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Best way to control 3v laser module using 5v stamp? — Parallax Forums

Best way to control 3v laser module using 5v stamp?

MorrolanMorrolan Posts: 98
edited 2009-11-02 17:48 in General Discussion
Hi,

I have a laser module rated at 3.1v (+-10%) that I want to be able to turn on from a Stamp. I know that there are several methods I can use like having a 3.3v rail and using a transistor, or even just using a voltage divider on the output pin, but what I would like to ask, is which method is the safest, simplest and best-practice?

Many Thanks in advance,
Morrolan

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Flying is simple. You just throw yourself at the ground and miss.

"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."
Stephen Hawking

Comments

  • James LongJames Long Posts: 1,181
    edited 2009-10-30 23:05
    Morrolan said...
    Hi,

    I have a laser module rated at 3.1v (+-10%) that I want to be able to turn on from a Stamp. I know that there are several methods I can use like having a 3.3v rail and using a transistor, or even just using a voltage divider on the output pin, but what I would like to ask, is which method is the safest, simplest and best-practice?

    Many Thanks in advance,
    Morrolan

    The safest method would be using a logic level mosfet tied to a 3.1 volt rail (3.3 is within specs). Also have a pull down resistor on the gate for the mosfet. You could also use an optoisolator, but I do think that is a little overkill.

    Any other way would be counting on the components to be within tolerance, or programming to be correct,which could toast the laser module.

    James L

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    James L
    Partner/Designer
    Lil Brother SMT Assembly Services

    Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
  • Mike GreenMike Green Posts: 23,101
    edited 2009-10-30 23:15
    Another safe solution is to use a 3.3V voltage regulator with a shutdown pin like the LT1129. You'd use a pulldown resistor (maybe 10K) that would be driven high by the Stamp to turn on the laser module.
  • James LongJames Long Posts: 1,181
    edited 2009-10-30 23:17
    Mike Green said...
    Another safe solution is to use a 3.3V voltage regulator with a shutdown pin like the LT1129. You'd use a pulldown resistor (maybe 10K) that would be driven high by the Stamp to turn on the laser module.

    That is a great idea, mainly because the part count has gone down at least one part.

    Good catch Mike.

    James L

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    James L
    Partner/Designer
    Lil Brother SMT Assembly Services

    Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
  • MorrolanMorrolan Posts: 98
    edited 2009-11-02 09:30
    Thanks Mike, sounds like a plan!

    Just to sum up - the Stamp pin would provide a 5v output to the 3.3v regulator which then obviously drops this to 3.3v (within module tolerance) which would then power the laser. The laser would be connected to GND via a 10k pulldown resistor.

    As the 5v output from the Stamp is 'clean' compared to say that from a battery, i assume that there will be no need to use caps to also provide a 'clean' 3.3v?

    Many thanks in advance,
    Morrolan

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Flying is simple. You just throw yourself at the ground and miss.

    "I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."
    Stephen Hawking
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-11-02 16:52
    Morrolan said...
    Just to sum up - the Stamp pin would provide a 5v output to the 3.3v regulator which then obviously drops this to 3.3v...
    You misinterpreted Mike's idea. The Vin rail of the reg would be tied directly to Vdd (i.e. +5V), not a Stamp pin. The Stamp would drive a separate enable pin on the regulator, which turns the regulator on and off. The 10K resistor is not attached to the laser but is used to pull the enable pin down, so that the laser won't be powered when the Stamp is in reset.

    -Phil
  • MorrolanMorrolan Posts: 98
    edited 2009-11-02 17:48
    Ahhh now it makes sense, I haven't come across a regulator with an enable/shutdown pin like that before.

    Thanks for the ideas, now to find somewhere that will sell them in the UK!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Flying is simple. You just throw yourself at the ground and miss.

    "I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."
    Stephen Hawking
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