About the article


based on a PIC16F84 microcontroller

This article describes a metronome and a diapason (electronic tuning fork) combined into a single unit. The circuit design philosophy was to keep the hardware as simple as possible, and to provide features comparable to those of high-end commercial units. This has been achieved by using a microcontroller chip PIC16F84.The PIC16C84 was programmed to take care of all functions, including the generation of beat ticks in metronome mode, the digital synthesis of pure tones (sinewaves) for the full range of notes (from C2 to B7) in diapason mode, and the driving of the LCD display module.In metronome mode, the circuit produce beat ticks whose sound is short and sharp, imitating that of a mechanical metronome. A useful feature is emphasising the first beat in each bar. This is done acoustically, by changing the pitch of the beat, and visually, by the lighting of a LED. An interesting feature is that the unit can provide irregular rhythms of 5/4th, 7/4th and 8/4th, as well as no rhythm — only regular beats imitating a mechanical metronome.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1 = 1 kOhm
R2 = 470Ohm
R3 = 47kOhm
R4 = 10Ohm
R5-R12 = 20kOhm 1%
R13-R20 = 10kOhm 1%
P1 = 10kOhm preset
P2 = 10kOhm logarithmic potentiometer
C1 = 100nF
C2,C3 = 22pF
C4 = 47nF
C5 = 4nF7
C6 = 100µ F 16V radial
C7,C8 = 10nF
C9 = 470µ F 16V radial
D1-D6 = 1N4148
D7 = LED, red, high efficiency
IC1 = PIC16F84-04/P, programmed, order no. 000198-41
IC2 = 74HC574
IC3 = LM386
IC4 = 7805
S1-S6 = pushbutton, Multimec CTL4 with cap D6K0
K2 = headphones socket, stereo, PCB mount, for 6.3mm dia. jack plug
LCD with 2 lines of 16 characters, e.g., PCF1602
Battery clip for PP3 (9V) battery
Enclosure: Retex, dim. Approx. 145 x 90 x 45mm (Conrad Electronics # 54 15 59)
PCB, order code 000189-1
Disk, all project software, order code 000198-11
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