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Batteries & Chargers

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by AtomSoft, Aug 4, 2008.

  1. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    A quick look at that link says its a 2 cell charger about 2.8V.?

    You say you have 6 cells at 1.2V, you need a 8.4V charger.????
    at about 0.2C say about 400 to 500mA.
     
    Last edited: Aug 8, 2008
  2. AtomSoft

    AtomSoft Well-Known Member

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    i mentioned i owned 6 batteries i can use lol

    If lets say i wanted the project to last minimum of 6-8 hours on a charge Would 5 batteries do it?

    5 x 1.2v = 6v @ 2500 mAh

    If im using about 170 mA (if BL isnt auto)
    2500 / 171 = 14.61xx (14 Hours)

    If i make a auto back like turn on, on interrupt that would make it 71mA total when off
    2500 / 71 = 35 Hours

    would that be correct?

    Now i would need a 6v charger
     
  3. AtomSoft

    AtomSoft Well-Known Member

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    If i follow my charger datasheet. It says i think:

    2 AA @ 2.8v (360mA) +/- 10%

    so 4 would be double?
    4 AA @ 5.6v (720mA) +/- 10% ? Doesnt seem right or is it?

    If anything i would make 2 separate chargers in 1. Like when connected to charger a PNP will OPEN the circuit leaving 2 AA & 2 AA not connected also a PNP wil open circuit to main power and will power device until unit is removed and power is restore battery wise. Does that malke any sense?
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    The sums look OK to me, looking at the discharge graph of your cells, assuming good fully charged cells,
    whats the cell voltage after 8 hours at both discharge currents [ with/without LED B/L]

    Looking at the graph it looks flat at 1.2V for most of the 0.2C rate.

    Next step would be to run the project for 8 hours, from fully charged, note the voltage
    then keep the test going until the cells goto 1.1v [ 5.5V]

    Type of Vreg, it must be LVDO +5V rated at least 250mA
    You can get LVDO's with a 0.45V drop out.



    Do you follow OK.?:)

    EDIT: I would estimate 12 hours with the B/L ON and about 24 hours with it OFF.
     
    Last edited: Aug 8, 2008
  6. AtomSoft

    AtomSoft Well-Known Member

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    im loving those estimates lol. I have to reread the post but the first thing about the graph is confusing can you rewrite the question please. Um i would have to order the LVDOs but will they have same pinout as the 7805? (im sure they are smaller form factor) Or are they 220 case? Any links to some?
     
  7. Hero999

    Hero999 Banned

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    What's value filter capacitor and the input voltage to this power supply?

    The filter capacitor looks too small.
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi atom,

    Look at these two options.
    http://www.maplin.co.uk/module.aspx?ModuleNo=46323&doy=9m8
    http://www.maplin.co.uk/module.aspx?ModuleNo=46321&doy=9m8

    The 10/12R resistor for the LED B/L could go before the Vreg if you use the 150mA version or after the Vreg if you use the 1Amp version.

    I would connect the B/L before the Vreg.
     
    Last edited: Aug 8, 2008
  9. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi atom,
    Some circuits to consider.

    Cct1 is a 150mA LVDO +5Vreg, with the B/L connection before the Vreg, push button for the B/L

    Cct1 is a 1Amp LVDO +5Vreg, B/L on the +5V line, push button for the B/L

    Cct3 is using the B/L LED's and an extra diode as a shunt regulator, giving a +4.6Vnom for the PIC logic, B/L must always be connected... its the el-cheapo version.:)
     

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    Last edited: Aug 9, 2008
  10. Hero999

    Hero999 Banned

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    No as they're connected in series the current wouldn't be double, it'd be the same.
     
  11. AtomSoft

    AtomSoft Well-Known Member

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    Thanks for tha Hero999 I had a feeling :D

    Ericgibbs:
    i think i would use the 1amp mostly because i know i will be adding things to this like at least:
    1 LED
    1 IR LED (Maybe some zigbee wireless)

    and maybe something else
     
  12. AtomSoft

    AtomSoft Well-Known Member

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    Last edited: Aug 9, 2008
  13. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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  14. AtomSoft

    AtomSoft Well-Known Member

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    This is going to be the transmitter really. I want to be able to send commands to a main module like. This will be a wireless transmitter. And the main will be anywhere from 25-80 ft away. I will be sending just like IR a device code and a command. But i dont want to use IR. I want another wireless solution.

    So if i press PC button and press 1 key i want it so send

    00010001 = pc
    00000001 = 0x01

    So the data sent would be:
    00010001 00000001

    I might make it single byte like

    0001 = PC (HIGH nybble)
    0001 = 0x01 (LOW nybble)

    so 00010001 would be PC and Key #1

    But the single byte leaves me with a limit of 15 devices and 15 commands. Which is actually enough. So 1 byte it is! lol :D
     
    Last edited: Aug 9, 2008
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi atom,
    Looking at the sparkfun pair, if you are using PIC's for the master and remote stations, have you considered using ascii and the UART for the commands.?
     
  16. AtomSoft

    AtomSoft Well-Known Member

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    actually, i was thinking about it. Either hardware or software UART should work right. I was thinking about XBEE but though it would be a overkill.
     
  17. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    You realise you wont need drivers eg: MAX232's at the PICs.

    If the carrier is going to be switched OFF between transmissions, it may require a short sync preamble, before the actual data.
     
  18. AtomSoft

    AtomSoft Well-Known Member

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    will switching it off actually save me much power? Remember if its lasing 12 hours on a charge now i dont mind loosing a few hours by leaving it on. My goal was for a 8hr up time.
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Looking at the datasheet the TX is 20mA at 5V and the RX 2 to 3 mA at 5V
    Thats not a lot.
     
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    If you're using plain licence free modules, you should use Manchester coding (or similar), just sending plain RS232 doesn't work for various reasons - check my tutorial.
     
  21. AtomSoft

    AtomSoft Well-Known Member

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    so ill leave it on most likely. Just to save on coding :D

    Just got my dipmicro order in . Mostly LEDs and 2 proto boards (not for this project) some 20mhz crystals and 18F448 and Some Toner Transfer. (lol now i need printer)

    Took about 9 days to get here (i ordered on Aug 1) Also i ordered from futurlec and nothing yet.

    EDIT

    I will check nigel ... Thanks
     
    Last edited: Aug 9, 2008

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