6Volt output on esc into the ROVCape?


#1

I noticed something while locking at the ESC thats noted in the BOM.

Hobbyking state that the ESC's have 6V BEC output, and if you connect them to the Cape board, you will send 6V into the 5V part of the Cape.

Shouldnt the Red(6V output) wire from the ESC been cut, or the mid pin of the headers on the cape?

I've read on some forums that systems with several ESC(Ie. Quadcopters) with BEC circuits sometimes conflict, and they end up with destroying the ESC because the BEC circuit doesn't support to be parallel connected with other BEC's.


#2

There is a jumper on the Cape, near the header pins for the ESCs. Pictured here:


Removing this pin will stop the 6v from going to the ESCs (which should then be powered using the 12V power source). Removing the pin looks like this:



#3

I saw the P13 jumper in the schematics, and i guessed this was the solution on the 5V/6V issue.

But i didnt read anything about it anywhere, and wanted to highlight this possible issue...

but this does not affect the paralelling of the BEC's, but you probably have a good trackrecord that its not a problem?


#4

Hi Thomas!


Since the OpenROV Cape can only supply a limited amount of current from its 5v output, it is preferable for the ESCs to supply power to the servo voltage bus instead. If someone has a project that doesn't use power-supplying ESCs (for instance if they are only using servos), a jumper can be placed across P13 to use the Cape's supply, but we've found that the on-board 5v supply is pretty limited and driving four servos at once may not work very well. If this is the case and a larger current source is needed for servo power, you'll notice that there is a ground terminal right next the P13 header- we've spaced it so that if you put an additional header pin there, you can attach an external 5v supply between that ground pin and the adjacent header on P13 which is attached to the servo power bus and power the system that way. As a secondary effect, the P13 jumper isolates the supply of the ESCs from the supply of the Cape so the issue you describe does not end up happening. Looking through the schematic for the Cape, it seems that there is no blocking diode to prevent the higher voltage (6v) ESC power from going into the lower (5v) Cape power supply. Good eye!

As a rule of thumb, one should avoid attaching power-supplying ESCs when a jumper is in place on P13.

Thank you!

Eric


#5

David & Eric,

thank you for very good and in-depth answers! this is important information that the users need to be aware off. nobody want to fry their brand new cape board ;-)

I work as an subsea electronics engineer and i tend to have a good eye for details that -could- be a problem.

I've become quite a big fan of this project, and ordered a Beaglebone, Cape and F100 webcam yesterday to start off with in my progress to build a OpenROV.

Keep up the good work!


#6

Thomas- it rocks to have you aboard, and I can't tell you how valuable this feedback is. If there is ever anything else we can help you with, let us know!

Eric


#7

Happy to help out! And the same goes for you guys, if there's a need for anything, drop me a message/mail etc, and i'll help however i can.

I work with alot of ROV equipment(subconn/seaconn cables/connectors, fiber mux boards, tethers etc) in my work, and i actually got this company a couple of kilometers from my workplace: http://www.argus-rs.no/
their ROV starred in a episode on Discovery's Mighty Ships show, the episode from G.O Sars(a norwegian maritime research vessel) (my father in-law actually works on the vessel aswell ;-)


#8

There is some confusion regarding this jumper in regards to using the ESCs that come with the KIT. When the Jumper is removed... nothing powers... no servor, no ESCs. So is it safe to assume that the jumper should be in place when using the KIT?


#9

The jumper _must_ be removed when the 18A hobbyking esc's are used.

But you must then do nothing with the red wire from the esc's. this must be connected together with the red and black.

this setup works.

but you must have 12V going to the main powerlines on the esc + to the cape at the same time.

Ref wiring schematics: https://github.com/OpenROV/openrov-electronics/blob/master/Openrov-wiring-rev1.pdf