WhiteBr0wnie_24
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Ultra Bright LEDs

Sun Aug 17, 2014 8:02 pm

Hey there!
I need help in one of my projects. I have the raspberry pi camera module and i want to add a high performance LED to my setup. I would like to turn the LED on and off with the GPIO, but it is not possible to power it with the raspberry pi. I dont want to use a transistor, so I want to ask you guys, if you know some sort of switch or something, that would fit my needs.

Tanks,
WhiteBr0wnie_24

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joan
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Re: Ultra Bright LEDs

Sun Aug 17, 2014 8:28 pm

I'd use a ULN2003A or similar. Mind you that's lots of transistors packaged up in a chip.

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Richard-TX
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Re: Ultra Bright LEDs

Sun Aug 17, 2014 8:57 pm

I think you are stuck if you exclude transistors.
Richard
Doing Unix since 1985.
The 9-25-2013 image of Wheezy can be found at:
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Gert van Loo
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Re: Ultra Bright LEDs

Sun Aug 17, 2014 9:00 pm

I dont want to use a transistor, so I want to ask you guys, if you know some sort of switch or something, that would fit my needs.
There is a bit of contradiction in the post.
A switch is normally a mechanical thing which you can not control from a GPIO.

You do not want to use a transistor but that IS the simplest solution.
A single NFET can easily drive a few hundred LEDs and requires only three wires to be connected.

gordon77
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Re: Ultra Bright LEDs

Sun Aug 17, 2014 9:05 pm

WhiteBr0wnie_24 wrote:Hey there!
I need help in one of my projects. I have the raspberry pi camera module and i want to add a high performance LED to my setup. I would like to turn the LED on and off with the GPIO, but it is not possible to power it with the raspberry pi. I dont want to use a transistor, so I want to ask you guys, if you know some sort of switch or something, that would fit my needs.

Tanks,
WhiteBr0wnie_24
What voltage and current are you switching? Are you looking for pwm?

WhiteBr0wnie_24
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Re: Ultra Bright LEDs

Sun Aug 17, 2014 10:03 pm

Thank you all, for you answers!

I could use transistors, but i would prefer an "out-of-the-box" solution.
@gordon77 No, I dont want to use pwm and the LEDs need 6V.

klricks
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 2:41 am

WhiteBr0wnie_24 wrote:Thank you all, for you answers!

I could use transistors, but i would prefer an "out-of-the-box" solution.
@gordon77 No, I dont want to use pwm and the LEDs need 6V.
A solid state relay may work if you don't care about cost.
These have opto isolation built in and can be triggered with a 3V 2mA control signal.
http://www.opto22.com/lp/ssr.aspx?cd=So ... MgodxV8AFg
Unless specified otherwise my response is based on the latest and fully updated RPiOS Buster w/ Desktop OS.

Duane Degn
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 4:16 am

You answered a couple of Grodon77's questions but you have not said anything about how much current the LED needs. This is important information when considering what sort of device to suggest.

WhiteBr0wnie_24
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 6:46 am

Duane Degn wrote:You answered a couple of Grodon77's questions but you have not said anything about how much current the LED needs. This is important information when considering what sort of device to suggest.
You are right, I haven't provided enough information for you guys, so let me do this now. I have a datasheet for the LED:

http://www.produktinfo.conrad.com/daten ... _NMN00.pdf

But to sum up, what it says:
U = 3.2V
I = 350mA

(I know, I said 6V, but these are cheaper, so I decided to switch to them ;) )
The RaspberryPi's GPIO have a 3V Pin, but can they handle that much current?

@klricks
I thought about using relays, but I'd like to see some alternatives too, before going on with my design.

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joan
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 7:04 am

I can't see much of a difference between a solid state relay and any other switch. If you can mount a relay you can mount a ULN2003A or similar.

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rpdom
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 7:40 am

WhiteBr0wnie_24 wrote:The RaspberryPi's GPIO have a 3V Pin, but can they handle that much current?
No. You can't take more than about 50mA total from the 3.3V pins. You'll need an external supply.

gordon77
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 7:57 am

WhiteBr0wnie_24 wrote:
Duane Degn wrote:You answered a couple of Grodon77's questions but you have not said anything about how much current the LED needs. This is important information when considering what sort of device to suggest.
You are right, I haven't provided enough information for you guys, so let me do this now. I have a datasheet for the LED:

http://www.produktinfo.conrad.com/daten ... _NMN00.pdf

But to sum up, what it says:
U = 3.2V
I = 350mA

(I know, I said 6V, but these are cheaper, so I decided to switch to them ;) )
The RaspberryPi's GPIO have a 3V Pin, but can they handle that much current?

@klricks
I thought about using relays, but I'd like to see some alternatives too, before going on with my design.
Take a look at a LCA710 soild state relay, upto 60V at 1.8A (in DC config), about £3 to £4. Just needs 1 resistor to interface.

johndough
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Re: Ultra Bright LEDs

Mon Aug 18, 2014 10:16 am

Hi

Looking from the other end and finding low current white LED's that could possibly be controlled by the GPIO

Bulb Size: 0.8mm x 1.1mm
Forward Current If: 5mA
Forward Voltage: 2.85V
LED Colour: White

and seeing if they could be cobbled into a cluster.

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Gert van Loo
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Re: Ultra Bright LEDs

Tue Aug 19, 2014 9:13 am

I could use transistors, but i would prefer an "out-of-the-box" solution.
@gordon77 No, I dont want to use pwm and the LEDs need 6V.
There is no out of the box solution. That would be a PCB you plug on the PI.
So you always have to connect at least three wires: Power, Ground, Enable.
The connections for those are different on every 'ready made' product.

I think your 'fear' of transistor is misplaced.
With a transistor/fet you will know how to connect the three wires.
My guess is that there are about a hundred different posts on this website all dealing
with 'how do I connect a transistor to the Pi'.
(I, as moderator, come across such a post once a week.)

As posted below: there are white LEDs which use a lot less power (voltage/current)
Don't forget that you will always need a resistor in series with your LED
(Or some other circuit like a special LED driver)
That is also valid if you switch the LED using a solid state relay any other means,
the exception is if you can find a special LED load balance circuit.
But those are a hundred times more complex then a transistor.

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