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Topic: IR sensor using 3-pin photo transistor (Read 1 time) previous topic - next topic

14beemsalaar

I am making IR sensors for my line following robot using arduino. The link to the circuit I'm making from is this.

http://m.instructables.com/id/DIY-Infrared-Sensor-Module/?ALLSTEPS

In the circuit it's given a photo diode with two legs but I am using a 3 pin photo transistor with collector connected to +5V and emitter yo the ground while I've left the base unconnected.

I did a few experiments and sometimes the led lights up but the intensity of it is extremely less and almost not visible. I tried changing the resistances but of no use.

Also, when I touch the base of the transistor with my finger, the led lights up. Why is that so? Kindly, let me know what to alter in the original circuit diagram for the sensor to work properly?

The components I'm using are:
1. IR Led.
2. ST-1KL3B  photo transistor
3. Normal Led.
4. 220 ohm resistance.
5. 1 ohm resistance.
6. 5 V from arduino.

The circuit I've made is attached herewith.

14beemsalaar

Due to restriction of file size. I cannot upload the circuit picture here. Sorry but please reply. Thank you.

CrossRoads

Or, upload it elsewhere and post a link to it.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

14beemsalaar

Or, upload it elsewhere and post a link to it.
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Or, upload it elsewhere and post a link to it.
See the original circuit from the link provided. I only placed the collector at the positive terminal( 5 V) while grounding the emitter and keeping the base unconnected. That's the only alteration I did.

Grumpy_Mike

#4
Jun 03, 2015, 10:17 pm Last Edit: Jun 03, 2015, 10:18 pm by Grumpy_Mike
Due to restriction of file size. I cannot upload the circuit picture here. Sorry but please reply. Thank you.
Then the picture is way too big, cut down the size and try again.

Quote
only placed the collector at the positive terminal( 5 V) while grounding the emitter and keeping the base unconnected. That's the only alteration I did.
Which is enough to stop it from working and fry the photo transistor.

Grumpy_Mike

#5
Jun 03, 2015, 10:20 pm Last Edit: Jun 03, 2015, 10:25 pm by Grumpy_Mike
After looking at that circuit I see it is up to the normal instructables standard. Pure crap by some one who has little understanding of electronics.

There is no current limiting on those IR diodes so they will fry. The wrong symbols are used on the schematic so it is impossible to tell how it is supposed to work.

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