Timed Dimming Help

Projects Programming
1

Hi,

Im very new to Arduino and Im trying to find some code that will allow me to dim an LED on and off at various times,

for example:

On: 10:00
Off: 19:00

I want the times to be hard coded.

Ive got an Arduino uno and a DS3231 RTC

Can anyone point me in the direction of some sample code?

Thanks!

2

start here

3

If you want to control the brightness of a led, look up pwm (pulse width modulation).

4

Thanks for your replies, Ive taken a look and started to write some code. Ive wired up my 24v LED via a IRF840 MOSFET

it sort of works but with strange results... it dimms to about 70-80% then back up to 100% using the following code:

int ledPin = 11;    // LED connected to digital pin 9

void setup() {
  // nothing happens in setup
}

void loop() {
  // fade in from min to max in increments of 5 points:
  for (int fadeValue = 0 ; fadeValue <= 255; fadeValue += 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }

  // fade out from max to min in increments of 5 points:
  for (int fadeValue = 255 ; fadeValue >= 0; fadeValue -= 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }
}

not sure why it wont fade to off!

any ideas?

5

What does a simple " analogWrite(ledPin, 0);" do? (no loops, just this statement in setup())

Do you have a schematic?

int ledPin = 11; // LED connected to digital pin 9

It helps when code and comment agree

6

wreckitsteve:
Thanks for your replies, Ive taken a look and started to write some code. Ive wired up my 24v LED via a IRF840 MOSFET

it sort of works but with strange results... it dimms to about 70-80% then back up to 100% using the following code:

int ledPin = 11;    // LED connected to digital pin 9

void setup() {
  // nothing happens in setup
}

void loop() {
  // fade in from min to max in increments of 5 points:
  for (int fadeValue = 0 ; fadeValue <= 255; fadeValue += 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }

// fade out from max to min in increments of 5 points:
  for (int fadeValue = 255 ; fadeValue >= 0; fadeValue -= 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }
}




not sure why it wont fade to off!

any ideas?

Sorry about the comment confusion, i forget to edit it. When i put the code you said in setup it just stays on about about 50% bright.

7

Do you have a schematic?

8

im totally new to electronics so dont know how to draw one yet

9

well i think ive solved it! I swapped out the MOSFET for a new one that I had (same type) and it now works like a dream!!

Maybe faulty MOSFET?

10

wreckitsteve:
Maybe faulty MOSFET?

An IRF840 is not a logic level mosfet.
The 5volt logic of an Arduino might or might not turn it on sufficiently.
You might have been lucky that the second fet had a lower gate threshold voltage.
Leo..

11

Wawa:
An IRF840 is not a logic level mosfet.
The 5volt logic of an Arduino might or might not turn it on sufficiently.
You might have been lucky that the second fet had a lower gate threshold voltage.
Leo..

Ahh i see, what MOSFET should I be looking for?

12

One described as "logic level"

13

CtrlAltElite:
One described as "logic level"

thank you