Prepare the header strip:Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - long pins down
Add the breakout board:Place the breakout board over the pins so that the short pins poke through the breakout pads
And Solder!Be sure to solder all 5 pins for reliable electrical contact.
(For tips on soldering, be sure to check out our Guide to Excellent Soldering).
You're done! Check your solder joints visually and continue onto the next steps
- Connect Vin to the power supply, 5V is fine. For 3V microntrollers, connect to 3.3V
- Connect GND to common power/data ground
- Connect the SCL pin to the I2C clock SCL pin on your Arduino. On an UNO & '328 based Arduino, this is also known as A5, on a Mega it is also known as digital 21 and on a Leonardo/Micro, digital 3
- Connect the SDA pin to the I2C data SDA pin on your Arduino. On an UNO & '328 based Arduino, this is also known as A4, on a Mega it is also known as digital 20 and on a Leonardo/Micro, digital 2
Connect the sensor to the four top-left pins, GND, SCL, SDA and 3V using alligator clips, soldered wire, or quality conductive stitching
The SI1145 has a fixed I2C address (0x60), you can only connect one sensor per microcontroller!
Place the Adafruit_SI1145 library folder your arduinosketchfolder/libraries/ folder.
You may need to create the libraries subfolder if its your first library. Restart the IDE.
We also have a great tutorial on Arduino library installation at:
In this screenshot I pointed a UV LED onto the sensor to simulate a really high UV index of 7. Indoors, expect to get a UV index of well below 1. Even glass windows are excellent at filtering UV light so if you want to measure the actual UV outside point the sensor right at the sun!
The SI1145 is primarily a UV index sensor, but it does have the ability to sense other kinds of light. However, those light levels aren't calibrated in our library. That is to say, unlike our Lux sensor, these are just values based on how much light the sensor sees, and there's no 'units' to them. Still, this might handy if you just want to keep track of light levels.
There's also another capability that SiLabs shoved into this chip - a proximity sensor! We haven't done much experimentation with this part of the sensor but it does sort of seem to work. Basically, if you connect an IR LED to the LED pin, the sensor will pulse the LED and measure how much IR light is reflected back. This can be used to do basic proximity sensing. If you are interested in trying out the prox sensor, grab an IR LED and connect the + side to 3V or so, and the - side to the LED pin.