Introduction: Temperature-Humidity Monitoring Using Digispark USB and RGB Led

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Digispark USB is an ATTINY85 powered tiny development board with on board USB plug in and compatible with Arduino IDE. You must install and set some required stuffs. Now, i want to introduce a minimalist but functional circuit for monitoring Temperature and Humidity information by using only a RGB led and DHT11.

By the only one RGB led how can we monitor the numerical values? Yep, we can't monitor numerically but we can monitor the temperature with color-sense way and also the humidity. Normally, if you use a room thermometers, you know that your measuring range is limited. And you are always interested in for an optimal range. For example, for a baby room we generally want the room temperature be in a specific 23~25 °C range for an healthy, comfortable environment. So, why would i need a wide range monitor? We can use an RGB led monitor/alarm to measure the range. It's so simple! Here the setup is;

Step 1: BOM and Setup

BOM:
1 x Digispark USB dev board
1 x RGB Led
1 x DHT11 sensor
1 x 1k resistor

Circuit is so simple as seen in the picture. Now, we only need to write some codes. The aim is firing the led for a different color for a specific condition:

if temperature < 23 °C then BLUE (for simulating cold sense)
if temperature >25 °C then RED (for simulating hot sense)
else then GREEN (for optimum, healthy sense)
and in addition;
if humidity is not in 15% ~ 40% range then flash the led colors respectively.

Note: These values are especially defined from some literature papers on health science.

Ok. You can download .ino file form attachments to upload your Digispark USB. The uploading procedure is simple like other boards but has some important tricks:

  • Digispark USB doesn't work like other arduino boards. You must click the upload button from Arduino IDE first and then plug the Digispark USB until you see the success message.
  • And Digispark USB is not stable for 5 volts feeding, i don't know why? This may be a Murphy effect special to me. :) Because of that, you must feed your Digispark USB for 3.3 volts.
  • I don't advise to use D1 pin. Because it is connected to Build_In Led. See the picture for wire connection.
  • And for your information, this board doesn't support serial monitor.


All done!

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