Week 9: Input Devices
Group Assignment: probe an input device's analog levels and digital signals
Individual Assignment: measure something: add a sensor to a microcontroller board that you have designed and read it
Hall Effect Sensor:
I chose this sensor because it is new for me, interesting, and could also come in handy for my final project.
Basically a Hall Effect Sensor measures the presence and strength of magnetic field.
Found a nice introductory video for this sensor here. It includes the summary of benefits of the sensor:
Board with Hall Effect Sensor!
Since we want to use a Hall Effect Sensor and since wires are forbidden, we must make a new board. Let's go!
Fortunately Dr. Neil has the schematic for a simple board with Hall Effect Sensor using Attiny. Thank you!
Here's my schematic and the PCB design:
It happened that Mithun walking by, and commented that I didn't properly do the board set-up:
And also "net classes" are required:
Here it is again, after passing the DRC perfectly:
Finally, here is the 3D viwer and the actual board.
Analysis: Saheen raised his eyebrow, specifically at the two pin header. Here's the issue: 1) The two pin header in my design is not in the right position - it should be closer to the edge to allow a programmer to be connected. 2) The two pin header is also not even required in my case. Neil had the two pin header for programming, but here we are using a marvelous UPDI/FTDI board developed by Saheen. This means that we can both program and read from one programmer and do not need two as does Neil. Moral of the story: don't blindly copy!
NEW Board with Hall Effect Sensor!
Given the aforementioned difficulties, it is necessary to make another board to test the Hall Effect Sensor.
This new version is more coherently designed and lookes sexier as well. Engraved without difficulty on the Rolland MDX.
Soldering was also fine, please refer to previous weeks' documentation.
Getting started Programming ATTiny412 with UPDI
Let's get started with the ATtiny 412 Pinout:
The big idea is that we will use an additional board called a programmer to program the ATtiny. In Arduino.
I started by reading some documentation from Adrien and Saheen as well as something on YouTube:
The first issue to program is setting it up. We will use the Arduino IDE but we need to configure for the ATTiny and some other settings.
1. Under File -> Preferences, copy "http://drazzy.com/package_drazzy.com_index.json" into the required space.
2. Now navigate to Boards manager and install "megaTinycore"
3. Finally choose your board, port and programmer.
If you don't know your programmer, you can choose to either be a genius or ask Saheen!
Now to test with the very simple blink program, we just need to change that pin to 3.
BTW it works. However, we will wait to add the Hall Effect Sensor before sharing a video...
Finally, some notes on the programming set-up and Saheen's board... There are actually 2 boards from Saheen here, together allowing for both communication and programming, with the modes being toggled by the switch in the middle board, which changes the mode between UPDI (programming) and FTDI (communication). It's a little tricky the first time because to download the program from the Arduino IDE, the switch must be at UPDI, whereas to start the serial communication and print the sensor value to the serial monitor, FTDI (for communication) must be engaged.
Inconsistent Readings:
Here's the initial program.
But unfortunately it was not consistent, since this Hall Effect sensor is old and needs to be set up in another way as shown by Nihal:
Instead of reprinting the board, Saheen suggested to add an additional resistor and capacitor to this board. Done:
Now with the modified board the program is working nicely with sensor value reacting to magnet presence:
More testing / programming of the Hall Effect:
Wanted to continue programming and keep track of the count of magnet interactions. Of course if a magnet approaches the sensor, and if delay is small like 10ms, it's very easy to count the one magnet interaction multiple times. We avoid that in this code:
Designed and printed a board with an attachable spinner. The magnet goes in the spinner and it is spun around, and we can keep track of how many times it goes around with our program. Also added an LED blink when detected.
The magnet can be detected (as indicated by LED) even if the magnet is passing over the sensor really fast.
Further development idea of a blinking fidget spinner with a faster spin resulting in faster blink...
Printed it out, added a bearing, works better: