video: LEGO Power Functions 8884 8879 PWM

http://www.youtube.com/watch?v=6RttvmTGm74



There's a lot of stuff to observe here, but to resume, this is a bunch of measurements on LEGO 8884 IR receiver, controlled by LEGO 8879 IR remote.
The LEGO 8879 remote controller has 7 levels for forward activate a motor, and another 7 levels for reverse, plus a stop button. Motor is controlled by PWM signals, with a frequency of 1150Hz, and duty cycles of: 0%, 26.6, 38.9, 51.2, 63.0, 75.0, 87.2 and 100%. The corresponding DC level output, depends on the voltage supplied by the battery box, and at a level of 100% the output of the receiver 8884 has the same voltage level as the voltage supplied to him by the 8881 battery box.

Photos at BrickShelf: http://www.brickshelf.com/cgi-bin/gal...

No music this time, so you can hear the motor running near the end of the video.


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video: LEGO 8884 receiver - current measurements

http://www.youtube.com/watch?v=0BvZz1sIaNo


The setup seen here is for measuring current input and output for LEGO 8884 IR receiver.
The power is supplied by 6 AA batteries placed on LEGO 8881 battery box, and the load for the 8884 receiver are 2 motors (8882 and 8883) in parallel, connected to just one output.
With the 2 motors running freely, no more than 150mA was pulled.
With the M motor 8883 stalled, the current went up at around 600mA.
With the XL motor 8882 stalled, was around 800mA.
With the 2 motor stalled, about 950mA.
The maximum input current measured was 1A, and for the output 980mA.
The batteries used were regular alkaline ones, and they're not fresh as can be seen from the voltage measured by meter at the left, so higher values for current may be achieved with fresh batteries, though the maximum current that the motor controller LB1863 used on the 8884 receiver, allow through GND pin is 1A, so we are close here.