dandy

Hi,

I was just helping some school kids to assemble a Line Follower.

My knowledge of electronics is primitive.

After wiring up the circuit on a veraboard, the motors dont seem to be working.

the sensors are functioning, so are the 74LS324N gates. I am using a ULN2004A Darlington type IC for motor control. the output from the gates are wired to the pin 1 and pin 2 of the ULN 2004A. The pin 8 is grounded and the Pin 9 is Vcc (12 v).

I have replaced the IC but have had no luck with getting the motors powered.

Any help would be of great relief.

Attached Files

line follower.pdf (27.0 KB, 48 views)

Nigel Goodwin

The motors are wired completely wrong, they should go to +ve and not ground - the ULN2004A is an open collector driver, and can only sink current, not source it.

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bloody-orc

Exactly as Nigel said before. You should have read the datasheet of the ULN more thoroughly... only sinking so the - wire from the motor not + wire.
But at least you are helping youngsters play with electronics and robotics wherever you live, and that is very kind of you

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dandy

Thanks bloody-orc, and Nigel.

As i had mentioned earlier, my electronics is very rusty.

bloody-orc, thanks for your your encouraging thoughts.

So guys when i check the output pins of the ULN2004, what should I be expecting? I mean what voltage should I be reading?

Also would like to add a buzzer when one of the sensors pass over a mirror.

so can i use the output from the gate to trigger a buzzer and if so, can you suggest me a simple circuit to do so? I have tried to use a BC 557 transistor, but i guess i wired it wrong.

Nigel Goodwin

Nothing! - it doesn't output a voltage, it simply switches the pin to ground - you need to connect the motors from the output pins to +ve. The output pin wikll then read the +ve voltage when NOT turned on, and will read near 0V when turned on.

I would suggest getting the motors working first!.

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dandy

Nigel

I got the motors working. Thanks to u and bloody-orc

if i feed the sensor to the pin 2 of 74LS324N instead of the pin 1, will it reverse the signal. i.e. the motors are running only if the sensor is active. I want the motors to run when the sensor is not active.

Now that I have got the motor working, with an additional bc557 and a peizo buzzer, can i have an sensors beep when it crosses a mirror? If so can u suggest a simple circuit.?

bloody-orc

Could you tell us what sensors are you using? what signal is it giving when there is a mirror and what when there is no mirror. and what kind of a buzzer are we talking about. Will it make a "horrible" noise when it is connected to power supply or will it just make a "click" when it is connected? then we/you know if it needs an extra modulation to get it buzzing on will a transistor do the job.

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phuanon

u use logic gate to design
I think it is hard