How the clock works
I finally decided to deal with the Arduino, as a result of which I made my first project: a fully mechanical digital clock.
Components
Electronics:
- (1) Arduino Nano.
- (2) PCA9685 16-channel 12-bit PWM servo motor drivers.
- (1) DS3231 Real Time Clock (RTC).
- (1) TTP223B touch switch.
- (33) SG90 servo motor.
- (2) 20KG powerful servo motors.
- (1) Servo motor signal switch.
- (1) 12V 6A power supply.
Materials:
- Walnut plywood 3 mm.
- Walnut veneer.
- Plexiglas 3 mm.
- Carbon steel wire.
- Screws.
- Permanent magnets.
- Metal balls 6 mm.
Equipment:
- Laser cutter Glowforge .
- Various tools.
Step 1: schematic and code
The schematic diagram of the device is quite simple. Everything connects to everything via SDA, SCL, ground and V + pins.
The code as a whole works according to the following principles:
- Each motor is controlled by one or two PCA9685 boards. Each digit has 7 segments - 14 servos for hours and 14 for minutes. There are two more powerful motors that turn the body, 4 raise the platform, and 1 for the colon.
- Time is taken from the real time clock chip.
- I included a touch switch in the circuit to be able to switch the clock formats (12/24 hours).
Step 2: prototyping
Numbers and numbers
Each number has 7 segments. Each segment is driven by a servo motor. One of the biggest challenges was to position the servos to minimize the overall size of the watch. Computer design helped a lot here.
I started with a single digit. The photo shows the paths in the lifting mechanism, along which, according to the original plan, the balls were supposed to move. I also wanted all the balls to fall first when the current time changed - but this system turned out to be too complicated. And it's good, since the clock is still working loudly enough - and every minute hundreds of balls falling would probably quickly become annoying.
Step 3: design
Upper body
The servomotors are connected to the connecting wires. One wire goes to each of the number segments, and there are four magnets for each segment. You just need to repeat it all 28 times.
The first layer is the magnets, the second holds the servos, the third holds the electronics, and then comes the back wall. Yes, maybe the layout is too tight - what to do.
On the side walls there are two 20Kg motors that rotate the entire body to load and unload the balls. By the way, in the future I will not use different materials for one project. I wanted the watch to be mostly transparent, with a little wood trim. It was very difficult to work with materials of different thicknesses, which also produce different cut thicknesses in a laser cutter.
Lifting mechanism (lower part)
The hoist has 4 motors to help raise and lower the platform where the steel balls line up with the number segments. Lifting is carried out by means of a simple rack and pinion transmission.
Legs
12V power is supplied through the bottom of the case. I managed to hide the wires well in one of the legs, so that the wires are not pinched there.
Step 4: finishing touches
When designing a watch, I constantly remembered the need to make a double design. One of the watches looks like they are made entirely of wood. And if you remove these overlays, you can see the insides and operation of the mechanism. Now I understand that I like them better with overlays, however, the project looks very cool without them.