Skip navigation

This is my first use of transistors in a project. I need to control a SainSmart 16-Channel Relay Module using an Arduino 101(3v3 GPIOs). This Relay Module uses 5 vdc through Opto couplers to power the relays. The input pins on the relay board are at 4.4 vdc and need to be brought to GND to switch on.

When I connected the Arduino 101(3v3 GPIOs) directly to the relay module some of the relays would stay on while others would be controlled by the Arduino. It all worked fine when I tried an Arduino UNO(5v GPIOs) in place of the 101. But, I want to use the BLE capabilities of the 101.

So my solution is to use  2N22222N2222 transistors because I’ve read they are good at general purpose low-mid power switching Below is the configuration I think is correct Any feed back would be greatly appreciated I’ve tried reading the Data Sheet but I’m mostly going off of other forum posts


Relay Board inputs; +4.4vdc, input to ground 4mA

Arduino 101; 3.3vdc GPIOs, max 20mA per GPIO

T1  2N22222N2222

R1: 10K, to reduce current through the Base to 0.33 mA

R2: 100K, drop down resistor. (is it needed?)





This video is all about interfacing BMP180 module with Arduino. BMP180 will help us to measure environmental temperature  and pressure and by using that we can calculate the altitude which can be used in various applications like weather monitoring, navigation etc. The BMP180 sensor module comes with I2C interface and with a default address 0x77 which is not configurable limiting stacking of multiple modules to that same I2C bus. In this tutorial we will interface the module with Arduino by using I2C interface that is analog input pin A4 and A5. And for this we are not going to use any library although if you are interested you can use any library available online which are actually pretty easy to use. Interfacing the module without any library will help us learn how it works as well as we can interface to other devices also where libraries are not available.




Links :

Website (BOSCH SensorTec):

Schematic :

Code :

Datasheet :


Subscribe YouTube :


Guys Subscribe to my channel for latest contents into your inbox.

Support me to keep going.



Website :

Twitter :

YouTube :

What do you thing about this project?

Have you some interesting ideas for expansion?


Filter Blog

By date: By tag: