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Congratulations to dougw for Force Sensitive Resistors and a USB ADC! You are the winner of a $200 Shopping Cart and earn the Grand Prize Trophy Badge!
Congratulations to baldengineer for Final Countdown - ADC from scratch demo video, milosrasic98 for Drone Motor Thrust Tester and dubbie for Micro Servo Tester #3 : Now With Pulse Generator! (Video now working)! You are the First Place winners of the $100 Shopping Cart and earn First Place Trophies!
The Data Conversion competition featured a number of great projects that explored A-D and D-A techniques. The grand prize winner of the competition was from dougw explored implementing an analog to digital converter without involving a microcontroller development system. It incorporated custom PCBs and used force sensitive resistors as sensors. The other winning projects were equally noteworthy. baldengineer built a SAR ADC to be used as an educational tool to explores Digital to Analog conversion (DAC). He live streamed the entire process (except for the final bits of code and a few bits of soldering) on his twitch account. milosrasic98 got a jump start on his project for our upcoming Attack of the Drones competition, with a winning entry in the Data Conversion competition. He's wanted to build a custom designed drone for a few years now, and while planning out the drone, his wishlist of the things to bring onboard grew to include a Raspberry Pi, Raspberry HQ Camera, and MKR LoRaWAN 1300. No doubt, inspired by our upcoming Arduino Day Workshop: NanoDrone II: AI and Computer Vision with LoRa (Win a PSoC6 and a Pair of MKR 1300 Boards!). Finally, dubbie rounds out the winning entries by making his own micro servo motor tester.
Also receiving first place votes was a heart rate monitoring wrist band by tvaibhav , a 4-20mA current loop based water level indicator for all sized water tanks by navadeepganeshu , Jan Cumps who focused on is keeping an analog signal digital as long as possible to avoid efficiency losses (and heat generation) of analog amplifiers, and ntewinkel who upcycled an old battery tester by digitizing it and making something useful rather than throwing it out.
Without further Ado here are your winners.......
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The Winners | The Grand Prize
Force Sensitive Resistors and a USB ADC by dougw :
This project is an exploration of implementing an analog to digital converter without involving a microcontroller development system. The project uses an MCP3208 (SPI 8 channel ADC) connected to an FT2232 (USB to SPI interface) to allow all the programming to be performed on the host PC. The project will incorporate at least 3 custom PCBs (1 for the ADC and several for sensors). The sensors used are force sensitive resistors (FSR). Before getting into the ADC interface, dougw explores force sensitive resistors and their interface requirements. The circuit provides a nice linear output that operates from a single supply and goes from zero volts at zero force all the way to the high rail at full force. It even provides some low pass filtering. The FT2232 translates USB to SPI, which connects to the MCP3208 A/D converter. The A/D is an 8 channel 12 bit SAR. I am running 4 sensor channels through low-pass filters to four of the A/D inputs and the same 4 sensor channels to 4 different A/D inputs, except with no filtering.
First Place Winners:
Visual ADC by baldengineer:
Any physical quantity in our world has to be converted to a voltage to be measured in electronics. Even if you have a sensor that outputs a digital bus like SPI or I2C, inside of that sensor is an ADC. There are many types, with Flash, SAR, and Sigma-Delta being very common. Like all things in engineering, there are advantages (and disadvantages) to each analog-to-digital converter type. If you've ever used an analogRead() on an Arduino, then you have used a SAR ADC! The other very cool thing about SARs is they have a digital-to-analog (DAC) inside of them. One of the key reasons baldengineer wanted to build a SAR ADC at its heart is a digital-to-analog converter (DAC). So it is a two-for-one project. A SAR ADC generates voltages through a DAC and then compares that analog voltage to the input voltage. This search takes some amount of time. If the input voltage changes while the search happens, then the search would fall apart. A "sample and hold" amplifier (S/H) holds a copy of the input voltage while the binary search happens. An S/H is a special op-amp circuit that charges up a capacitor and maintains the voltage until it samples again. A SAR ADC generates voltages through a DAC and then compares that analog voltage to the input voltage. This search takes some amount of time. If the input voltage changes while the search happens, then the search would fall apart. A "sample and hold" amplifier (S/H) holds a copy of the input voltage while the binary search happens. An S/H is a special op-amp circuit that charges up a capacitor and maintains the voltage until it samples again. For the final version of the project, he put all of the analog electronics onto perma-protoboards.
You can watch the entire stream of this project (except for the final bits of code and a few bits of soldering) here: https://www.twitch.tv/baldengineer
Drone Motor Thrust Tester by milosrasic98:
For his Data Conversion project, milosrasic98 initial idea was to create a simple pocket signal generator since he does not have one. He started looking at the Data Conversion page and saw a lot of project ideas based on data acquisition and charting and later on, the upcoming Attack of the Drones competition was announced. And that's how he got to this project. He's wanted to build a custom designed drone for a few years now, with most of the parts just scattered in different bins. As he started planning out the drone, he grew his wish list for the things onboard, Raspberry, Raspberry HQ Camera, why not make a gimbal for the camera, retractable legs and he's sure the list will go on and on... His main goal is designing a drone platform where je can fly it like a normal drone, but also be able to work on control algorithms, data acquisition and so on.
Micro Server Motor Tester by dubbie :
For the Data Conversion Project14 challenge dubbie decided that he wanted to use a multi-turn potentiometer so he started to make a micro servo motor tester. He wanted a servo motor tester for some time but didn't want to spend any money, plus he could always knock together a Nano project that did the job. So combining a multi-turn pot with a Nano to make a proper piece of test equipment seemed a good idea. He also wanted to try and make a good looking 3D printed casing to go with this. The display is Adafruit compatible so he just used their libraries. He has not used button inputs on his projects for a very long time so it was a challenge to get that working. Identifying how the debounce would work and then how to use it to select the mode. At present there are only have two modes: Servo Tester and Pulse Generator, but it would be easy to add further modes, perhaps such as a DVM. He wrote the code to produce pulses to implement the pulse generator mode of the Micro Servo Tester.
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| The Runners Up | Runners Up:
The following members received votes from the judges and would make worthy winners.
HEART RATE MONITORING WRIST BAND by tvaibhav:
Heart rate, body temperature and blood pressure monitoring are very important parameters of human body. Doctors use various kind of medical apparatus like thermometer for checking fever or body temperature, BP monitor for blood pressure measurement and heart rate monitor for heart rate measurement. In this project, tvaibhav built a heart rate monitoring wrist band which counts the number of heartbeats in a minute. It uses a heartbeat sensor module which senses the heartbeat upon putting a finger on the sensor. This band converts the analog data(the heart beat) into the digital data by the max30102 module and the result is shown on the OLED display.
AquaLoop: 4-20mA current loop based water level indicator by navadeepganeshu :
This is project AquaLoop, design of 4-20mA current loop based water level indicator for all sized water tanks. The main target is to make the system robust, low noise, less lossy over a distance for signal transmission. He uses a BC547 based water level indicator circuit, OPA211 Op-Amp for signal conditioning, UA741 Op-Amp with BC557 as a current transmitter, LM393 comparators for driving the bar LEDs and an R2R ladder network for signal conditioning. No microcontroller, No coding, All analog and data conversion.
DAC: Class-D signals by Jan Cumps:
This project focuses on is keeping an analog signal digital as long as possible - including the power amplifier - and by doing that, avoid all that efficiency losses (and heat generation) of analog amplifiers. When you think about a DAC, you often imagine a mechanism that generates an output level based on a numeric value. E.g.: 0x00 is 0 V, 0XFF = 5 V, any value in between is a proportional part of 5 V. Another popular DAC mechanism is duty cycle modulation. You 'll know it from Arduino analog out pins. In that case, the device outputs a square wave with fixed frequency. The % of the square wave that's high, defines the output voltage. E.g.: 0x00 is a duty cycle of 0% - the signal always stays low and is 0V. 0XFF is 100% duty cycle. The signal is always high at 5 V. Any value in between makes the signal partly high, partly low. The output voltage is again the proportional part of 5 V. A 3rd option is PWM: In this case, the pulse width is modulated. It is again a square wave (pulse wave is a more appropriate name). The difference with duty cycle modulation is that frequency isn't constant. Together with the duty cycle, like the second option above, frequency can be modulated (stretched). Options 2 and 3 use the time domain to translate digital to analog. While option 1 uses the voltage domain directly. In the time domain modulated signals; it's not the level of the signal that determines the output. It's the amount of time that the signal stays high that determines it. For this project, Jan Cumps implements a Texas Instrument application note. His activity was to port it to a generally available LaunchPad. The note is written for an upscale evaluation board with a higher end controller.
The Unnecessarily Complex Battery Tester by ntewinkel:
This is the story of the sage of my vintage battery tester update into the digital world. You take a good old fashioned, mostly unreliable and hard-to-use tester, and turn it into an equally difficult to use and equally unreliable micro controller powered tester!
So, in a nutshell, the finished project takes: 1) an analog value (battery voltage) 2) converts it into digital (Arduino analogRead) 3) thinks about it a bit and categorizes it into one of 5 output categories, and then 4) using PWM (Arduino analogWrite) outputs an analog value to the gauge, but... 5) Rather than using the full infinite range of the gauge in good ole analog fashion, it steps to 1 of 5 areas... kind of a digital thing to do.
ntewinkel recently found an old household battery tester while cleaning up, and it was terribly unreliable to use - the gauge doesn't always work, the contacts are sketchy at best. He was about to recycle it, but then he thought the gauge on it might be fun for a project so he tucked it away in a drawer. When this Data Conversion challenge popped up, he immediately had an idea - maybe he could digitize the thing to make it more useful for his purpose: identify what a battery can be used for. He found that some tech items need nearly full batteries to operate well, and even wall clocks can be fussy. The one thing that's not fussy is the cheap little LED string lights - they can light up with nearly dead batteries, though not as bright.
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