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Old 10-21-2010, 02:30 AM   #1
chuckjaxfl
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Does anyone know a source for normally closed SSR's?

 
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Old 10-21-2010, 04:34 AM   #2
renevdb
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You need to be more specific. What are you switching and what is your input.
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Old 10-21-2010, 05:08 AM   #3
JonW
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Use something like a SPDT reed relay to power the SSR through the NC contacts. When you then energize the reed relay, it will break the circuit to the SSR.

 
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Old 10-21-2010, 05:50 AM   #4
ClaudiusB
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Quote:
Originally Posted by chuckjaxfl View Post
Does anyone know a source for normally closed SSR's?
Search for MOSFET form B SS relays, made by many manufacturers.
MOSFET's are DC devices, also available for AC switching.


Cheers,
ClaudiusB

 
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Old 10-21-2010, 08:55 AM   #5
hrafnkell
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SSRs are usually normally closed. Apply power and they open.

 
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Old 10-21-2010, 04:55 PM   #6
chuckjaxfl
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Quote:
Originally Posted by renevdb View Post
You need to be more specific. What are you switching and what is your input.
Fair enough.

I want to run an HLT (115v 2kw) and a RIMS Tube (220v 3.5kw) from the same 115v 20A outlet. I want the PID controlling the RIMS tube to run 2 SSR's: the first closing, powering the RIMS heater on, and the other opening, to cut power to the HLT element.

So, the input would need to be PID driven. On the controlled side, it could be 115V 20A, or it could be low voltage DC, either way.

 
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Old 10-21-2010, 04:58 PM   #7
chuckjaxfl
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Quote:
Originally Posted by JonW View Post
Use something like a SPDT reed relay to power the SSR through the NC contacts. When you then energize the reed relay, it will break the circuit to the SSR.
That's plan B, but I was hoping to keep the control solid state.

 
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Old 10-21-2010, 04:59 PM   #8
chuckjaxfl
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Quote:
Originally Posted by ClaudiusB View Post
Search for MOSFET form B SS relays, made by many manufacturers.
MOSFET's are DC devices, also available for AC switching.


Cheers,
ClaudiusB
I've always heard of MOSFET's, but don't know what they are. I guess I know what I'm going to be reading about tonight.

 
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Old 10-21-2010, 06:26 PM   #9
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Quote:
Originally Posted by chuckjaxfl View Post
That's plan B, but I was hoping to keep the control solid state.
It might not be an SSR, but reed relays are fast and rated for billions of operations.

 
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Old 10-21-2010, 07:12 PM   #10
smizak
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Quote:
Originally Posted by chuckjaxfl View Post
That's plan B, but I was hoping to keep the control solid state.
Problem with solid state is that you need some sort of energized circuit to do anything. I second the relay idea, there are mechanical relays designed for billions of operations, very reliable.
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