infrared ground/object sensor for robot navigation

i used this sensor on 2 of my robots. those were working on a table surface, so the robots had to detect when they have arrived to the edge, to stop, and turn back... it can sence also obstacles in the way.

Step 1 A simple version with bipolar transistors

first i made a simple version with bipolas transistors. the full schematics of that small robot is attached (not the same robot as in the front page).

the point in the operation is:
1. an oscillator generates a square wave.
2. an infrared led with narrow angle transmits this signal as infrared light/ray.
3. this is reflecting back from obstackles within the viewing angle, basically from a viewing spot on the ground, or in front of the robot.
4. there is a photodiode or phototransistor next to the IR-LED, with also narrow angle pointed to the same spot as the LED was. phototransistor was used on the bipolar version, and photodiode on the IC version.
5. there is a receiver circuit connected to the sensor, detecting if there is reflected signal or not.
6. if there is a signal (within a specified frequency band, like 5khz-150khz), then the output goes to logic high level, otherwise to low level. this signal can be used by a microcontroller, or by an analog control logic. there is signal if there is an obstacle/ground within the sensing range, which is about 5-15 centimeters.

Comments

[Ma77h3w]

I did something like this. Use the microcontroller to strobe various LEDs on the robot and measure the output directly from them with it's 4 analogue inputs. It measured the voltage from a phototransistor when the LED was both off and on.. and could approximate distance (if used in a maze where the walls all had the same reflective properties). Found it worked at a lot larger ranges with normal white or red LEDs than with inferred and a phototransistor or LDR.. but maybe that was just the Inferred components I had

[jimsondefrancia05]

hi can u make me one of that sensor you build i willing to pay u and send me some videos so i can see if it is really working reply as soon as possible

[buenos]

sorry, but i am not making anything anymore, i am a hardware development engineer (only designing computer motherboards). i dont want to waste my time on this for you, the 50-100 dollars what you would pay wouldnt compensate me. i am afraid, you have to buid it yourself. or ask an electronics technician to make it.

[t.rohner]

Whoa, this is some schematic. It reminds me of the "good" old times, when i started out with electronics.(Well we had OP-Amps like the 741 back then...) We used to produce infrared light barriers on "thick film", these are ceramic substrates with screen-printed conductors(silver-palladium) and resistors(carbon compound), the rest were SMD devices. This was 25 years ago, SMD was rather high-tech then. It's nice to see someone, who can still use plain transistors not only to increase the current of a controller output...

[buenos]

hi. actually, a have designed this transistor circuit in 2000, so a littlebit more than 8 years ago.

[alex-sharetskiy]

This might b]e better off in the Tech section of the Forums