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91  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: June 06, 2011, 11:22:47 am
like this
92  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: June 06, 2011, 10:43:04 am
This says it supports pwm http://www.instructables.com/id/Super-simple-high-power-LED-driver/

would it not work with the setup I just mentioned?
93  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: June 06, 2011, 10:28:14 am
But can't I use 5940 > non inverting transistor setup > constant current driver ?
94  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: June 06, 2011, 07:19:13 am
Can I use this instead? - http://users.telenet.be/davshomepage/current-source.htm

Will it perform the amplification as well or will I need to use it with a transistor?

If so how would the outputs of the 5940 connect with it?


Cheers
95  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: June 05, 2011, 06:45:34 am
Right, I get you.


So either I use something non inverting like this - http://docs-europe.electrocomponents.com/webdocs/0608/0900766b80608e30.pdf

or I need to invert the signal again. What's the best way to invert (cheaply and) without amplifying again?


How can I tell if this is inverting or not? - http://docs-europe.electrocomponents.com/webdocs/0b87/0900766b80b878b6.pdf

And another question - with any transistor setup, how can I tell what input current will give me what output current? Ie how much amplification is taking place


Thanks Grumpy

96  Using Arduino / Programming Questions / Re: Urgent! - how to send multiple serial streams to Arduino on: June 05, 2011, 06:08:29 am
Is that because it's a byte, not an int?

When receiving serial data to the arduino, does it always come in byte form? 
97  Using Arduino / Programming Questions / Re: Urgent! - how to send multiple serial streams to Arduino on: June 03, 2011, 12:09:27 pm
How can I make sure that the right x value for a goes to the pin for a?

Ie that it is syncronised.

Can I send a carriage return after every message and get the Arduino to use this to begin reading through the bytes each time?



Many Thanks!!
98  Using Arduino / Programming Questions / Re: Urgent! - how to send multiple serial streams to Arduino on: June 03, 2011, 12:00:18 pm
Code:
const int Pin10 = 10;      // the pin that the LED is attached to


void setup()
{
  // initialize the serial communication:
  Serial.begin(9600);
  // initialize the ledPin as an output:
  pinMode(Pin10, OUTPUT);

}

void loop() {
  byte brightness;

  // check if data has been sent from the computer:
  if (Serial.available()) {
    // read the most recent byte (which will be from 0 to 255):
    brightness = Serial.read();
    // set the brightness of the LED:
if (brightness = 0) {
      analogWrite(Pin10, 0);
}
      else{
      analogWrite(Pin10, 255);        
      }      
  
    delay(10);
  }
}
99  Using Arduino / Programming Questions / Urgent! - how to send multiple serial streams to Arduino on: June 03, 2011, 11:37:48 am
Hi, I need to try to figure this out in the next 2 hours!

I'm trying to send 3 variables from a piece of software over serial to the arduino to control the pwm value of three leds independently.

I've got it working successfully with one led being controlled but dont know how to do the same with more than one.


In the software I'm using I can format the serial in any way and I was thinking something like -

a x b x c x   (where x is the variable value)

then the Arduino will send the value after 'a' to led 1, the value after 'b' to led 2 etc.....

Can anyone help?  smiley-eek

a,x,b,x,c,x,

so I need the arduino to
100  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: May 26, 2011, 06:15:20 pm
No?!  I don't.  Arrgh

Why?
101  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: May 24, 2011, 07:19:25 pm
Ok, seems that it's only wise to take around 30mA from each channel of the 5940 -
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1238693450


Some interesting discussion there though


So it seems ok to use something like UDN2981A or a mosfet on the output of 5940, I just will miss out the benefits of constant current, meaning more fiddling around matching leds and limiting resistors, but with the benefit of a well documented arduino library, easy availability, and low cost?


smiley
102  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: May 24, 2011, 06:38:58 pm
Just came across this - http://www.jjoseph.org/misc_projects/high_power_rgb_led_controller


"To simplify the number of components, this design uses three TLC5940 outputs in parallel per LED color, achieving 360mA (3x120mA)"


Is it ok to do this (combine outputs so aggregating current?)

If not, surely I can just use two of these chips together, mirroring the outputs, each feeding seperate smaller led groups of 120ma taking me to my >200mA goal?
103  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: May 24, 2011, 05:48:32 pm
This seems like their best multi channel chip - http://www.national.com/pf/LM/LM3464.html#Overview Only 4 channels smiley-sad

Also are smd so I would need an adapter for each one

Will be very expensive (£8 for each chip and £5 for each adapter = £52 for 16 channels!)
104  Using Arduino / LEDs and Multiplexing / Re: multiplexing with pwm? on: May 24, 2011, 05:31:29 pm
Thanks Andrew.

Your lightuino board looks like it would do the trick but I reckon it will be out of budget (at least it is functionally overspecified for this project). How much do you sell them for (including UK p&p if you have any idea) and what's the lead time?

It also seems that I may well need more than 16 channels. If not now then a little further down the line. Can you get >4 bits pwm when not multiplexing?


I'm getting a bit lost though. @Madworm -

but will the 5940/UDN2981A combo work for my needs, allowing for the fact that I will need to use a current limiting resistor on each channel, and it may be tricky to get perfectly matched brightness between channels?

It's crucial that i can do pwm on each channel and (I think) crucial that I can get at least >200ma per channel.

I'll have another look on the national semiconductor site. Last time I looked part of it wasn't working. Will chips from these guys be difficult to address from the arduino? A benefit of the 5940 is that there is already a library for it.

This is seeming like a more difficult job than I first imagined!
105  Using Arduino / General Electronics / Re: Stripboard template pdf on: May 20, 2011, 03:53:01 pm
Just finished it, took me all night... uploading now............

smiley

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