The Line-Following Mini-Tank

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keiji313
Newbie Pyro
Posts: 3
Joined: Tue Aug 02, 2011 3:59 pm

hi again..

Postby keiji313 » Thu Oct 06, 2011 3:57 am

are you a Filipino?? If so, where did you buy the IR Sensor pair? the receiver and emitter?

ThePyroElectro
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Joined: Mon Nov 12, 2007 9:24 pm
Location: Earth
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Postby ThePyroElectro » Thu Oct 06, 2011 5:26 am

Hi,

I'm not filipino, sorry.

You can find the IR Emitter here:
http://www.pyroelectro.com/parts/IR_Emitter_Diode
IR Receiver here:
http://www.pyroelectro.com/parts/IR_Detector

This company ships international.

fathi
Newbie Pyro
Posts: 2
Joined: Fri Mar 07, 2014 8:10 pm

Re: The Line-Following Mini-Tank

Postby fathi » Fri Mar 07, 2014 8:55 pm

hi Mr I admit that your site attracted me , I am new in the field, so please be patient with me.I have some questions.
can I use the( phototransistor+IR emitter) from broken computer mouse (it has 3 pairs).?

how can I calibrate the trimpot (potentiometer)?

can I use 100 micro farade capacitor or10 micro farade insted of 47 ?

execuse me but I think according to the schematic the two motors will work continuously not affected with the
state of tip120 transistors, so the current will flow from the positive side across the diodes D5 D6 to the motors then across
R11 OR R12 ,then D7 D8 TO THE GROUND.I think that the led and the companion resistor should be connected in series with the motors.

what is the goal of putting D3, D4 and D5 D6 ?

how can I know the values of resistors trasnsistors with a different power sourse let s say 12V ?

how can Q2 Q3 affect( Q4 Q5) witch its base can get current directly across R2 R3?

thank you very much.

fathi
Newbie Pyro
Posts: 2
Joined: Fri Mar 07, 2014 8:10 pm

Re: The Line-Following Mini-Tank

Postby fathi » Mon Mar 17, 2014 4:20 pm

I am waiting for replies from pyroelectro.

ThePyroElectro
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Re: The Line-Following Mini-Tank

Postby ThePyroElectro » Tue Mar 18, 2014 5:17 pm

Hi Fathi,

Using a phototransistor + emitter from a computer mouse would likely change the design, so unless you're willing to figure out exactly how it works and plugs into the circuit, I wouldn't recommend going this route. Especially since a new phototransistor + emitter diode are so cheap to buy!

The trimpot is used to calibrate sensitivity of the circuit. When you turn the trimpot with a screwdriver it changes the resistance value altering the voltage hitting the base of Q1.

100uF or 10uF instead 47 microfarad is definitely ok.

Here's how the transistors should be in the two different states:

Code: Select all

 (IR sensed white)
Q1 - Off
Q2 - On
Q3 - Off
Q4 - On (M1 On)
Q5 - Off (M2 Off)

 (IR sensed black)
Q1 - On
Q2 - Off
Q3 - On
Q4 - Off (M1 off)
Q5 - On (M2 on)


I added D5 and D6 just so that there was a 0.7v voltage drop from my 3.7v battery. The motors are 3v motors and I didn't want to hurt them.

D3 and D4 can prevent the motors from going backwards, but they are generally useless and could be omitted.

Most of these resistors are used as pull-up/pull-down and not much current flows through them. Changing to +12v wouldn't impact the control side of the circuit, only the Q4/Q5 motor power side of the circuit.

You could put the LED's in series with the motors and that would work too. I believe the way I set it up, there was just enough leakage current through D3 and D4 to turn on the LEDs...perhaps I got lucky there.

Q3 affects Q4 because normally R2 is pulling up Q4's base turning Q4 on. When Q3 is turned on, this connects Q4's base to ground turning Q4 off and thus M1 off.

Q2 affects Q5 in the same way. Q2 on means Q5's base is ground, turning M2 off.

Hope this helps.


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