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Electronics => Beginners => Topic started by: 67mustang-man on February 22, 2016, 06:06:35 pm

Title: Solid state or Relay, Trigger is -12v .200ma?
Post by: 67mustang-man on February 22, 2016, 06:06:35 pm

I have a Vertex Standard radio and to trigger from external speaker to PA speaker you need to use a relay to switch over from one speaker to the next as they share the same audio source. they have a trigger on the radio that comes out of a DB HD15 plug it triggers the relay on the negative side of 12v and a max of .200ma What would be the best way to trigger this solid state transistors and no relay or a mixture of both?

Any simple schematics one could provide as well would be great.

Thank you

Title: Re: Solid state or Relay, Trigger is -12v .200ma?
Post by: Zero999 on February 22, 2016, 08:24:10 pm

A small relay is probably best, considering the speaker signal is AC. A diode should be connected in reverse parallel with the relay coil to protect the driver transistor from the back EMF.

Title: Re: Solid state or Relay, Trigger is -12v .200ma?
Post by: 67mustang-man on February 22, 2016, 08:47:53 pm

So a simple DPDT Relay would would work best, now what do you mean a diode in parallel with the relay coil, as in across the + - side of the relay?

Thank you for the input, I will look for a 200ma relay.

Title: Re: Solid state or Relay, Trigger is -12v .200ma?
Post by: Zero999 on February 22, 2016, 11:23:13 pm

The diode should go in reverse parallel with the relay coil.
(http://i0.wp.com/progeny.co.uk/wp-content/uploads/2014/01/image003.png?w=634)

Title: Re: Solid state or Relay, Trigger is -12v .200ma?
Post by: 67mustang-man on February 22, 2016, 11:43:12 pm

Wonderful and this diode should not affect the radio? Great I will build this for my radio, I am new to some of this stuff. I want to learn temp push button but latching relays and what not for other radio projects I have in the future. Thank you.

John