Revision as of 05:35, 24 May 2016

Grading Criteria

Syringe Pump

Abstract

The project will use an Android application to determine how much liquid the syringe outputs using a pump powered by a stepper motor. The application will communicate with a Bluetooth module attached to the SJ One board which will control the stepper motor driver to determine how many steps the stepper motor will take on the syringe pump. The application takes in the direction for outputting liquid and reversing the position and the number of milliliters for output. The application has details about the syringe pump's position so the user does not have to remember what position the pump is in. The SJ One board is programmed with two tasks, one for receiving the UART signals from the phone and the other for telling the stepper motor drive how many steps to take with the stepper motor. A queue is used to determine when the shared data can be used by each task. The program initially has the terminal and Bluetooth task at higher priorities than the stepper motor drive task, but the queue can make either of the two main tasks wait. The stepper motor and SJ One board are powered with a 24V DC power supply and USB to micro USB wall adapter.

Objectives & Introduction

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Team Members & Responsibilities

• Nicholas Foulk
  • Documentation/diagrams
  • Ordering Parts
  • SJSUOne Board Bluetooth Communications
• Anson Jiang
  • Android Application with Bluetooth Communications
  • Debugging
  • Documentation
• Danny Luong
  • Syringe Pump task
  • Documentation
  • Debugging

Schedule

Parts List & Cost

Give a simple list of the cost of your project broken down by components. Do not write long stories here.

Design & Implementation

The design section goes over hardware, software design, and implementation.

Hardware Design

Here we have a schematic of the connections we have with the SJ one board and the stepper motor driver and blue tooth module. The stepper motor is already drawn in. Most of the connections on the stepper motor driver are built onto the driver board.

Figure 1. Syringe Pump

Figure 2. Top Level Diagram

Figure 3. Schematic of HC-06 Bluetooth Module and A4988 Stepper Motor Driver

Hardware Interface

Here is a detailed list of all of the hardware connections made between the SJ One Board, stepper motor driver, and stepper motor.

Stepper Motor Driver

• GND is connected to a female plug
  
• Vcc is connected to a female plug
  

Figure 9. Nema 17 Stepper Motor

Stepper motor wires connected to stepper motor driver

• A+
  
• A-
  
• B+
  
• B-
  

Figure 8. A4988 Stepper Motor

Bluetooth Connection HC 06 Module with SJ One Board

• Pin 0.0 was used as an UART TX pin.
  
• Pin 0.1 was used as an UART RX pin.
  

Figure 7. HC-06 Bluetooth Module

Six SJSUOne pins were used for controlling the stepper motor driver,not including power and ground pins.

• Pin 2.0 was used as an output GPIO pin for the stepper motor driver's enable pin that allows for motor control when LOW.
  
• Pin 2.1 was used as an output GPIO pin for the stepper motor driver's ms1 pin that allows for the configuration of full,half,quarter,eighth,sixteenth steps of the motor.
  
• Pin 2.2 was used as an output GPIO pin for the stepper motor driver's ms2 pin that allows for the configuration of full,half,quarter,eighth,sixteenth steps of the motor.
  
• Pin 2.3 was used as an output GPIO pin for the stepper motor driver's ms3 pin that allows for the configuration of full,half,quarter,eighth,sixteenth steps of the motor.
  
• Pin 2.4 was used as an output GPIO pin for the stepper motor driver's step procedure that allows the motor to do one step (if ms1,ms2,ms3 are LOW) on a LOW to HIGH transition.
  
• Pin 2.5 was used as an input and output GPIO pin for the stepper motor driver's direction that allows for the motor to go in the forward direction when HIGH and the backward direction when LOW.
  

Software Design

Figure 4. Software FlowChart of Syringe Pump

Implementation

Here are the sub-sections of our project.

Android application

Figure 6. Syringe Pump Control

The application accepts user input that is between 0 to 30 (max amount of liquid per our syringe) to represent a milliliter equivalent output. The input needs to be rounded to the nearest .5mL (how accurate our product will be). The application converts the mL output to an appropriate number of letters to be sent through the Bluetooth UART connection on the SJ One board to decode in a later step. The software protocol is to send the amount of liquid to the SJSU One board starting with an 'x' byte to signal the start of data transfer. Then the appropriate letters are sent ('a' = 1 step, 'b' = 10 steps, 'c' = 100 steps, 'd' = 1000 steps) afterwards until the exact amount is sent and then a byte 'y' is sent to signal the end of the data transfer. After the data is done being sent, the application will disable input until the stepper motor task sends a byte to signal that the process is complete to allow for another execution. The user has the ability to change the direction the stepper motor is turning so the syringe holder can be pulled back when done.

Figure 5. Main Menu

Bluetooth receiver task

The task is designed to wait for a message from the Android application and handle the data transfer. It will discard all bytes sent until a start byte of 'x' is sent and it will enter a loop to receive all of the letters and translate it to the equivalent liquid output to calculate the total amount of liquid to be output from the syringe. It will discard all other bytes that are not part of the decoding key and will exit the loop once a done byte of 'y' is sent. The program will then multiply the amount of mL of the requested output with the number of steps per milliliter to determine the result and send it in a queue.

Stepper Motor task

This task will wait forever until data from the Bluetooth receiver task is put into the queue. The stepper motor task will take the amount of steps data from the queue and create a low to high transition on the step pin. The motor steps amount an appropriate number of times to push the syringe to dispense the liquid. The task is looped to allow the user to continue sending requests until the they press the on-app button to finish their session.

Testing & Technical Challenges

Describe the challenges of your project. What advice would you give yourself or someone else if your project can be started from scratch again? Make a smooth transition to testing section and described what it took to test your project.

Technical Challenges

Ordering parts and keeping track of what is being order

Getting 3D printed parts on time was hard since most places needed atleast a week for production and shipping. We needed to focus on other aspects of our project while waiting for it. There are so many parts in our project that you are bound to forget to order something or order a wrong part. It is crucial to to start ordering parts as early as possible in our opinion because we didn't realize we were missing components until we started building. There were two separate times in the project when we had to order more parts. In addition, the parts were expensive and doing some shopping could potentially help reduce the cost.

Part Compatibility

The metal rod we ordered was 1 meter long and a 300-330 millimeter portion need to be cut for the system, so we went to a store to buy a hack saw. Cutting the metal rod took ages and the cut didn't come out as smooth as we had hoped. We would suggest finding a store that would do the cutting for you. The metal rod also had a tight fit with the hex bolt on the second 3D printed part. At first the hex bolt took a few attempts to break and the smoothness of the rotation can effect output measurements.The couple holding the shaft of the stepper motor and metal rod wasn't tight enough. We had to force it to clamp down on the metal rod to make it spin.

Soldering Issues

The pins needed to be soldered to the stepper motor driver for the power and SJ one board connections. Soldering the wires directly to the holes of the board caused problems because the wires became unstable and loose often. Soldering the wires was only required for the power supply and stepper motor connections to the stepper motor driver. As a result of the wires become loose, the stepper motor wires needed to be cut shorter every time they need to be re-soldered.

Troubleshooting

Sometimes the SJ one board doesn't power up properly or the stepper motor connections aren't working causing us to have to reset the system. Stepper motors are inherently inaccurate because they don't have a feedback loop and our program needed to be adjusted a number of times because of it. The UART communication caused us a few issues because of the translation between character and integers because UART requires byte transfers.

Accuracy

Stepper motors have no feedback loop and are known for being less precise so we sometimes have trouble getting the output as accurate as we want it.Making sure you have an accurate relational number between steps and milliliters is crucial for getting an accurate output no matter how much you are trying to output. Since there is no feedback loop in stepper motors we are not constantly tracking the position the syringe is currently in and as a result we have to set a static starting position at start up every time or find a method of back tracking what has been done.

Testing

Once the system was setup we attached the tube with luers because outputting liquid was easier with it as opposed to a needle. We found it easier to connect the SJ One board to one computer and another computer attached to the phone application since separate people worked on each component. The two people made adjustments by communicating what they wanted and reworked the software flow process to better the system. During the times when the system didn't work at the beginning of the day we used a multi meter to find unusual behavior.

Conclusion

Project Video

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Project Demo Video: https://www.youtube.com/watch?v=dI20_U0IZW8

Learning Outcomes

1. Knowledge of stepper motors and stepper motor driver.
2. Bluetooth communication.
3. Android application development with bluetooth.
4. Interfacing hardware and software.
5. Experience using uart
6. Experience using queues
7. Powering SJ one board and stepper motor driver using power supply.

Project Source Code

• Sourceforge Source Code Link
• Github Source Code Link

References

Acknowledgement

We would like to thank our professor, Preet Kang, for giving us advice on what we can do to make our project better and keep us motivated throughout the process of doing it. The advice of boxing the hardware to make it look like a sellable product was helpful. We would also like to thank him for giving us the background knowledge needed to make the Real Time Operating System program running on our SJ One board.

References Used

NEMA 17 Stepper Motor Datasheet http://www.pbclinear.com/Download/DataSheet/Stepper-Motor-Support-Document.pdf

A4988 Stepper Motor Driver Datasheet https://cdn.sparkfun.com/datasheets/Robotics/A4988-Datasheet.pdf

Stepper Motor Driver Schematic https://cdn.sparkfun.com/datasheets/Robotics/BigEasyDriver_v16.pdf

HC-06 Bluetooth Module Datasheet ftp://imall.iteadstudio.com/Modules/IM120723010/DS_IM120723010.pdf

Android Bluetooth Documentation https://developer.android.com/guide/topics/connectivity/bluetooth.html