Not really a tutorial as I'm no good at writing tutorials, but important to know nevertheless.
WARNING: Relays can be used to switch very high voltages. Here in the UK 240VAC can easily kill a person, so be very careful when handling relays.
What is a relay, well I look at it in 2 ways.
As the digital out pins on the Arduino/ATmega328p and the WeMos/8266 send out different voltages, it's a good idea to purchase a relay that triggers at both 3.3v and 5v, that's where the SRD-05VDC-SL-C relay comes into its own. I do not recommend that you use a DC to DC BUCK converter Booster on your WeMos/8266, just use a 3.3v to 5v relay or if you are using a D1 Mini you can purchase a 3.3v relay shield or use a 3.3v to 5v relay. The 5v relay triggers when it receives a voltage of around 5v, the 3.3v to 5v relay will trigger in between 3.3v and 5v, it's good for both Arduino and WeMos.
The operating voltage of the Arduino/ATmega328p is 5v and the digital pins when set to OUTPUT sends out 5v. The WeMos/8266 on the other hand has a operating voltage of 3.3v, and yes you guessed it, the digital pins when set to OUTPUT sends out 3.3v, you can measure the voltages with a multimeter and double check it yourself.
If you are using an Arduino Uno or Mega etc and for some strange reason you only have 3.3v relays, you have 3 options.
3.3v to 5v triggered relay
5v triggered relay
3.3v D1 Mini relay shield
WARNING: Relays can be used to switch very high voltages. Here in the UK 240VAC can easily kill a person, so be very careful when handling relays.
What is a relay, well I look at it in 2 ways.
- A device for switching both Low and High voltage On/Off by means of a similar or smaller voltage.
- A device for redirecting both Low and High voltage (from one part of a circuit to another part) from NC (Normally Closed) to NO (Normally Open) and vice versa by means of a similar or smaller voltage.
As the digital out pins on the Arduino/ATmega328p and the WeMos/8266 send out different voltages, it's a good idea to purchase a relay that triggers at both 3.3v and 5v, that's where the SRD-05VDC-SL-C relay comes into its own. I do not recommend that you use a DC to DC BUCK converter Booster on your WeMos/8266, just use a 3.3v to 5v relay or if you are using a D1 Mini you can purchase a 3.3v relay shield or use a 3.3v to 5v relay. The 5v relay triggers when it receives a voltage of around 5v, the 3.3v to 5v relay will trigger in between 3.3v and 5v, it's good for both Arduino and WeMos.
The operating voltage of the Arduino/ATmega328p is 5v and the digital pins when set to OUTPUT sends out 5v. The WeMos/8266 on the other hand has a operating voltage of 3.3v, and yes you guessed it, the digital pins when set to OUTPUT sends out 3.3v, you can measure the voltages with a multimeter and double check it yourself.
If you are using an Arduino Uno or Mega etc and for some strange reason you only have 3.3v relays, you have 3 options.
- You can use a voltage divider circuit using 2 resistors to drop the voltage from 5v to 3.3v.
- You can use a DC to DC 5v to 3.3v step down module.
- You can use IIC I2C DC 5v to 3.3v logic level converter for 2 or more relays, but you might as well just purchase 3.3v relays.
3.3v to 5v triggered relay
5v triggered relay
3.3v D1 Mini relay shield
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