Sharp IR distance sensor improvement
Sharp IR distance sensors are very often used in robotics. But I always found it annoying, that they do not recognize very small objects, chair legs or even walls if the Sharp IR is set to an unfavorable angle to the wall. Here is the idea I came up:
The internal IR LED is disconnected from the Sharp IR distance sensor LED driver:
The LED driver triggers now a PNP transistor and this transistor triggers again a couple of IR LEDs which are placed around the Sharp sensor as close as possible to the original LED, because the CCD seems to be anisotropic. Reflection from the oposite direction of the original LED are ignored:
What it actually does is that:
On my prototype are four 3mm IR LEDs placed around the Sharp (the 2 LEDs on the left do not have any influence on the measuring, which I found out later). The sensor is now able to detect a 3mm diameter steel rod at 25 cm distance.
Further developements could include:
*** Update 2011.6.19 ***
Just a small rendering how a costum PCB for the Sharp could look like. The IR laser diode sitting on the place of the original IR LED. A driver for the IR laser diode is then necessary:
*** Update 2011.6.25 ***
Sharp Ladar prototype finished. The IR Laser has 30mW. The laser has three wires, red, black, and yellow. By setting the yellow wire high or low you can enable/disable the laser. This is a great feature for control. The laser has an adjustable focus as well.
LADAR mounted on RoverX:
Original voltage/distance graph vs voltage/distance graph with laser instead of built in IR LED (new graph not scaled):