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# PSoC 4 MCU

New Contributor

## RGB LED RESISTORS?

Hello,

I have just received the CY8CKIT-042 PSoC 4 Pioneer kit and I just completed my first video... Blinking an output led!

I got the the actual example from the video to compile and work!

So since the blinking led is an RGB led connected to outputs P0[2], P0{3] and P1[6]  of the PSoC4, I couldn't help noticing that the P0[2] and P0[3] pins of the RGB are connected to 1.5K resistor, but P1[6] pin is connected to a 2.2K resistor? If the 3 leds in the RGB led have the same power consumption, why is P1[6] pin connected to a higher value resistor?

Also, in the kit I just recieved what PSoC MCU is it exactly....

Is it the PSoC 4200, PSoC 4200M, 4200-L or the 4200 DS???

Thank you for all help and support!

r

1 Solution
Honored Contributor II

## Re: RGB LED RESISTORS?

RoRo,

As /odissey1 indicated the resistors are to trim the current into each of the LED.

LED intensity is dependent on current.

Here is a part of the datasheet for the LED part.  Notice that the RED LED has an average 2.0V forward drop (Vf) but the GREEN and BLUE LEDs have a average forward drop of 3.2V.

Using the Vf(avg) value for each R (P1.6) G (P0.2) and B (P0.3) LEDs:

Assumptions

P4_VDD = 4.8V

LEDs are GND'd through the port pins for illumination.

I (of LED) = (P4_VDD - Vf (of LED))/ R (of LED)

I (of R LED) = (4.8V - 2.0V) / 2.2K = 1.27mA

I (of G LED) = (4.8V - 3.2V) / 1.5K = 1.07mA

I (of B LED) = (4.8V - 3.2V) / 1.5K = 1.07mA

The IC is a 4200.  No M, L or DS part.

Len
"Engineering is an Art. The Art of Compromise."
3 Replies
Honored Contributor II

## Re: RGB LED RESISTORS?

RoRo,

The CY8CKIT-042 comes with P4200. Resistors are different to match the brightness of LEDs.

You may find an annotation component useful for identifying pins on the kit

Honored Contributor II

## Re: RGB LED RESISTORS?

RoRo,

As /odissey1 indicated the resistors are to trim the current into each of the LED.

LED intensity is dependent on current.

Here is a part of the datasheet for the LED part.  Notice that the RED LED has an average 2.0V forward drop (Vf) but the GREEN and BLUE LEDs have a average forward drop of 3.2V.

Using the Vf(avg) value for each R (P1.6) G (P0.2) and B (P0.3) LEDs:

Assumptions

P4_VDD = 4.8V

LEDs are GND'd through the port pins for illumination.

I (of LED) = (P4_VDD - Vf (of LED))/ R (of LED)

I (of R LED) = (4.8V - 2.0V) / 2.2K = 1.27mA

I (of G LED) = (4.8V - 3.2V) / 1.5K = 1.07mA

I (of B LED) = (4.8V - 3.2V) / 1.5K = 1.07mA

The IC is a 4200.  No M, L or DS part.

Len
"Engineering is an Art. The Art of Compromise."
New Contributor