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Relay to switch a relay?

Alec Hayward

Jan 22, 2016
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Hi, is it possible to switch a relay with a relay? I have a RF module from ebay which uses a DC 10A relay, but I need a 25A relay. The tracks on cheaply made boards can break easily if modified, so I was hoping to tie the output of a relay to switch the coil of a bigger relay?

Hope you understand
 

HellasTechn

Apr 14, 2013
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Yes you can. Why not ?

Just check if you need diodes in parallel with the relay's coil.

i doubt you do though.
 

Alec Hayward

Jan 22, 2016
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Hello again, my parts came from eBay. But my second relay isn't working. I connected 12v to the comms on the first relay.

Then on the NO I connected the coil of the second relay then too gnd. However it is not working. =( please help
 

davenn

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Sep 5, 2009
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I connected 12v to the comms on the first relay.

Then on the NO I connected the coil of the second relay then too gnd. However it is not working. =( please help

sounds like you made a wiring error

is the second relay coil also 12V DC ?

I will draw a cct
 

davenn

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Sep 5, 2009
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dual relay.GIF

The first relay, transistor and resistor is what already exists on your board
or something similar to that
 

Alec Hayward

Jan 22, 2016
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Yes this is how I connected it. I even checked the datasheet for my additional relay. So I knew which one was the coil.

I haven't used a diode for second relay.
 

davenn

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Omey Cool

May 30, 2016
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May 30, 2016
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Please do check if the voltage provided by circuit/board is enough to drive the relay. you know you cannot operate a 12 v relay with 5v supply.
 

Harald Kapp

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Nov 17, 2011
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Please do check if the voltage provided by circuit/board is enough to drive the relay. you know you cannot operate a 12 v relay with 5v supply.
This the OP has done:
I connected 12v to the comms on the first relay.
and a related questuin has been asked before:
is the second relay coil also 12V DC ?

@Omey Cool : You're welcome to contribute to this forum, but please read the full thread before posting replies that do not fit the issue at hand well (cf. your post in the thread 'LED monitoring')
 

Omey Cool

May 30, 2016
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I was having same problem and that was a simple issue of power supply. Thats why i suggested to check supply.

And i am pretty new here! :p
Will do better next time.
Thx
 

DatLe

May 31, 2016
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May 31, 2016
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Hi, I draw not good. ^^
Please re-check new 25A relay power input for relay coil.
27367032885_2c9ded5f7d_b.jpg
 
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