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Published December 29, 2017 © GPL3+

Poor Man's Theremin using Bolt IoT

Wave your hand in the air and make annoying buzzer tones!

BeginnerProtip19 minutes1,355

Things used in this project

Hardware components

Bolt IoT Bolt WiFi Module

Resistor 10k ohm

Photo resistor

Buzzer

Jumper wires (generic)

Breadboard (generic)

Software apps and online services

Bolt IoT Bolt Cloud

Hand tools and fabrication machines

Soldering iron (generic)

Story

A Theremin is a really cool music instrument with two antennas which can be played without physical contact. In this project, we decided to recreate a similar effect by using the components usually included in the box with a Bolt IoT Wi-Fi module, i.e. a buzzer and a photo-resistor.

Hardware Setup

The hardware connections are really easy and involve connecting a Buzzer to pin 0, a digital I/O pin on the Bolt module and a Light Dependent Resistor (LDR) on pin A0 (Analog Input). The light intensity incident on the LDR changes its resistance. A potential divider circuit with a 10k Ohm resistor allows the MCU to read the voltage across the LDR. You can read more about how that works in these blogs:

https://diyhacking.com/arduino-ldr-sensor/

http://physicsnet.co.uk/a-level-physics-as-a2/current-electricity/potential-divider/

By waving your hand above the LDR, you change the incident light intensity. Based on this value, we set a PWM signal to be generated onto the piezo-electric buzzer. The Bolt Wi-Fi module supports software PWM on all 5 digital I/O pins (0 to 4).

To read more about PWM and tones, check out:

http://www.egr.msu.edu/classes/ece480/capstone/fall14/group07/PDFs/PWM_Application_Note.pdf

https://www.arduino.cc/reference/en/language/functions/advanced-io/tone/

The Fritzing Breadboard view clarifies the connections to be made:

Software Setup

The python script attached below has two functions. One to read the analog sensor value and the other to write the same value directly to the buzzer. This results in an interesting albeit slightly annoying tone which you could exploit for the growth of your musicianship skills.

That's it! :D It shouldn't take you more than 20 minutes to put this project together and start annoying all your dear ones this holiday season! :) Check us out on Indiegogo, back us, and spread the word! We have exclusive discounts for developers and the first batch of Bolts ships out in Februrary 2018 :)

Code

theremin.py

import time
from boltiot import Bolt
import json

api_key = "your_api_key"
d_id = "your_device_id"

client= Bolt(api_key, d_id)


def get_light_intensity(pin):
    """
    Get light intensity.
    """
    response = client.analogRead(pin)
    print response
    data = json.loads(response)
    return int(data['value'])

def play_buzzer(pin, value):
    """
    Control the buzzer
    """
    response = client.analogWrite(pin, value)
    print response

while True:
    light_intensity = get_light_intensity("A0")
    print "light intensity is", light_intensity
    play_buzzer('0',light_intensity)

Credits

Mayank Joneja

6 projects • 42 followers

Embedded Hardware Development and Robotics. Networked Embedded Systems | IoT | Wireless Sensor Networks | Design Thinking

R

7 projects • 94 followers

Senior Software Developer

Poor Man's Theremin using Bolt IoT