Introduction
OddBot (Russell) sent me a DAGU Playful Puppy Robot kit to check out. This little guy is really neat. A copy of this review is posted on
LetsMakeRobots.
Components
Chasis
The chasis for the Puppy Robot is made from laser cut arcylic. The main mounting plate is 3mm clear acryilc, and includes many holes and slots for mounting components. You can find this mounting plate on a few of DAGU's robot kits.
The parts for the legs are eight identical pieces made from 2mm frosted arcryilc with mouting positions for mini servos and optional LEDs. The legs are cleverly designed so that the same part can be used for both upper and lower leg segments, and for any of the four legs depending on how they are assembled. This probably helps keep cost for the kit down, since it simplfies design and manufacturing.
Servos
The kit also uses ten
Dagu Micro Servos, which are very light weight and inexpensive. It is impressive that the robot can use these small servos.
Compound Infrared Sensor
This sensor, also known as the Dagu IR Compound Eye, originated from a design OddBot
posted right here on LMR. This sensor is also used in several of DAGU's robot kits. It consists of an array of four pairs of IR photo transistors and IR LEDs. You can use this sensor as a simple range finder, and for obstacle avoidance or tracking. With some clever programming you can measure the ambient IR light level, and adjust sensor readings so you can work in various lighting conditions.
Pan and Tilt Kit
This is another DAGU design that originated right here on LMR. It started its life as a simple sensor mounting bracket, and
evolved with input from the community. It is a very nice and versitile design that can be used to mount a variety of sensors or other components. It is designed to use two of the micro servos included with the kit.
If you buy the pan and tilt unit as a separate kit, it comes with all the mounting hardware, and two of the micro servos. DAGU uses this kit in several of their robots.
Magician Robot Controller
Ah, now on to the brains of the operation. This controller is a relatively new design from DAGU, and I like it a lot. I like flexibility in controller board designs, and this one delivers it. For about the cost of an Arduino board, you get a fully Arduino compatible processor, integrated 0.8A dual motor drivers, nice power options, and good connectors for your servos, sensors motors and batteries.
The motor drivers consist of two h-bridges built from discrete components and a quad NAND gate chip for logic control, shown below. The design allows you to bypass the h-bridges in case you don't need them, and would rather put the digital outputs used for motor control to another use.
Eight of the digital outputs have been set up to control servos; they are interfaced through a bank of connectors with power and ground pins all set up to connect your servos. you can of course use these pins to control something else, but many robot builders like to stick with the three pin servo connector layout for convenience anyway. Power for these connections can be selected as +5V from the regulator or directly from the battery.
The analog pins are also grouped with +5V regulated power and ground.
Power for the board is delivered through the screw terminals for the battery. The same type of screw terminals are used for the motors. A nice SPDT switch is included right at the edge of the board.
You can use as little as 6V or as much as 9V to power the board. The onboard Low Drop Out (LDO) voltage regulator delivers a clean +5V and up to 1A of current. If you need more current, you can stand the regulator upright and add a heat sink to bring it up to the maximum capacity of 1.5A. The board includes a reverse polarity protection diode, so you won't damage anything if you accidently connect the battery leads backwards... a nice feature.
Overally, this is a great board that could be the basis for a small robot of your own design. It is quality manufactured and provides plenty of flexibility. I'd certainly consider this controller for my own robot designs.
Kit Assembly
The kit is designed for no-soldering required. The Magician board comes fully assembled. All you have to do is follow the provided instructions carefully to build the chassis and connect all the wiring. The instructions are pretty good. A few steps may require careful study to avoid making mistakes.
All those wires!
If there is one nit to pick on this kit, it is the wiring. Don't get me wrong, the kit is very good. However, assembly requires piecing together jumper wires to get to the correct lengths. It's a bit annoying, and subject to accidental disconnections, especially when handled by kids.
There's also a somewhat goofy set up to include an additional power diode to drop the power from the batteries down enough so that you don't send too much voltage to the servos. You wind up with an awkward jumper arrangement that could be better.
Chosing a Battery
The instructions say that the kit works best with a small 7.4V LiPo 2300mAh battery. However, since many people may not have access to a LiPo charger, you can use six rechargable AA NiMH batteries with a capacity rating of 2000mAh or better. NiMH batteries are easier to come by and to maintain.
Programming
The kit comes with example code for the Arduino IDE. There are separate versions of the code, depending on which battery option you decided to go with.
The code is well laid out and commented. You may need to make adjustments to some parameters to get everything working smoothly. Other than that, everything should work out of the box.
Of course, since it is all open, you can change the programming and try to add different behaviors for your puppy. I'm sure Russell would be gratified to see customizations on his code.
Results
Fun! The robot manages to capture the playfullness of a puppy. My two kids (ages 4 and 7) both enjoyed playing with it. Keep a spare set of batteries charged up, so you can keep the kids happy when the installed set wear down.
I'll add some video to this review when I get a chance.
How can I get one?
