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Running Propeller off LiPo or LiIon? — Parallax Forums

Running Propeller off LiPo or LiIon?

groggorygroggory Posts: 205
edited 2012-02-18 04:12 in Propeller 1
I am thinking of running a propeller directly off a lipo or liion cell...no voltage regulator.

What are the ramifications of this? I imagine the propeller will use a bit more power when running at say... 4.2V instead of the specified 3.3V.

I'm not sure what the VIN max of the propeller is. I know that 5V will do bad things to the prop, but I don't know about this middle ground.

Please educate me.

Thank you.

Comments

  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-02-17 12:17
    I think I remember hearing about props being damaged at 3.9v, but I'm not sure. Remember that current draw is the square of voltage, so you'll actually have less battery draw if you use an LDO such as an XC6221.
  • RaymanRayman Posts: 14,845
    edited 2012-02-17 12:17
    Datasheet says 4.0 V absolute max. I don't think I'd run over that...

    Why not use an LDO regulator? I don't think you'd save any power by not using a regulator...
  • Dave HeinDave Hein Posts: 6,347
    edited 2012-02-17 12:23
    Rayman wrote: »
    Datasheet says 4.0 V absolute max. I don't think I'd run over that...
    The data sheet also says that the supply voltage range is 2.7 to 3.6 volts. I suppose a voltage between 3.6 and 4 volts won't kill it, but it's not spec'ed to run above 3.6.
  • LeonLeon Posts: 7,620
    edited 2012-02-17 12:29
    If you want to run without a regulator, use a couple of AA cells. I often do that with other MCUs with similar power requirements.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-02-17 13:05
    Lithium primary cells are 3V. A single CR123, for example, can provide 1.5 Ah of service.

    -Phil
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-02-17 13:33
    I did run aProp at 4.2 Volts for a short while when I was toying with the idea of planting the supply volts centrally beween 3.3 Volts and the 5 Volts of a Z80. Nothing untowards seemed to happen but then i wasn't running anything demanding on the Prop. A diode would drop the 4.2 Volts back to 3.5 (ish) volts or a LDO would be better if one can be found that doesn't spike its quiesant current up as it approaches minimal input/output voltage difference. The specs are there to tell what is, and is not, intended opperating areas - everything else if your own fault.

    I can state with absolute certainty that 9 Volts is too high ...
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-02-17 15:05
    Toby Seckshund wrote: »
    ... or an LDO would be better if one can be found that doesn't spike its quiescent current up as it approaches minimal input/output voltage difference.
    Did you check the XC6221 datasheet?
  • Mark_TMark_T Posts: 1,981
    edited 2012-02-17 15:49
    Dave Hein wrote: »
    The data sheet also says that the supply voltage range is 2.7 to 3.6 volts. I suppose a voltage between 3.6 and 4 volts won't kill it, but it's not spec'ed to run above 3.6.
    LiFePO4 (lithium iron phosphate) batteries are about 3.3V, and much more fire-safe than other lithium rechargeables, and are only supposed to be charged to a max of 3.6V anyway, so I think they're a good match to 3V3 circuitry. CR123 sized cells aren't too pricey on ebay either.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-02-18 04:12
    @ Circuitsoft

    That reg certainly seems to have sorted out the current spike that a lot of the older ones had.

    I can just about hold focus on that size of packaging too!
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