Commit 10abc7de by Michael Oduor

Week 12 and 14 updates

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......@@ -10,6 +10,18 @@ Add an output device to a microcontroller board you've designed, and program it
**Group assignment**
Measure the power consumption of an output device.
## Group Assignment
For this task, we ([Alok](http://fabacademy.org/2019/labs/oulu/students/alok-sethi/assignments/week11/), [Jobin](http://fabacademy.org/2019/labs/oulu/students/jobin-varghese/assignments/week11/), [Sahan](http://fabacademy.org/2019/labs/oulu/students/sahan-wickramaarachchi/week11.html), and [Yasir](http://fabacademy.org/2019/labs/oulu/students/yasir-shafiullah/week%2011.html)) measured the power consumption of a 5 mm LED and an RGB LED (the one used in the individual assignment above). The consumption of the LEDs was measured by directly powering them with a variable power supply and varying the voltage and current in order to measure the resulting effect on the brightness of the LEDs.
![](../images/week12/led.jpg)
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 very short time without being damaged [^2]. The peak forward current is the absolute maximum current that an LED can handle and this is only for a short period of time. The peak forward current, specified on a datasheet, can only be applied to an LED for the time period specified. This time period is either specified as a fraction of a duty cycle or as a time in milliseconds [^3].
![](../images/week12/measure.png)
<sup>Measurement values for 5 mm Green LED</sup>
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 current is increased the LEDs brighten and if decreased, the LEDs become dimmer. According to the [data sheet](https://media.digikey.com/pdf/Data%20Sheets/CREE%20Power/CLV1A-FKB_Rev5.pdf), 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 in order 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.
## Individual assignment
For this assignment, I used the board from the [previous week](http://fabacademy.org/2019/labs/oulu/students/michael-oduor/assignments/week11/) to test the [FS90R continuous servo](https://www.pololu.com/product/2820).
......@@ -46,20 +58,7 @@ The board design is another matter completely! After multiple tries, I still can
![](../images/week12/routing.png)
Now I am thinking of splitting the overall design and having at least the IR proximity sensors on a separate board and use headers to connect the IR sensor board to the main board. With this component removed, maybe it will be easier to route the main board. Although, [Antti](http://archive.fabacademy.org/fabacademy2016/fablaboulu/students/161/) suggested to try to get everything working on the main board, but this has already taken longer than I would have liked it to. As there are more demanding assignments coming up, if separating the components in different boards works even though it might lead to a bit extra work, then that is the option I will go for if fastens the process of creating the design files.
## Group Assignment
For this task, we ([Alok](http://fabacademy.org/2019/labs/oulu/students/alok-sethi/assignments/week11/), [Jobin](http://fabacademy.org/2019/labs/oulu/students/jobin-varghese/assignments/week11/), [Sahan](http://fabacademy.org/2019/labs/oulu/students/sahan-wickramaarachchi/week11.html), and [Yasir](http://fabacademy.org/2019/labs/oulu/students/yasir-shafiullah/week%2011.html)) measured the power consumption of a 5 mm LED and an RGB LED (the one used in the individual assignment above). The consumption of the LEDs was measured by directly powering them with a variable power supply and varying the voltage and current in order to measure the resulting effect on the brightness of the LEDs.
![](../images/week12/led.jpg)
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 very short time without being damaged [^2]. The peak forward current is the absolute maximum current that an LED can handle and this is only for a short period of time. The peak forward current, specified on a datasheet, can only be applied to an LED for the time period specified. This time period is either specified as a fraction of a duty cycle or as a time in milliseconds [^3].
![](../images/week12/measure.png)
<sup>Measurement values for 5 mm Green LED</sup>
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 current is increased the LEDs brighten and if decreased, the LEDs become dimmer. According to the [data sheet](https://media.digikey.com/pdf/Data%20Sheets/CREE%20Power/CLV1A-FKB_Rev5.pdf), 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 in order 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.
Now I am thinking of splitting the overall design and having at least the IR proximity sensors on a separate board and use headers to connect the IR sensor board to the main board. With this component removed, maybe it will be easier to route the main board. Although, [Antti](http://archive.fabacademy.org/fabacademy2016/fablaboulu/students/161/) suggested to try to get everything working on the main board, but this has already taken longer than I would have liked it to. As there are more demanding assignments coming up, if separating the components in different boards works even though it might lead to a bit extra work , then that is the option I will go for if it fastens the process of creating the design files. Or, I will just use fewer components and build on the project later.
## Files
......
......@@ -77,7 +77,7 @@ Using this connector, I built a network consisting of the boards from [Electroni
![](../images/week14/nodes.png)
<sup>Wired node</sup>
When I type a node number (either 1, 2 or 3), in Arduino IDE's serial monitor, the LED on the board blinks and the node number is printed. Nodes 1 and 2 work as expected but there is no response or any output given from the third node. I will revisit this when I have time as there was no problem with the board.
When I type a node number (either 1, 2 or 3), in Arduino IDE's serial monitor, the LED on the board blinks and the node number is printed. Nodes 1 and 2 work as expected but there is no response or any output given from the third node. I will revisit this later when I have time.
![](../images/week14/serial-m.png)
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