Misadventures in power electronics


If you have a story, rant or suggestion about limitations of power products (power supplies, ESC, etc) on your UAV, post it in the comments below.  I am specifically interested in feedback or thoughts on shortcomings in the power products that we at 3DR make, so we can incorporate that feedback in the next generation of products.

A little bit about myself:

I came to 3DR in early May, from General Atomics Electromagnetic Systems.  While at GA, I worked on EMALS, AAG and the Railgun team.  I am a graduate of UC San Diego with a BS in electrical engineering (circuits and systems depth).  My current role at 3DR is in engineering, where I mostly work on research, development, and new product design.  

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  • I want a esc with a simple single button on it to program it instead of buying expencive ones to use a programming ard or using the radio method

  • I've also been thinking of adding integrated PM to the next version of my home made PDBs ( could this be interesting for anyone else or is the PDB shape/size too dependant on the wide variety of air frames out there?

  • - PM with higher current capability

    - 6S capable PM

    - Adding multiple simultaneous power feed monitoring to the APM and MissionPlanner code would be a nice addition as well. My hexa currently has a 6S battery powering the ESCs through a 3DR PM with its regulator removed and connected to two of the APM 2.5's analog inputs. Two more 3S batteries wired in parallel powering avionics are run through a second intact 3DR PM connected to the PM input. I have to change BATT_VOLT_PIN and BATT_CURR_PIN depending on which battery I want to monitor.

  • You can also eliminate 1 more connector by soldering it to your ESC.

  • Hi Jeff,

    If the power module could failover from the ESC BEC to the APM BEC, that would be great.  I realize multi-rotors, this wouldn't help, but for aircraft, the ESC could fail

    The size of the power module isn't really an issue for me; although I could see where it would be for some people since I can only guess what they are doing with it. 6S+ just to monitor volts/amps and power the APM with a second to power cameras/servos.

    Possible options:

    1) For a multi-rotor, the ESCs power them selves off the pack.  The APM could be powered off 1 ESC BEC or the Power Module.  If either power source fails, the second should be able to take over.  Since very little power would be required, the power module can be tiny.

    2) Aircraft/Camera option.  Perhaps the ESC doesn't have enough BEC amps or can not generate the 5.37V to power the APM with the jumper.  A larger power module model could be used to power the cameras and servos.

    In my case, I have a X8 wing running 6S at 50A I am using a 20A BEC (CC Talon 90) to power the APM and the servos.  I am looking at getting a Attopilot to monitor voltage/current only.  Idealy what I would want is the ability to run the servos/APM off of either the ESC BEC or the power module with failover capability.

    Hobbyking does offer a redundant BEC system which I am looking into as well.

  • I want to buy from 3DR...but it's simply too expensive. I ended up buying from a reseller last time, because it was cheaper, even after paying the local taxes. How can that be possible, unless 3DR is gouging me on the shipping?

    Shipping from 3dr direct to Switzerland incurs *another* $20 of shipping import tax on top, if you buy an APM - that's $58 of total shipping. 25% on top of the order itself.
  • Matthew, yeah, those connectors suck, I have stopped using them.  XT60, and XT90 for me!  They are really nicely made connectors.

    The problem with Deans connectors, is they rely on the plastic body to load them.  The body can deform due to soldering heat, or excessive loads.  This can lead to inadequate contact pressure, which leads to poor contact.  Poor contact leads to heat, which leads to less contact pressure...  It's just a poor design.  I'm not saying that 3DR shouldn't offer them, but I don't think they should promote them.

    Janne, yes, that's another thing.  The ESC's need an external resonator.

    I personally would not be that interested in a kill switch.  It's something else to go wrong.  If it could be simple, light, and reliable, then OK.  But I haven't seen anything like that yet.

    Almost forgot, and this is a big one.  I've said this before, I'll say it again:

    Provide dual power input to the system.  The main battery connector, as well as a balance plug connector.  The balance plug connector runs through a 10 ohm resistor.  The idea is, you can power up the system through the balance plug.  Charge the ESC caps.  And power the autopilot in safety.  When you are ready to fly, plug in the main battery power.  If, while tweaking the autopilot, you have an accidental start, the motors will only turn about 1 revolution before the caps drain and the system goes dead.

    It's a nice safe way to bring up the system.  I got this idea from the "anti-spark" circuit on my helicopter ESC.  This is how it works.  I forgot to plug in the main power when I went to start, and the system just goes "Pew" and dies.  I realized this is a nice safe way to power the autopilot in safety while working on the system.

  • there is a uk store I'm sure the shipping prices from there would be cheaper no?

    for all you that didnt know.....


  • I can buy from goodluckbuy, and get free shipping. Jdrones also have a free shipping option. 3DR *only* have the $38 option.
  • Shipping is flat rate in other words. 10grams worth of cables, or an APM - it's still $38.
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