WeMos V2 Relay Shield (HCWEMO0005)

Wemos ESP8266 based development boards and shields
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WeMos V2 Relay Shield (HCWEMO0005)

Post by admin » Tue Nov 22, 2016 11:17 am


This relay shield is designed to be used with the WeMos mini & mini Pro ESP8266 based development boards (see item HCWEMO0002). Adding this shield to your WeMos mini development board provides it with the ability to switch high voltage, or high power devices from a single digital pin. Included with the shield is a set of header pins which can be optionally fitted (soldering required) to allow for the shield to be easily inserted and removed from the D1 mini.

Although this module is intended for use with the Wemos development boards it can of course also be used as a standalone relay module requiring a single 5V supply and one digital pin (5V & 3.3V compatible) to control it.



NO: 5A(250VAC/30VDC), 10A(125VAC), MAX:1250VA/150W
NC: 3A(250VAC/30VDC), MAX:750VA/90W

Example Arduino Sketch:

Code: Select all

/* WeMos relay example - HobbyComponents.com */
#include <ESP8266WiFi.h>
#define PIN D1 // Relay shield is controlled by digital pin D1
void setup()
  pinMode(PIN, OUTPUT); // Set the pin to an output
void loop()
  digitalWrite(PIN, HIGH); // Energise the relay
  delay(1000); // Wait for another second
  digitalWrite(PIN, LOW); // De-energise the relay
  delay(1000); // Wait for a second



Libraries, example code, and diagrams are provided as an additional free service by Hobby Components and are not sold as part of this product. We do no provide any guarantees or warranties as to their accuracy or fitness for purpose.

Descriptions and diagrams on this page are copyright Hobby Components Ltd and may not be reproduced without permission.
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Posts: 1
Joined: Mon Aug 27, 2018 3:16 am

Re: WeMos V2 Relay Shield (HCWEMO0005)

Post by philrich123 » Mon Aug 27, 2018 9:52 pm


What's quite annoying with this shield is that it use the D1 pin. The wemos module use it for i2c. There is a Lolin V2.0.0 of this shield where you can chose the IO, but I have the one described here and I wanted to use it with different IO.

So what I have done before soldering the headers, is placing a cut lead of a through-hole component formed as the picture below.
Then cutting the circuit between D1 and the base resistor of the transistor driving the relay, and soldering a wire to the Dx you want.
Just a remark here, I have selected the D4 IO witch is not a good idea because it is used by the build in resistor of the wemos D1 module :? .

Another annoying thing is that the legs of the headers are to short for this module to make it "piggy back possible". So I had to solder it on the top of the shield with smalls wires, Not very clean but it does the job.
With This you can plug the 1Button shield over it. I Just cut the low part of this last one to gain easy access to the screws of the relay shield connector.

Hope that will help !
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Re: WeMos V2 Relay Shield (HCWEMO0005)

Post by BaconRanch » Tue Mar 12, 2019 1:04 am


I believe this was the best place to post my question ......I am trying to use a Wemos D1 mini in a project and was told I need an optoisolator, which apparently is only for Arduino based boards, does anyone know what a Wemos equivalent is? I do not have a background in this, just muddling through and learning as I go. The optoisolator isolates 2 separate circuits and reduces the input voltage, which is exactly what I need to do.

My project is to hard wire into a Budweiser goal light that uses an electric imp card, using the Wemos flashed with Tasmota, I can then use the goal event of the light to trigger all my custom and Hue lights in my home with Home Assistant. I am using the Bud goal lights speaker wires' current as the event trigger.

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