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BS2 +5V on board regulator w/ BOE — Parallax Forums

BS2 +5V on board regulator w/ BOE

jsmasterkingjsmasterking Posts: 35
edited 2006-02-28 00:00 in BASIC Stamp
When using the Board of Education, does the +5V Regulator on the Basic Stamp 2 regulate the power for the PIC?

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Post Edited (jsmasterking) : 6/21/2006 12:44:47 PM GMT

Comments

  • Russ FergusonRuss Ferguson Posts: 206
    edited 2006-02-26 20:29
    The schematic for the BOE showes that the stamp socket pin 21 Vdd is only used to provide power for the RESET pin.

    Stamp socket pin 24 is connected to Vin and not to the 7805 5v out. The BOE Rev C schematic is on this page:

    http://www.parallax.com/dl/docs/prod/boards/BOERevC.pdf
    jsmasterking said...
    When using the Board of Education, does the +5V Regulator on the Basic Stamp 2 regulate the power for the PIC?

    So the answer is no, the BOE schematic showes that the 7805 5v regulator on the BOE is not·connected to any pin of·the STAMP socket.
  • allanlane5allanlane5 Posts: 3,815
    edited 2006-02-26 20:31
    No. The +5 volt regulator on the BOE board supplies power to the Vdd pin on the BS2. The +5 volt regulator on the BS2 module itself is a very clever one that allows you to use it two ways. In the 'normal' way you supply 5.5 to 24 volts to the 'Vin' pin, and it supplies +5 volts to the PIC and to the Vdd pin.

    In the 'other' way, you supply +5 volts to the Vdd pin directly, and the regulator does nothing, but without any damage to the regulator or impact to the Vdd line.

    P.S. oh, dear, and now the question has been answered both ways.· I'll go check the schematic.· Or you could wait until Jon or Chris weighs in with the authoritative Parallax answer.

    P.P.S and it looks like, from the schematic, that in fact the on-module regulator DOES provide power for the BS2 on the BOE, while the BOE-board regulator powers the rest of the circuitry.· Sorry about that.

    Post Edited (allanlane5) : 2/26/2006 8:37:36 PM GMT
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-02-26 20:32
    Russ,

    ·· I think his answer would be yes, since he mentions the regulator on the BASIC Stamp 2 not the BOE.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Russ FergusonRuss Ferguson Posts: 206
    edited 2006-02-26 21:19
    Thank you Chris:

    Correction: Yes, the +5V regulator on the Basic Stamp 2 module is used to regulate the power for the PIC.



    I have a related question -

    The 7805 appears to have·some builtin overcurrent protection at somewhere around 2 amp.

    Does the little regulator on the BS2 module have a similar overcurrent protection? Does it play a factor in protecting the pins when too much current is sourced?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-02-26 21:59
    Russ,

    ·· Most regulators, including the one on the BASIC Stamp are supposed to shut down when they are over-current or over-temp (thermal shutdown).· Of course in the real world this isn't always the case.· Certain circumstances cause some regulators to simply fail.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • allanlane5allanlane5 Posts: 3,815
    edited 2006-02-26 23:19
    And no, any thermal protection or over-current protection built in to the regulators don't protect the pins of the PIC. This is why you can burn out the pins of the pic. However, all it takes is a 220 ohm resistor in series with the PIC pin, and you can protect it yourself (at least from +5 volt signals).
  • Russ FergusonRuss Ferguson Posts: 206
    edited 2006-02-27 03:47
    Thank you for the feedback about the LM2936 regulator on the Stamp module.
  • jsmasterkingjsmasterking Posts: 35
    edited 2006-02-27 21:59
    What I was trying to·ask was:·Does the PIC on the BS2 receive power from the regulator on the BS2 or the regulator·on the BOE.

    If from the regulator on the BS2:·What does the regulator on the BOE do?
    If from the regulator on the BOE: What is the function of the on-board regulator?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    ·on····· plane··········································, when catching ducks

    "In this house, we obey the laws of thermodynamics!"
    ··············································································^
    http://profiles.yahoo.com/jsmasterking

    Post Edited (jsmasterking) : 6/21/2006 12:44:42 PM GMT
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-02-28 00:00
    Well your question was answered...The PIC chip is powered from the BASIC Stamp internal regulator.· The BOE regulator is for powering other devices since the regulator on the BASIC Stamp can only provide about 40mA.· So instead you should use the BOE regulator for powering LCD Displays, EEPROM chips, ADCs, RTCs, etc.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
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