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looking for a dc to dc power supply and how do I know the max current? — Parallax Forums

looking for a dc to dc power supply and how do I know the max current?

LudisLudis Posts: 69
in Accessories

Hello,

For my project, I require 3.3 V (for the P1 and segment LEDs) and 5V for Pixel LEDs in the same package.

I think I need a 12V DC to DC converter with 2 outputs (3.3 and 5V DC). I think 4-5 Amps are needed but not completely sure.

I'm looking for something similar to Parallax part 32133. Ideally the converter would have a 2.1mm input jack and output both 3.3 and 5V. The size would be small. I'm making an LED a wall clock. Is this what I should be using OR should I be using something else? Should I build a similar circuit that is on the Propeller Professional Development Board (32111)?

Can someone help me figure out what the max current is?
1x50 piece pixel lights that come with Parallax part 64030. Label says 5Vdc/0.3W. I'm assuming that means per pixel.
10 x KWA-541CPGB LED segments.
1x RTC DS233 that comes with Parallax kit 64030.
1xP1 at 80MHz

Thanks

Comments

  • MicksterMickster Posts: 2,698

    I have used the ATX 200W Pico PSU on several projects.

    Aliexpress, Ebay, etc.

  • LudisLudis Posts: 69

    ok thanks! I'll look into that

  • DigitalBobDigitalBob Posts: 1,513

    The 5V 0.3 watt should be 60 Ma. And the P1 total current out all pins is 300 Ma.

  • DigitalBobDigitalBob Posts: 1,513

    Led segments can suck some juice, So 25 Ma. per segement X 14 segments X 10 , like 3500 Ma. , I think 5 amps should do ya.

  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2021-03-20 09:41

    P1 current "absolute maximums" quoted from the datasheet have nothing at all to do with typical operating currents or usage. Rarely would the P1 ever go beyond 100ma and it is easy to use an LDO linear regulator from 5V to 3.3V which is what I do even in my industrial projects. There are plenty of 7805 style 3-pin regulators that can do this (switch down to 5V) as a small component, no need for modules. You can even use two of these, one for the pixel strips and another for the segments.

  • LudisLudis Posts: 69
    edited 2021-03-24 01:25

    @DigitalBob said:
    Led segments can suck some juice, So 25 Ma. per segement X 14 segments X 10 , like 3500 Ma. , I think 5 amps should do ya.

    OK nice! thanks. I wasn't sure if the pixel LED was per pixel or total (all 50). If I powered on multiple pixels at full brightness with white (red blue and green full) my P1 would shutdown. My power adaptor that i'm currently using on my Propeller Professional Development Board is a 1amp adjustable radioshack 3-12 volts DC. I prefer to talk in the maximums knowing they may not be reached. Like a safety factor!

  • LudisLudis Posts: 69
    edited 2021-03-24 02:00

    @"Peter Jakacki" said:
    P1 current "absolute maximums" quoted from the datasheet have nothing at all to do with typical operating currents or usage. Rarely would the P1 ever go beyond 100ma and it is easy to use an LDO linear regulator from 5V to 3.3V which is what I do even in my industrial projects. There are plenty of 7805 style 3-pin regulators that can do this (switch down to 5V) as a small component, no need for modules. You can even use two of these, one for the pixel strips and another for the segments.

    OK great. Good idea to use a regulator for the pixel strip and another for segments displays. I found a 7805CT for 1A. Do you think the LM1084 would work? adjustable to 5 and 3.3 V with 5A.

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