Review: The Service Droid kit from Dagu
December 9, 2013
I have received my Service Droid kit along with the Rover 5 robot chassis on a Monday evening. Excited, I opened up the package to reveal 2 big boxes, one with the Rover 5 and the other with the actual SD kit. The base comes assembled, with a battery box, a screwdriver (with a magnetized Phillips end), an Allen key (hex wrench) and a little bag with silicone lubricant. The droid kit comes with lots of parts grouped in separate labeled bags for easier assembly. To do the assembly, I used a cutter, a plier and the screwdriver from the Rover 5 box. After a while I needed a metric ruler to measure screw and tubing sizes to avoid screw ups.
The kit has the plastic parts laser cut in pannels with thin tabs that hold the pieces in place. You need to break the tabs and then cut them off, then peel the protection film on both sides. The hardware is found in compartment bags or ziplock bags. There are many types of screws, nuts, tube spacers, ball bearings, and there is always at least one extra provided. In the end, you will have a bag of spare hardware, good to be used on any attachments you may want to add to this robot or to other projects. This kit is not for a beginner, unless there is some more experienced help available. The plate that connects to the Rover 5 chassys has lots of holes to make it esier to mount different controllers and there is a bag of different size standoffs just for this purpose, which are a great addition to the kit. There are holes for routing the servo cables and a spiral harness for each arm to protect the cables and give a more professional look. All in all, the kit is verry well thought and a great design. I am very pleased to have it.
The assembly manual has Lego style assembly instructions grouped in steps, each requiring a few parts to be assembled. Although a picture is worth a thousand words, sometimes a little more advice would be helpful. In each step, there are parts that are easier to be assembled first, then the others, and that is not obvious at a first glance. You need to carefully read all the text in the step. Something is easy to miss and later is hard to correct. Be sure to center all servos before installing them. Try not to rotate the servo's shaft when you push the servo horn in. The idea is to have the robot look like in the picture on the box when all the servos are centered.
The kit does not come with electronics, you need to add your own. A Mini Driver is recommended for driving the motors and a Spider controller is recommended for the servos and sensors. These 2 controllers will communicate over the I2C interface. OddBot has provided code for the Mini Driver and a sample code for the Spider in remote control mode. I will use one of my uBotino boards for the motors and the encoders and a second one for the servos and other sensors. I remember from my early trials with my MiniEric robot that motors with encoders and lots of servos in one controller do not work well together, too many interrupts and the servos jitter. OddBot came to the same conclusion, that's why he suggested the Spider controller as the main controller. The robot can function with the Spider as the brain, or you can add a Raspberry Pi or an Android phone to get more processing power for more advanced stuff.
And now, let's see how my assemby came together.
Since I have little free time available, mostly in the evening, after the 1 year old goes to sleep, I decided to assemble the robot in a few evenings, instead of just waiting for the weekend. That proved to be verry wise, because preparing the plastic parts, screw in all those tiny screws, carefully follow the steps from the manual, took more time than I thought. In total, I think it took me about 12 hours (6 evenings, 2 hours each) to assemble the robot, together with preparation of the battery wires change of the motor plugs, making a couple of power cables for the controller boards. I wanted to get pictures at every step, but after a couple of evenings I forgot to do that, so I have no pictures of the arms assembly. Sorry about that...
Wonderful looking boxes, I'll be sure to keep them!
The content of the Service Droid box:
The parts for the (first) wrist:
First evening, I assembled one wrist:
Then the scoop, so here they are together:
Second evening, I assembled the pincer (and later the second wrist):
Third evening, the body:
And the neck:
Then I mounted the body on the Rover 5 base and the uBotino with the servos and encoders connected:
Fourth evening, I assambled the right arm:
Fifth evening, both arms assembled:
The wiring done, at the moment everything is connected to one uBotino, later I'll add the second one and move the servos over:
Doesn't this robot look great?
I can't wait to see it in action! I really love this robot! Cheers!