Circuit design problem

Rob Melville's picture

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Joined: Nov 12, 2019

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Circuit design problem
November 20, 2019 - 5:05pm

HI, i have designed a control cabinet with 24vdc control circuit. for some reason the control relay burns out. the psu is RS 122-2216 the relay RS 144-1609. the relay is powered on when contacts on a timer are closed. when this occcures the coil on the relay overheats. what have i got wrong? all wiring checks out. 

any help greatly appreciated

Thanks

Bilal's picture

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Joined: Nov 19, 2019

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Can you please share your
November 20, 2019 - 5:36pm

Can you please share your diagram

Rob Melville's picture

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diagram
November 20, 2019 - 9:35pm

Hi Bilal

i dont have the full diagram here at work so have done a quick basic sketch 

circuit.jpg

Ashutosh's picture

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Joined: Aug 27, 2018

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what is your relay rating
November 28, 2019 - 10:46am

I am confused with your relay part number, in the question you state it is RS 144-1609, but in the circuit diagram you have written RS 145-1602. So which exactly is your relay part number?

Hey I tried searching for your relay part number RS 145-1602 and found this

https://docs.rs-online.com/2277/0900766b81633c5f.pdf

This relay is rated for 24V so yes it should work for you, but make sure the part number is RS 145-1602 because other relays have diferent part number

Capture.PNG

Once you are sure with the relay part number if the heating problem is still there then it should be because of your Load. Note that this relay can only dive 12A at 250VAC. What load are you using and how have you connected it?

And I dont see any short circuit like Jim stated and you wont be needing any resistance for this. Your PSU outputing 24V should be able to drive your 24V relay directly through your timer 

Jim's picture
Jim

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Joined: Nov 18, 2019

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relay burns out
November 27, 2019 - 2:21am

Relay burns out because it's a short circuit.  You need a load in series with the relay at a minimum.

Rob Melville's picture

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Ah ok, what would you suugest
November 27, 2019 - 4:07pm

Ah ok, what would you suugest, resistor?

Sourav Gupta's picture

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Careful about the Relay
December 8, 2019 - 1:38am

The relay has a freewheel diode, therefore the relay has a polarity. If you riverse bias the diode it will conduct and dissipate heat depending on the psu current rating.
The diode is a very sensitive device that fails in regorous situations and creates dead shot.

Use the relay properly.

Ashutosh's picture

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Mechanical Relay has polarity???
December 9, 2019 - 10:21am

therefore the relay has a polarity

How can a relay have polarity??. It is a mechanical relay which operates on coil. So coils will not have polairty. just like an inductor or solenoid 

Are you telling that the frewheel diode is in-built into the relay? I dont think so 

 

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PCB
March 23, 2020 - 3:23pm

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