Category Archives: Bucket Wheel Excavator

Vacation in Iceland /Cycling

No, Cycling in Iceland is not the topic.

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This should have stand at the beginning:

There is another reason why I was so eager for the bucket wheel excavator. I live in a former surface mining area and an original bucket wheel excavator stands in the middle of a field near my home.

   Bucket wheel excavator type SRs 1500

Panoramic view from left:

  • Lausitzring (Eurospeedway) with 6.5MW wind wheel / approx. 200m high, behind it a large wind farm (> 90 MW)
  • Bucket wheel excavator SRs 1500
  • Solar park (150 MW)
  • On the far right of the horizon (very small) Brown coal power plant Schwarze Pumpe (1,6 GW)


And: I got a blog entry at 🙂

From the original to the modified version

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Here in advance the original and the finished modification. an important goal was to keep the excavator as original as possible.

    original version

    finished modification 

Details of the mdificationo will follow later.

In 3 steps to success

In 3 steps to success

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Essentially, the project consists of three parts:

  1. The Lego modification
    • It mainly consists of the modifications necessary to install the 4 additional motors.
    • In addition, space for the controller and the battery must be found
  2. The adaptation of the controller to the hardware.
    • A Raspberry Pi 3 is used.
    • Since the motors are operated with 9V and can not be connected directly to the Raspberry Pi, an adapter board with motor drivers and step-up converter must be developed.
  3. The programming
    • The remote control shall be done with a Wiimote, because there is a simple Python library.
    • For programming, Python (2.xx) is used on Raspbian.


Part 1: The modification

Part 1: The modification

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As mentioned earlier, the goal was to make the modifications with as few changes aspossible. Nevertheless, this is not gone without additional parts.

I ordered the 4 M-motors as well as the leads directly at All other parts were from  KieselBrick over  Brickscout , which I can absolutely recommend.

Unfortunately, I cannot provide an exact part list, since I have selected the parts ad hoc and could also reuse many parts, which were left by the modifications before.

1: The landing gear

The original is driving, but only straight ahead, no steering is available. In addition, the engine sits at the top of the main transmission. That is why I have installed 2 M motors below, which are controllable separately. The inspiration got here , but ultimately I have built my own variant, which seems to be a bit easier to me.

The cable to the motors I have centrally guided over the axis of rotation, so a turning of the tower is still possible.

2: The Tower

Originally, the turning of the tower is also solved by the gearbox with the XL motor. I separated the connection between gearbox and linkage and inserted at this point an M-Motor with a worm wheel.


3: Bucket wheel

The lifting and lowering of the bucket wheel is originally only possible manually. But here it is also very easy to use an M-motor with a worm wheel.

4: Wheel and conveyor belt

Remains the drive of the bucket wheel and the conveyor belts: I left it as it is. The XL engine does it quite nice. The last degree of freedom, the turning of the small conveyor belt, I left unchanged.

Part 2: Adaptation board

Part 2: Adaptation board

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Before I describe the board itself, a few words about the battery. 

As a rechargeable battery a Powerbank is used. One with 2 USB ports, one for the Raspberry Pi and one for the motors. The form factor should be such that it can be easily installed. I choosed a flat square shaped type that has a high-power output. This is important, as the motors demand a relevant current (details can be googled). Unfortunately, that was not enough. The battery reacts very sensitive to the starting current of the motors, ie the overcurrent protection often turned off the battery, which was quite annoying. Luckily I have found another battery with similar dimensions and a little more nominal current rating.  This here  is it, however, nobody knows how it will be available …

I need:

  • 4 x motor control with change of direction for the 4 M motors
  • 1 x simple motor control for the XL motor
  • Step-up converter to provide the 9V from 5V

For the motor control of the M motors I use the L293D, a robust, proven DC motor driver, the version with the integrated diodes. 
Since the XL motor does not need a reversing of the direction of rotation, a relay is sufficient, I use a DIL14 reed relay (type 3570-1210-053, 5V) with 0.5A switching current. 
The step-up converter is an LM2577-ADJ, robust technology, slightly oversized, no problems expected. 
An RGB status LED, ready.

As a housing for the Raspberry Pi I took a Lego-compatible case. The board is to fit exactly so that it can be installed with Lego parts. The following pictures show the solution.

Part 3: Program and procedure

Part 3: Program and procedure

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As already mentioned, the heart is a Raspberry Pi 3. The built-in Bluetooth module is handy and can be paired with a Wiimote. 
Operating system is the current Raspbian, and Python version 2.x is used, since the used Wiimote library does not work with version 3.x. 
Ah yes, a tutorial about how to install the library and how to connect the Wiimote is available on this page , for example. Of course, with the Pi 3 you can skip the installation of a Bluetooth dongle.

Here is a section of the Python program:

 while True:

    buttons = wii.state['buttons']

  #Achtung: WiiMote wird quer gehalten, deshalb RIGHT --> Vorwaerts
    if(buttons & cwiid.BTN_RIGHT):
      if(buttons & cwiid.BTN_DOWN):     #DOWN --> rightfor
      elif(buttons & cwiid.BTN_UP):     #UP --> leftfor
    elif(buttons & cwiid.BTN_LEFT):     #LEFT --> Rueckwaerts
      if(buttons & cwiid.BTN_DOWN):     #DOWN --> rightback
      elif(buttons & cwiid.BTN_UP):     #UP --> leftback
      if(buttons & cwiid.BTN_UP):       #UP --> leftturn
      elif(buttons &cwiid.BTN_DOWN):    #DOWN --> rightturn

#Turm drehen mit 1 und 2
    if(buttons & cwiid.BTN_1):
    elif(buttons & cwiid.BTN_2):

#Turm heben mit + und -
    if(buttons & cwiid.BTN_PLUS):
    elif(buttons & cwiid.BTN_MINUS):

#Band und Bagger
    if(buttons & cwiid.BTN_A):
      if(pressed == '0' and run == 'stop'):
        pressed = 'A'
      elif(pressed == '0' and run == 'run'):
        pressed = 'A'
      pressed = '0'


And here is the layout of the Wiimote:

Because no monitor and no keyboard will be plugged into the Pi, the program must start automatically. The Status LED, which is always blue when power is on, flashes red briefly when the Wiimote can be paired (simultaneous pressing 1 and 2). If the pairing is successful, the green LED is additionally lit. 
If the pairing is unsuccessful, the program terminates, but Pi remains on. 
After the pairing has been completed, you can play with the excavator. 
If you have finished, separate the Wiimote with the Home button. Then the Pi shut down. Holding the B button (on the back) while pressing Home will close the connection. The Pi does not shut down.

Last part: it works!

Last part: it works!

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Finally two more videos:

Video 1: Start and switch off the Raspberry Pi 3 (approx. 56 s)


Video 2: Functional presentation (approx. 3 min)



The bucket wheel excavator from Lego Technic 42055

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Finally! I got the bucket wheel excavator from Lego as a birthday gift.

To build it was great, but of course I was not satisfied. Just one engine that drives everything, oh really!

That’s why I have modified the bucket wheel excavator so that all previously driven functions can be independently controlled by remote control. In addition, it is now also steerable and the bucket wheel can also be lowered by motor.

Pictures, video and description will be available soon.

From the original to the modified version

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