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relay switch lifetime

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dmta

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hi everyone !!!!!!!!

I want to switch 7 light bulbs using a relays (for a decoration purpose). i'm using 230Vrms-50Hz
here is my WORST case scenario

switching speed 1Hz straight for about 12hours
maximum power of bulb 100W

this is the relay i'm using

my questions are,

will the relay be able to handle it ? (i know its pushing it but still...)

the other option i have is to use triacs and triac drivers (which is quite expensive). can anyone suggest some other method ?

regards
 

Hi dear
i think for 100w , triac isn't expensive...its better than relay because of lost power and speed and easy controlling.
 

thank you greentree !!!!!!!
furthermore i'm not using any zero crossing detection when switching (i am using a PIC micro). will this be a problem and do i have to implement snubber a circuit ?
 

You need isolation from the power line for the PIC so use a solid-state relay. You won't need a snubber with that.
 

dmta said:
thank you greentree !!!!!!!
furthermore i'm not using any zero crossing detection when switching (i am using a PIC micro). will this be a problem and do i have to implement snubber a circuit ?
Click to expand...
:wink:you can use opto triac before your power triac actually !
 

hi and thak you both !!!!!

if i'm using the triac option this what i'm thinking to do.(PDF)

At this moment i'm giving a PWM signal of 1kHz. But when i vary the Ton time i'm not getting the expected result. the screen shot shows what i'm getting. what should i do ?????
 

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  • triac.bmp
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dmta said:
hi and thak you both !!!!!

if i'm using the triac option this what i'm thinking to do.(PDF)

At this moment i'm giving a PWM signal of 1kHz. But when i vary the Ton time i'm not getting the expected result. the screen shot shows what i'm getting. what should i do ?????
Click to expand...

Hi dear
please connect your pwm first to a Low pass filter and then put it to your opto that has Zero Cross Detector(moc3043)
I hope be helpful


Best Wishes
Green Tree
 
Last edited:

You can't use a high frequency PWM signal with an SCR. The SCR turns on for a complete cycle when triggered. You need a phase control (light dimmer) circuit. Originally you said a 1Hz PWM and now 1kHz. Which is it?
 

Hi dear crutschow

isn't important the freq of your pwm when you convert it to dc voltage with LPF (low pass filter)...
 

Hi to both of you.
The original 1Hz was just the maximum switching frequency if I'm using a relay (it's not intended to dim the light as that would need a higher frequency)
If I'm using a triac I figured I could add a dimming option also. The 1Khz is if I'm using a triac.

Anyways, the PWM will be supplied by a PIC. So what could I do to dimm the light ?
 

So what could I do to dimm the light ?
Click to expand...
Use phase angle control as suggested by crutschow.

Generally, if you bring in new problems to the thread (e.g. light dimming as in post #6) tell clearly what you want to achieve. It's really mysterious what 1 kHz PWM has to do with "relay switch lifetime".
 

Besides, PWM for dimming an AC waveform with a Triac won't work.

If you want to dim, then you have to use phase control, which in very few words means synchronizing a delay with the waveform's zero-crossing.

Google the term, there are dozens and dozens of images that explain the concept.
 

if your opto triac be Zero Cross Detector so there isn't any problem...(at my way)

- - - Updated - - -

triac.jpg

I think this is useful for you...
 

A ZCD will not work for phase control, because phase control turns on the triac at a non-zero voltage, which a ZCD would prevent.

ZCD works for simple on/off controls on which one wants to avoid EMI by turning the triac on at zero voltage.

And by definition, a Triac turns off by ittself at zero current.
 

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