A microcontroller pin has a limited amount of current you can supply which is typically enough to light up one LED at a time. For instance the PIC32MX250F128B microcontroller the absolute maximum current drawn by any I/O pin is 15mA referencing the datasheet. By using a transistor you can increase this amount significantly, the PN2222A is capable of sinking up to 450mA and the IRLU024NPBF is capable of sinking 15A. You can even control higher voltages then your microcontroller pin could normally handle as well.

This example will demonstrate using two different transistors to switch on and off several LED's from one I/O pin. This example is sinking around 200mA of current for the eight LED's connected to each transistor. The setup used in this demo draws under 6mA of current from the microcontroller pin when using a PN2222A transistor and basically 0mA using a IRLU024NPBF. I purchased the transistors from Tayda Electronics, making the  IRLU024NPBF sixty-five cents and the PN2222A five cents each.

Items used:
1   PIC32MX250F128B microcontroller board
9   White LED's with 220ohm resistors
2   830 point Breadboards
2   470 OHM resistor (one for each transistor)
1   PN2222A transistor
1   IRLU024NPBF transistor
Some black 22AWG solid wire
Some red 22AWG solid wire
A few jumper wires

PN2222A pinout photo can be found here:
http://bit.ly/1C6FxQz

IRLU024NPBF pinout photo can be found here:
http://bit.ly/1eYSJg0

See the video below for a demo of it being controlled by a PIC32 microcontroller and a simplified version of the circuit schematic connections to each of the different transistors used.

Direct video link: https://youtu.be/6XEnEG-1PdQ

This is a simple starter tutorial to work with a Bluetooth module (HC-05 or HC-06) using the PIC32BLUE Android application (you can use PIC32BLUE+ and/or PIC32BTN apps instead too depending on which example code you are using that is attached below).

Materials used:

1) One Microcontroller (PIC32MX250F128B)

2) One Bluetooth module

3) Four jumper wires (male to female)

4) Power source (10,000 mAh power bank battery pack 5volts)

5) Android phone/tablet with PIC32BLUE installed (device must have Bluetooth capability)

 
Important note, the Bluetooth module power source and inputs should be at 3.3 volts only. VCC on the Bluetooth module should be connected to 3.3 volts and GND should be connected to ground seen in the photo.


The power bank is optional and can be switched out with power source and the jumper wire connection style may vary depending on the connectors available on your microcontroller board to make the necessary connections.

Connections between the microcontroller pins to the stepper motor PCB are as follows:

Bluetooth Module <----to----> PIC32 Microcontroller Pin

         RXD   <--------------wire------------>   TX

         TXD   <--------------wire------------>   RX

Note: RX means receive and TX means transmit, so the Bluetooth module will transmit to the microcontrollers receive pin and vice versa.

Note2: You may want to change the code attached in this post to use a different serial port, so you will want to replace the word “Serial” in the code to either Serial0 or Serial1, etc according to the pins you would like to connect to.


A quick and easy way of replacing all of the ‘Serial’ words with a few quick steps is the following:

When in MPIDE with the code sketch opened, hold down the “ctrl” (control) key on your keyboard then press the “F” key, a pop-up will show, you can then type the word Serial inside the “Find:” section and type the word Serial0 (or whichever one you wanted to use) into the “Replace with:” section, once both sections have what you wanted to change click on the “Replace All” button and all the changes have been made throughout the code example.


The connections will vary according to the microcontroller board you are using so be sure to check your datasheet or board’s manual for pinouts to ensure you are connecting to the correct pins. You can also navigate to where you have the MPIDE folder installed on your computer then follow the following file path below to see all of the available board folders then select the folder for your current board and reference the Board_Defs.h file, scrolling down in that file until you see the “Serial Port Declarations”. Note: as soon as the softwareSerial library is added into MPIDE I will be sure to update this post with an example using softwareSerial for an easier connection/wiring example with consistent pin number connections between board selections.


Windows file path example below once inside the MPIDE folder on your computer:

***\hardware\pic32\variants\...


For using the DP32 board settings I used the following connections and changed the provided code to use Serial0 :

Bluetooth Module <----to----> PIC32 Microcontroller Pin

         RXD   <--------------wire------------>   14

         TXD   <--------------wire------------>    6

Five different code examples attached below. Be sure to read through them and choose which one fits your needs the best. They are listed as the easiest first to the hardest last.

This is a simple starter tutorial for the 28BYJ-48 stepper motors as seen in the pictures above which may come with different looking PCB’s, but function the same.

Materials used:

1) One Microcontroller (PIC32MX250F128B)

2) One 28BYJ-48 stepper motor with ULN2003 PCB

3) Four jumper wires (male to female)

4) Two jumper wires (female to female)

5) Power source (10,000 mAh power bank battery pack 5volts)

The power bank is optional and can be switched out with any 5 volt power source and the jumper wire connection style may vary depending on the connectors available on your microcontroller board to make the necessary connections. You will want to be sure that the power source can provide well over 200mA or 0.2amps since it will be required for the stepper motor and your microcontroller current requirements.

For the code examples attached I used the digital pins 13,12,11,10. You can use any digital pin, just make sure you change it accordingly in the code example attached if you do. This was put together using MPIDE for PIC32 microcontrollers, but the code will work with Arduino or similar microcontrollers as well.

Connections between the microcontroller pins to the stepper motor PCB are as follows:

Stepper motor PCB <----to----> PIC32 Microcontroller Pin

         IN1   <--------------wire------------>   13

         IN2   <--------------wire------------>   12

         IN3   <--------------wire------------>   11

         IN4   <--------------wire------------>   10

   

The plus sign on the stepper PCB will be connected to 5 volts (red wire in front on photos) and the minus sign will be connected to ground (black wire in front on photos). Also, depending on the stepper motor PCB the plus sign and minus sign might be located behind or in front of the pin connectors.

On the stepper motor PCB make sure that there is a jumper on the two pins closest to the resistors as seen in the photo near the 5 volt input connection. Sometimes depending who you purchase the stepper motor from, the jumper might be missing, the jumper is needed in order for it to function (the black jumper/connector seen in photo).

If you’re interested in a detailed video explanation of how stepper motors work, I recommend this one: http://bit.ly/1MeFP7N

Direct video link: https://youtu.be/EOM6aipshaI

If anyone has ever wondered what the max frequency for the chipKIT Pi (or chipKIT DP32) is compared to the Arduino UNO using digitalWrite(), check out the differences below:

This was taken using the Analog Discovery™ using WaveForms™. The PIC32 is on top and the Uno is on the bottom in the image.

PIC32 frequency on average is roughly around 403.23 kHz (PIC32MX250F128B).

UNO frequency on average is roughly around 128.87 kHz (ATmega328).

The PIC32 has roughly a 3.13 times faster frequency than the UNO using the digitalWrite() function.

This test used the following code segment below for both:

#define pin_Toggle 13

void setup() {
  pinMode(pin_Toggle, OUTPUT);
}

void loop() {
  while(1)
  {
    digitalWrite(pin_Toggle, HIGH);
    digitalWrite(pin_Toggle, LOW);
    digitalWrite(pin_Toggle, HIGH);
    digitalWrite(pin_Toggle, LOW);
    digitalWrite(pin_Toggle, HIGH);
    digitalWrite(pin_Toggle, LOW);
  }
}