[newB question] i need advices and guidance for new project

Hi guys,

It’s been a while since I’ve been tickled by arduino and as a totally new arduino user I’d like some help.

I already have some solid coding abilities, and I’m familiar to Processing.

For my first project I’d like to create a clock, kinda similar to this one :

I’ve got pretty much the same wheels, comming from a cash register, but without the stepper; only the wheels.

So, first, I was wondering what kind of motors would suit this project the best. Stepper motor ? continuous servo ? or even something else.

Then, considering the choosen motor, what kind of arduino board or other components will I need ?

Thanks you in advance for any suggestion you have.
Cheers

Rondelle: So, first, I was wondering what kind of motors would suit this project the best. Stepper motor ? continuous servo ? or even something else.

If you use a Stepper you will probably want to have some kind of index sensor so you can sense a starting position (Steppers only move relative to current position). A "continuous rotation servo" is basically a gearmotor. It has no position feedback so you would need a way to sense the absolute position of each wheel.

I think the best bet is a hobby servo per wheel, geared up (with gears or pulleys) about 2:1 so the 180° travel of the servo can move the wheel to any position in its 360° range. Then you just need to note what positions show which digit. The main limitation is that the wheel can't go more than 360° and would have to spin back through all the digits to get from 9 to 0. You could have it alternate between Date and Time which would cause a lot of movement anyway so the spinning would be less obtrusive.

If I understand those sorts of wheels you need a single impulse for every time unit (perhaps every minute) so that the least significant wheel moves forwards one digit. A full revolution of that wheel will then cause the next wheel to move forward one digit.

If that is how it works any device that can provide the impulse will be suitable. A servo would probably be the simplest to use if you can arrange things so a short sweep of the arm moves the wheel one digit and when the arm returns to the home position it does not affect the wheel. Think of it as an arrangement that can press and release a button once a minute.

You will need a Real Time Clock (RTC) module if you want to keep to the correct time.

Any Arduino would be suitable. The code will be very simple.

…R

Thanks for your help.

I'll delve into this a bit and will go back to you. As you both said, servo is probably the easiest solution.

I'm gonna try to find a gearing solution, for a 1:2 ratio, so i can have a 360° control over the wheels. And I also need to think about the disposition of the whole system.

Then i'll experiment with code.

Do you guys have some good addresses for things like gears, parts ect ? That could ship to EU ?

Thanks.

try ebay?? ive seen so many servos and the like there. if not an easily accessible solution would be to salvage some stepper motors from older outdated electronics such as printers. many times old printers will have two steppers in them. the stepper motor is the motor that has the ability to move in degree increments. if you find your steppers you can pair its range to the gearing that you need for travel. most likely you can also find several plastic gears in printers. no guarantee that their ratios will serve your purpose but they are there for the salvaging if you want to go that route. I have taken many of them apart and they have steppers fully capable of turning wheels. just my 2cents, good luck

So far the best cheap source of small gears that I have found is to take the gears from cheap servos. And you get a free electric motor.

...R

those number wheels are not connected. but appear to be in pairs. it seems that they are moved by a solenoid, not a motor. one impulse moves digit 1 it increments it by a value of 1.

once that turns over to 0, it sends an impulse to the 10's place solenoid. if you have this device, you only need to pulse the solenoids.

are rutting gutting it, and adding gearing so that the internal gears from the 1's place, trip the 10's place as it moved between 9 and 0. , like a car odometer.?

you could make i so you only need one motor and one indicator. the motor type is of no importance. you run it till the indicator trips.

your motor runs until the 1's place changed digits. then you stop the motor. the gearing between the 9 and 0 advance the next wheel.

seems more data about your assembly is needed. you can have 4 motors and move each digit easily. or you can make a gear train that requires only one motor, or just a solenoid.

silverdrgn: [...] I have taken many of them apart and they have steppers fully capable of turning wheels. just my 2cents, good luck

I've just disassembled one this afternoon, an old printer that I kept for salvaging. I found in it 4 steppers motors, each one having a feedback system (a plastic wheel with some sort of dot partern), but it will be hard for me to understand and use those index sensors.

I aslo found a lot of gears that I need to take a look at, and a axle of the perfect radius for my wheels.

dave-in-nj: it seems that they are moved by a solenoid, not a motor. seems more data about your assembly is needed.

You're probably right, but I only got the numbered wheels. Something like 12 numbered wheels, and also a pair with currencies.

Also I find that the solution with 4 motors to manipulate 4 wheels best suits my project. It let me change any digit on the go. (I think about some possible addons to my clock, for exemple displaying temperature pushing a button)