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  1. #11
    Quote Originally Posted by m_c View Post
    I normally include an electrolytic cap on the output of linear regulators, then add a ceramic near the input of anything that may be affected by noise.

    Although things may work without caps on the linear regs, it's not good practise. Lots of linear regulators specify minimum capacitence on the output lines in their datasheets.
    Hi MC , I'm more than happy to take your advice on this, what should I include and where .. Remember I'm a total Noob and I'm just following someone schematic. I have some CFR50 carbon film resistor,10K 0.5W will these do ?

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  2. #12
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing BUILD LOG: 3 Axis CNC router Has been a member for 9-10 years. Has a total post count of 1,833. Received thanks 192 times, giving thanks to others 5 times.
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    Last edited by m_c; 20-05-2014 at 10:48 PM.

  3. #13
    Quote Originally Posted by m_c View Post
    Capacitors aren't resistors ;)

    I usually go for 220uF electrolytics of a suitable volatge for throughole linear regulators, but that's probably overkill.
    I'll check some datasheets later to see what you can get away with.
    Thanks MC very much appreciated, I’d like to think of this project as evolving so adding things to make it better is exactly right

    I have some 220 uF 25v Low ESR 8mm dia x 15 mm high 3.5 mm LS ( UPW1E221MPD) from a project also some Panasonic small-form but not sure what stats
    Last edited by Fivetide; 11-05-2013 at 10:28 PM.

    Fiction is far more plausible when wrapped around a thread of truth

    Nothing great was ever achieved without enthusiasm.
    Ralph Waldo Emerson

  4. #14
    Quote Originally Posted by Fivetide View Post
    Thanks MC very much appreciated, I’d like to think of this project as evolving so adding things to make it better is exactly right

    I have some 220 uF 25v Low ESR 8mm dia x 15 mm high 3.5 mm LS ( UPW1E221MPD) from a project also some Panasonic small-form but not sure what stats
    They would be fine - you don't need anything special like low ESR, but no problem using them. Still need ceramic capacitors on the input.

    What voltage are you supplying to the 5V regulators and at what current?
    Last edited by Jonathan; 11-05-2013 at 10:38 PM.
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  5. #15
    Quote Originally Posted by Jonathan View Post
    They would be fine - you don't need anything special like low ESR, but no problem using them. Still need ceramic capacitors on the input.

    What voltage are you supplying to the 5V regulators and at what current?
    The idea is to drop 7.2 v to a 5 v 1 amp and the other is 7.2 to 5 v 1.5 amp...the first feeds the raspberry pi the 2nd a USB hub

    Fiction is far more plausible when wrapped around a thread of truth

    Nothing great was ever achieved without enthusiasm.
    Ralph Waldo Emerson

  6. #16
    Ok, so you have (7.2-5)*1.5=3.3W dissipated by the regulator... you'll need a heatsink on that. The datasheet for your regulator (link?) should specify the junction to case thermal resistance which you can use to find the required size of heatsink, which may well require making more room on the circuit board.
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  7. #17
    What Ian said is that the regulator has a low thermal output , I donít know Reg one

    Fiction is far more plausible when wrapped around a thread of truth

    Nothing great was ever achieved without enthusiasm.
    Ralph Waldo Emerson

  8. #18
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing BUILD LOG: 3 Axis CNC router Has been a member for 9-10 years. Has a total post count of 1,833. Received thanks 192 times, giving thanks to others 5 times.
    justanothefpissedoffuser
    Last edited by m_c; 20-05-2014 at 10:48 PM.

  9. #19
    Oh so they're switching, not linear, regulators - disregard what I said about the power dissipation then as that's irrelevant. I'd still use some small capacitors though.

    You're pushing your luck asking for 1.5A from a regulator rated for 1.0A.
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  10. #20
    Quote Originally Posted by Jonathan View Post
    Oh so they're switching, not linear, regulators - disregard what I said about the power dissipation then as that's irrelevant. I'd still use some small capacitors though.

    You're pushing your luck asking for 1.5A from a regulator rated for 1.0A.
    Hi Jonathan, yes there are 2 regulators R-785 0-1.0 and R-78B5.0-1.5 the 1 amp is for the Raspi and the 1.5 is for the USB the 1.0 amp has 2 output 2 pin Molex’s, one powers the Pi itself and the other powers Independantly RC-servo controller board for Raspberry PI Version 3

    Click image for larger version. 

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