While browsing through DX.com’s new arrivals section, I stumbled upon this package:
Seeing as I still had a bet with a friend to, at some point in our lives, do a real-life Robot Wars, I figured I’d give it a shot. It just got in a few days ago, so I figured I’d write a quick review.
The dx.com site can be a bit cryptic, so here’s a full list of what I found in my package:
- A chassis consisting of two acrylic plates with three copper pillars (both 0.43cm thick, 4cm in between)
- Four DC-motors with gearboxes pre-attached to the bottom plate.
- 4 tires that nicely fit the motor gearboxes.
- A Dual H-Bridge Motor Driver based on the L298N IC, already attached to the chassis (appears to be the same as this product)
- An Arduino Uno (R1) clone, with USB-cable (1M)
- An Arduino Sensor Shield v4.0 clone.
- An ultrasonic module marked HC-SR04 (appears to be the same as this product)
- Three (3) line-hunting sensor modules, on a single PCB so not easily detachable. (appears to be the same as this product)
- A remote control (“Special for MP3” with MP3 related buttons) with IR-receiver. (Appears to be the same as this product)
- A Battery holder for 6 AA batteries
- A Battery holder for a single 9V block with a power-jack fitting the Arduino
- A small breadboard (17 rows, 5×2 pins each) with adhesive tape on the bottom and two screw holes. (appears to be the same as this product)
- A “Tower Pro Micro Servo 9G SG90” with a bunch of attachment pieces. (appears to be the same as this product, including the pictured accessories)
- 30 female-to-female jumper wires. (Similar to this product, although those are slightly thinner)
- Some kind of turret or camera mounting platform requiring two servos for pan and tilt movement (Same as this product, looks like this when complete)
- An assortment of screws
- 10 nuts
- 10 short bolts (philips head, 0.5cm)
- 10 longer bolts (philips head, 1cm)
- 6 short copper cylinders (1cm)
- 3 longer copper cylinders with bolt-ending (2cm + 0.5cm screw thread)
Missing or misnamed parts
From the dx.com description, I noticed a few flaws:
- Both acrylic plates appear to be roughly 5mm thick, instead of the stated 3mm and 5mm.
- The “Holder kit” seems to refer to the 9V block battery holder.
- the “Steering gear” seems to refer to the pan-tilt holder, which appears to be completely unrelated to steering.
- The copper pillars packaged are 3x4cm, 3x2cm, 6x1cm (instead of the 3×3.5, 2×2, 6×0.6)
When you order on a site like dx.com, you know that it’s not always the best quality you can get. However, this package was pretty bad quality wise even compared to a lot of other things I bought at dx.com. Here’s a few of the things I noticed first, on a per component basis:
- There were a lot of bent pins on both the arduino and the sensor shield. They didn’t even fit together without manually bending everything back.
- The silkscreen on the Arduino is barely readable, much much worse than an earlier Arduino clone I ordered from dx.com.
- The power jack on the 9V Block battery is so fragile that it falls apart when you try to pull it from the Arduino.
- Several of the LEDs on the motor shield just didn’t work (although the shield itself did)
- The motor gearboxes were horrible without manually oiling it.
When you look at the complete package, it doesn’t really get any better. Nothing really seems to fit together:
- The only components to actually fit the chassis are the ones already mounted on it (motor-driver and motors), and the pan-tilt thing.
- There are no holes that match those in the arduino, none that match either of the battery-packs, none that match any of the sensors.
- The pan-tilt system needs two servos, but the package only contains one. Furthermore, the pan part needs a servo attachment piece that isn’t packaged with the servo.
- Neither of the battery boxes seem to pack enough power to easily power the motors.
- The remote features a lot of buttons specific to an audio-player, which doesn’t really fit an RC-car. Apart from that, it’s IR which has horrible range, and requires both the remote and the receiver to be aimed precisely.
All in all, the quality is far from perfect.
Seeing as most of the components can be bought seperately on DX.com, I figured I’d check out how much it’d cost if bought seperately. Here’s the list:
- Arduino UNO Clone, $17.40 (with the added benefit that this is apparently an R3, whereas the package comes with R1)
- Arduino Sensor Shield v4.0 Clone, $7.40
- L298N Stepper Motor Driver Controller Board for Arduino, $6.70
- HC-SR04 Ultrasonic Sensor Distance Measuring Module Clone, $4.60
- Three Arduino Line Hunting Sensor Modules, $3.80/pieces, $11.40 total
- IR Receiver Module Wireless Remote Control Kit for Arduino, $5.30
- 6 x AA Batteries Holder with DC2.1 Power Jack for Arduino, $2.40
- 9V Battery Holder Case Box with Leads, $3.90 (Note that this one does not contain the jack, but the 6xAA one does, so you can solder that over)
- 170 Points Mini Breadboard – White, $2.20
- SG90 Mini Servo with Gears and Parts (2Kg Torque), $4.00
- 30cm Breadboard Wires for Electronic DIY (40-Cable Pack), $4.90
- Camera Platform Mount for Aircraft FPV 9G – Black, $4.70
Parts I couldn’t find:
- The acrylic chassis
- Motors, gearboxes and tires
- Nuts/Bolts/Screws assortment
The total comes down to precisely $74.90, whereas the complete package costs $79.60 at the moment of writing. That’s only $4.70 more for the acrylic parts, motors, and wheels, which seems like a fairly good deal. If you know how to use all the parts, and could probably use them in other projects anyway, this might be a pretty good buy.
If you’re expecting a complete kit that you can easily put together and then program using the arduino, this will be a complete let-down. However, if you’re creative enough and willing to get your hands dirty, I think there’s loads of potential in this kit for a nice RC-car.
Yes, it doesn’t really fit out of the box, but it’s easy enough to drill a few extra holes in the acrylic plates.
Some things that I feel might be worth trying:
- Buy one of those cheap bluetooth to UART kits, and use an Android (or other bluetooth-capable) phone to control it.
- Hack up a wireless Wii nunchuck as a remote control. (Wii expansions use I2C, which is easy to control using an Arduino)
- Use a single thumbstick or a full blown joystick shield as a remote control instead, possibly paired with the 433 solution.
- Get an RC-battery and use that instead of the packaged battery-packs