Sunday, June 24, 2012

PF Servo in action

As efferman commented to the previous post, there is a new video showing how the PF Servo turns proportionally if controlled with a PF Speed Remote (8879) - The same if connected to the PF Rechargeable Battery (8878).
The PF Servo turns 90 degrees in both directions. See below.



As I also commented to the same post it works as per the known LPF RC Protocol, which is public.
With a PF IR Remote Control (8885) it goes full left/right when the sticks are pressed forward/back (depends on polarity switch). When there is no signal arriving it returns to the center like a regular servo. It behaves similarly when attached to a regular PF Battery Box (8881, 88000).

Now if connected to the PF Speed Remote or the PF Rechargeable Battery it receives pulse width modulated signals (PWM) while attached to the PF IR Receiver (8884) or the Battery, which provide proportional control, and it turns proportionally according to the received signal. That's why it does not return to the center automatically. The Stop button must make it return to the center though.

Hope it is clear now!

14 comments:

Allanp said...

This is fantastic, this servo is living up to all of my expectations so far. It will be very usful for controlling gearboxes and pneumatics remotely aswell. In the older video of it at the toyfair it also looks as tho it has plenty of power. Fantastic! I wonder if a stick remote will be released with proportional control and return to centre when the stick is releasd. Now I guess we are waiting for more info on the L-motors. What is their speed/torque characteristics? It looks as tho it has an internal motor that is wider than that of the m-motor and longer (but not as wide) as the XL motor with not much room for internal gearing. As such i'm hoping for a motor much faster than the m-motor and maybe not quite as much torque, but with it's extra speed should give a greater overall mechanicle power output similar to the XL motor. That's what i'm hoping for anyway. Can TLG strike gold twice?

Allanp said...

Oh, one thing I forgot. It looks as tho the motor is not turning completely in sync with the speed dial. Sometimes he turns the dial fast and the motor has to catch up, pausing between each step. This is not such a big issue and will hopefully be fixed with a new remote (as regular motors controlled by the train remote also seem to increase speed gradually).

Fernando Correia said...

@Allanp

The PF Speed Remote has never been that great, other than for the new LEGO Trains. But that's a topic for another post in a week from now. ;)

Allanp said...

You can tell by the light on the remote that the remote itself is sending the delayed singals to turn. The motor is always turning when the light is on, never turning when the light is off. This means that the delay is not caused by the motor or the recievers, it's from the remote.
Thankyou for all this juicey info!

Fernando Correia said...

@Allanp

The way the speed remote behaves is like that - If one turns a dial fast it seems to buffer a sequence of PWM increments or decrements, which it then sends at its own pace.
You can observe this by the LED blinking even after you released the dial button.

The Speed Remote seems also not 100% accurate, once it can occasionally miss sending signal as the dials bounce in each step.

AVCampos said...

Given the original purpose of the remote control, I'd say that behaviour is intentional: TLG probably wouldn't want kids to be able to abruptly change speed on the trains, so the remote gradually sends speed commands until the output speed matches the position on the dial.

Indeed, with the new servo motor, the door is open for a new remote control capable of variable speed. :)

thirdwig said...

I like what I see here. Great job TLG.

efferman said...

we have pictures
http://www.doktor-brick.de/index.php?page=Thread&threadID=392

Fernando Correia said...

Super!

The Monsters new 90º connector comes also with the Crawler! :)

AVCampos said...

Thinking about the video with the beam and wheels turning, I now remember how moderately (in a relative way, of course) disappointed I was to see it turning so slowly. But this can also be explained by the train remote's behaviour, which continuously sends signals to gradually change speed (or, in this case, position) from the initial dial setting to the new one.

If a new remote control that directly sends the desired power level (or an NXT equipped with an IR Link and proper software) is used, I suspect the servo will act much faster. Indeed, as far as I remember from those early Toy Fair videos, the Crawler, using the standard remote that instantly sends full power commands, steered much quicker.

AVCampos said...

@efferman: to see the images on the page you linked to, one has to register... Isn't there any chance to host them on some other, non-registration-required, site?

Fernando Correia said...

@AVCampos

That would depend also on the gear ratios involved on the steering mechanism.

Fernando Correia said...

@AVCampos

There are lots of them embedded, if you page-down.

efferman said...

the owner "the mind" wants no copying of the pictures. on eurobricks i have posted two pictures in the crawler thread

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