Hello, OP-AMP Differential Drive Robot for my class project

[KhainiRobot]

Well Hello everyone;

I need help.....serious help, I have no Idea what i am doing.

I have a class project to make a differential drive robot using Operational amplifier circuitry. We are not allowed to use micro controllers, neither programming.

The robot has to go in a straight line and when it hits/detects a wall in front if it, It  has to turn.

I have already have 2 geared motors, 2 wheels and a caster wheel.

I also have bunch of resistors, capacitors, op amps, diodes, transistors and much more from my previous class ( I didn't use op-amps in my previous class).

So i believe, I need the wheels, motors, caster wheel, couple of op-amps and sensors to keep the wheels at a steady rate to go in a straight line.

I have 1 question....

How the hell do i put everything together, what goes first...seconds...third...etc...

Can I pull this off?

[Soeren]

Hi,

The robot has to go in a straight line and when it hits/detects a wall in front if it, It  has to turn.

How straight should it go?

I have already have 2 geared motors, 2 wheels and a caster wheel.

Data and/or links to datasheets for the motors?
Diameter of wheels?

So i believe, I need the wheels, motors, caster wheel, couple of op-amps and sensors to keep the wheels at a steady rate to go in a straight line.

And some power transistors.

I have 1 question....

How the hell do i put everything together, what goes first...seconds...third...etc...

Can you follow a schematic diagram?

Can I pull this off?

Hey, you said 1 question, don't push it   

[KhainiRobot]

"How straight should it go?"

Both of the motors are supposed to output the same speed via sensors helping it. Velocity of the left wheel should = Velocity of right wheel

Link for the motor: http://www.solarbotics.com/products/gm9/

Link for the wheels: http://www.solarbotics.com/products/gmpw/


Yes I can follow a schematic diagram.

Thank you for your response

( I do know I need to use a Low-Pass filter XD)

[Soeren]

Hi,

Fine so far. Are you allowed to use an H-bridge chip and/or power transistors?
An L293, not the suffix-D version, would make things easier for you.

I assume you want it to be able to reverse the motors to avoid being stranded up against a wall?

[KhainiRobot]

I believe we are allowed to use that because he only told us not to use micro controllers and no programming.

Do you want me to order the L293 part?

Yes, you are right about the part of going reverse to avoid hitting the wall.

[Soeren]

Hi,

I believe we are allowed to use that because he only told us not to use micro controllers and no programming.

Strange teacher... Hardware logic is just another way of "programming".

Do you want me to order the L293 part?

I's more a question of what you want to order.

Anyway, here's a circuit to try. It uses an L293 and a 4093 as the active components.
The reverse delay is made by R1/C1 for the left side and R6/C3 for the right side.

The LED's and their resistors is just meant as a test aid and can be removed when it works. LED1 and LED4 could be green, for easier differentiation. They show which direction the motor will turn.

The bumper switches (attached to SW1+, SW1-, SW2+ and SW2-) could be made of piano wire that touches a contact point when hitting a wall. It will have to cover each front "corner", so that both a direct hit and a slanted hit will make contact.

Yes, you are right about the part of going reverse to avoid hitting the wall.

You will have to mount it so that the switch covering the physical left corner controls the right side motor and v.v.

[KhainiRobot]

I cannot find 4093. Can I use a NAND gate( replacing the 4093)?

[Soeren]

Hi,

I cannot find 4093. Can I use a NAND gate( replacing the 4093)?

4093 IS a quad dual input NAND gate. It's about as common as the 555.

You can use a 4011 instead (in this app), the only difference is that it haven't got Schmitt trigger inputs, so it will be a little harder to calculate R1/C1 for the reverse time, but with a bit of trial and error, you should be able to get there.

[KhainiRobot]

funny, i got the 4093 easily but I am having a hard time finding L293 on the web. All i see is L293D,L293N,L293B and more...

[Soeren]

Hi,

funny, i got the 4093 easily

Told you so   

but I am having a hard time finding L293 on the web. All i see is L293D,L293N,L293B and more...

You can use a SN754410 instead, it's pin compatible and all.