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Moving Project to Custom PCB... — Parallax Forums

Moving Project to Custom PCB...

dannyboyfldannyboyfl Posts: 4
edited 2013-05-01 18:16 in Propeller 1
I'm trying to work out my power details for my project....

How much power do I need to supply the propeller chip? I'm using 4 cogs and sending PWM to 3 devices.

3.3V and how many ???mAs


Thanks for any help!
dan.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2013-04-30 09:04
    There are graphs in the Propeller datasheet that give the current drain under various conditions. There's a certain amount of current used by the hub logic, then each active cog uses a certain amount of current. This varies with the temperature and system clock speed. Each output pin takes additional current that depends on what's connected to it including the capacitance of the device and the connecting wires (the Prop has to charge that capacitance).

    At 80MHz, 4 active cogs and 4 idle cogs plus the hub will draw about 50mA with nothing connected to the I/O pins and "room temperature" (25C) operating conditions. Plan ahead for additional needs. I'd probably use a regulator that can supply 100mA, just in case I might need it in the future.
  • dannyboyfldannyboyfl Posts: 4
    edited 2013-04-30 09:24
    That's very helpful! Thanks Mr. Mike for the info and fast replay!
  • JonnyMacJonnyMac Posts: 9,107
    edited 2013-04-30 15:52
    You'll never hurt yourself having a regulator that will supply more current than you need -- unless it becomes a serious cost thing. Most of my projects use this 3.3v regulator

    -- http://www.digikey.com/product-detail/en/LM2937IMP-3.3/LM2937IMP-3.3CT-ND/3701578

    It's good for 400mA which provides lots of overhead to run all the cogs and drive IO pins as I might need.
  • skylightskylight Posts: 1,915
    edited 2013-05-01 07:28
    For my project I supplied battery power using fresh batteries at the working voltage and just took a current reading with a multimeter I presume this is an accurate way of working out total current?
  • kwinnkwinn Posts: 8,697
    edited 2013-05-01 18:16
    skylight wrote: »
    For my project I supplied battery power using fresh batteries at the working voltage and just took a current reading with a multimeter I presume this is an accurate way of working out total current?

    Should be if it was running all the software and I/O devices it would power in actual use.
  • kwinnkwinn Posts: 8,697
    edited 2013-05-01 18:16
    skylight wrote: »
    For my project I supplied battery power using fresh batteries at the working voltage and just took a current reading with a multimeter I presume this is an accurate way of working out total current?

    Should be if it was running all the software and I/O devices it would power in actual use.
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