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1  Using Arduino / LEDs and Multiplexing / RGB Led strip. Color differences after use. on: April 16, 2011, 12:47:02 pm
Hello

I've been powering my 5050 SMD 300 LED 5 meter strip from dealextreme.com with my home made arduino powered device.

I just noticed there are a bit of color differences with the red lights. First I thought it was the LEDs, but after having a closer look it looks like its groups of 3 and 3 LEDs are different. Could that mean that the resistors are of poor quality?

The LED strip is rated for 12v, but after measuring it looks like my linear wallwart is supplying 12.4v in this configuration. Could the additional 0.4v wear the resistors or the LEDs. Bear in mind these are cheap chinese LED strips, which means the parts are most likely not overrated for durability.

Thanks

2  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: April 02, 2011, 03:17:51 pm
Thanks for your help guys. I hooked this up today and it works perfectly! The MOSFETs dont even go lukewarm, as opposed to the ones in my chinese controller which fried itself.

It's driving a 5 meter "300led 5050" LED strip from dealextreme.com

Now I need ideas on how to control it. I'm thinking slowly rotating colors - controllable from my PC smiley
3  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 28, 2011, 01:00:00 am
It's a good idea to add decoupling on the Vin - voltage regulator specs usually specify an input-side decoupling capacitor as well as output side.

What current will the MOSFETs have to carry? - those MOSFETs will need heatsinking above 2 or 3 amps.

Decoupling capacitors are those two that sit between Vin and GND, and Vout and GND in my drawing right?

I believe the MOSGET are going to carry just under 1 amp each, but I already bought heatsinks just in case smiley Just need to find some way of screwing them on since I dont have thermal adhesive.

4  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 28, 2011, 12:57:50 am
Resistors can be any power rating from 1/10 watt up...

I'll stick to my cheap 1/4 watt ones then smiley
5  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 27, 2011, 04:51:13 am
Quote
Is 10k and 220 just random numbers, or are they something I need to calculate to fit my circuit?

Neither random nor calculated. Just good nominal values to use. In truth the transistor will work without either resistor, it's just for protection and circuit safety.

Lefty


I see... Do these resistors have to be sized accordingly, or can I just use cheap ones I already have since they are on 5v not on the 12v pwm?

Also if someone could have a quick look on the left part of my drawing, with the MOSFETs. The right breadboard is almost copied off a guide here, so I believe it should be right.

My end goal is to pack all this into a package which is as small as possible. Maybe I should think of adding some kind of short-circuit and overheating protection?

6  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 26, 2011, 10:51:55 am
One of the reasons I was concerned, I saw some guy had a problem where the MOSFET never would turn fully off.

By "10k input gate-to-sorce pulldown" do you mean a 10k resistor from the MOSFET gate pin to MOSFET source pin? I think I saw a drawing where there was a 10k resistor from get to ground, is that wrong?

Why would 220 ohm resistor protect the mosfet? From voltage spikes? Will the MOSFET fully saturate/turn on if I use this resistor?

Thanks for the replies smiley

The 10K should be from Gate to Source. But usually the source (of an N-FET) is grounded, so "same thing"...  So gate can't float around or pick up noise easily..

The 220 Ohm series resistor protects the Arduino output.  Just at the moment the Arduino output goes from about Gnd to about +5V it has to charge up the small capacitance inside the FET.  This might momentarily draw a "spike" of current from the Arduino.. Probably not damaging it but possibly disrupting it's operation.  This happens so fast that the FET still turns fully on "fast"..    (This is not like a bipolar transistor where you have to keep supplying Base current. But even in that case , 220 ohms will work.)

Keep on asking these kinds of questions!  The WHY will apply to new situations you find, and it will all make more sense over time. 


Aaaah of course. I think I'm beginning to understand now. Is 10k and 220 just random numbers, or are they something I need to calculate to fit my circuit?

I have attached the fritzing diagram I have made so far. The big RGB LED in the diagram is meant to be LED strip with integrated resistors etc.
7  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 26, 2011, 06:06:12 am
This is a "logic gate level" device.. I think you'd have no problem just driving it like the Darlington you had, up to 5 Amps output or so.

A 10K input Gate-to-Source pulldown and a 220 ohm series resistor from Arduino pins would be nice conservative design..

Modern Power FETs are So nice!

One of the reasons I was concerned, I saw some guy had a problem where the MOSFET never would turn fully off.

By "10k input gate-to-sorce pulldown" do you mean a 10k resistor from the MOSFET gate pin to MOSFET source pin? I think I saw a drawing where there was a 10k resistor from get to ground, is that wrong?

Why would 220 ohm resistor protect the mosfet? From voltage spikes? Will the MOSFET fully saturate/turn on if I use this resistor?

Thanks for the replies smiley
8  Using Arduino / General Electronics / Re: Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 26, 2011, 05:43:36 am
Thanks for the quick response. I have a drawing, just need to update it a bit, I'll post it later smiley

The MOSFET I'm going to use is: http://www.sparkfun.com/products/10213
9  Using Arduino / General Electronics / Darlington array (ULN2003) to N-Channel MOSFET (RFP30N06LE) on: March 26, 2011, 05:20:17 am
I have a working project where I am using an ULN2003 darlington array to power an RGB LED strip.

I want to expand to a bigger strip and have therefore bought some MOSFETs from sparkfun as these could be controlled directly from a microcontroller...

I have seen a few projects with MOSFETs, and some use transistors to drive the gate. Some use pull-up resistors and some use resistors to protect the mosfet. Now I'm not sure what I need. I thought this was just replace the darlington with the MOSFET smiley-sad

Looking for some advice smiley How to wire it all up. I have 12v supply voltage and 5v from the arduino board, also using the PWM outputs on arduino.
10  Using Arduino / Project Guidance / Re: Barebones arduino on: March 25, 2011, 06:52:47 pm

Looks interesting, but a bit too advanced for me I think :O
11  Using Arduino / Project Guidance / Re: Barebones arduino on: March 25, 2011, 06:52:12 pm

That is exactly what I'm looking for, thanks!
12  Using Arduino / Project Guidance / Barebones arduino on: March 25, 2011, 06:24:58 pm
Hi

I'm looking for some help in creating a stripped down version of arduino.

I will program the chip on the duemilanove board I have purchased, and move the chip over to a breadboard.

So basically I need to know which pins to use. I guess I need to feed it with 5 volts and hook it up to ground, also somehow hook a crystal up for accurate timing for PWM.

Any clues?
13  Forum 2005-2010 (read only) / Syntax & Programs / Re: using the ps2 device library on: November 24, 2009, 08:31:30 pm
Thanks for the reply.

Actually i tried this earlier kindof. I commented out #include "WConstants.h" and it compiled without errors, i didnt add the other include file though, will try that. I didn't get the library to work but I'll continue to try tomorrow.

I assume clock and data goes to digital pings, ground to ground, and 5 volt should be unconnected since arduino gets its own poweR?
14  Forum 2005-2010 (read only) / Syntax & Programs / Re: using the ps2 device library on: November 24, 2009, 09:22:56 am
Getting the same error smiley-sad

I'm clueless.
15  Forum 2005-2010 (read only) / Interfacing / Re: Arduino acting as keyboard on: November 13, 2009, 02:21:12 am
Thanks for the replies guys smiley

The ps2 library captainobvious linked was exactly what i needed smiley-kitty
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