Experience of using Solid State Relay Boards?

[Oetsch]

Hi

for the operation of 2 Motorised Valves (230VAC) I´m using 2 Shelly 2.5. But now I´m also using an ESP8266 (D1 mini) very close.
So I thought with the intention to save some energy/money by elemination of the 2 shellys (~5€ per year)and switching the valves also by the ESP unit.
Also the simplification by using less devices is an intention behind but I will need to switch 230VAC at very limited space.

So instead of a releay board I thought of using a Solid State Relay Board.

Do you have any experience in using this type?



The input is specified for 5V or 3-24VDC this is not so clear by the given information and a total max. current of 72mA for the 4 channel board.

This should also work if i use an PCF8574 only for this board or what dou you think?

https://de.aliexpress.com/item/32900650 ... fromDetail

Thx!

[TD-er]

Most solid state relay are from a switching point just an LED, like an optocoupler.
So it is very easy to operate from ESPEasy.

For your design make sure to check whether the inputs have common anode or common cathode.

Another thing to keep in mind is the AC side of the solid state relay.
Almost all only switch on zero-crossing so this also implies they can only be used on AC voltage.

It is also a plus, since you will cause a lot less peak currents when switching.

Lots of "Chinese" solid state relay units also have "Chinese" specs, regarding the max. current they claim to handle.
Keep this in mind when designing your circuit and also allow for enough heat dissipation.
Some allow for mounting to a heat sink.
They do have a voltage drop (see datasheet) which can be as high as 1.2V (or more).
Switching 1 Amp at a voltage drop of 1V results in 1 Watt heat in the SSR (Solid State Relay)

[Oetsch]

Thx.

For the AC side and in point of heating I do not really expect a problem. The MOVs are realy small and Chinese Spec says 5W. Because of inrush current let it be 50W/~0,22A for a very short period. Normal operiation of this valve is 15 to 20 sec. so expecting no problems when Chinese Spec says 2A for the SSR.

I´m more woried about the trigger signal from ESP or PCF8574. I prefer using PCF8574 because i will have less wires between two housings and the PCF8574 is easier to use with 5VDC. I do have to convert the I2C signal from 5 to 3.3V (2 wires) and for ESP it would be each signal/channel.
But for PCF8574 I´m worried about the limited current. It´s recommended for max. possible current to switch ground. So will need common Anode of the SSR Board.

So as nobody has used this board before I will need a data sheet before going on.

Edit:
Sadly no datasheets could be found by me so far.
Current understanding ist that the SSR are powered (low voltage side) from the general powr supply of the board.
The trigger signal is transfered by an optocoupler for each channel. This brings also in the galavanic isolation.

The boards are availble as High level trigger and low level trigger. My understanding is that this means how or what type of optocoupler is used.
For PCF8574 which should be operated in current sink connection, I think low level trigger version should work fine. The diode inside of the optocoupler is connected in common anode "method".

Will see if it works...

[Wookbert]

Will see if it works...

So what’s the outcome? Did you connect the SSR directly to the ESP8266 D1 mini in the end or did you add additional circuitry?

[Milan]

Hi. I connected Wemos D1 mini directly to SSR because SSR module has optocoupler. I control the pool filtration engine.

[Wookbert]

Here’s a closer look at the PCB of this 2-Channel SSR Board, which can carries the model name HY-M284. It’s impossible to find a genuine, official datasheet nor schematic. The best/closest match I was able to find is the schematic shown below of a very similar looking module from sainsmart.com.

HY-M284.png (1.02 MiB) Viewed 7793 times

2 Channel SSR Module Solid State Relais HY-M284 Schematic.png (216.43 KiB) Viewed 7793 times

@TD-er
Question: AFAIK a device must not draw more than 12 mA max. from a single GPIO on the Wemos D1 mini/ESP8266. So does the J3Y transistor and 10K resistor on the module ensure that there are less than those 12 mA drawn @ 3.3V and the Wemos D1 mini doesn't get roasted?

The board as such draws 160 mA @ 5V, but for the triggering the figures are claimed to be this:

Bildschirmfoto 2022-02-09 um 01.44.42.png (43.58 KiB) Viewed 7793 times

Road? Is that a translation error for Channel 1 and Channel 2? Also: What's the difference between working current and trigger current?

[TD-er]

The 12 mA is what you draw from the 5V and is what is drawn by the 2 LEDs (a SSR is a LED as seen from the low voltage side)
The ESP only has to deal with the 2x 10k resistor, which is perfectly fine for an ESP.
Only thing you need to keep in mind is that not all pins on the ESP are wired equal.
Some do have a pull-up resistor (e.g. GPIO-0 and -2) and some even have a pull-down (e.g. GPIO-15)

So it might differ per GPIO how well these SSR will work