wires to the LED are black and red. These colours do not seem to match the colours of the wires on your switch. I think you will have to contact Bulgin to explain why the wire colours on your switch do not match the colours shown on the data sheet. I think the wire colours should also be shown as text as well as coloured wires on the data sheet.

Les.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
The wiring colour code is on page 4 of the data sheet.

For the 4 wire 19mm one, brown and slate are the LED, yellow and green are the switch.
(I'm guessing that the dark one in the photos is green?)

The 22mm 4 wire one shows different colours - try those?

Trying combinations to find the LED, without operating the switch, should not do any harm no matter how you connect them.

Once you identify the LED, the other two must be the switch.

Going through the datasheet again, the colours are definitely confusing and inconsistent...
The range summary at the end of the sheet shows the switch as always green & yellow, with the LED wires varying in colour depending on the LED combination.
 
Last edited:

JimB

Super Moderator
Most Helpful Member
The data sheet provided by rjenkinsgb is much clearer than the one from the link in post #1
Agreed.

But even then it is a poor datasheet.
A few simple words would make all the difference.

Bulgin technical writers...
... You failed.

JimB
 

gubavac111

New Member
Thank you all for your replies.

This is how I determined the wiring:

I already have onboard a similar Bulgin piezo button, it's just 22mm instead of 19 and it is latching instead of momentary.

You can see this 22mm button and label below:

1656684102104.png


BROWN is +
WHITE is -
GREEN and YELLOW are NO contacts

I assumed the new button would have the same pinout.

I did a small test - I've connected every combination of 2 wires to 24VDC on the new button.

The only time the button illuminated was when I connected BR to + and WH to -, so I am sure what is the purpose of BR and WH.

When I connected GR and YE on 24VDC, I got a short, and damaged the button.

Regarding the YE and GR, I know they are NO contacts because, when I would connect the button to PLC input in the below manner, it would activate PLC input whenever I would press the button:

1656684555460.png



The button didn't get damaged while being connected to PLC, btw.
 

gubavac111

New Member
If you connect the switch contacts directly across the 24V supply, then you will almost certainly blow the switch. However, it's no good copying the 22mm one, as the 19mm one seems to use different colours - according to the really crappy datasheet.

I understand that if I connect the switch contacts directly across the 24V supply, that I will almost certainly blow the switch.

What do you think of the way I connected it to the PLC? Is that OK?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I understand that if I connect the switch contacts directly across the 24V supply, that I will almost certainly blow the switch.

What do you think of the way I connected it to the PLC? Is that OK?
The picture above looks OK, assuming that's the exact switch you're using - but why not leave the 24V connection off (it's only to illuminate the LED), and make sure the switching works correctly before you try adding the LED.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
What do you think of the way I connected it to the PLC? Is that OK?
You show it switching to ground? The commonest setup on PLCs (and the only option on many types) is to have inputs switching to power.
It depends on the particular PLC and, if it is reversible, whether the input common for that bank is to ground or power.

If a normal switch works in the same configuration, then the arrangement is OK.

Depending on the PLC input design, it may need an additional load across the PLC input?
If you get 20V or more across the switch when its wired, it should be OK.
 

gubavac111

New Member
The picture above looks OK, assuming that's the exact switch you're using - but why not leave the 24V connection off (it's only to illuminate the LED), and make sure the switching works correctly before you try adding the LED.
Are you saying that I leave BR and WH disconnected and only connect GR and YE?

It doesn't work that way.

I think there is some semiconductor inside that needs to be powered up to pass the current once the you press piezo button, so I guess BR and WH must be powered up by 24V.

I've checked if the resistance between GR and YE changes (when BR and WH are disconnected) if you just press piezo button, but there is no change.
 

gubavac111

New Member
You show it switching to ground? The commonest setup on PLCs (and the only option on many types) is to have inputs switching to power.
It depends on the particular PLC and, if it is reversible, whether the input common for that bank is to ground or power.

If a normal switch works in the same configuration, then the arrangement is OK.

Depending on the PLC input design, it may need an additional load across the PLC input?
If you get 20V or more across the switch when its wired, it should be OK.

PLC inputs are switching to the ground, that's why I connected it that way.

What do you mean "and additional load" - you mean a resistor? If yes, how exactly to connect it?


"If you get 20V or more across the switch when its wired, it should be OK." - between which wires?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Are you saying that I leave BR and WH disconnected and only connect GR and YE?

It doesn't work that way.

I think there is some semiconductor inside that needs to be powered up to pass the current once the you press piezo button, so I guess BR and WH must be powered up by 24V.

I've checked if the resistance between GR and YE changes (when BR and WH are disconnected) if you just press piezo button, but there is no change.

Considering they make the buttons without LED's, then they can't be relying on the LED power feed to work the switch.

As far as I'm aware, pressing the piezo generates a voltage, and that is presumably used to power itself. Another option would for it to be via a pullup resistor, in the external circuit.

However, the completely useless datasheet, which tells you nothing, means perhaps you should go to a more reputable manufacturer?.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
That series of switches includes ones without LEDs; they do not require power to work (other than the "latching toggle" one).

The LED is a totally separate indicator lamp in the momentary type.

The switching device is triggered by voltage from a piezo transducer & also possibly powered by stored energy - they probably draw a few microamps when open circuit & charge a small capacitor to hold the switch on for a short time when pressed.

Once you have found the LED wires, ignore them for now.

Just use the other two. Connect to power with a simple load in series - eg. a 24V led & resistor combination.
Try both polarities in case it only works one way.
 
Solution

Nigel Goodwin

Super Moderator
Most Helpful Member
That series of switches includes ones without LEDs; they do not require power to work (other than the "latching toggle" one).

The LED is a totally separate indicator lamp in the momentary type.

The switching device is triggered by voltage from a piezo transducer & also possibly powered by stored energy - they probably draw a few microamps when open circuit & charge a small capacitor to hold the switch on for a short time when pressed.

Once you have found the LED wires, ignore them for now.

Just use the other two. Connect to power with a simple load in series - eg. a 24V led & resistor combination.
Try both polarities in case it only works one way.
He, he - just too late :D
 

danadak

Active Member
For future work when you are connecting stuff that you think may
have wiring errors set your supply up for constant current at the V
you are interested in. Set the target operating V. Then take the
current control all the way down to 0, short the output of the
supply, and adjust current to max you want to allow. Say datasheet
max of device you are trying to connect. Then start connecting stuff
while watching the V, if it dips appreciably then that connection is
wrong. Keeping in mind the host for the connection is working OK.

Or use a limiting R, not as good as above but can help sometimes from
blowing stuff up.


Regards, Dana.
 

gubavac111

New Member
That series of switches includes ones without LEDs; they do not require power to work (other than the "latching toggle" one).

The LED is a totally separate indicator lamp in the momentary type.

The switching device is triggered by voltage from a piezo transducer & also possibly powered by stored energy - they probably draw a few microamps when open circuit & charge a small capacitor to hold the switch on for a short time when pressed.

Once you have found the LED wires, ignore them for now.

Just use the other two. Connect to power with a simple load in series - eg. a 24V led & resistor combination.
Try both polarities in case it only works one way.

You are completely right, the momentary switch works without 24V delivered to them.

I've connected the switch to PLC by just using the GR and YE wires on my switch (BR and WH are for LED supply) and it works perfectly.

So, I've connected GR to the 0V and YE to the PLC input. All good, let's see if any of switches burns out...
 

gubavac111

New Member
For future work when you are connecting stuff that you think may
have wiring errors set your supply up for constant current at the V
you are interested in. Set the target operating V. Then take the
current control all the way down to 0, short the output of the
supply, and adjust current to max you want to allow. Say datasheet
max of device you are trying to connect. Then start connecting stuff
while watching the V, if it dips appreciably then that connection is
wrong. Keeping in mind the host for the connection is working OK.

Or use a limiting R, not as good as above but can help sometimes from
blowing stuff up.


Regards, Dana.

Excellent idea, will do.
 

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