5v Pin Barely Showing 1v

Discussion in 'The Projects Forum' started by cousintroy, Aug 31, 2017.

  1. cousintroy

    Thread Starter New Member

    Aug 31, 2017
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    Hello all,

    I am glad I came across this site as I am a 37 year old learning how to soldering and work with electronics and have taught myself up to this point. I have no real support from anyone around me that can help me/mentor me so I have had to go to magazines, Youtube, and other sites to learn about soldering, electronics, power, etc. And, for the most part, I have done pretty good at figuring things out when they don't work. However, the latest issue I am stuck on and believe I may know the issue but I am not 100% so that is why I searched for a site like this.

    I did a search here but, since I am definitely new to this field, I wasn't sure what to look for. I am starting off by building a racing drone and I have two PCB boards connected to each other via gnd/5v pins. One board connects to a LiPo battery and then provides the 5v power to the other board. The other board is where the issue is. It powers up correctly as I am able to power and run my four motors via a 6-pin, three row connectors but I have another row where I have soldered a 6-pin, single-row connector to the board. On this row, I am to connect a receiver to three pins, one gnd, one 5v, and one sbus.

    When connected to the 5v/gnd pins...the receiver doesn't power. I have verified the receiver works as I have connected it to the 5v/gnd that powers the board and it works just fine. I have connected my multimeter to the two pins and see it register barely 1v (again...new so I could be reading this wrong). One thing I remember when I soldered this row is that I got the gnd pin too hot and somehow managed to push the pin to where it sits lower than the other pins (I.E. pushed it through the plastic casing and it hangs more through the bottom than the top). My solder joint looks good as it is the shape of a volcano on both the gnd and 5v.

    What I am wondering is why I am not getting 5v out of these pins? Did I push the pin too far in and its not making a good connection with the cable (I believe its called a DuPont connector), could something be wrong with the board, could my soldering joints still not be that good?

    Any help would be appreciated! Although I have this problem, I am loving working on electronics and wished I started at a younger age!

    Troy
     
  2. MrChips

    Moderator

    Oct 2, 2009
    16,900
    5,210
    Troy, welcome to AAC Forum. I trust that your membership here will be a rewarding and enjoyable experience.

    It is difficult to imagine what could have gone wrong, not being able to actually see your physical setup, boards and circuit.
    It would help if you could supply identification numbers, photos, circuit schematics, etc.
    If 5V supply drops to 1V then there must be a low resistance path somewhere that is taking a lot of current.
     
  3. cousintroy

    Thread Starter New Member

    Aug 31, 2017
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    0
    MrChips...completely agree without more information. I am currently at work and away from my setup but I will get pictures. Until then, I whipped up a quick diagram and this shows the connections. The dotted line indicates if I were to bypass the gnd/5v cables to the flight controller and connect it straight into a gnd/5v connector on the PDB, the receiver will work.
    circuit schematic.png
     
  4. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
    6,393
    1,485
    Or a high resistance path preventing the 5V getting to its destination.

    Can you measure the voltage on the 5V pin without the receiver connected?
    If that is there then connect the receiver and measure the voltage on that pin again (perhaps on the back of the board if it is now inaccessible from the front).
    If the pin is still 5V, but there is no 5V on the receiver then it would seem that the cable is not connecting properly to the pin. Be aware that this could be at either end of the cable.
     
  5. cousintroy

    Thread Starter New Member

    Aug 31, 2017
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    0
    AlbertHall,

    With my very limited knowledge of a multimeter, here is what I tested and the results:
    • Each cable that I connect for the gnd/5v/sbus I tested resistance (I think that is what I tested). Basically I put one end of my tester on each cable and got the noise on my multimeter saying that the cables are good.
    • I touched my multimeter to the gnd/5v on the flight controller and tested the voltage. This is where I am seeing a number roughly 0.9v to 1.2v
    The 5v pin is the correct height (flush with the other pins) and only the gnd pin is sitting lower due to me accidentally pushing it through while I was soldering on the other side of the pcb board.

    Troy
     
  6. cousintroy

    Thread Starter New Member

    Aug 31, 2017
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    I will also test this when I get home tonight to see what the voltage is reading without the receiver connected.
     
  7. cousintroy

    Thread Starter New Member

    Aug 31, 2017
    6
    0
    All,

    I tested every potential path on the board and to the endpoint and I was just not seeing where the issue was. Not sure if this is the right way to do it but since it is just a pet project for fun, what I ended up doing is tinning my gnd and 5v cables and soldering them to the bottom of the board where I soldered the pins to the board. After I did that, I was able to properly power the receiver and get it to pair with my transmitter.

    Not sure if I did something to the board or something else is going on but I was able to hack it together. Thanks for your inputs!
     
  8. MrChips

    Moderator

    Oct 2, 2009
    16,900
    5,210
    Sounds like you had a bad connection that was giving a high resistance or no connection.
     
  9. cousintroy

    Thread Starter New Member

    Aug 31, 2017
    6
    0
    You are probably right. I will have to research and read up on those problems and see if I can prevent it in the future. Thanks again!
     
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