Question from a really new Newbie :)

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,
I am newbie in a very real sense :slight_smile:
I have experience with processing but havent made any project yet in Arduino but that status may change soon if I can achieve what I am looking for.

For the same, I am here to ask you all for some basic help and guidance, I hope that is OK.

So I have a few questions which I am not sure how to approach, hence I dont have anything which I have tried.
I will start by describing what I am trying to make.

I am trying to build a tiny wearable tapping device. Something that can be worn on a finger and a motor can be used to create regular interval 'taps', the speed of which can be adjusted using a potentiometer.

I have uploaded a video on youtube to show what the device does: - YouTube

Here are the things I want to know before I can go ahead and start purchasing the right stuff to build it:

  1. Should I be using Arduino Uno or Mega or LilyPad.... My confusion is, which one will be best option to control a stepper motor.
  2. This leads to me second question, is the stepper motor the right choice to create this kind of tapping motion? Or should I be looking at some other types of motors.
  3. Which is the smallest stepper motor that I can purchase? Is there a good website where I can find them? I was able to find a couple on the internet but they were a bit bigger in size and needed 12V or 15V power. Are there any 3V or 6V steppers? I found one here but looks a bit big: https://www.sparkfun.com/products/10846 I searched for tiny steppers and I found this (but looks like its beyond my technical skills to extract one from a Bluray drive): World’s Smallest Stepper Motor with Arduino and EasyDriver - Electronics Blog

If I can get these things sorted out, then I can start experimenting with the code myself and see what I can achieve.
But since these are the basic things I need to device before I start to build, I am stuck :frowning:

I look forward to your opinions and suggestions.

2

[Just a small update:]
Found one more link on stepper motor on this forum.
http://forum.arduino.cc/index.php?topic=266799.0

Reading it right now.

3

I found some more smaller stepper motors here: http://www.omc-stepperonline.com/stepper-motors-nema-8-stepper-motors-c-1_32.html

Can these be directly connected to Arduino or need some controller in-between?

4

Can these be directly connected to Arduino or need some controller in-between?

You couldn't safely connect even the tiny vibra motor in your phone directly to an Arduino.
Yes, you need a buffer.

5

Thanks AWOL
What kind of buffer boards work for such motors? Anything particular I should look for?

6

Can someone tell me if I should go for a Stepper Motor or a Servo?

I saw in some videos that one can turn the servo in both direction, is that something that might work for what I am trying to achieve?

btw. I saw that Servos can be connected directly to Arduino, is that right?

7

If you have a flyback diode to protect the arduino and the motor will /not/ consume more than 40ma then yeah you could....

Those tiny motors in phones consume how much power?

8

Servos have their driver electronics built-in, but need a lot of current, separate
power from the Arduino is normally needed.

The smallest steppers are bipolar and this makes the drive electronics much bigger
than the stepper!

For a simple tapping motion a solenoid is the way to go, but finding the right one
could be tricky.

9

For a simple tapping motion a solenoid is the way to go, but finding the right one
could be tricky.

Well, you could always roll your own. I think I've seen magnet wire down to 34G on Ebay. Bobbin is another matter but the armature could be just a simple bolt. I'm sure there's lots of apps on how many turns to do for a given inductance. Drive it with a FET off a PWM output. I guess it can be as small as it needs to be. As for the Arduino, the slickest I've seen is a tiny 32U4 board by DFRobot. Beetle Board - Compatible with Arduino Leonardo - ATmega32U4 - DFRobot It only comes from China so better figure about 2 weeks to get it. LilyPad or ProMicro might be a quicker choice.

10

MarkT:
..., separate power from the Arduino is normally needed.

Hi,
I plan to use either a single Duracell 12V battery or a set of AA's connected together to power 12V.
Would that be OK?

11

ssdesign:
I plan to use either a single Duracell 12V battery or a set of AA's connected together to power 12V.
Would that be OK?

Not for servos no, since they're usually 6VDC.

Just to clarify on the connections: with a servo the yellow wire which is the control line, does go direct to the Arduino, but the power must be separate.

Similarly, if you have a DC motor, you would drive through a transistor*, the base of which would be to an Arduino i/o pin. The transistor would then switch the external power.

*or more complicated, an h-bridge if you need direction control.

12

Those tiny motors in phones consume how much power?

I've measured in excess of 70mA.

13

If i were you, I would do some studying on small servo motors:
http://www.servocity.com/html/s3102_micro_mg.html#.VBnoePldWHc
This servo runs at a speed of .20 sec/60degrees - fast enough for some fast tapping.
This particular servo runs @ 3-5v - so ok for 4 AA batteries.
Of course, this is just the 1st one I ran across and the price may be a bit steep - but it is just an example.
Stepper motors are larger, heavier.
Liner steppers are usually very costly.
btw, there are some very small "Arduino Compatible" microcontrollers out there.
look into the Digispark from Digistump - this is going way small, but believe it or not, if you only have a Servo & potentiometer to be wiring up - this could work for you.

With a bit of mechanical gimmickry, you could have this servo push a lever/fulcrum to get the throw you need with short movement of the the Servo. since you're tapping your finger, I'm sure you don't need a lot of torque (power).
I'm curious as to what exactly the purpose of your device will be? You've got me stumped!

Russ from Coral Springs, Fl.