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I am planning to make a POV (persistence of vision) display using ATmega328 with 5 red LEDs for display.
Below are my aims:

  • I want to power it with cr2032 coin cell, so power consumption has to be taken care, I am ready to keep single or 2 coin cell in parallel to meet current requirement.

    1. Using 8MHz clock instead of 16MHz can help
      • Does it require separate boot-loader to be installed?
      • During boot-loading do I require to put external 16MHz clock?
      • How to ask controller to use the internal 8MHz clock?
    2. Supply voltage of 3V instead of 5V can also help, and cr2032 gives out 3V
      • What care should I take while using it at 3V?
      • Any mechanism to set the threshold for controller to stop working?
  • To reduce the weight of whole circuit so I can rotate the board using small toy motor (I don't have a gear box).
    I am planning to control the speed of motor using LM317 voltage regulator as a constant current source.
    I will mount the LEDs on straw, keep the controller and the coin cells at the center. (Guessing that will reduce the torque required by the motor as torque=Force*radius and weight being at center reduced the radius)

  • I am okay, if this circuit works for just few hours OR days.

  • This video from "GreatScott" covers this type of project very well. m.youtube.com/watch?v=57carjNxI9A – Paul Apr 7 '17 at 6:45
  • In the Atmega datasheet, you can read that 16mhz may not work at 3V. You'll probably have to program it using an USBasp or something comperable, to also be able to change the fuse bits. – Paul Apr 7 '17 at 6:47
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    It may also help to have some kind of feedback that indicates whenever a full turn has been made. This way the display can be synchronized to the speed of the motor, and keep orientated right. Then you can most likely alsof skip the LM317 – Paul Apr 7 '17 at 6:49
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    Why not use an Arduino LilyPad? – Mikael Patel Apr 7 '17 at 8:54
  • Welcome to StackExchange. Be sure to take the Tour at arduino.stackexchange.com/tour to see how it works here. – SDsolar Apr 8 '17 at 3:30
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Not exactly an answer, but too big to place into the "comments" area.

Clock For the 8MHz vs 16MHz, you should be able to run your project at 1MHz. Just use a bare AVR MCU with the Internal 8MHz oscillator divided by 8 - search for AVR Fuses. You can program it using an ISP (or and Arduino as ISP)

Battery About the CR2032 or coin-cells in general are not designed to constantly supply current. You can use it for very low currents, up to 2-4mA or in pulses. Otherwise you damage the cell, reducing it's total usable capacity. Maybe have a look on sub AAA batteries instead of coin-cells.

Motor For the motor, have a look on the micro coreless dc motors. They are really tiny and should offer an excellent efficiency. Motor example

Motor Driver Not sure about the LM317. You don't want any kind of regulation as it would waste energy. To drive the motor a small Mosfet should do the trick. You can control the Mosfet using PWM, which will define the motor speed. Don't forget to implement some kind of rotary encoder to count the motor RPM so you can precise speed control - a tiny magnet and a hall-sensor should be enough.

  • Indeed. If the motor is powered by something else, this could work at a low clock rate. But if the motor is supposed to be powered by this circuit, ie, it rotates itself, then a more capable power source is needed. – Chris Stratton May 14 '17 at 15:57
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1. You said you wanted to use your Atmega328 at minimal power usage so you asked how can I use my Atmega at 8mhz. So for doing that first you need to bootloader your Atmega with a 8mhz Bootloader so that it could work with its internal 8mhz source.

2. You said you wanted to use coin cells. But coin cells provide a very low amount of power and they are used for small projects. So instead you could use Lithium Ion batteries or AAA batteries.

3. You said you will probably look forward to use LM317 as motor controller and a small toy DC motor. Well if you would use LM317 i.e. Voltage regulator you would ended up with a lot of power consumed by it. So I would probably say you to use a MOSFET as Talk said. Now for the motor it's ok upto when you are okay with it. Now I can't say you specifically which motor you looking for as there are many motors with many shapes and features. And that could be done by just searching on Google.

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