Hi, I have 7 parallel LED's that I am trying to dim using the PWM pins. I need a board that will fit within a 3"x2"x0.3" box, So i picked the FLORA.
The problem is that I can’t seem to get the full brightness out of the FLORA.
For reference, I have hooked 2 LEDS (in parallel) to a separate 3.3v source, the LEDs are very bright. My meter says they are pulling around 40mA from the power supply.
But when I hook the same LED's between Pin D9 and GND of the FLORA, the LED's only seem to get 8mA.
I was planning on putting a pair of LEDs on each pin, but it looks like they will only be 1/4 the brightness.
The advertising says: "The FLORA has an onboard 3.3v 150mA regulator." I think I also read somewhere that each pin of the Flora could put out only like 40 mA each.
My questions:
Am I doing something wrong?
Should the LED's be in series ?
Do I need some kind of LED driver instead?
What about this TLS59711 driver. It seems to let you 60 ma per channel !!!
https://www.adafruit.com/products/1455
What about these boards, would they work for me ? They are tiny and claim that each pin can handle 40-50mA:
http://arduino.cc/en/Main/ArduinoBoardMicro
http://arduino.cc/en/Main/ArduinoBoardLilyPadUSB
-Greg
LED link: http://www.luckylight.cn/UploadFiles/V020W-W6-1E-RL.pdf
=================================
The code I’m using is basically the same as the Fade.ino example
(With the DIM_VALUE of 0-254)
void setup() {
pinMode(9, OUTPUT);
}
void loop() {
analogWrite(9,DIM_VALUE);
}
==================================
PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLORA ?
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PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLORA ?
Last edited by GJGeist on Mon Jul 28, 2014 9:33 am, edited 1 time in total.
- adafruit_support_bill
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Re: PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLOR
40mA is the absolute maximum rating for a Flora pin. Overloading the pin can damage it.
To drive 7 leds in parallel, you need something capable of handling the current (7x20mA = 140mA) You can use the PWM pin to drive a transistor that will switch the current: https://www.adafruit.com/product/756
Another option is to use a dedicated PWM led driver: https://www.adafruit.com/products/1455
That will let you control up to 12 sets of leds individually.
To drive 7 leds in parallel, you need something capable of handling the current (7x20mA = 140mA) You can use the PWM pin to drive a transistor that will switch the current: https://www.adafruit.com/product/756
Another option is to use a dedicated PWM led driver: https://www.adafruit.com/products/1455
That will let you control up to 12 sets of leds individually.
-
- Posts: 3
- Joined: Sun Jul 27, 2014 11:47 pm
Re: PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLOR
Bill:
So if each pin can handle 40 mA, shouldn't I be able to drive one 20 mA LED at full power ? With one LED all I can get the FLORA to provide is around 8 mA.
-Greg
So if each pin can handle 40 mA, shouldn't I be able to drive one 20 mA LED at full power ? With one LED all I can get the FLORA to provide is around 8 mA.
-Greg
- adafruit_support_bill
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Re: PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLOR
What is the forward voltage of the LED you are using and how do you have it connected?
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Re: PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLOR
Forward Voltage:
Min 2.8v
Typ 33.4v
Max 3.8v
If =20mA
Im hooking the LED between Pins GND and D9 of the FLORA.
LED link: http://www.luckylight.cn/UploadFiles/V020W-W6-1E-RL.pdf
=================================
The code I’m using is basically the same as the Fade.ino example
(With the DIM_VALUE of 0-254)
void setup() {
pinMode(9, OUTPUT);
}
void loop() {
analogWrite(9,DIM_VALUE);
}
==================================
Min 2.8v
Typ 33.4v
Max 3.8v
If =20mA
Im hooking the LED between Pins GND and D9 of the FLORA.
LED link: http://www.luckylight.cn/UploadFiles/V020W-W6-1E-RL.pdf
=================================
The code I’m using is basically the same as the Fade.ino example
(With the DIM_VALUE of 0-254)
void setup() {
pinMode(9, OUTPUT);
}
void loop() {
analogWrite(9,DIM_VALUE);
}
==================================
- adafruit_support_bill
- Posts: 88088
- Joined: Sat Feb 07, 2009 10:11 am
Re: PWM Dimming 140 mA (7pcs x 20mA each) won’t work on FLOR
See the forward current vs forward voltage chart on the top-right of page 5. The Flora pins will output at most 3.3v, so you would never get 20mA.
Please be positive and constructive with your questions and comments.