Videos of 2 PF Receivers Powering One PF Motor

[DLuders]

Over on Flckr, Mahjqa posted a video showing how 2 Power Functions Receivers can help the acceleration of a single PF Motor. He wrote,

"This is in response to Sunskytechnic's idea to put two receivers to a single motor: www.flickr.com/photos/sunskytechnic/4885520621/ .

"I made two identical cars, where an XL motor is geared up 1:9 to the wheels. The right car has a single receiver, the left one has two. Weight has been added to both cars. Both cars use fully-charged PF batteries. I did additional runs with the batteries switched, with the same results.

"It seems like the car with two receivers has a tiny advantage when accelerating, but the top speed remains the same."

On YouTube, Sunmint1 shows how to wire it up: "Multiple receiver output are connected to one point and fed to a motor.

The benefits are 1) more power 2) enhanced signal acceptance. Two sample vehicles are presented (4WD MOC and 8043 mod)."

Of particular note is the last 45 seconds of that video. It shows how a Lego 8043 Motorized Excavator can respond with GREATER POWER by adding a second Power Functions Receiver. Is there anybody out there who would like to try it out on their underpowered 8043? Some comments about the idea are on the bottom of

.

[Mortymore]

...

"It seems like the car with two receivers has a tiny advantage when accelerating, but the top speed remains the same."[/color]

...

That makes sense, since the dual channel H-bridge motor driver LB1836 that's responsible on the receiver 8884 for running the motors has a 1A current limit, and a XL motor 8882 may well draw instantly more than that at start-up, if the power supplied provides so, giving the motor 2 channels, each from 2 receivers, is allowing it to draw a maximum current of 2A.

Then, when the motor is running normally, if it only draws 200mA...600mA... there's no difference if its power is provided trough 1 or 2 receivers, because only one was perfectly capable of keep him running at that speed.

But the guy of this video is nuts for reversing the output of the receiver, since is making a short circuit and serious damage could occur. I believe that has LEGO provided current limit protection on the 8881 battery box, the same may be true for the 8878 battery box, or else it could have ended up dead.

Cumps

Edited September 3, 2010 by Mortymore

[hoeij]

Of particular note is the last 45 seconds of that video. It shows how a Lego 8043 Motorized Excavator can respond with GREATER POWER by adding a second Power Functions Receiver.

Bad idea for two reasons: (1) you can make an electrical short-cut, and (2) you don't want more current going through your M-motor because that'll shorten its lifetime.

You're much better off with one of the other solutions posted in the 8043 threads, such as wait for lego's improved LA's, or use an XL motor, or help the motor by adding a rubber band.

[Mortymore]

... and (2) you don't want more current going through your M-motor because that'll shorten its lifetime.

...

Well.. for what I've read here and there, the Excavator 8043 is taking care of the M-motors without needing any extra help.

Now I don't know if I laugh of the joke, or should cry

I don't see any problems by adding 2 receivers in parallel to power one motor. That same motor if was running directly from a battery box would draw at most the same current, and I don't see how that can shorten the motors life. I mean... it's not possible to make some amount of current flow through how many receivers you want, that the battery box can't provide.

Cumps

Edited September 3, 2010 by Mortymore

[rgbrown]

Good grief.

I applaud the author's "faith in the Lego engineers" that they won't blow anything up by short-circuiting things. Also impressed with his willingness to drive cars through ponds.

Other than that, Mortymore said everything I was going to say ... except that there is a way to destroy your M-motors a bit faster if you want to, by hooking up parallel battery boxes together with your parallel receivers before you near-stall the motor on your 8043. Hey, if you're really lucky you might even get something to melt!!

Let me guess, next up will be series battery boxes?