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Topic: Oh my Darlington, Oh my Darlington, oh my DARLINGTON...CLEMENTINE (Read 1 time) previous topic - next topic

santiago82

I'm tired sorry, but I have some Darlington arrays coming and I have virtually no idea how to wire them up for my LEDs.  What I need them to do is bypass the 5v limit I'm encountering with the Arudino because well, I'm looking at 15+ Leds on this and I'm pretty lost

Darlington

Basically how do I wire one LED to be powered externally and have the Arduino control its function.  If I could see a diagram I can extrapolate from there.
Just because a design works does not make it a good design. ~ Anonymous

Wawa

That chip is basically a bunch of transistor switches to ground, with build-in base current limiting resistors.

Arduino pin (digital, or PWM for dimming) can be connected directly to a darlington input (1B-8B).
Led, with current limiting resistor, between LED supply and darlington output (1C-8C).
The darlington diodes (COM) must be tied to that same supply, but that can be ignored for resistive loads and LEDs.

Note that a darlington has a high volt-drop (loss) when 'on'.
That makes them unsuitable for power LEDs.
Leo..

JCA34F


Grumpy_Mike

Quote
Basically how do I wire one LED to be powered externally and have the Arduino control its function.
Connect the ground of that board to the ground of the Arduino and to the ground of the high voltage power supply.

Then connect an Arduino output to one of the chips inputs.

Then connect the anode of the first LED of the string to the positive of the power supply, the cathode of the last LED in the string to your resistor, and the other end of the resistor to the chip's output pin.

santiago82

That chip is basically a bunch of transistor switches to ground, with build-in base current limiting resistors.

Arduino pin (digital, or PWM for dimming) can be connected directly to a darlington input (1B-8B).
Led, with current limiting resistor, between LED supply and darlington output (1C-8C).
The darlington diodes (COM) must be tied to that same supply, but that can be ignored for resistive loads and LEDs.

Note that a darlington has a high volt-drop (loss) when 'on'.
That makes them unsuitable for power LEDs.
Leo..
So I wasted my money then?
Just because a design works does not make it a good design. ~ Anonymous

Wawa


TomGeorge

Hi,
Have you googled?

uln2803a arduino

Do I understand that your LEDs will be supplied with current from a supply higher than the Arduino 5V?
If so you have not wasted your money.
The ULN2003 is ideal for doing what you need with an array of LEDS.
15+ LEDs, do you mean.
15+ individual outputs or outputs with more than one LED in the output?

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

santiago82

More than 1 LED.  Some circuits are looking at 2-4.  Not counting a shift register to free up pins
Just because a design works does not make it a good design. ~ Anonymous

santiago82

Depends on which LEDs you're talking about.
Leo..
Small LEDs.  5mm to 1.8mm.  3.1v down to 2.2v apiece depending on color.  20 mA a piece.
Just because a design works does not make it a good design. ~ Anonymous

Paul__B

Do I understand that your LEDs will be supplied with current from a supply higher than the Arduino 5V?
If so you have not wasted your money.
The ULN2003 is ideal for doing what you need with an array of LEDS.
Not really.

More than 1 LED.  Some circuits are looking at 2-4.  Not counting a shift register to free up pins
If you proposed to use a shift register, you should be using a TPIC6B595 which is a shift register capable of driving higher voltage parts, including LEDs.

OTOH, the LEDs you describe can be driven by an Arduino output directly with a resistor, say 220 Ohms.

santiago82

I'm using a 74HC595 for one circuit driving 12 LEDs.  It works on breadboard.
Just because a design works does not make it a good design. ~ Anonymous

CrossRoads

74HC595 shouldn't be driving more than 7-8mA per output pin, otherwise it is overstressed and will be damaged over time.  The VCC & Gnd pin are only rated to 70mA Absolute Max, above that and things are likely to fail.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

santiago82

Ok I need to describe what the shift is doing because there is a lot going on with this build. 

The Shift register is going to handle 12 LEDs.  6 LEDs on either side of this model I'm building.  At one time no more than 4 LEDs will be lit on both sides and only two to a pin(1 red and 1yellow so low voltage).  If I numbered them 1-12: LED1&4 and 7&10 would be on, then off as it moved to 2&5 and 8&11 and then 3&6 and 9&12. 

The Darlington is so I can handle a programed blinking sequence with a Red and Green Led as they are wired in series, as well as the 7 interiors white LEDs which will be static.
Just because a design works does not make it a good design. ~ Anonymous

TomGeorge

Ok I need to describe what the shift is doing because there is a lot going on with this build.  

The Shift register is going to handle 12 LEDs.  6 LEDs on either side of this model I'm building.  At one time no more than 4 LEDs will be lit on both sides and only two to a pin(1 red and 1yellow so low voltage).  If I numbered them 1-12: LED1&4 and 7&10 would be on, then off as it moved to 2&5 and 8&11 and then 3&6 and 9&12.  

The Darlington is so I can handle a programed blinking sequence with a Red and Green Led as they are wired in series, as well as the 7 interiors white LEDs which will be static.
I hope you don't want to control the RED and GREEN LED in series, but individually turn them ON and OFF?
I think we need to see a wiring concept, diagram of your LED layout.
Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

santiago82

That might be a bit hard at this point but I'll bring up a picture tomorrow via Frizling that approximates the circuit as it technically doesn't exist outside of breadboard.  I was hoping to but apparently I can't even with the Darlington in play...which means I need to utilize another pin to have them both blink
Just because a design works does not make it a good design. ~ Anonymous

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