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|  ___|  | |    / _ \              | |                           / __  \|  _  |/  | |___  /
| |_ __ _| |__ / /_\ \ ___ __ _  __| | ___ _ __ ___  _   _       `' / /'| |/' |`| |    / / 
|  _/ _` | '_ \|  _  |/ __/ _` |/ _` |/ _ \ '_ ` _ \| | | |        / /  |  /| | | |   / /  
| || (_| | |_) | | | | (_| (_| | (_| |  __/ | | | | | |_| |      ./ /___\ |_/ /_| |_./ /   
\_| \__,_|_.__/\_| |_/\___\__,_|\__,_|\___|_| |_| |_|\__, |      \_____/ \___/ \___/\_/    
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Student Archive || Student no - 183 || FabLab CEPT, Ahmedabad |

output devices

index

• ../ back to homepage
• Intro
• learning from the datasheet
• Designing the circuit
• Learning about n-mosfets

/Assignment goals

• Described your design and fabrication process using words/images/screenshots
• Explained the programming process/es you used and how the microcontroller datasheet helped you
• Explained problems and how you fixed them
• Included original design files and code

Intro - Choosing the output device

My final project consists of a spherical bin that has to be rotated 2-3 rotations at a leisurely pace at periodic intervals, I've acquired a 12v 10 rpm - geared DC motor for the above mentioned purpose.

• I don't need precision in terms of rotational degrees; so that rules out the need for stepper motors or encoders
• I need slow gradual movements, hence the geared low rpm motors, I wonder if it is preferred that I fabricate the gears for a vanilla DC motor instead of buying a geared motor.Learning about gear ratios and gear profiles does seem intriguing; I'll make this a part of the next spiral for the project.

the chosen Motor

• 10 RPM geared motor
• Rated at 12Volts
• Manufacturer - Maruschi
• Retail Cost ~10$

Learning about MOSFETs and H-bridges

• MOSFETs and H-Bridges are some fascinating components, (like every other component to a fresher like me)
• Summarising on a MOSFET, when a voltage is apllied across one of it's three pins (the gate pin in particular) it allows current to flow across the other two pins which are labelled appropriately 'Gate' and 'Source'
• So, the idea is to use a digital pin output from an attiny to drive the gate whenever I need to run the motor

Learning's from Datasheet

The pinout diagram from the datasheet is what I used to pick the digital pin I needed to drive the gate of the n-mosfet

I selected PA1 - it is a general I/O port and the description is as follows

The block diagram for a I/O pin

I used arduino libraries to toggle the pins on/off as seen in the part-code below

void loop() {
  digitalWrite(8, HIGH);   // turn the MOSFET-GATE on (HIGH is the voltage level)

the command digitalWrite is doing the following

invoking the compiled version of FabModules

Selecting the 1/64 profile to mill traces

Selecting the 1/32 profile to cut edges

Milled boards :)

Designing the circuit

Adding components in the schematic is done through this dialog, 'a' is the keyboard shortcut to add components.

This is the CvPCB window where all the components you have added to your schematic will need to be assigned footprints here

After assigning footprints, one has to generate the netlist and then read that netlist in PCBnew - which is the PCB layout software

Milling and Stuffing

View post on imgur.com

Programming

Used Arduino UNo as the programmer, reluctantly as my FabISP's micro-usb port is very finnicky and the lab's avrmsk2 wasn't responding

 
              void setup() {
  // initialize digital pin 13 as an output.
  pinMode(8, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(8, HIGH);   // turn the MOSFET-GATE on (HIGH is the voltage level)
  delay(10000);              // wait for 10 secondS
  digitalWrite(8, LOW);    // turn the MOSFET-GATE off by making the voltage LOW
  delay(300000);              // wait for 5 MINUTES
          

Demo video

In the final project

File Downloads

• KiCAD design files - older-versions Download KiCAD ver1 Download KiCAD ver2
• KiCAD design files - final version PCB Design file Schematic Footprint libraryNetlist
• Fritzing sketch / simulation Download Fritzing sketch
• Code in .txt Download Code