So, long time no write. Essentially, this post is meant to cover the rigors of building and using the DFRobot Shop Rover kit. The notion that this is easy to build has been rightly considered but there are some aspects which may be cumbersome to do (ode to SPath). This kit is available from RobotShop.com and is essentially an Arduino with tank treads. The original price is $89 but i got it for a 50% discount courtesy Instructables! It supports the Arduino programming environment and all available shields can be used with it (but to make your own shields you need a custom GPB which supports the retarded pin spacing……………. another way for suppliers to make more $$$$! Open source or money making, choose your side!).
The contents of the kit are as follows:
1.The PCB which contains the arduino board (fully soldered and ready to use).
2.The metal spars which are used to join the treads to the board.
3.Tamiya dual motor gearbox
4.Tamiya tank tread kit
(Tamiya is a famous supplier of DIY kits and they recently got the MAKE award for best illustrations. Extremely meticulous and easy to read, although some things are so obvious they need not be stated.) The only thing different from a normal arduino is that it has a motor driver built in (L293N) and extra ports for pins such as RX, TX, GND etc. to support Robotshop’s own custom shields. Additionally, it has a temperature sensor (LM35), an LDR and 6 ultra bright SMD LED’s around the board, each of which you can selectively enable or disable based on your requirements.
The construction itself is fairly straightforward and will delight the first time bot builder as everything required is already there (including a small tube of grease for the gearbox). No more running of to SP Road for any small component which slipped your mind the last time you were there!
The construction process is as follows:
1.Make the gearbox:
Construct the gearbox according to the illustrations. One screw-up here (pun intended) and you will have to dismantle the whole assembly. Luckily, no glue is involved so its fairly simple to dismantle it. Take note of all the components at the beginning and keep them safe. If you lose or break a piece, replacements are far from easy to get, especially for those in India. After you are done, put a dab of grease on each of the assemblies to enable
smoother operation. Do not attach the motors just yet. There is some prepping to be done which I will elaborate at a later stage.
2.Make the tank treads:
The tank treads will come in sections which you will have to join to get the required length. The method of attaching the different sections is novel yet completely %^&#$*#*! The sections have a kind of hole at one end while the other ends have a T-shaped section. The technique is to bend the T so that it becomes an |, stuff it down the hole and then reform the T so that it latches on. Its quite capable of withstanding anything you throw at it after you have joined the sections, but while joining if you break a part, bye bye tank.
3.Attach the metal spars to the board. This is the easiest part of the whole build. No instructions are given for this part. But then if you don’t get this, maybe philately is a better hobby and mostly won’t endanger your immediate environment. Take note that the gearbox and the spars use a common connection point, so attach both at the same time.
4.Finally use the remaining items in the tank tread kit to assemble the bot taking into consideration the overall size of the bot. This is mainly done by looking at the picture and is fairly self explanatory (like some portions in EVS !).
Solder the leads on the motor, taking care of the fact that they are long enough to reach the screw hole connectors on the board. Cover the connection points in insulation tape so that the connections on the main board don’t get shorted. For safety considerations, its better if you also tape the underside of the board. Next, slide the motors into postion and connect the leads to the screw hole connectors while taking note the polarity. In layman terms, connect motor to battery, find rotate which way, do same for other motor, connect both in same direction. This doesn’t actually matter as each pin is individually programmable, but it allows you to rip off code from the examples given (thats what it s all about!!).
It is powered by 4 AA batteries, but it should work for supplies ranging from 6 to 9V. Do not try using the cheap ‘HIGH WATT’ 9V batteries as they cannot give a stable voltage for extended periods of time. I almost died when I tried one and thought the motor driver was not working. OH THE HORROR!!! Then I used 4 Duracells and all was well.
Congratulations!! You have just finished building a very capable and handy machine for a myriad of experiments, or general all-round fun! You can make it autonomous by mounting a myriad of sensors on the board but take note of the fact that the power drain will also increase. Or you can make it wirelessly controlled by adding Xbee/Bluetooth/Wifi etc. I have a BluesmIRf module, so I’ll be controlling it using and Android phone. I’ll put a tutorial for that in one of my future posts.
My next post will be soon so wait for it………………. like what else can you do??