Grove - Solid State Relay

Grove – Solid State Relay is a non-contact electronic switch module that has relay features. Based on S208T02, it has a maximum output of 250VAC/4A, with a switching speed less than 10ms. This module is equipped with acrylic base and a 3D-printed protection insulation shield, for user’s safety. The featured LED indicates that the relay is on. It can be widely used in various areas such as computer peripheral interfaces, temperature/speed/light adjustment, servo control, petrochemical, medical instrumentations, financial devices, coal, meters, traffic signals, etc.


Application Ideas


Item Min Typical Max Uint
Input Voltage
Input Current
Output Voltage
Output Current
Operating frequency
Operating temperature
Turn-on time
Turn-off time
Net Weight

Interface Function



With Arduino

The Grove - Solid State Relay has a variety of applications. Here we elaborate on how to use it to control a bulb.

First off, you'll need to connect it to the Arduino like so:

1. Connect the Grove - Solid State Relay to Digital 13 of Grove-Base Shield via a Grove 4 pin wire.
2. Plug Grove-Base Shield onto Arduino and connect Arduino to PC via a USB cable.
3. Connect the bulb to OUTPUT of Grove - Solid State Relay.

You need upload the below code. Please click here if you do not how to upload.

  Grove - Solid State Relay Demo Code
  The ssr will turn on for 5s and then turn off for 5s, and so on.

int ssrControlPin = 13;
void setup() {                
  // initialize the digital pin as an output.
  pinMode(ssrControlPin, OUTPUT);     

void loop() {
  digitalWrite(ssrControlPin, HIGH);      // set the SSR on
  delay(5000);                            // wait for 5 second
  digitalWrite(ssrControlPin, LOW);       // set the SSR off
  delay(5000);                            // wait for 5 second

After upload the code, you can see the bulb will light 5s and then turn off for 5s, and so on.

With Raspberry Pi

1.You should have got a raspberry pi and a grovepi or grovepi+.
2.You should have completed configuring the development enviroment, otherwise follow here.

4.Navigate to the demos' directory:

   cd yourpath/GrovePi/Software/Python/
   nano   # "Ctrl+x" to exit #
import time
import grovepi

# Connect the Grove Solid State Relay to digital port D4
relay = 4


while True:
        # switch on for 5 seconds
        print "on"

        # switch off for 5 seconds
        print "off"

    except KeyboardInterrupt:
    except IOError:
        print "Error"

5.Run the demo.

   sudo python

Test Report

1.Experimental purposes

  1) Thermal performance of Grove – Solid State Relay(S208T02)

  2) Limit load current of Grove – SSR

  3) Measures to improve the limit load current

2.Experimental Principle

By recording SSR chip temperature at different current and different time points, analysis the data and draw conclusions.
Figure 1 is screenshot from S208T02 datasheet, we can see that at different heat sink and different temperature, SSR’s current is different.

Figure 1: RMS ON-state Current vs Ambient Temperature

There needs a temperature sensor to get the temperature of the chip. I use DS18B20 whose detection range is -25-125℃ to meet the requirements.
Figure 2 shows the experimental equipment and installation plans, the temperature sensor is tied to the right side of the heat sink, to make the temperature that 18b20 detects as close as possible to the heat sink temperature, smear between the sensor and the heat sink thermal plastic. Between the heat sink and SSR coated thermal plastic. Therefore, the temperature of the 18b20 is equal to the temperature of SSR.

Figure 2: Test Temperature

3.Experimental data

Table1 time vs temperature
1min 5min 10min 20min stable time
0.5A 31.40 33.75 34.75 35.00 15min
1A 31.8 36.75 39.6 40.56 18min
2A 34.5 46.6 48.88 51.13 20min
3A 35.56 52.81 58.88 60.06 17min
4A 38.00 57.88 63.88 67.00 19min
5A 44.00 66.00 73.12 75.37 19min

Note 1: The unit of temperature in the table is ℃
Note 2: When tested room temperature is 28 ℃

4.Expansion experiment

  In order to prove that improve the level of heat sink will improve the SSR limit operating current, I did an expansion experiment.
  Cuz I hadn’t a larger heat sink on hand, so I installed a fan (which I take for my PC’s CPU) above the SSR. As shown in Figure 3.

Figure 3: Expansion experiment

I just test the stable time of different operating current, as shown in Table 2.

Table2 Stable time of expansion experiment
6.0A 6.5A 7.0A 7.5A
Stable time 54.44℃ 57.63℃ 60.06℃ 62.38℃

5.Expansion experiment

From the above experimental results, the following conclusions can be drawn:

1). When current is fixed, with the passage of time, the temperature will stabilize at a certain value. This value is related with the current, the current increases, the stable temperature are greater. At 2A, stable temperature will be more that 50 ℃, So, when the SSR work, you should not touch it.
2). Combined with Figure 1 and our data, I consider that the Grove – SSR can operator 4A load current at max.
3). If load current larger than 5A, such as 7A, you should install a fun on it , or other cooling measures, but it’s not recommended.


Ask questions on Seeed forum.


Grove - Solid State Relay Eagle File

Grove - Solid State Relay Demo Code

S208T02 Datasheet

Grove - Solid State Relay in PDF

Grove - Solid State Relay Test Report

Copyright (c) 2008-2016 Seeed Development Limited ( /
This static html page was created from