Circuit problem

[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.

 

[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.

 

[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

 

[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]

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?

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.

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.

I would suggest getting the motors working first!.

 

[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.

 

[phuanon]

u use logic gate to design
I think it is hard