Go Down

Topic: Fun with Arduino - a Series of Introductory Videos (Read 23383 times) previous topic - next topic

RudyB


The delay() statement that we used so far for our timing stalls the Arduino. This leads to a complete lack of feedback when we change the cycle time while the cycle is running. Luckily there is a solution: we can use the Arduino internal clock, which counts milliseconds from the moment the Arduino is started. We can read the clock using the millis() statement and we can decide if it is time for action.

Fun with Arduino 13 Timer with millis(), no delay(), Multitasking


Youtube channel on Model Railway, Traincontroller, Arduino and more

RudyB


Now that we know how to get rid of the delay(0 and use millis() in stead (video 13) we can finalize our Automatic Day Night Light Cycle unit to have direct on screen feedback of cycle time adjustment by the user and to have the cycle stop, and the lights turn off, immediately when the switch is set to 'off'.

Our unit has quite nice specifications:
- Configurable timing, via keyboard or via analog input with on screen display
-  An option to randomize the times to give it some 'livelyness'
- On screen display of the on/off, day/night state and the cycles times


Fun with Arduino 14 Day Night Cycle with millis(), no Delay, Direct Feedback


Youtube channel on Model Railway, Traincontroller, Arduino and more

RudyB


We used analogRead() to read the voltage on our potentiometer. The Arduino also has the opposite instruction: analogWrite(). This name is somewhat misleading. Unlike with an analog input, where a 10 bit A/D converter is used, the Arduino does not have a D/A converter on board.

The analogWrite() function uses a technique called Pulse Width Modulation. A digital output switches between HIGH and LOW in a fast pace, whereby the HIGH percentage is proportional to the analog value we wish to send out. If a device that receives the signal is too slow to follow the switching frequency, the result is it 'sees' the average of the on/off times. This also holds for light ... even though LEDs are fast enough to follow the switch frequency, our human eyes + brain are not and we see an average brightness.


Fun with Arduino 15 LED Dimmer, analogWrite(), Pulse Width Modulation


Youtube channel on Model Railway, Traincontroller, Arduino and more

RudyB

Fun with Arduino 16 LED Dimming with Fade, analogWrite(), millis()

Now that we know how to dim LEDs with analoWrite(), we can go a step further and change the dimming over time to create a gradual fade in or out. This is a nice effect for instance for LED strips mounted under kitchen cabinets, or for LED strip overhead lighting on a model railway layout to simulate a gradual change from night to day. And also for the red/green transition of railway signals along the track a fade gives just that little extra eye candy.

Fun with Arduino 16 LED Dimming with Fade, analogWrite(), millis()


Youtube channel on Model Railway, Traincontroller, Arduino and more

Go Up