10-26-2018, 10:30 AM
You're correct, I send 12v to the power bar so most relays can be used, if someone has 5v relays a DC-DC is used to drop 12v to 5v. The part your missing is all those assembled relay module boards use MOSFET's for the GND of the relay to switch it on/off. Even though you are sending 12v to your relay board the signal wires from controller only put out 3.3v. This works because the MOSFETS are Logic type and switch on with only 3.3v, a regular MOSFET typically requires 10v to turn on so it must be Logic or also know as "enhancement type". The datasheet will say on the first page typically.
You have it correct on wiring the MOSFET.
Here's a very basic diagram to follow.
http://www.learningaboutelectronics.com/...ircuit.png
Gate = signal pin from controller
Source = common GND
Drain = -GND on SSR input
On the + of SSR input you can use any DC voltage that falls in the correct range.
Just thinking I gave you bad advice a couple posts up, you NEVER want to connect the 3.3v from controller signal wire directly to the SSR even if the SSR can switch with 3v. The +3.3v signal wire from the controller can only handle very low currents and the relay could draw more or just push the pin to it's max. MOSFET's should always be used directly from the source pin as they require very little current to switch.
One other thing, you might want to add a snubber circuit, some have this built in but lots don't so do some searching on this. There's a few types and not to difficult to add, just more components to work with. :(
You have it correct on wiring the MOSFET.
Here's a very basic diagram to follow.
http://www.learningaboutelectronics.com/...ircuit.png
Gate = signal pin from controller
Source = common GND
Drain = -GND on SSR input
On the + of SSR input you can use any DC voltage that falls in the correct range.
Just thinking I gave you bad advice a couple posts up, you NEVER want to connect the 3.3v from controller signal wire directly to the SSR even if the SSR can switch with 3v. The +3.3v signal wire from the controller can only handle very low currents and the relay could draw more or just push the pin to it's max. MOSFET's should always be used directly from the source pin as they require very little current to switch.
One other thing, you might want to add a snubber circuit, some have this built in but lots don't so do some searching on this. There's a few types and not to difficult to add, just more components to work with. :(
