Friday, October 29, 2010

Final(?) Hardware Specs and Costs

- base: Wholesale rc car Product-10pcs/lot Mclaren model car Remote control toy ~29€ (40 USD)
- mc:Arduino Fio Sparkfun [SF-DEV-09712] - 19,22 €
- batteries: Polymer Lithium Ion Batteries - 1100mAh Sparkfun [SF-PRT-00339] - 6,41 €
- xbee modem: XBee 1mW Wire Antenna Sparkfun [SF-WRL-08665] - 22,43 €
- build hbridge from lab components: ~10€ (l293e = 6.6€)
- steering servo (not sure if necessary): HobbyKing Online R/C Hobby Store : HXT900 9g / 1.6kg / .12sec Micro Servo ~2€

putting all together, individual robot cost: ~90€
real costs to lab per robot (excluding xbee modem and hbridge costs): ~57€

EXTRA EQUIPMENT
50% extra batteries:
3+ Polymer Lithium Ion Batteries - 1100mAh [SF-PRT-00339] - 6,41 €
Xbee device to use with the computer:
2x XBee Explorer Dongle [SF-WRL-09819] - 23,07 €
Device to program the arduino:
2x FTDI Basic Breakout - 3.3V [SF-DEV-09873] - 12,82 €
Devices to change the bootloader of arduino (required to wireless program arduino)
1x Pocket AVR Programmer [SF-PGM-09825] - 12,82 €
1x AVR - ICSP Adapter [SF-DEV-09046] - 5,77 €
2x 2x5 AVR ICSP Male Header [SF-PRT-00778] - 0,51 €
Acessories for connections
4x Break Away Female Headers [SF-PRT-00115] - 0,96 €
4x Break Away Headers - Right Angle [SF-PRT-00553] - 0,96 €
4x Break Away Headers - Straight [SF-PRT-00116] - 0,64 €
USB cables to power arduino, recharge batteries, use programmer, use xbee explorer, use avr
4x USB miniB Cable - 6 Foot [SF-CAB-00598] - 2,69 €

Wednesday, October 27, 2010

IW02 Test Report

This is the report of the tests conducted with the RC car chassis, to validate the viability of using such solution. The setup was first assembled in a breadboard linking an Arduino Duemilanove, a Xbee Series 2 and an H-Bridge (L293E). Another Xbee modem was connected to a laptop and sent messages to the remote one (in the car).



This first test was successful, with signals sent via wireless to command the traction motor of the car.
The next step was to build an Arduino compatible shield containing the Xbee and the H-Bridge, to finally test the capability of the car to start the motor with a load applied (the car weight). This test also had good results. The car was fully mobile, and several situations were tested.


Unfortunately the batteries soon wore off and the Arduino board could not obtain enough power. Another minor problem found was a lag of wireless messages, although it was not constant.
The next step is to install new batteries and measure the minimum voltage to start moving the car, and also assess if the servo that came with the RC chassis is good enough for our research purposes.

Monday, October 25, 2010

Current Costs of Robot Base

Estimated current costs (excluding shipping costs):

-base: ~17€ (26 USD)
-mc: ~17€
-batteries: ~6.5€
-xbee modem: ~25€

total so far: 65.5€

what is missing?
deppending if I manage to use the h-bridge that comes with the base:

- build hbridge from lab components: ~10€ (l293e = 6.6€)
- buy motor driver shield:
--- Adafruit Motor/Stepper/Servo Shield for Arduino kit [v1.0] - the best and cheaper ~ 20.5
--- SparkFun Electronics - Ardumoto - Motor Driver Shield ~ 22€
--- Arduino - ArduinoMotorShield ~ 20.5

the xbee support:
- SparkFun Electronics - XBee Wireless Shield
- SparkFun Electronics - XBee Explorer Regulated ~9€ (may require some hardware modifications, don't change ttl signals level)
- SparkFun Electronics - Breakout Board for XBee Module (must build connections and level changer if to use a 5V board) ~ 4.5€
- XBee adapter - Simple wireless communication ~10€ (regulate power and ttl levels, pinout needs adapter)
- Arduino - ArduinoXbeeShield ~17.5€

steering servo:
- HobbyKing Online R/C Hobby Store : HXT900 9g / 1.6kg / .12sec Micro Servo ~ 2€

so, putting all together:
- expensive solution: 105€
- cheap sollution: 82€

Hardware Links II

New hardware specifications for the robot (must create a name)

Base:
1/28 firelap2.0 miniz rc car chassis products, from alibaba.com
Wholesale rc car Product-10pcs/lot Mclaren model car Remote control toy (new website)

Microcontroller:
Arduino Wiki English
Arduino - ArduinoBoardPro (cheaper and cleaner, must decide for whether 3.3V or 5V, this choice may have an implication in the use of arduino compatible shields?)

Wireless:

Arduino - ArduinoXbeeShield (too expensive)
SparkFun Electronics - XBee Explorer Regulated (cheaper and more simple, but may have some design problems: SparkFun Electronics • View topic - XBee Explorer Regulated Bug)
alternatives: XBee adapter - Simple wireless communication or SparkFun Electronics - Breakout Board for XBee Module

Batteries:
RS Cargadores y baterías recargables de NiMH, electrónica de consumo
note: for 5 cars = 20 batteries plus 50% to recharge backups, around 30 batteries, plus 2 chargers, or a big one?

Servos (not completely sure if the are necessary):
HobbyKing Online R/C Hobby Store : Turnigy TG9e 9g / 1.5kg / 0.10sec Eco Micro Servo
HobbyKing Online R/C Hobby Store : HXT500 5g / .8kg / .10sec Micro Servo
HobbyKing Online R/C Hobby Store : HXT900 9g / 1.6kg / .12sec Micro Servo

Xbee Explorer Regulated

I am finding problems related to the xbee adaptor I intented to use.

Arduino + Xbee

Arduino - ArduinoBoardFioProgramming

Sparkfun european distributors

Tienda BricoGeek.com - BricoGeek.com
lipoly.de, Everything for the electric flight
Watterott electronic

Robot Base

the new website to buy the chassis: Wholesale rc car Product-10pcs/lot Mclaren model car Remote control toy

Sunday, October 24, 2010

Week Review

Effort was mostly spent in validating the base proposal in order to proceed with the purchase process.
The short term goal is to evaluate the traction dc motor from the robot base, by wireless commands sent via xbee. I am afraid that the minimal speed that I could keep the robot moving would be too fast. The test setup:
iw02 base + 4 AAA batteries + arduino + h-bridge + xbee <---> xbee + laptop
I will send speed commands via arduino and evaluate the base movements.
Note: Can I measure the voltage at the motor terminals with arduino?
I will use the xbee modems at AT mode, so one modem will echo commands received from the other (Arduino - ArduinoXbeeShield, XBEE Basics - Community Tutorials).
The next step is to evaluate the steering servo performance, acoording to results, a new servo would have to be bought.