Arduino and Transistors Question - RE: School Musical Production

If you want to drive the strips easily then using a logic level FET will work the easiest for you

something like this, a few K gate resistor would be all thats needed between the Arduino and the FET

http://canada.newark.com/fairchild-semiconductor/fdp7030bl/n-channel-mosfet-30v-60a-to-220/dp/38C7149

and with your loads they will not require heat sinks as the on resistance is only 0.009ohms so even at 60Amps thats only 0.6W so at 2 Amps its only 0.02W.

now you mention running and other patterns, if your using all one color strips running on 12 V then the whole strip will be on or off, or using PWM any brightness in between

if you use strips that have LEDs like WS2812B then you dont need drivers, they will work on 5V and you can make any LED be any color and intensity you like (Yes, every individual LED)

AdaFruit sell them under the brand of NEOPixel https://learn.adafruit.com/adafruit-neopixel-uberguide

you can also get LED strips that are RGB so you can change the strip color but all the strip will be the same

either way, with the exception of the strips with the WS2811/12 LEDs, the FET I linked in will work easily for you

You can avoid using resistors if you use a logic level FET instead of bipolar transistors.

The NTD4906N-35G is a low cost power FET that will not get hot at this current.

This transistor will generate less than .025 watts of heat when driving 2 Amps:

If you want to limit the transient current to the transistor gate you could insert a resistor between the arduino and the transistor - anywhere from 1K to 10K ohms should be fine.

A really quick reply....apologies.

Your transistor solution doesn't have enough gain to drive them properly.

I posted somewhere else here ... can't find it immediately

Fets are a good idea. so follow Doug  and John

Rather than pay an exorbitant price for leds, send an email to Doug

http://www.dougswordclocks.com/

He has them for his clocks at a much better price ... tell him I sent you (Mark Beckett from NZ)

Cheers

Mark

I have tubes of logic level FETs they are so useful to increase the operating range of your microcontroller's switching function. Simple plug and go as per Doug's circuit and often good for 10A depending on the model for a few cents!

I would imaging if you are driving a Metre or two of lights you will probably need a bit of Aluminum strip as a heatsink or if you are doing a PB some copper fill for the same purpose.

I think for simplicity the stick on strips are a good idea, although I think they may be very bright in this application.

Thank you everyone for your feedback.

It seems that the best option for this project is FETs (from the above feedback).  Douglas' schematic seems like the way to go except with only one LED strip in the circuit.

1.  Can anyone suggest a suitable FET from Jaycar as this is where I will be sourcing all my materials?

Just to clarify:

i.  The circuit will power only ONE LED strip.  I will be having 7 of the same circuit on a PCB to accommodate 7 LED strips.

ii.  Logic voltage will be 5 volts (from arduino)

iii. Circuit voltage will be 12 volts from an external power source.

Thanks again guys for all the help!

Looks like the  choice isnt that great at least at the UK Jaycar you may consider going for the low power 2n7000 FET on the output of the Logic then have it switch the Gate of the bigger FETS they have using the available 12V supply.

The few IRF transistors are more suited to 5V minimum........

Doh .....Saw Arduino...

IRF540 should be OK in that case

I'd try and get the part specified by Douglas if you could BTW as this looks like an Excellent part.

Otherwise the '540 again if you are stuck with Jaycar only

I think the 2N7000 is ruled out.  --> maximum current of 2 Amps drain.

The IRF540N (which Jaycar AU supply) seems like a contender with maximum drain current of 33 Amps.

All I really want to know is:

1. Will I be able to use  xxxxxx part without damaging the lights or Controller (Arduino) and with low heat?

2. How to use the FET in a circuit correctly --> which has partly been answered by Douglas.  From my own research I think I might need a resistor from the Arduino to the Gate of the FET.

3.  How much current will come out of the Arduino due to the FET controlling the 2 Amp load ?

Sorry the one I suggested wont work, but this one should http://www.jaycar.com.au/productView.asp?ID=ZK8821 10+ current rating and at 0.016ohms it should be good for your needs

pdf here http://www.vishay.com/docs/72512/72512.pdf

oh and you get 2 in one package

The 2n7000 was merely a throw away to drive the gate of a bigger FET not for driving the LOAD directly

1) Most probably use a bit of aluminum strip as a heat sink  for each of the FETs if you want to be safe

2) Yep, Douglas is right ...this stuff is that easy!! The Gate of the FET is high impedance any way no real need for a resistor

3)Bugger all !! The FET is doing all the heavy lifting and all you need to do is keep the Gate On

4) Consider the 2n7000 to drive the IRF540 then you can operate the gateof the '540 from say 12V and really turn the gate hard on, lowering the Rds(on) as much as possible decreasing the dissipation.