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Powering The Signal Pin With More Than 3.3 Volts?

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Help robot56 with their question and receive $10 of EZ-Credit to get more robots and parts from our store. The following information was provided about their previous efforts searching tutorials for a resolution.

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#1

I know that the signal pin is regulated at 3.3 volts on the V4. I have a led array that I am powering from the signal and ground pin but 3.3 volts doesn't seem to be enough voltage.

Is there a way that I can power the LED's with more voltage and still be able to script light sequences?

I was looking at electronic PWM switches from servocity.com but they are ridiculously expensive in my opinion and figured there would have to be an easier way than to spend $30 for each port.

Thank you for your time
Aaron

I have found a few conversations, tutorials and activities that may help with your question. Take a look at these links. I've sorted them by what I believe to be most relevant but that is not always the case as I'm still learning.


Also, consider reviewing the Learn section for informative lessons and activities. Check it out!


#2

Take a look at this older thread, in post #14:
http://www.ez-robot.com/Community/Forum/Thread?threadId=7305&page=2

This topic comes up often and the transistor switch is about the easiest and most well known solution. The example pictures shows a common usages with a common micro controller like an Arduino, but the usages is the same with an EZb.

Take a look at that link and if you have follow up questions be sure to ask! Many of use have build similar circuits so if you get try it and have issues or questions don't be afraid to ask.
Smile

#3

You can use a level shifter as well if you just want to jump the signal from 3.4 to 5v. (post #30 of the same thread Justin listed). Draws a little more amps to bump the voltage up.

Direct link to product: http://www.ezsbc.com/index.php/catalogsearch/result/?q=LS1#.VRBnl47F_e4

Alan

#4

Umm, has anyone had success with that shift level register? Shift level registers make me frown. Frown

I mean, there are step up converters too...but, ehh. Tongue

#5

Thank you for your input guys.. Im glad i am not the only one facing this dilema! Grin

#6

It seems like a current issue, rather than voltage. Almost all LEDs can achieve full brightness with a forward voltage of 3.2V or less. The ez-bv4 I/O only have driving current up to 10mA so that may be where your current limitation lies. Is your LED matrix common cathode or common anode? Maybe you can post a diagram of what you are trying to achieve.

#7

hi @Jeremie. It is just a simple parallel circuit powering 4-5 LED's on each port. I a set of red and blue led's on each digital port (total 2 ports).

I have another led array that doesn't need to be controlled on or off so i was able to turn up the voltage making the lights brighter.. However with the 3.3v regulator it is hard to achieve the same level of light.

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#8

If I'm not mistaken it looks like you are not using any resistors for current limiting. You may be over-driving the LEDs, while they will work and be very bright my personal experience in the past is that they will burn out over a period of time.

LEDs usually have a high voltage maximum (~30V) and they are current driven (~20mA) so voltage doesn't matter too much as long as it's above the forward voltage (Vf) of the LED. I would probably suggest the same as the other forum members, use your input voltage controlled by a simple transistor like a 2N2222 (switching the ground connection to the LEDs ON and OFF) but make sure you use a high wattage resistor if you use a single resistor for current limiting. You can get away with lower wattage resistors if you use a resistor per LED.

You can then control the transistor with an ez-b digital pin and do PWM dimming to your heart's content Smile

Here's a sample diagram:
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#9

I forgot to add that I have used level shifters in the past and almost 100% of the time found that they do not drive current...at all.....so trying to drive LEDs from a level shifter wouldn't help. There are LED driving chips out there that can do this sort of thing but a simple transistor circuit would likely suffice for this application, it's probably much cheaper as well.