omron solid state relay

[steveeeee]

hi, i' interested in using an 8 channel solid state relay board because they are cheap on ebay. they use the 5v G3MB-202P omron solid state relays http://people.ece.cornell.edu/land/...daw33/RemoteOutlet/datasheets/D20G3MB0503.pdf

i can drive it from my MCU no problem but the output side i'm switching 12v dc at 250ma.

the spec on the relay says output load 2 A at 100 to 240 VAC. does that mean it will not work at 12vdc like a normal relay would?

 

[(*steve*)]

This is a time when checking the datasheets doesn't reveal all.

However, it does note on the datasheet for the zero crossing version that the turn on and turn off times are approximately "1/2 of load power source cycle + 1 ms max.".

This indicates that the zero crossing type would not work for a DC load.

However, I didn't look at the specs for the non-zero-crossing variant.

Typically these SSRs use a pair of mosfets to switch the load. As such, they exhibit a resistive characteristic and should work effectively on DC.

From DC, you may need to de-rate them somewhat as the majority of the power dissipated may be in one of the mosfets (and bizarrely it may be the one that's not conducting)

 

[steveeeee]

thanks, so i think you are saying it will not work for DC because it is zero crossing type according to spec on ebay page:
SSR Spec.:
Manufacturer: OMRON
Part number: G3MB-202P, 5V version.
Isolation: Phototriac.
Zero cross: Yes.
Rated output load: 2A at 100 to 240VAC.(50/60Hz).
Load type: General purpose.

 

[(*steve*)]

Note that it says it is a phototriac.

It may turn on with DC (depending on how the zero crossing works), but it can't turn off.

 

[steveeeee]

Note that it says it is a phototriac.

It may turn on with DC (depending on how the zero crossing works), but it can't turn off.

not a whole load of use then. i'll use a conventional relay bank then. should have enough drive from the Atmega2560. i guess to be sure i could us an octal line buffer

thanks

 

[(*steve*)]

There are other SSR's available. You may be able to replace the ones on that board with pin-compatible devices to switch DC. (I have no idea if this is possible or economically sensible) but it's a thought.

edit: 8 channel relay boards using real relays are also very cheap.