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Current on 5v Vdd Basic Stamp I Rev Dx — Parallax Forums

Current on 5v Vdd Basic Stamp I Rev Dx

DonivanDonivan Posts: 23
edited 2006-05-07 19:05 in BASIC Stamp
How much current does the Basic Stamp I Rev Dx board have available to outside components on its Vdd pin? I want to use this for a 5v Relay (about 90 ma) but can't find the specs of the on-board 5v voltage regulator.

Thanks,
Donivan

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-07 18:52
    Donivan,

    ·· 90mA is definately too much.· Always try to use an external power supply to power devices like that.· Especially inductive devices.· Have the BASIC Stamp drive them through something like a transistor, not directly.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-05-07 18:53
    That's too much -- you should use an external regulator (always a good idea). I would also suggest driving the relay through a transistor for some isolation and make sure you put a backlash diode across the coil.

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    Jon Williams
    Applications Engineer, Parallax
  • DonivanDonivan Posts: 23
    edited 2006-05-07 18:58
    I'm driving the relay through a Darlington array chip (ULN2803) which I think provides protection for said relay. I'll power the relay though some exernal power.

    Thanks!

    P.S. Do you know how much I can actually draw from Vdd without it being a problem?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-07 19:05
    Donivan,

    ·· This is a quote from our website knowledge base.

    How much current can the BASIC Stamp microcontroller’s on-board regulator provide?

    The built in 5-volt regulator on the BASIC Stamp 1 module and BASIC Stamp 2 module can supply 50mA of current if powered by a 12-volt source. The BASIC Stamp 1 module consumes 1mA leaving 49mA available to power external devices not including any devices connected to the I/O pins.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
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