Solid state relays

[krtw]

I wanted to replace the noisy mechanical relay in my house furnace with an SSR. However I can't figure out how to wire the SSR. I understand the mechanical relay and how its wired. There are 6 terminals, Two are the +/- output voltage going to the blower motor, Two are the +/- input of the relay (line voltage) and two are the coil terminals (coil voltage activates the relay). On all the SSRs I have seen there are only 4 terminals, labled input and output. Some of the SSRs are calling the input the "coil" voltage so i can only assume that is the activating signal, and if so where does the actual input go for the line voltage?

 

[Optikon]

I wanted to replace the noisy mechanical relay in my house furnace with an SSR. However I can't figure out how to wire the SSR. I understand the mechanical relay and how its wired. There are 6 terminals, Two are the +/- output voltage going to the blower motor, Two are the +/- input of the relay (line voltage) and two are the coil terminals (coil voltage activates the relay). On all the SSRs I have seen there are only 4 terminals, labled input and output. Some of the SSRs are calling the input the "coil" voltage so i can only assume that is the activating signal, and if so where does the actual input go for the line voltage?

Get a datasheet for the part, otherwise there could be smoke. There are usually two terminals for the "coil" which, is likely and LED or transistor circuit in the case of an SSR and the "output" which, might be a triac or MOSFET structure of some kind.

Sounds like your SSR switches both the HOT and NEUTRAL (?) (That would be the +/- in & out pair)

 

[ericgibbs]

There are 6 terminals,

Two are the +/- output voltage going to the blower motor,
These are the relay contacts that close to start the blower.

Two are the +/- input of the relay (line voltage) and
These two could be the supply to the relay coil, one of which is switched by these two below.?

two are the coil terminals (coil voltage activates the relay).
Are these two connected to the manual On/Off switch.?

On all the SSRs I have seen there are only 4 terminals, labled input
The input is the control voltage that switches the SSR, there are range of control voltages, eg: 3 to30Vdc, 3 to 30Vac and 90 to 280Vac.

and output. Some of the SSRs are calling the input the "coil" voltage so i can only assume that is the activating signal, and if so where does the actual input go for the line voltage?
The LINE wire of the mains is connected to the Output terminals, which is switched by the SSR

hi,
The replacement of a mech relay with a SSR is not a direct swop.

The SSR expects on the Input a Control voltage. Which would be switched by a remote manual or automatic switch closing.

The SSR only switches one wire of the mains wires, usually the LINE wire.

Do you follow OK.?

 

[johnsmith123]

Eric can you post any links or schematic that would work in the circuit above? Any part numbers for a SSR that would also work in the above circuit?

This is interesting, I would also like to know as I have a few devices that use a mechanical relay.

I have used opto-isolators on low voltage circuits but nothing involving 120VAC.

Your input is always appreciated and well respected.

Best Regards

 

[ericgibbs]

Eric can you post any links or schematic that would work in the circuit above? Any part numbers for a SSR that would also work in the above circuit?

This is interesting, I would also like to know as I have a few devices that use a mechanical relay.

I have used opto-isolators on low voltage circuits but nothing involving 120VAC.

Your input is always appreciated and well respected.

Best Regards

hi John,
Is the 90v thry 280V 'ac' control input type you are interested in using.?

EDIT: added pdf

 

[johnsmith123]

hi John,
Is the 90v thry 280V 'ac' control input type you are interested in using.?

it would be 110 - 120VAC.

thanks

 

[ericgibbs]

it would be 110 - 120VAC.

thanks

Look at my EDIT, it covers 110Vac.

I am not asking the load switching voltage but the SSR control voltage.

 

[johnsmith123]

WOW!

very expensive!! (see the attachment)

I was just curious on how to (for example) control a 120VAC appliance with a 3 to 5V microcontroller without using a mechanical relay.

 

[ericgibbs]

WOW!

very expensive!! (see the attachment)

I was just curious on how to (for example) control a 120VAC appliance with a 3 to 5V microcontroller without using a mechanical relay.

You can get cheaper versions for pcb mounting, driven by a +3V thru +30V dc signal from a mpu or transistor.

Or you could use this type:

 

[ericgibbs]

Hi John,
Look thru these:

Welcome to rswww.com

 

[johnsmith123]

thanks Eric.

I found another sharp SSR #S102T02 only $5.70 from Digi-key.
Almost the same as the one you recommended (#S102S02)
except that the price is a lot better!

Thanks again for the help!

 

[krtw]

hi,
The replacement of a mech relay with a SSR is not a direct swop.

The SSR expects on the Input a Control voltage. Which would be switched by a remote manual or automatic switch closing.

The SSR only switches one wire of the mains wires, usually the LINE wire.

Do you follow OK.?

Thanks for the help. If the input is the control voltage then where would the line voltage connect to? The input for the crydom SSRs is labled -/+, terminals 1-2.....the only terminals left are the ouput terminals 3-4. If I can't figure this out I will try to find a quieter mechanical relay, or just shield the one I have to reduce/elliminate the noise it makes.
Thanks again.

 

[ericgibbs]

Thanks for the help. If the input is the control voltage then where would the line voltage connect to? The input for the crydom SSRs is labled -/+, terminals 1-2.....the only terminals left are the ouput terminals 3-4. If I can't figure this out I will try to find a quieter mechanical relay, or just shield the one I have to reduce/elliminate the noise it makes.
Thanks again.

Hi,
Look at this image.

Some users put the Load in the LINE side of the SSR, which IMHO is not a good idea, the Load may not be 'powered' but its Live with respect to neutral/earth.