6v or 5v powering Crius v2 board and peripherals?

[jimbo385]

Hi guys,

I have the Turnigy 3-in-1 Heli 5A UBEC & Low Voltage Alarm which is a great bec unit. It allows me to set the voltage of the bec as either 5v or 6v.

Which is better 5v or 6v for the board and all other ancillary equipment?

Thanks.

[cuongvd]

I think you will burn the board if you go with 6V. As i check, the Vin connector will go to a  diode then a fuse then to the main Vcc for the whole board (all the connector with + sign, except all the connector s for ESCs/servos they are connected to the Vin pin by the yellow jumper)
There is no regulator on the board. So the max you can go with is 5.3V on that Vin pin ,the diode and the fuse will drop around 0.3V but if you draw more current, it will drop more

I don';t like that, because when you go with 5V then you have couple stuffs like GPS, telemetry, OSD display, .. and you supply those by connecting them to the +5V on those serial, i2c connectors it will bring down the +5V to 4.3-4.4V even when it idle.
My solution is using 5V BEC connect to the Vin pin then connect those peripherals + pin direct to the BEC instead of the +5V on the board.

[jimbo385]

Many thanks for your reply.

That makes a lot of sense!

I think that one should run everything that requires 5v off of the bec!

Cheers.

[Mark_W]

Agreed re 5v; however, I notice that all the advice is to power the whole lot from one BEC & cut the wires from the others; whilst this clearly makes sense in that you can';t cross-connect them to the same power rail, I';ve been wondering if one BEC can';t power the APM + receiver, and a second BEC power peripherals eg sonar, camera; with a common ground, and separate Vcc rail, there shouldn';t be a problem that I can see.
Reasons for doing this would be less load on primary BEC; resilience should a peripheral die & affect it';s power supply; & reduced noise between devices. There are 3 BEC';s spare on my quad.

I';ll say again, to forestall replies in this vein, you shouldn';t cross-connect the +5 rails. Is there, however, any reason not to do this ?

Mark

[AM556]

I don';t like that, because when you go with 5V then you have couple stuffs like GPS, telemetry, OSD display, .. and you supply those by connecting them to the +5V on those serial, i2c connectors it will bring down the +5V to 4.3-4.4V even when it idle.
My solution is using 5V BEC connect to the Vin pin then connect those peripherals + pin direct to the BEC instead of the +5V on the board.

I can';t see why it matters where you connect the load. If you connect the same ancillaries before the board, there will be a voltage drop to the board, then the diode voltage drop on top. The resultant voltage available to the board components would be the same. Would they not?

[cuongvd]

I can';t see why it matters where you connect the load.

I';m using CC BEC at 5.1V, I have Spektrum Rx, ublox GPS, 3DR radio, Oled screen. I connected those after the board, as I said the voltage dropped to 4.3-4.5V when my quad is in IDLE. It will drop more when you have more thing plug in. Gps, 3dr radio, Oled screen can run as low as 3.3V but the spec of Spektrum Rx is 3.5-9.6V. So I don';t feel comfy when I use it close to the spec like that.

[AM556]

Yep, I understand that it does matter in relation to you needing a certain voltage for an item.
What I should have said is, the potential when shared in a parallel circuit gives no priority to one component over another and doesn';t matter where you place an item within the same circuit. Placing a power hungry device at the end of the line will cause a voltage drop to all devices irrespective of their position.
My workaround has been to fit 2 ubecs.

[ausi1972]

If you have a Crius V2 board then you will need to remove and add a short wire in place of the Diode near the motor rail. Powering it from 5V will result in a voltage drop sufficient to cause brownouts of the board.
See PDF attached.

Then just power from 5V and it will be perfect. Remember to add a piece of open cell foam (from a scouring pad works great) over the barometer.

[cuongvd]

That diode for reverse polarity protection and also block the power from the board/USB draw back to the ESC or the Bec, so you need to very careful after cross it.

[realpastaman]

That diode for reverse polarity protection and also block the power from the board/USB draw back to the ESC or the Bec, so you need to very careful after cross it.

I';ve also done some tests after I had intermittent start up problems -

Checking the voltage on the serial + - pins seems to be ~ 0.3 Volts down on whatever the board is supplied with. This seems to be the case whether the board is supplied
via the external + - input (with jumper removed) or via an esc bec supply (with jumper connected).

Fed from 5.3 - 5.4 volts the board seems to start every time. I';m interested for simplicity to short out the diode and power from the esc 5v bec (with jumper attached). I do however understand that there is a risk to connect the USB whilst the flight controller is powered.

Usually I don';t like to connect the USB whilst the board has its own power on.

Anyone had more experience in this area?