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Topic: Help with LED Cluster needed (Urgent) (Read 2 times) previous topic - next topic

Grumpy_Mike

Why search for op amps?
You want a logic level FET and a 12 V supply, a 9V battery pack is not sufficient.

Runaway Pancake

#6
Apr 22, 2012, 01:27 am Last Edit: Apr 22, 2012, 04:36 am by Runaway Pancake Reason: 1
Maplin doesn't have a lot in the way of MOSFETS, two actually.
They have an IRF540, but it will require an NPN in front of it, to switch the gate voltage (5V not enough.)

http://arduino.cc/forum/index.php?action=dlattach;topic=101169.0;attach=16753;image

In that schematic, the LED cluster and those 33? resistors is/are the block labelled "Load".
It's "On" when the Arduino output is LOW and it's "Off" when the Arduino output is HIGH.

* * * I know that there are NPNs good with getting > 200mA and more stuffed down them, but I was thinking how 1 cluster turns into 2, turns into 4...  
Anyway, I don't know what's "ideal", but this'll get the job done.  It's not beta-dependent and V_ce isn't an issue either. * * *
"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

cschmeer

I only need that one cluster and I want to use the simplest way possible. Would that be by using the Logic Level Mosfet you described in the first post?
I have ordered one off eBay, hope it arrives soon...

Grumpy_Mike

Well you could get the NPN transistor and the FET from Maplins today, it will do the same job as the logic level FET.

cschmeer

#9
Apr 22, 2012, 10:26 am Last Edit: Apr 22, 2012, 10:36 am by cschmeer Reason: 1
Thanks for helping everyone. Just to make sure are these all the things I need?

http://www.maplin.co.uk/480-piece-e3-resistor-starter-pack-42453
for one 4K7ohm resistor.

http://www.maplin.co.uk/mos-fet-transistors-33843
one IRF540A MOS-FET transistor.

http://www.maplin.co.uk/33andohm-to-91andohmmetal-film-0.6w-resistors-341561
three 33ohm resistors

As I said, I am a total newbie in electronics, still kind of clueless (see illustration of my cluelessness below) :smiley-zipper:  :smiley-red:

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