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16  Forum 2005-2010 (read only) / Interfacing / Re: Connecting many RGB LEDs to same PWM pins? on: November 03, 2007, 08:08:47 pm
 smiley Thnx for the sweet help on explaining this.
Ehh.. (getting my Electronics for Dummies book), lets say I do this for 4pin RGB LEDs.

For 1 PWM pin:

So, I get 1 transistor that can handle enough power to use for my LEDs

Put the PWM pin off the Arduino to Basis/Gate.
Put a decent power suply to the Emitter/Source.
Put My LEDs to the Collector/Drain.

And than do this also for 2 other pins....

Than I simple hook all the Red pins together, the Green pins together, and the blue pins together (ofcours connected to the proper collectors/gains).

Next I connect all the commen, where I connect the commen? Does that goes to the negative pole from the power suply?

Also, I am sure I need some resistors here somewhere (one always needs resistors smiley-wink )

If you say this could work, I will post a drawing.

edit: something like this? (can you sugest a decent transistor?, and this is for a 4 pin RGB LED smiley-wink )

edit2: Ahh. I read It is best to give each seperate LED a Resistor, should I place it before or after my LED?
17  Forum 2005-2010 (read only) / Interfacing / Connecting many RGB LEDs to same PWM pins? on: November 03, 2007, 05:26:05 pm
Halo, I want to be able to color a glass plate using a lot off RGB Leds, for now it is okay if the entire plate is the same color.
(In the end it should be wireless using the Xbee, but lets start with the basics)

I can make 1 LED dim and change color, but I need more light than 1 LED.

1.  What kind off LEDs should I use? I read that it is not possible to connect thos 4 Pins RGB LEDs (with commen cathode) in series, so is it better to get a bunch off Red, Green and Blue ones?

2. I know my Arduino can only power so many LEDs, so how do I go arround and connect them together using a second power source?

3. An idea I was thinking off PWM-ing a transistor for this, would it work? what transistor would you recommend me?

4. Isn't PWM-ing a pin and recieving DATA from the PC interfering with eachother? perhaps different ways, like using the 555.

Any other tips/hint are also welcome, thank you for your time, I am a newbee, so keep it simple.
18  Forum 2005-2010 (read only) / Interfacing / Re: What USB does Arduino Use?? (USB1.1 or USB2.0) on: October 29, 2006, 05:16:08 pm
There where also some touchscreens near the place I wanted to use my arduino, they usesd RS232 cable, remebered it was very expensive, but now we have the USB1.1 -> Cat5 extendere solution, and we can also use a mouse and keyboard for debugging.

Hope I can simply plug in my Arduino and make it work.

Thank you for the reply kg4wsv.

So, basicly you say, you made your own RS232 cable (sorry, my naming convention isn't soo good, but I asume you know what I mean) buy taking some piece off Cat5cable, and solder your own connetors, and it works? That trick is great to know smiley

But I serious wonder about the shielding problem you will have, than again, as you said with low data-rates it should not realy mather. Think I could try it with some trial-and-error, hehe.. low budget rules smiley-wink

Once again, thank you for your time, I am just a beginner to this great world off electronics.
19  Forum 2005-2010 (read only) / Interfacing / Re: What USB does Arduino Use?? (USB1.1 or USB2.0) on: October 22, 2006, 08:05:13 pm
So the Arduino is USB1.???????????
(was the only thing I wanted to know)

Thnx for the replies, and mentioning the USB extendercable, very interseting.

Ehh... a decent RS232  Cable off that Lenght will cost the same as that USB1.1 - CAt5 converter.

Also,  cabling cat5 (AKA standard network cable) is way more easy since the plugs are very small.
20  Forum 2005-2010 (read only) / Interfacing / What USB does Arduino Use?? (USB1.1 or USB2.0) on: October 20, 2006, 08:43:52 am
I wanne use my Arduino as a home made interface to Controll a computer, the only problem is that the interface and the computer are like 50 metres appart. I can buy an USB -> CAT5 -> USB extender to solve this.
The thing is, an USB1.1 one costs arround 100 euro, while a device for USB 2.0 is arround 800 euro.

So my question, what USB does the Arduinol needs, since the data transfer is based on RS232, I assume it can run on the old USB1.1.

Hope some one can tell me this.

21  Forum 2005-2010 (read only) / Interfacing / Re: How do I know what resistor to use?? on: September 07, 2006, 06:22:36 am
 smiley thanks, so, because the LED has almost no resistance, and the voltage stays the same, the amperage gets very high, but our microcontroller can not provide more than ~20mA (without overheating it) so we us a resitor. I understand that, thank you!! smiley

My calculations make it a 250 Ohm resistor, but a 220 Ohm should work as well??

(Now, we want to keep it below 20mA (=0.02A) at 5 volts, so we use Ohms law: R = V / I = 5 / 0.02 = 250)
22  Forum 2005-2010 (read only) / Interfacing / How do I know what resistor to use?? on: September 06, 2006, 07:14:02 am
Okay, NoObisch Q,

I wonder how I would know how many Ohm a resistor should be, when I am designing a circuit on my own.

Like the KnightRider example, they use 220 Ohm, why (and why use a resistor here anyway??)

I am also using Google offcours, but here I have a feeling I can ask stuff I don't get.
(I have a medical background, doing electronics as a hobby).

Thnx for the time and Greetz from the Netherlands!!
23  Forum 2005-2010 (read only) / Interfacing / Re: pressure sensor on: August 30, 2006, 05:22:21 am
 smiley-wink I am new to this, but I read that a thermistor is a resistor that changes when the temperature changes.
Running and waving people do not change temperature, only blowing people do.
So just read the restance change and you would know if some one is blowing (or not).
24  Forum 2005-2010 (read only) / Interfacing / Re: pressure sensor on: August 29, 2006, 08:53:03 am
I am not an expert, but I think it would be better to use a THERMISTOR, calibrated at the room temperature, assuming the room temperature is stabel. This way, running or waving people (who move air, but aren't blowing) doesn't get meseared.

Hmzz thinking about it, Just place it in the end off a hollow tube or something, so it will  only detect straight blows.. than you can use apreasure sensor as well.
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