My name is Asher and I am a rising junior at The Heschel School.

Velleman MK171 Voice Changer

For my third and final starter project, I built a voice changer, which is powered by a 9V battery. I got the kit from the Velleman website ( By speaking into the microphone, the device can add vibrato to the voice, change the pitch and alter it to sound like a robot. These effects are done with an HT8950 Voice Modulator.

In doing this project, I learned how to solder two pieces of metal together. The kit included pegs to solder into the circuit and then the battery wires could be soldered directly to said pins. To do this, I had to add a small amount of solder to both the pin and the wire, which I would then solder together. This took me several attempts and was one of the problems I faced. Also, while the kit told me to solder on a speaker to the pins, the kit did not include a speaker. So, in order to for the device to work, I had to use cables to attach my circuit to another student’s voice changer, which had a speaker, in order for the voice changer to be amplified. This also took several attempts, and I had accepted that my circuit had a short, until I realized that I forgot to turn the volume on, which had been the problem.

This project took me a day to complete. The battery applies power to the circuit, which flows through ten resistors and ten capacitors. When someone speaks into the microphone, the microphone    converts those sound waves into an electrical current, which goes through the circuit, through the voice modulator, the power amplifier and eventually through the speaker. In the circuit, the pitch of the current can be heightened or lowered by pressing two pitch buttons which send a signal to the voice modulator and can slow down or speed up the current, changing the pitch. Similarly, with the vibrato and robot buttons, the voice modulator changes the frequencies of the electrical signal from the microphone to the speaker, emitting an altered sound. However, for the electrical current to travel to this stage, it is lowered through resistors, temporarily stored and shot out in capacitors, it passes through LEDs (light emitting diodes) which show that the current is flowing, and go through a diode which assures it is travelling in the right direction. I found that each kit I used offer less instruction and I had to rely on prior knowledge as well as internet searches to assemble it. I am satisfied with the end results of this kit.



For my second starter project I built the Metro-Gnome, which is a metronome powered by four AA batteries. I got the kit from the sparkfun wesbsite ( A metronome is a device that makes repetitive ticks at a constant rate in beats per minute. It is often used by musicians when learning a new piece, or to keep a steady pace. When I learn a difficult piece on the guitar, I use a metronome and steadily learn to play the piece increasingly faster.

I soldered much more easily and quickly with this project than with my first starter project. The project took me about an hour and a half to complete and it was basically all soldering. The only problem I encountered was trying to fit the microcontroller into the PCB, since there were 28 pegs to fit. However, this only took about 2 minutes to fix. It runs on a ATMega microcontroller and uses two LED (light emitting diode) displays for output. The LED displays show how many BPM (beats per minute) the metronome is playing. The metronome works by repetitively shooting an electric current around the circuit, from the battery pack, through the different capacitors and resistors into the buzzer which makes a short beep every time a current flows through it. The buzzer in this circuit (piezo) creates sound when a current passes through it. The voltage is applied to a piezoelectric disk, causing the disk to flex back and forth, creating a sound.

In the circuit, the current passes through two different types of capacitors, electrolytic and ceramic. In a capacitor, the electrons are stored for a short amount of time, and then shot back out. The current also flows through a diode, which assures that the current is only flowing in one direction. The current also uses a 10k resistor which lowers the overall voltage of the system and stabilizes the circuit. The up and down buttons control the speed at which the electrons flow through the circuit, which is done through the microcontroller. I feel like my soldering skills improve with each project as well as my overall understanding of how circuits work.


MintyBoost v3.0 Kit- Battery-powered USB charger for your gadgets

For my first starter project, I built a MintyBoost (, which is a portable phone charger powered by AA batteries. Most of the work involved soldering and it took me about two hours to complete. It was challenging, as I had never soldered before and it was where I encountered most of my problems. I had to de-solder because my iron was dirty and a hole in the circuit was blocked by some gunk. I also had to de-solder one of the battery wires because the wire part was too short and it slipped out of place as I was soldering it.

As I was testing the product with a multimeter, I saw that my reading was low- instead of being around 5 volts, it was at about 3.1 volts. Then, I realized that I forgot to insert the boost converter chip. After inserting the chip, my reading was at about 5 volts. I picked the MintyBoost as my starter project because it was a good way to learn soldering and I always find myself in need of a portable phone charger, and thought it would be more fulfilling if I built it myself.

During this project, I learned how to do certain things which are essential to creating larger, and more complex projects. This included soldering, and using a multimeter. Overall, I was successful in building the MintyBoost and I am very pleased with the results. In the MintyBoost, there is a circuit that receives a flow of electrons from two AA batteries. These electrons then pass through several different types of resistors, such as 3.3k resistors, 75k 1% resistors and 49.9k 1% resistors. These resistors control how much electricity is flowing through the circuit. The electrons then go through capacitors which store electricity within the circuit. One of the capacitors helps stabilize the output voltage, while the other one helps the boost converter chip generate a precise voltage. Similarly, the electrolytic capacitors, which stabilize the input and output voltages. Finally, the boost converter chip transfers the electricity at a greater voltage than the input into the USB and into the charger.


  • Joh K. Drinda

    Hi Asher,

    I enjoy music electronics and whistling to music. My electret Mic gives me a lots of audio feedback, even I put the speaker far away and move the Mic around. So, I was thinking… maybe it is possible to use this chip’s vibrato frequency shifter as to stop or at least reduce the audio feedback looping.
    Q: Can its vibrato be adjusted max. 5% shift ? If yes, what will be the resistor values?
    Thank you for the Info, Joh from Chile
    To reward you for your efforts, here’s how I whistle to Elvis:

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