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Powering a Stamp via USB — Parallax Forums

Powering a Stamp via USB

Steve JoblinSteve Joblin Posts: 784
edited 2006-09-29 15:45 in BASIC Stamp
Is it possible to power a Stamp from a USB Port?· If so, how would I do it?· Can I tap off from my USB2SER?

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-09-29 00:28
    Steve,
    ·
    ·· While it is technically possible, getting to the power could prove interesting, not to mention the care you would have to take to not exceed the maximum current draw from the USB Port.· For starters, the USB2SER is running at 3.3V unless the power was picked right at the USB connector.· Second, for a standard BASIC Stamp the USB2SER cannot be used to program it since the USB2SER outputs are TTL, while the BASIC Stamp Modules are RS-232 input.
    ·
    ·· Using a device such as USB2SER to pick power off will only provide you with a total maximum draw of 100 mA off the port.· This includes the BASIC Stamp and anything else you’re powering on the same circuit.· It also includes the current draw of anything connected to the I/O pins, such as LEDs or even transistors.· I hope this helps.· Take care.

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    Chris Savage
    Parallax Tech Support
  • NewzedNewzed Posts: 2,503
    edited 2006-09-29 11:49
    I have designed and built a Stamp board that is powered from a USB·port and programmed via the standard DB9 serial port.· Works quite well.

    Sid

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    Sid Weaver
    Need a TV Module?

    Newzed@aol.com
    ·
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-09-29 15:19
    Sid,
    ·
    ·· I would recommend anyone that was going to make a BASIC Stamp Board powered by USB to use the FTDI Chip so they could program through the same port without having to have multiple cables to the PC.· The FTDI Chips add Virtual COM Port connectivity to your board and the new FT232R makes it even easier with almost no external parts.

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    Chris Savage
    Parallax Tech Support
  • NewzedNewzed Posts: 2,503
    edited 2006-09-29 15:25
    Chris, if I ever redesign the board I will do that.· When I started designing the prototype, I thought about the beginner who might get confused with the FTDI routine.· That's why I made it USB powered, serial programmed.

    Sid

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    Sid Weaver
    Need a TV Module?

    Newzed@aol.com
    ·
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-09-29 15:45
    Sid,
    ·
    ·· To the PC and BASIC Stamp, the FTDI is a Serial Port.· Neither side knows any difference.· There is no special programming required on the BASIC Stamp or the PC side.· You only need to have the USB Driver installed on the PC side, which many people now have.· We have several example schematics available for how to created such an interface, and if one were so inclined, by using surface mount components you could create a stand-alone board using OEM components which would significantly reduce the cost of the whole thing.· Take care.

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    Chris Savage
    Parallax Tech Support
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