Community Question

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
robot56
Commented March 2015
Thank you for your input guys.. Im glad i am not the only one facing this dilema! :D
Jeremie
Commented March 2015
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.
robot56
Commented March 2015
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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Jeremie
Commented March 2015
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 :)

Here's a sample diagram:
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Jeremie
Commented March 2015
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.
Question
Avatarrobot56
Asked on Monday, March 23, 2015