Voltage regulators

[Ethan Spitz]

Is it legal to use a voltage regulator on the output from the digital side car to convert the 6V output to 4.8V power a 4.8V servo?

Ethan

[Al Skierkiewicz]

Ethan,
<R48> All electrical loads (motors, actuators, compressors) must be supplied by an approved power regulating device (speed controller, relay module, or Digital Sidecar PWM port) that is controlled by the cRIO-FRC on the ROBOT.

B. Servos must be directly connected to the PWM ports on the Digital Sidecar. They must not be connected to speed controllers or relay modules.

I would expect the answer to be no based on this rule.

[Ethan Spitz]

Ok, thanks!
Ethan

[Ethan Spitz]

Is there a way we could legally reduce the voltage to 4.8?

[sanddrag]

Just a note, most servos that will work on 4.8 Volts will work (better) on 6 volts. I don't believe I've seen a standard hobby servo that won't take 6 volts, but perhaps they do exist.

[Ethan Spitz]

Originally Posted by sanddrag

Just a note, most servos that will work on 4.8 Volts will work (better) on 6 volts. I don't believe I've seen a standard hobby servo that won't take 6 volts, but perhaps they do exist.

Yeah, it says specifically it will not work on a 6V system

[WizenedEE]

Does the removal of the 6V jumpers on the digital sidecar not let it draw enough current? If that works, go ahead and try it. There's no way a 4.8V servo won't work on 5V.

Otherwise, no, you can't use it.

[Ethan Spitz]

I'll have to give that a try, I know our other servos don't work without the jumpers in.

I currently have the question in Q&A just in case voltage regulars are allowed

[Fletch1373]

I noticed something last year that I found somewhat odd. It appeared that the PWM connections on the Digital Sidecar never output 5V, only 6V and only with the jumper in place. I know the old IFI controllers had 5V pins everywhere.

It's definitely possible that we had a broken sidecar, but it's also possible that FIRST made a change for some reason.

[Ethan Spitz]

Originally Posted by Fletch1373

I noticed something last year that I found somewhat odd. It appeared that the PWM connections on the Digital Sidecar never output 5V, only 6V and only with the jumper in place. I know the old IFI controllers had 5V pins everywhere.

It's definitely possible that we had a broken sidecar, but it's also possible that FIRST made a change for some reason.

Yeah, I don't think its going to work because If I remember correctly I tested the output voltage with no jumper and it wasn't anything usable

[sanddrag]

Originally Posted by Ethan Spitz

Yeah, it says specifically it will not work on a 6V system

I'm curious, what is the make and model of the servo?

[Ethan Spitz]

Originally Posted by sanddrag

I'm curious, what is the make and model of the servo?

http://www.jrradios.com/Products/Def...ProdID=JRPS791

[Al Skierkiewicz]

Ethan,
The digital side car jumpers are there to supply 6 volts for servos. If you remove the jumpers there is no voltage. There is no easy way, using the digital side car, to provide 4.8 volts to the servos you linked to in your post. If the GDC allows this variation then we can discuss some alternatives.

[EricVanWyk]

Originally Posted by Fletch1373

I noticed something last year that I found somewhat odd. It appeared that the PWM connections on the Digital Sidecar never output 5V, only 6V and only with the jumper in place. I know the old IFI controllers had 5V pins everywhere.

It's definitely possible that we had a broken sidecar, but it's also possible that FIRST made a change for some reason.

Nope, your DSC is operating as intended.

The reason for the jumper is that some hobby speed controllers push voltage on that pin. This is commonly found in RC cars / planes. This would be a problem for our purposes, as they may end up fighting and/or backpowering that rail. So, a simple jumper pulls that circuit out of the equation.

It just so happens that the Victor and the Jaguar don't do this, so the jumper was just a nuisance in the past, but it lets us be forward compatible for whenever the GDC allows more leeway in motor controller selection.

[EricVanWyk]

Originally Posted by Ethan Spitz

Is there a way we could legally reduce the voltage to 4.8?

I propose that you ask the GDC if the following setup is legal:

Remove the jumper from the port you are going to use.
Jump power from one of the DSC's many 5V pins to the jumper pin closer to the PWM port.



It is kinda ugly, but it does the trick, doesn't really pose any safety concerns, and might be legal (if unintended) under the current wording.