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Powering a Prop chip — Parallax Forums

Powering a Prop chip

Buck RogersBuck Rogers Posts: 2,185
in Propeller 1
Hello!
Can the whole Prop setup, program storage and the Prop itself be configured to run on one of the reasonably easily available CR2032 batteries? Or despite being a 3.3v device inside it requires 5v outside it to work properly.

I ask because I'm considering my first stand alone Prop project. Nothing serious or what, this is just for fun.

Comments

  • cheezuscheezus Posts: 298
    Yes, it can be done. Depending on what you want to do with it you might have a problem with battery life. I've run an entire project off of 3v using lipo batteries (with a nominal voltage of 3.4 volts) I'd recommend using a high efficiency switching regulator if going this route.

    The real deciding factor is how much CURRENT your project would need. If you're lighting a bunch of LEDs then that battery isn't going to last long. :smile:
  • Mike GreenMike Green Posts: 23,101
    The Propeller chip, its EEPROM, and an SD card for file storage can all be run off a single CR2032 coin cell along with a small OLED display and 4x4 keypad. You could use 3 Propeller output pins to supply power to the SD card, display, and keypad so they could be switched off when not needed. The Propeller chip could spend much of the time asleep so it wouldn't draw much current.
  • jmgjmg Posts: 15,173
    Buck Rogers wrote: »
    Hello!
    Can the whole Prop setup, program storage and the Prop itself be configured to run on one of the reasonably easily available CR2032 batteries? Or despite being a 3.3v device inside it requires 5v outside it to work properly.

    I ask because I'm considering my first stand alone Prop project. Nothing serious or what, this is just for fun.

    This thread has good info on Voltage/Power possibilities :

    https://forums.parallax.com/discussion/129731/prop-limbo-how-low-power-voltage-can-it-go/p1
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2018-12-20 21:43
    You do have to manage power carefully, per the link jmg posted.

    Things like SD cards can draw a slug of current when they first power up, and also when they write data. A CR2032 simply can't supply that level of pulse current. It might be done with a large reservoir capacitor in parallel. The same thing applies for most wireless modules. Super capacitor in parallel with the battery. CR2025 capacity is around 200mAh, and it is 3.0 volts open circuit. To get full capacity out of it (assuming a single cell, not a series stack) you need to allow your circuit to operate down to 2.7 or 2.8 volts. The Prop's internal brownout detector triggers at 2.6 volts, so you'd better provide an external reset instead unless the load is going to be steady at microamp levels.

    A half AA thionyl chloride primary cell can provide more pulse current, and more leeway, at 3.6 volts nominal.
  • Buck RogersBuck Rogers Posts: 2,185
    Oh wow!
    Thank you all. That's a lot of stuff to consider. Tracy I certainly do remember that thread from several years earlier. It gave me a lot of ideas to consider. It took a while but oddly enough it arrived with my thread.

    However... I'm going to wait a bit longer before I continue with this idea. It is too <DELETED EXPLETIVE!> hard to accomplish properly with my talents. (Currently.)

    ---
    No sponsor.
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2018-12-21 17:18
    I certainly don't mean discourage you from trying it. It doesn't take much in the way of hardware to get it going to blink an LED. Target CR2032, 200mAh battery life @ 3.0V. one cog
    RCSLOW ~ 10µA, 20000 hours
    superbright red led flashed for 20ms once per second at 2mA on RCSLOW.
    [(0.01mA * 980ms) + (2mA * 20ms)] / 1000ms = 50 µA average current.
    CR2032 life ~ 200mAh / 0.05mA = 4000 hours.

    Continuous operation at higher speed, one cog...
    RCFAST (~12Mhz) ~ 2mA, 100 hours
    XTAL1 (5MHz running) ~ 1mA
    XTAL1+PLL2X (10 MHz running) ~ 2.4mA
  • TubularTubular Posts: 4,702
    Buck, what did you have in mind as a first project?

    Something Christmas related?

    Definitely have a go
  • Buck RogersBuck Rogers Posts: 2,185
    Something for fun.

    A time manipulator.
  • WhitWhit Posts: 4,191
    Buck Rogers wrote: »
    A time manipulator.

    I think for that, you'll need a flux capacitor. ;-)

  • msrobotsmsrobots Posts: 3,709
    Buck Rogers wrote: »
    Something for fun.

    A time manipulator.

    @"Buck Rogers",

    are you again confused about this whole summer and winter time mess?

    remember, 2 times a year, but you do not need to change the time, it is OK if you just change your clocks.

    Enjoy!

    Mike
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