lm317circuit help

Discussion in 'The Projects Forum' started by coboda, Feb 26, 2014.

  1. coboda

    Thread Starter New Member

    Feb 19, 2014
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    I got 2 lm317 circuits both adjusted to output 2.78 volts they're powered from a single 5v usb adapter my goal is to power two wiimotes simultaneously from the same power source. when i check the circuits with a multimeter i get 5.2v input and 2.78 output on both circuits but when i plug both wiimotes in and turn them on they only power on for a few seconds then the led indicator light on the circuit goes dim and both wiimotes turn off. i wait a few seconds and the ligt gets bright again. i'm guessing i need to install an amp some where on the circuit but i dont know how to go about doing this and i have limited space on my perfboard.

    [​IMG]
     
  2. antonv

    Member

    Nov 27, 2012
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    How much current do the WIImotes take? Do the regulators get hot?
     
  3. coboda

    Thread Starter New Member

    Feb 19, 2014
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    2.5 - 3v and 15-35Ma and the regulators stay cool
     
  4. antonv

    Member

    Nov 27, 2012
    149
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    Could you post a schematic of the regulator circuits?
     
  5. coboda

    Thread Starter New Member

    Feb 19, 2014
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  6. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Have you tried monitoring the input and output voltages during the startup/shutdown or just made static readings?
     
  7. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
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    My guess would to much current draw ...
    Why don't you use a different voltage regulator and instead of running a dual voltage regs ,only use one and tap off the output ??
    Also the lm317 need atleast 10ma each..
     
    Last edited: Feb 27, 2014
  8. antonv

    Member

    Nov 27, 2012
    149
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    If your currents are accurate then they are not the problem and I think you easily meet the regulators' minimum current.

    How about the quality of your solder joints?
     
  9. Farfugnugin

    New Member

    Feb 18, 2014
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    0
    Your schematic looks pretty bone standard imo, so barring a bad regulator i wouldn't personally expect there to be any problems at all with the design. Based on what you describe, and more importantly that fact that your indicator led is before the lm317's, i would guess that the problem is actually in whatever supply you are using to power it with.

    You say you are drawing 35 mA per regulator output, your also going to have 5 or 6 mA being pulled down by the sense resistors on each regulator, then some exess power dissipating by voltage drop across the regulators, and another 15 mA or so burned off by the LED, so your probably drawing overall around [speculation] 110 or so mA overall. If this circuit is being power by a standard computer USB port, from what i've read, its not uncommon for certain ports to be limited to 150mA or so MAX, so you may just be close to the limit of current draw from your power source. Either that or the transient response of your power source is too slow, the current spike when you turn stuff on and it takes a second for the source's regulator to catch up. Try using a different port (i think current limit depends on port? someone correct me if im wrong) as some ports on a motherboard will have a cap of 500mA. Or maybe try a USB phone charger?

    Best bet would be to put a meter on the input lines (better still a scope if you have one) and see if theres a voltage drop when you make your connections. Should at least narrow it down.

    BTW: awesome choice for a project enclosure ;)
     
    Last edited: Mar 1, 2014
  10. coboda

    Thread Starter New Member

    Feb 19, 2014
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    I was actually running it from a 5v Lg cellphone usb charger that was plugged into a 120 house line. but now instead of splitting the line i ran both circuits to there own 5v chargers boxes. I got 2 usb male plugs hanging out the nes controller now kind of a sausage fest but i needed to get a working model. it works fine no problems so far but I definitely still wanna get it working of one power source. I got like 50 different voltage regulators in my inventory I can try but I haven't researched them yet I not hip to their specs
     
  11. coboda

    Thread Starter New Member

    Feb 19, 2014
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    What would you recommend I have a ton of different regulators i've pulled off boards im not hip to their specs though. I probably got at least 50 different types
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    There are hundreds upon thousands of regulator IC's out there. It would be much easier if you simply created a list of what you have available, and post it.

    However, I suggest that you try using a 100uF to a 10,000uF cap on the input side, and a 10uF on each regulator output, and see if this affects a change.
     
  13. daviddeakin

    Active Member

    Aug 6, 2009
    207
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    That leaves only 2.42V across the regulator, which is close to the drop-out voltage of an LM317, especially if the input voltage sags under load. Perhaps you need a low drop out regulator instead?
     
  14. coboda

    Thread Starter New Member

    Feb 19, 2014
    14
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    here's a list of regulators it's not the complete list of what I have but if none of these will work ill go de-solder some more

    LA6500 3v6
    4236 d5lc20u
    KIA 7805A
    D882
    KIA 7808A
    STV9375 842334Z
    A2005
    3601 K2251
    C5511
    02688
    0138 D1c504M
    2636 D5LC20U
    C5682 3f4
    SE140 3611N
    KIA 7812A
    LA6500 3v0
    K2876
    C4632
    79M12A JRC M303fG
    LA6500 3v7


    I haven't tried your suggestion with the capacitors yet because I dont have any available but if i cant get any regulators to work im make a run to radioshack
     
  15. coboda

    Thread Starter New Member

    Feb 19, 2014
    14
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    I tweaked my design a tad I'm know trying to power 4 wiimotes. I'm getting a 2.78v reading on all four outputs but I can still only power one wiimote at a time and the regulator get ver hot if i plug in more then one remote hmmmmm....
     
  16. coboda

    Thread Starter New Member

    Feb 19, 2014
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    here's the schematic of the new circuit. https://scontent-b-ord.xx.fbcdn.net/hphotos-ash3/t1.0-9/1010112_1431088443796100_1129035960_n.jpg

    when I have two wiimotes connected i'm getting a steady 3.08v on all four outputs but randomly when I'm turning them on and off or plugging and unpluging/ switching ports I'll hear this sound like a dog whistle and my voltage drops below 0.5v and the regulator gets super hot.

    i was thinking there might be short somewhere but everything looks good on that end. any thoughts?
     
  17. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    You may have a bad capacitor or one connected backwards.
     
  18. coboda

    Thread Starter New Member

    Feb 19, 2014
    14
    0
    Well I got the circuit working working 100% it's been in operation for 3 days with no problems I made some changes though I have 5v going to two usb outputs and to lm317 adjusted to 3.13v going to two usb outputs. the 3v powers two wiimotes and 5v powers sensor bar and 3 leds in my arcade buttons which are wired to a keyboard pcb [​IMG]
     
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