assignment 13. 27 april 2016

Output Devices

 

Add an output device to a microcontroller board you've designed and program it to do something



Since it happened during input devices, I have been working with more than one device. First I think that stepper motors work fine into my project, but further I notice that The prothotype would be smaller than I though initially and the rotation of the engine would be limitated to 90°, so I could use servo-motor as well.

1. Output device/ Stepper motor control board (week13)

Build a board only using drivers.
Do it working using Arduino board
Do it working using Fabduino board

Download Board files

Download Arduino files

2. Output device/ Servo motor (week 15)

Build a board including ATTiny 44
Do it working using Arduino board
Do it working using Fabduino board

Download Board files

Download Arduino files

1. Output device/ Stepper motor control board

I´m not sure if my project would be succesfully moved using a servo-motor or I should use a stronger motor. Besides it depends on the kind of movement I finally will arrange, only a displacement along Z-axis or some kind of sophisticated tranformation from rotation to Z movement.

By now I am going to try stepper motors, not least because I have some experience using servo motors and I believe that Stepper motors are a bit more complicated to move.

Stepper motors fall somewhere in between a regular DC motor and a servo motor. They have the advantage that they can be positioned accurately, moved forward or backwards one 'step' at a time, but they can also rotate continuously.
For my output device I decided to modify Neil's hello.stepper.bipolar board in order to run the outputs to an Arduino. I wanted to use a bipolar motor as it is stronger and offers more torque power than a unipolar one, while one can actively control the position on a step motor. By now I am focused on the control of the input and output devices using Grasshopper, so I decided to discard the MC of the original design. Due to the fact that I have built a Fabduino ( Satshakit ) and it is powerfull enough to control both devices.
In this way I designed my output board using the components set out bellow:


2 A4953 drivers, both required to power one 4-wire bipolar stepper motor.
0.1uF capacitor
10uF capacitor
I also took the two 4 pin headers from the hello.stepper using one to connect the driver outputs to the motor and the other being connected to an external 9V battery supply needed to run the motor. My RS Step has holes for a 6 pin Arduino header. These are for: Inputs 1/2 (from the first A4953), Inputs 3/4 (from the second A4953), GND, and VREF.

Eagle scheme

Tracing of the board

Finished work!

 

 

1. Connecting servo!

I tried to work with the hello_servo board, so I modified the original Neil’s board introducing one new circuit compound with a resistor and a LED.

Issues:

I had to fit a true-hole 22 microF capacitor

Problems:

Does not work at all, overheating of the regulator.

The true-hole capacitor is polarizer, I toke into account that one leg was shorter than the other one but I did not mind about it. After that I chaged the arrangement but The problem continued.

I read about that: Applying a negative voltage for an extended period to an electrolytic capacitor results in a briefly exciting, but catastrophic, failure. They’ll make a pop, and the top of the cap will either swell or burst open. From then on the cap will be as good as dead, acting like a short circuit.

In spite of the fact that it seemed nice I probed to change it using another brand new one but I did not get any fullfilling result.

I tried to cut the added circuit just in case it had not been working properly, but the problem was continuing.

It looks great but does not work. The voltage regulator heats just you plug the GND-VCC conections.

 

Second trial! New Output board/ Servo motor control board

When I started to work with this board I realised that the regulator component I had, was not the same that Neil´s original board so I modified it into the first scheme, nevertheless I did arrange the component in the wrong way. At last, reading for second time the datasheet I noticed that I was wrong.

Taking advantage of the mistake, I decided to introduce a 4 PIN HD bus in order to communicate the output board with the input board one.

I have connected the pin 2 with the tab 2 as It was arranged in the original board. I have read the datasheet at the begining and I noted this point on my notebook, but I did it wrong. So did not focused the problem well enough. At last I recised the datasheet and I found the mistake!

Scheme of the correct board, at last!!

So I wanna give you an advise!

Arrangement of the regulator pins

Modified board, a bridge was enough in this case! Completely operative!!