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Topic: Which circuit? (Read 299 times) previous topic - next topic

Mika857

I have a problem with the Ir-transistors. With the first circuit the values are different(like the sensor on pin0 had a value about 30 and the value of the pin4 is about 0. And with the second cicuit the sensor on pin0 worked perfectly but the other sensors didnt work.

larryd

OP's images.






#2 will not work.


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MrMark

What are you trying to accomplish, and what sensor part are you using?

Confusing things about the post:

1) Text says "IR-transistors" while drawing shows diodes.

2) If it's really diodes they should should be reverse biased rather than forward biased as shown in the schematics.  One would have to see the component datasheet to determine if resistor values are appropriate.

3) If the first schematic represents the actual circuit, an ADC reading of either 30 or 0 seem implausible.  I'd expect something on the order of 800 or more.

jremington

#3
Sep 09, 2019, 07:00 pm Last Edit: Sep 09, 2019, 07:01 pm by jremington
Please post a link to the product page or data sheet for the sensors and tell us the exact part identification.

If the sensors are photodiodes, neither circuit will work, as diagrammed.

Mika857

#4
Sep 11, 2019, 03:59 pm Last Edit: Sep 11, 2019, 04:02 pm by Mika857
I dind't buy those sensors but I can send you a pic.

They have got 2 electrodes.

jremington

#5
Sep 11, 2019, 04:47 pm Last Edit: Sep 11, 2019, 04:47 pm by jremington
Post a link to the data sheet.

If you don't know what you have, then start over with known parts, as we would only be guessing what they are.

MrMark

Obviously it's best to have the datasheet for what you're working with to properly select circuit resistor values and such, but if you have a voltmeter with a diode test setting, it would be easy enough to determine whether you've got a photodiode or a phototransistor. 

A photodiode will show low resistance with one polarity and high with the reverse.  A phototransistor will have high resistance with both polarities when it is shielded from light.  Both device types are commonly sold in the sort of package pictured.

Mika857

#7
Sep 12, 2019, 04:06 pm Last Edit: Sep 12, 2019, 04:25 pm by Mika857
Thank you, but the problem is now, I dont have a voltmeter.
But in school there is one with this I can show in circa 2-3 weeks.

But could you send me a circuit for both cases, that I can try both and look for the best values?

Sorry I know I sound very dumb but I'm not very experienced in electronics.

MrMark

#8
Sep 12, 2019, 04:50 pm Last Edit: Sep 12, 2019, 04:56 pm by MrMark
Simple Photodiode Circuit: from (from here)
Vout goes to the Arduino analog input. This is similar your first picture in the original post except your schematic shows the diodes forward rather than reverse biased.

Simple Phototransistor Circuit:
VA3 goes to the Arduino analog input.

For both of these circuits the optimum resistor values are determined by the characteristics of your particular device and the desired operating conditions.  You can try these circuit configurations with your device and see if you get some light dependent response at the Arduino ADC input.  It's unlikely you can damage the device with 5 volts and a series resistor of at least 1k Ohm whatever you do and you can experiment with different resistance values if you have them available.

If you are pursuing electronics as a hobby, a voltmeter, even the cheapest you can find, is going to be tremendously helpful.

Mika857

#9
Sep 13, 2019, 03:45 pm Last Edit: Sep 13, 2019, 03:49 pm by Mika857
Ok thank you so much, but what can I do when I want to connect 5(or more)

jremington

#10
Sep 13, 2019, 05:06 pm Last Edit: Sep 13, 2019, 05:06 pm by jremington
Make five copies of the circuit.

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