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12. Output devices

Assignment topic

Individual assignment: add an output device to a microcontroller board you’ve designed, and program it to do something.

Group assignment: Measure the power consumption of an output device


This week, I am planning to make my output device LCD for my final project. I design and develop an Attiny 44A microcontroller based LCD module and program for display my name in the first raw and second raw is set as a simple counter. For group work, we measured the power conception of 5 mm LED and RGB LED.

Individual Assignment

First, I started to learn about the LCD pinout. We have here LCD module for 16x2 characters from Lumex Optocomponent. I go through the datasheet of LCD. Its pins are not sequential, the Supply voltage is 5V, and the supply current is 2-3 mA. I first learn LCD pin order, Pin configuration and electrical characteristics before starting the schematic and board design in Eagle. See the below figure which describes the important features LCD to be known before starting the design.

PCB design

I have used Neil’s board design first. I used Attiny 44A as the microcontroller. I am planned to use FTDI connector for powering the board and LCD. Also added an LED indicator for the power connections. I separate LCD 10 pins in two parts, such as 2X2 pin header and 2x3 pin header. Pin header 2x2 used for data bus (DB) that is LCD- 11, 12, 13, 14 to the microcontroller board (Pins 10, 11, 12, 13). While pin header 2x3 is connected to the power, GND, Register signal (RS), and Enable (E) pins.

See the picture of my schematic design using Eagle software,

After the schematic design, successfully generates the board and connections. See the board design in the below figure,

Then, I followed previous week documentation for trace png image for milling,

Followed by making the outline png image for milling

Then I used remote fab mod used for making rml file for trace an outline for Rolland milling machine. The result of milling shown below figure. After milling, I cleaned the PCB and started to solder the components. See the milled board before and after soldering all the component in the below figure,

I used 16 pins of FTDI connector pin for the LCD module. I carefully solder the LCD module; after that, I connected all the necessary connections by checking the design files. After all connections, I used the Arduino IDE for the program the LCD board. I edited an example code by adding my name for display and second raw display a continues to counter. I power the LCD board using my input device board. See the working of my output device in the below figure,

Group Assignment

For group work, we measured the power conception of 5 mm LED and RGB LED. The consumption of the LEDs was measured by directly powering them with a variable power supply and varying the voltage and current to measure the effect on the brightness of the LEDs. Our group includes Alok, Michael, Sahan and Yasir. See some of the measurements images below,

In both tests, we burnt out the LEDs by exceeding their voltage and current limits. For the 5 mm LED, this was 6.5 V and 188 mA (it is probably lower than these values). Blue and Green LEDs can be fed with a maximum current of 100 mA (Peak Forward Current) for a concise time without being damaged. The peak forward current is the absolute maximum current that an LED can handle, and this is only for a short period. The peak forward current, specified on a datasheet, can only be applied to an LED for the period specified. This period is either specified as a fraction of a duty cycle or as a time in milliseconds. See the detailed analysis table below,

For the RGB, we repeated the same process as with the 5 mm LED, testing the effect of varying the voltage and current on the brightness. If the current is increased, the LEDs brighten, and if deceased, the LEDs become dimmer. According to the datasheet, this LED has Forward Voltage ranging from 2 - 4 V. 2 - 2.6 V for Red, 3.2 - 4 V for Green, and 3.2 - 4 V for Blue. The absolute maximum ratings for the Forward Current (the current flowing across the LED from positive to negative for the LED to get power) for Red is 50 mA, and for Green and Blue, it is 25 mA (milliamps) when powered individually as we did. We tested the power consumption from a low of 1.60 V and 0.001 Amps, which didn’t power on the LED, to a high of 6.5 V and .200 A. Red was very dim at 1.9V, and 0.001 Amps and the optimal value was 2.3 V and 20 mA. With the recommended electrical characteristics of 20 mA, Red has an average forward voltage of 2.0 V, Green 3.2 V, and Blue 3.2 V, respectively.


This week, I made an LCD module which is needed for my final project. Also, learn LED and RGB operation, characteristics and power conception through group assignment

Design Files

Code Used