SSR question

[Lucky-Luka]

Hi all
Can anyone tell me how can this relay be ok with such a broad input voltage?
I haven't found a schematic for this kind of relay module.
Thanks
https://www.ebay.it/itm/322209858572

[wraper]

It's not a mechanical relay but SSR (solid state relay). It has a circuit that limits the current flowing through LED emitter of optocoupler. 3-32V input voltage range is the most common for SSR. Older types often had around 5V minimum voltage.

[Lucky-Luka]

GTD-W-5A
I haven't found a datasheet to understand the current needed for the control input

[wraper]

It self limits the current. If source is capable to supply at least 20-30mA, generally you should be fine.

[Lucky-Luka]

So I cannot drive it using a GPIO pin of an Arduino...
I need a bjt or a mos with that relay, right?

[Terry Bites]

The description says the relay will be on when the control input excedes 3V and off when the control volage is less than 0.5V.
It also says that the relay state for control voltages between 0.5-2.5 is not defined, it might be on or off or random.
The maximum control voltage is 32V.

They say it can be driven from an Arduino. This is cause for concern, the worst case output voltages may be out of specification for this relay.
You do need to add a a driver to the GPIO. eg

[Lucky-Luka]

then couldn't I just use a power mosfet instead of a relay and that bjt?

[CaptDon]

That depends somewhat on what load you intend to drive and if that load is inductive and may sens inductive kick-back spikes into your digital world. The SSR gives you the benefit of superb isolation between the driving signal and the load. It also allows for loads connected to other voltage sources, in some cases (the usual use) even the A.C. mains.

[Lucky-Luka]

They say it can be driven from an Arduino. This is cause for concern, the worst case output voltages may be out of specification for this relay.

Why?

[wraper]

So I cannot drive it using a GPIO pin of an Arduino...
I need a bjt or a mos with that relay, right?

Why? Atmega328 is allowed to supply 40mA per pin (with limitation on overall current thru multiple pins).

[Lucky-Luka]

Post #5

[Zero999]

So I cannot drive it using a GPIO pin of an Arduino...
I need a bjt or a mos with that relay, right?

Why? Atmega328 is allowed to supply 40mA per pin (with limitation on overall current thru multiple pins).

What's the supply voltage? If it's 3V, the output voltage will be too low.

[wraper]

Arduino uses 5V.

[Zero999]

Arduino uses 5V.

It should be fine, if it doesn't push the total current draw above 200mA.

[james_s]

I have driven SSRs directly from Arduinos (and other AVRs) without any issues, it will be fine.

[BeBuLamar]

GTD-W-5A
I haven't found a datasheet to understand the current needed for the control input

Most SSR only needs about 10mA.

[Lucky-Luka]

Arduino uses 5V.

I am using an Arduino that runs at 3.3V

[Lucky-Luka]

Arduino uses 5V.

It should be fine, if it doesn't push the total current draw above 200mA.

I use a 3.3V Arduino

[Zero999]

Arduino uses 5V.

It should be fine, if it doesn't push the total current draw above 200mA.

I use a 3.3V Arduino

Then use the circuit posted by Terry Bytes.
https://www.eevblog.com/forum/beginners/ssr-question/msg4154950/#msg4154950

[Lucky-Luka]

That works if I don't have an octocoupler on the module