So I asked my Dad what he wanted for Christmas, and he said a Talking Metronome. He’s learning to play the piano you see and is dissatisfied with regular tick-tock metronomes. So I had a look around. Talking metronomes are not all that easy to buy. The only product I found was the Boss DB90 which costs $250 and is kinda complicated. So I have decided to build my own. How hard could it be?
I will be attempting to build this out of parts and software that I have already developed for other projects plus whatever I can find in my parts box. I’ll start with one of my RS422/485 Bit Rate Converter boards which has a really nice 32-bit ARM7 computer on it, wire it up to some buttons, an LED display and a DAC to produce the audio output.. I have only placed the parts for the CPU and switchmode power regulator, I won’t be needing the serial ports. That pin header is the programming port for the CPU.
I also have my MIDI Sync Box circuit board which I designed years ago when I thought I could launch a MIDI clock source device – I never launched the product but I have a few old prototype boards lying about. It’s perfect for mounting the LEDs and rotary encoder for the tempo knob. It also has all the multiplexing circuitry for the LEDs, rotary encoder and additional buttons. I won’t place the PIC microcontroller, I’ll just wire the ARM straight up to it.
I’ll have to change the resistor values for the LEDs because the board will now be running at 3.3 volts instead of 5 volts. I guesstimate that 100Ω should just about do it. Only problem is that I’m completely out of 100Ω through-hole resistors.
So today I have assembled the ARM board and tomorrow I will need to go shopping. The parts I will need to buy are:
- Some 100Ω resistors
- A small amplifier module which can run off 9-12V
- A small loudspeaker
- A suitable box to put it all in
Not that much stuff. I could probably have built an amplifier out of bits I have lying around but a pre-built module will save me a lot of time.