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Time delay on relay needed

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rparigoris

Joined: 24 Nov 2009
Posts: 804

Posted: Sun Oct 09, 2022 8:47 pm Post subject: Time delay on relay needed

Hi Group

I am working on a project where an Arduino is completely unhappy if a 12 volt buzzer is connected to it's 10 amp relay. We tried an awful lot of things including installing another relay and even a separate battery to power the second relay and buzzer. the only thing that works is putting the buzzer on the Arduino relay if you wait one second. Then all is well. 

Question:

Can someone point me to a 12 volt coil relay with a approx. 1 second time on delay that can handle 2 amps or more  12VDC? Or how can I delay the 12 volt relay i have from coming on for a second.



Thx.

Ron P.

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user9253

Joined: 28 Mar 2008
Posts: 1932
Location: Riley TWP Michigan

Posted: Mon Oct 10, 2022 6:11 am Post subject: Re: Time delay on relay needed

Do a Google search for "capacitor time delay circuit".

One of the results of my search turned up this one with a delay of 1.5 seconds.

https://www.arrow.com/en/research-and-events/articles/make-a-simple-capacitor-transistor-timing-circuit

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_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Oct 10, 2022 6:36 am Post subject: Time delay on relay needed

At 11:47 PM 10/9/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>



 Hi Group

 I am working on a project where an Arduino is completely unhappy if a 12 volt buzzer is connected to it's 10 amp relay. 	


    What kind of 'buzzer'? A legacy electro-mechanical device

    like we used to build in Cub Scouts?



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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rparigoris

Joined: 24 Nov 2009
Posts: 804

Posted: Mon Oct 10, 2022 11:24 am Post subject: Re: Time delay on relay needed

Hi Joe  Thank you for reply.



Bob:

The Buzzer is an electro mechanical:

https://www.amazon.com/gp/product/B000XBJ3AE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The Arduino is powered by a 12 volt battery going through a converter to make 5 volts for the Arduino. The buzzer is using the 12 volts to operate. We put it on a scope today and saw perturbations of the 5 volts peak to peak of between 10 and 12 volts.

We added transorbs and .1 mF ceramic capacitors across the two parallel buzzers and also a .1 mF ceramic capacitor just before the DC to DC converter. Got peak to peak down to 5 to 6 volts. So far it seems to be working OK.



Ron P.

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 11, 2022 8:56 am Post subject: Time delay on relay needed

 	  Quote: 	
		  Bob:

 The Buzzer is an electro mechanical:

  https://www.amazon.com/gp/product/B000XBJ3AE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 

 The Arduino is powered by a 12 volt battery going through a converter to make 5 volts for the Arduino. The buzzer is using the 12 volts to operate. We put it on a scope today and saw perturbations of the 5 volts peak to peak of between 10 and 12 volts.

 We added transorbs and .1 mF ceramic capacitors across the two parallel buzzers and also a .1 mF ceramic capacitor just before the DC to DC converter. Got peak to peak down to 5 to 6 volts. So far it seems to be working OK.



 Ron P. 	


    That style of buzzer is one of many examples

    of the classic 'model-T spark coil' physics. What

    you're experiencing is conducted noise in the form

    of fast-rise time transients generated every

    time the points in the buzzer break. This can be

    a very 'potent' noise source for some situations.



    In fact, legacy DO160 qualification testing used

    to include what was commonly called a 'chattering

    relay' noise test illustrated here. The "timer"

    switch was simply the normally closed contacts

    of the test fixture relay, I.e. a 'buzzer'.



    The Model-T spark coil was another 'buzzer' where

    the buzzer coil shared a core with a bazillion

    turns of fine wire where one could exploit very

    high voltage transients that would jump the

    gap in a spark plug.



    A modern exploitation of the same phenomenon

    is illustrated in a 'shower of sparks' starting

    ignition for an M14 radial engine I crafted for

    a YAK driver.



    So, getting back you your close encounter of

    the unhappy kind, your potential victim is a

    micro-controller that runs on 3.3 volts DC.

    It doesn't take much of a transient to express

    itself as aberrant noise. Data in the uC

    lives in a 3 volt, tens of megaHertz world

    exceedingly vulnerable to fast rise

    transients.



    As you've already discovered, suppression of

    the buzzer's coil collapse transient mitigates

    the problem. If you have access to the buzzer's

    coil terminals, it would be interesting to see

    if a simple suppression diode would stop the

    problem. If not, then some network of external

    components is indicated to reduce this potent

    noise source from irritating your microcontroller. 



 



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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