Get the SoR Robotics Android App on Android Market for FREE. See this forum post for details.
0 Members and 1 Guest are viewing this topic.
Or use a 20kohm Pot here in series with a 100ohm resistor for white line following calibration.
I think you don't get me any way...In above it is 20K then R2 changes too 220k
Anyway I want to add some more doubt:-1.) I am little confused how to find cathode and anode of Photo diode as it is black(opaque) from out.
2.) As per schematic value of all resistance is given, whenever i use pott. meter they never set to accurate and changes every time. so I want to have five sensors in BOT can i do multiplex with resistance to reduce the numbers of resistance.
Some PT's have 3 pins (base, emitter and collector)and look exactly like a common transistor, only with a window (whether "black" to the naked eye or water clear)
or do you want to 5 sensors and want to save 4 resistors by using more I/O pins?
In three terminal the surface are is big so, i think it will pick some stray Infrared rays also,right?
Quoteor do you want to 5 sensors and want to save 4 resistors by using more I/O pins?Yes...
The circuit you are telling is totally diff. is there anyy way to find Resistance values?
The devices you have, do they resemble 3mm LED's, only black?
Each "op-amp-comparator" has got hysteresis by the 4.7 MOhm resistors, to avoid oscillation around the shifting point and they all share the same reference voltage from the wiper of VR1.
If you want to make it as cheap as possible, just go with the first circuit on the page you referred to, the one without op-amps. The outputs can go directly to the I/O pins of a controller.
ou just need to make one circuit, to find the best resistor value. Use a potentiometer or a trimmer to dial it in, then de-solder it without disturbing the position of the wiper and measure its value. Finally install resistors with the same value as you measured.
QuoteThe devices you have, do they resemble 3mm LED's, only black?Sorry i don't get u?
Can you explain me more about hysteresis in comparator, how??that mean using gain block will not have hysteresis, right??
QuoteIf you want to make it as cheap as possible, just go with the first circuit on the page you referred to, the one without op-amps. The outputs can go directly to the I/O pins of a controller.No way i don't want to losses quality of signal...!!
OK, I was just using that second gain block op-amp circuit in SOR the value of R2 was given as 200K but i don't find that efficient as compare to 20-30K .......so, i think 20K pot. meter is best.
But in some cases like outdoor using line follower will causes problem in its sensitivity, then how to change the reff. voltage..?
Do you know the name of the PT's and do you have a link to the datasheet?
Measure the needed resistance in all possible environments, outdoor in strong sun light,
I think its local Photo transistor....no data sheet provided.and how to differ between photo diode and photo transistor?
I have measure the resistance in sunlight it was very less (negligible),
can i use freq. modulation then filter it ..?as we do this in Television remote control???
I am really suck with this circuit,
i don't understand this simple circuit is creating so much problem with IR as there is no datasheet for Photo diode I can't surely identifies the -ve and +ve terminal ( cathode and anode) + The value of R2 as i am using 50K pot. meter varying it is also not changing so much reference voltage to op-amp .....
any hint or suggestion that any one wants to give me for this problem will be appreciated..!!
Remember to position the PT as it will be used on a 'bot.
QuoteRemember to position the PT as it will be used on a 'bot.Sorry, i didn't get you..!!
Put photo-transistor to where it has to be on the robot and then take measurements Soeren asked You for.
OK, i am just testing it on Bread board for now..!!my reading are:-----a. Dark condition 3.8V max 1V minb. Bright .7V max .21V minc. Normal 3.3V max .20V minmax mean black and white -> min.
I forget to add these value of Resistance used..!!R2-> 28K(pot) + 4.7K ( series) R1 with IR Tx -> 600Ohms
Build this basic circuit:With the values:Vcc = 5VR1 = 220 OhmR2 = 100 kOhmNo potentiometers, just the above mentioned resistors (and the LED and the PT of course)![...]Remember to position the PT as it will be used on a 'bot.
Apart from that, where did you get a 600 Ohm resistor? There's no 600 Ohm resistors in the standard ranges.
1. in room medium white -> 0.12V black-> 0.16V2. in room bright " 0.14V " 0.18V3. outside not so bright 0.13V 0.17V