Let's Make Robots!

infrared sensors

I've got two sets of phototransistors and infrared emitters put together to make two IR distance sensors. They are both connected in the same way, both powered by my Arduino Uno, both with the same resistor, etc. But when I check the values I'm getting from them, one of them ranges from about 980 - 1010, with the higher value closest to the sensor. The other, however, goes from about 350 - 570, with the higher value the furthest from the sensor.

Arduino to processing

So I have a Sharp IR sensor connected to my Arduino, feeding to my pc the values of its analog input, via the Serial connection.

To do this, I'm using the Serial.write() command. I want to be able to read these values into processing, but when I use the Serial.read() command in Processing, the values it picks up are nothing like what the Arduino Serial monitor is giving me, and are unaffected by the IR sensor.

What am I doing wrong, and how can I get processing to read these values from the IR sensor?

Any help is appreciated.

Infrared Receiver

I've found heaps of places that sell IR emitter LEDs, like these ones: http://littlebirdelectronics.com/products/infrared-led-950nm-1pcs

But I can't seem to find any IR receiver LEDs, like the black ones used by many in their distance or motion sensors.

Can anyone point me to a place selling them, preferably in Australia?

So I'm new to LMR, and this is my first robot. For now, it's just an Arduino Uno, a motor driver circuit, and two motors. The motor driver circuit I got from here: … Read more

Powering an Arduino: batteries/USB

I have an Arduino, with a Sharp IR sensor connected to it, and code that basically says:

If analog value from Sharp > certain value, turn LED on.

else, turn LED off.

When I plug my Arduino into my computer, and power it via USB, this works perfectly.

However, when I power it by batteries (4 x AAA), the LED is always on, even when there is nothing near the Sharp at all. Can anyone give an explanation of why this happens, or a solution to this problem?

IR v. Sonar

I've been making plan for an obstacle-avoiding robot, and was originally planning to use a Sharp IR range finder for it (10 - 80cm), but after seeing other sonar range finders, and other people's projects (the majority of the ones I see seem to use sonar), I was wondering:

Which is better: IR or sonar?

'Cos IR recievers can be affected by ambient IR light, and the best i;ve seen goes up to 150cm, whereas I;ve seen sonar ones up to 7.4m, roundabout, and they can't be affected by ambient sound (I think).

L293D Motor Driver

Hey, can anyone tell me if the L293D motor driver chip can take an analog value to its input pins?

Or does it have to be a logical 1 or 0?

Just wondering if I can drive my motor at variable speeds with it, or if I only get one speed or no speed.

Here is a diagram of the chip:

 

Capacitors

Hi y'all, just joined LMR, fantastic site, lovin' it already . . .

 

I am a bit of a beginner to robotics, I mean I can program and all that, and make these things, but I know not how or why they work.

One thing I have been wondering is about capacitors:

When designing a circuit, how does one know where to place capacitors, or why to have them, or how they function in that position?

With this circuit in particular (from here: http://letsmakerobots.com/node/2074), why the caps?

those two in the top-right, why do they both need to be there?