Pushkar Kolhe

Interestingness

pushkar — Sun, 24 Jan 2010 23:04:09 +0000

HCI/Devices:
Chronos Wireless Watch from TI

Astrophotography:
Astropix

Helicontrol with Arduino

pushkar — Sun, 10 Jan 2010 01:00:23 +0000

Heli’s motor take up very high current. So, a motor driver that supports less than 4 or 5 Amps was out of the question. We did not have FET’s to make a H-Bridge, so we hacked upon the radio box of the heli and connected a cable to the FET bridge already there. We also tested PWM control on these connections and it worked!

Cable hacked to provide PWM into the radio box to directly control speed of motors

I also soldered a quick and a compact prototype board that would interface the Arduino Pro with all our sensors. I tried to install the accelerometer and the 2 gyros in the XY and YZ plane, so that, they revolve around a common center (This is not really required).

Circuit - Top

Circuit - Bottom

Circuit - Side

Circuit - Final

Rangefinder using Arduino and Servo

pushkar — Sat, 19 Dec 2009 00:10:04 +0000

A Hokuyo Range sensor costs you $2000 and a cheapo SHARP IR sensor with a servo is $20, max!. The difference between them is probably only that the range sensor is more mechanically stable and hence faster. The range sensor that we hacked is actually an IR sensor pasted over a servo. And a servo is slower than a DC motor. But, in our project our range sensor is 100 times better because it is 100 times cheaper and more importantly 20 times lighter. It should serve us enough to find obstacles. We might later add 3 IR sensor on the servos to get more data.

Add pan tilt to the SHARP IR sensor and it becomes better than the Hokuyo Range sensor! More on that later…

Here is what we came up with…

Following is the raw data and the corresponding position data we got from this. The position data is not calibrated and hence the walls appear curved. The SHARP IR sensor has a non-linear curve. A good calibration article is on the Acroname website.

RAW Range Data

2D Range Data

MiniUAV Project Started

pushkar — Thu, 10 Dec 2009 06:55:03 +0000

We (me and Jon) are bored to hell. I saw this cheap $30 single rotor helicopter toy at Fry’s and bought it, with the motivation that I would some day make it into a drone. We flew it in the Klaus atrium. After it broke several Christmas decorations and itself, we searched for a more stable coaxial helicopter. We settled on the 3 Channel 9060 Overlord Double Co-Axial Helicopter from XHeli for 50 bucks :-) and 12 :-( for shipping. Anyways, it looks like this:

Coaxial Heli

It is stable. The remote control is great. You can set the power of the main rotor using the left joystick once and it remains there. Later, we also found out that it can lift approximately 110 grams of more weight.

Alongwith the heli, we bought a bunch of other stuff that we thought was useful:

Arduino Pro with ATMEGA 328 (5V board)
FTDI Breakout for programming
Servos
2 XBee Series 2.5 with USB breakout boards

Sensors:

Analog ADXL335 (3 axis sensors)
Silicon Sensing CRS07 Gyros (11S & 13S)
SHARP IR Distance Measuring Sensors