Maker Giovanni Bernardo has written up a project built for his drum-loving son: a PIC-powered digital metronome, functional for beats from 10 to 999 beats per minute (BPM) in 2/4, 3/4, and 4/4 time.
"My son wanted to sign up for drum lessons," Bernardo explains. "When practising at home it necessarily requires a metronome and so far we have used an application for Android, on a mobile. Obviously, from the need to have a metronome to wanting to make it myself with a PIC microcontroller was a short process because I remember when I was little and I enrolled in a guitar course: They sold me an electronic metronome made with a NE555 to a the price I remember at the time was exorbitant (perhaps around 50 thousand lire), money that I took out of my 'bribes' and which earned me a reproach from my father for the exaggerated price."
Rather than another seemingly-overpriced off-the-shelf metronome, then, Bernardo set about designing his own - the MetroMik, named for his son Michael. "The circuit is powered by a 18650 LiPo cell and uses four breakout boards," Bernardo explains. "That is, the boards that we makers like so much because they already have everything included — they save us a lot of time in the construction and also cost less than the individual components!"
These breakout boards handled charging of the lithium polymer battery, a separate step-up module to take the battery output and bump it up to 10V to power the amplifier and down to 3.3V again for the PIC microcontroller at the heart of the build, an LM386-based amplifier board, and a three-digit seven-segment LED display for feedback.
Interestingly, Bernardo opted not to design a custom enclosure for the project but instead picked something from a catalogue. "The Bahar container used is very particular and made especially for this application," he explains. "It is a handheld container that is made especially to be in the hand, but in addition it has a closable bracket that allows you to place it on a slightly inclined table. Needless to say, as soon as the I saw in the catalogue it was love at first sight and the whole metronome project revolved around this container."