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How to get 7.27VDC from 3VDC — Parallax Forums

How to get 7.27VDC from 3VDC

T ChapT Chap Posts: 4,223
edited 2012-04-23 19:40 in General Discussion
I was trying to see how a remote lighting flash device works, which runs off two 1.5V batteries. I noticed that for the flash output, it has a fixed 7.27VDC output that goes low for 50us for the trigger. There are two other outputs that vary from 0 to 3.88VDC. I looked up voltage multipliers and see that they are mostly AC versions. Just out of curiosity, how do you think they are doing this?

Comments

  • T ChapT Chap Posts: 4,223
    edited 2012-04-20 19:22
    I haven't look at the board yet to see what they are doing, but maybe this is the trick:

    http://datasheets.maxim-ic.com/en/ds/MAX606-MAX607.pdf
    These devices operate from a 3V to 5.5V input and provide
    a ±4% accurate output that is preset to 5V or 12V,
    or adjustable from VIN to 12.5V. They can provide up to
    180mA of output current at 5V.
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2012-04-20 20:52
    Yes, they're boost switching regulators. I don't like bread boarding switching regulators, so I usually just get a canned solution like this one from Pololu:

    http://www.pololu.com/catalog/product/799

    This thing is REALLY tiny. Wear some +4 diopter reading glasses when working with it!

    -- Gordon
  • T ChapT Chap Posts: 4,223
    edited 2012-04-20 21:00
    Good call! Thanks.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-04-21 17:43
    GordonMcComb wrote: »
    ...
    This thing is REALLY tiny. ...

    Gordon, thank you for linking to this! I was trying to solve a problem today and this little gadget looks like it is exactly what I need.

    Since you seem in the business of answering prayers today, about that Jag I keep asking for....
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2012-04-21 21:26
    ElectricAye wrote: »
    Since you seem in the business of answering prayers today, about that Jag I keep asking for....

    After I get mine!

    FYI, tomorrow's pot luck will be deviled eggs. I just have to remember to put them back into the refrigerator from when I made them yesterday.

    Below are very much like the two cars the family had when I was growing up. Not that I ever got to drive them. We had a '64 E-Type, and a '57 Mark III. My stepfather was a true piece of work, but he had good taste in cars. And I had my first taste of Lucas electrical systems!

    -- Gordon
    250px-SeriesoneJag.jpg
    250 x 107 - 13K
    250px-Jaguar_Mark_VIII_in_Hertfordshire.jpg
    250 x 150 - 14K
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-04-21 21:40
    GordonMcComb wrote: »
    ...

    Below are very much like the two cars the family had when I was growing up....

    Groovy, man, sure beats what I was hauled around in.

    hippie-bus.jpg
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2012-04-21 21:47
    We had a beat up red '67 Econoline that I was allowed to drive. You'd think a 17 year old being able to drive his dates around in a van would be a cool thing. And it might have been, except for the carpet cleaning supplies that were in the back. For some reason that put a damper on things.

    -- Gordon
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-04-22 07:01
    GordonMcComb wrote: »
    .....except for the carpet cleaning supplies that were in the back. ...

    Ah, but such supplies could have provided the perfect segue to more happy times, a kind of roving subliminal suggestion machine on wheels.

    8528300040.jpg
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2012-04-23 18:37
    ElectricAye wrote: »
    Gordon, thank you for linking to this! I was trying to solve a problem today and this little gadget looks like it is exactly what I need.

    Since you seem in the business of answering prayers today, about that Jag I keep asking for....

    I have been looking for some boost switching regulators boards for some time .....> also I ordered some to try out Thanks for the link
  • frank freedmanfrank freedman Posts: 1,983
    edited 2012-04-23 18:58
    ElectricAye wrote: »
    Ah, but such supplies could have provided the perfect segue to more happy times, a kind of roving subliminal suggestion machine on wheels.

    8528300040.jpg

    Perhaps a bit more subliminal than say just buying a date her first vacuum cleaner......
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2012-04-23 19:40
    I've forgotten what this thread was about...

    Anyway, I'm glad the Pololu link was helpful. The boost is the kind of product I wish Parallax stocked. That and a small level-shifting module. The one that SparkFun makes and sells is smaller and cheaper than anything I could build -- and it handles up to four bidirectional I/O lines. Sometimes series resistors just don't cut it.

    On setting up the boost board: take note of the warning Pololu provides on their site regarding adjusting the voltage. There are many cautions and considerations, but they're common for switching boost regulators. I recommend using a plastic trimmer screwdriver rather than metal so there are no capacitive effects. Adjust slowly, periodically removing the screwdriver so that pressure on the pot doesn't affect its setting.

    Take note they also have a version with a lower range:

    http://www.pololu.com/catalog/product/791

    as well as a much less expensive fixed voltage model if you're wanting 5V output:

    http://www.pololu.com/catalog/product/798

    -- Gordon
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