[Tutorial] Modify ROBOT STARTER KIT V2 - Educational robot to teach kids how to build and code

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Sold by Watterott Robot V2 Starter Kit is a great platform for robots beginners. There's even a book about it: "robot build with Arduino"Markus Knapp. Enough Advertising made. I have assembled this robot with self-lasered parts. Here are misbehaving with some things that can be eradicated by simple means.
An educational robot to teach kids how to build and code
An educational robot to teach kids how to build and code
The robot kit was originally developed by Aleks aka 5V junkie for the 'BotMakers' Forum. It is a further development of his 'We make robots' Starter Kit. The main changes relate to the chassis, which now consists of laser-etched parts, while the first version was held together mainly by double-sided tape. Unfortunately, both forums BotMakers.de and WirmachenRoboter.com for some time offline. I had lasered me the chassis itself. Since the chassis layout plansare public and I Lasercut a course in anyway Fab Lab Berlin had booked, this was my demo project for the course. The remaining parts for the robot I already had in stock. The robot is very compact, but still offers room for expansion.
Here is the list of changes that I made to the robot. Recommended for imitation, but without guarantee.

Suppressed engines

The engines of the starter kits are DC gear motors (Solarbotics GM9). The brush of the DC motors produce neat disturbances in the electrical connections and can also affect other electronics, in particular sensors. Basically motors should be suppressed, regardless of whether interference occurs or not. For this purpose, a ceramic capacitors (KERKO) is required with about 100 nF per engine. This capacitor is simply soldered in parallel across the motor terminals.
IMG_4670.JPG
Required components:
  • 2 x 100nF ceramic capacitors

More powerful engines

Something more engine power complacent? Here comes the tuning tip for more power. The built-in gearmotors DC motors are of type 130, a common size for engines is also in many toy models. Instead of the brave, power-saving variant, as used in GM9 gear motor, there is also a more powerful power version .Thus, the small robot runs the same times faster properly. Of course, at the cost of greater power consumption, ie the battery / batteries are empty faster.
IMG_4672.JPG
For the conversion of the old engines are removed from the gearbox. The motors are held only by a plastic tab. If you remove it carefully, you can pull out the engines. The motor pinion can be easily removed with tongs from the engine and place it on the new more powerful engine. The engine again put back into the transmission and secure it with the plastic tab. Voila.
IMG_4683.JPG
Required components:
  • 2 x Brushed DC motor 130-size 800mA stall

Smooth IR Sensor Power Supply

The infrared sensor (Sharp GP2Y0A21YK0F) is a cheap way to measure distances to objects that are in front of the robot.Unfortunately, the output of these sensors is not very stable and are therefore not return exact values. The problem is the power supply of the sensor. I had already some time ago blogged . Here, too, capacitors help to eliminate the interference. This, however, 2 capacitors are required. A small ceramic capacitor of 100 nF as the motors for the small peak and a large thick electrolytic capacitor of the 100uF for gross fluctuations in the output signal.The best SMD components are suitable. Due to the small size of device, these capacitors fit directly to the power supply pins of the sensor. The capacitors must be attached to the sensor as close as possible.
Roboter-StarterKit-v2.jpg
Required components:
  • 1 x 100nF SMD 0805 multilayer capacitor
  • 1 x 100uF SMD 1206 multilayer capacitor

Buffering power supply

The servo for the front sensor is another source of interference.When starting it soaks very much electricity, which can lead to short voltage dips. Since the 4 AA cells already are too short for safe operation, it may cause a reset of the Arduino board. Remedy is also possible through an electrolytic capacitor (Elko) of 470..1000μF that is suspended in the supply line to the servo. This supplies the servo with the necessary power, without which there is greater voltage dips.
The electrolytic capacitor is soldered onto the back of the motor to the terminals of Shields Out ~ 6. The polarity of the capacitors must be considered.
IMG_4688.JPG
Required components:
  • 1 x Elko radial, 105 ° C, low ESR, 1000μF, 10V

Batteries instead of batteries

Not only for environmental reasons. Batteries are longer term cheaper than batteries. Unfortunately, 4 rechargeable batteries are not to provide the robot with the necessary voltage capable of due to the lower cell voltage. Batteries have 1.2V nominal voltage per cell, 1.5V batteries. This results in 4-cell battery for 4.8V and 6V batteries in. The input voltage range for the Arduino board is 6-20V, 7-12V are recommended. This is just something already on batteries.

Savings option 1

To solve this problem the Arduino electronics are supplied directly to the battery voltage on VCC, not Vin. For this purpose, it is necessary to input voltage (Vin) of the Arduino board and the motor voltage (Vmot) to separate the motor Shields. Normally, these two voltages are connected to each other by a bridge on the motor shield. This bridge has to go. This is done with a sharp knife, a small file or a Dremel with mini cutter or cutting disc.
Watch Out!
  • These conversions are only possible when using batteries, not on batteries. Otherwise the input chip drying is too high.
  • If the connections risk of total loss of the electronics
  • Automatic voltage switching between USB and external power supply is undermined by it. When connected via USB connection between Vin and VCC must be necessarily solved
On the following screen, the bottom of the engine Shields can be seen. The bridge is located below the center of the board and is labeled Vin connect. The interconnect between the two solder pads must be removed.
IMG_4677.JPG
Granted, this method is not without its dangers. Here, the Arduino is connected Baord bypassing the onboard voltage converter with Vin directly from the engine Shield and powered by the battery voltage. A single wire is sufficient, which is inserted on one side with a female connector on one of the free slots of the I2C engine Shields and stuck on the other side in the Vin screw.
IMG_4694.JPG
Required components:
  • 1-way socket
  • 10cm insulated wire red

Deluxe variant 2 Step Up Converter

In this variant, the battery voltage is highly regulated and stabilized by means of a step-up transformer to a value within the recommended input range. Modifications to the motor shield are not necessary. A suitable step-up converter is for example the LM2577 . This is a finished module on eBay, or Amazon Deal Extreme. The converter generates from an input voltage in the range of 3..30V an adjustable output voltage of 4..30V. In a boost converter low input voltage is converted into a higher output voltage. Warning, the modules can be easily confused with step-down converters with LM2596 IC. That buck that make a larger input voltage, a lower output voltage.
IMG_4696.JPG
The step-up converter is installed between the battery and the power supply to the motor shield with. On that occasion, you should also install a toggle switch is equal to activate / deactivate the robot. The step-up converter is set before connecting to the Moto-Shield, with the help of the potentiometer to an output voltage of 7.5V. On the one hand, this value is within the recommended voltage range of 7..12V for the Arduino board and motor shield. On the other hand fall to the motor driver from approximately 1.5V, while the motors are designed for self-6V.Thus, the ideal value is 7.5V. The step-up converter module fits very well to the bottom of the robot behind the battery compartment. Just stick with hot glue.
IMG_4697.JPG
Required components:
  • SainSmart LM2577 Power Converter StepUp
  • Optional toggle switch
  • 10cm insulated wire 2 x red, 1 x black
Location: Hoa Kỳ

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