hi, so this is my first time with an arduino project.
Using the UNO, what i want to do, is this;
From 7am, i would like the first 3 LEDs on the bottom to fade in until they are at their full brightness, followed by the second then the third over the next 2 hours, then i would like all 9 LEDs to stay on until 6pm, then from the top row fade the LEDs down again until all LEDs are fully off over the following 2 hours, until 7am the next day, then repeat.
Thanks for any help!
Your average Arduino has enough pins so its onw LED to every pin. BUT they are not "analog" out (PWM capable).
Two possibilities - you do "bit bang" - which is a fun way of saying you turn the LED On and Off fast enough in the right ratio in your program to have the same effect.
The other one is to add some extra electronics to multiplex the PWM on the LEDs or even have the external chips do the PWM.
And the 3rd one is to write your specifications a lttle clearer. If each row has the same dimming, then you can either wire the LEDs in series and use the PWM pins you have - you are only steering 3 groups. And some other possible combinations depending on exactly what patterns you want
thanks. heres what i have in mind;
the less wired up like this
(ardunio pin example)
|--[ r ]------0-0-0---- pin 9
GRND |--[ r ]------0-0-0---- pin 10
|--[ r ]------0-0-0---- pin 11
0= leds
so if i where to 'bit bang' it, how would i start programming it to fade in from the bottom row? (in this example pin 11)
i just need something to start with to get an idea!
Thanks
Regarding the wiring, you cannot put three LEDs in series, even red ones, and drive them from 5V. If you have an 8V regulated supply to power the UNO, you can use three transistors to drive your three chains of three. If the supply is unregulated, you want to use constant current drive circuits for the LEDs.
There are a number of PWM capable pins on the UNO, but you can only use three at a time IIRC. Mind you, you appear to want only to PWM one at a time, so even that is not a problem.
Arrange your circuit first, and then experiment with "AnalogWrite()".
Are you going to use a RTC to determine your times?
After looking into the rtc I'm thinking the ds1302 would be the best bet, to trigger the sequence.
So if I use an transistor on each line of leds, would the coding remain the same as if it where 3 individual leds running off the 3 pwm pins?
Thanks
Would it work if Instead of running the leds in 3 separate lines of series, have the leds in parallel, obviously the leds won't be as bright, but could the arduino handle 3 leds in parallel from one pin?
Or would it be easier to wire it as a matrix configuration like this example here;
http://www.tuline.com/dru/content/arduino-3x3-row-column-scan-led-matrix-pwm
That way I could sequence the LEDs to appear to be on constantly when they are turning on and off thus reducing power consumption right?
Mccluskey1181:
So if I use an transistor on each line of leds, would the coding remain the same as if it where 3 individual leds running off the 3 pwm pins?
Of course.
Mccluskey1181:
Would it work if Instead of running the leds in 3 separate lines of series, have the leds in parallel, obviously the leds won't be as bright, but could the arduino handle 3 leds in parallel from one pin?
Only if you limit the current to 7 mA per LED as the port pin is only specified for 20 mA. They will of course, not be as bright as if you use transistors to supply the LEDs with their maximum rated current.
Mccluskey1181:
Or would it be easier to wire it as a matrix configuration like this example here;
http://www.tuline.com/dru/content/arduino-3x3-row-column-scan-led-matrix-pwm
That way I could sequence the LEDs to appear to be on constantly when they are turning on and off thus reducing power consumption right?
Easier - no.
You would certainly reduce power consumption, but again, the average current per LED would be down to 7 mA and they would not be as bright as if you use transistors.