ULN2003A and AT89C55 Problem

[shashavali_m]

uln2003a sound

Hi,

I have connected (AT89c55) P1^7 port pin to ULN2003A and output of the ULN2003 is connected to a buzzer.
Problem is that am not able to switch on the Buzzer.

Please help me

Thanks in Advance..

 

[pauloynski]

uln2003`buzzer

Is this a self-oscilating buzzer or not?

 

[shashavali_m]

uln2003a schemtic

Its a 5V Buzzer and self oscillating...

 

[pauloynski]

how to test at89c55

First confirm if the buzzer is connected with the right polarity and if it is suited to the voltage you are using. After that confirm if is there any voltage across it when you try to turn it on (you may use a voltmeter if you have static operation). Even if it is not static a simpler voltmeter should show some voltage across it. If there is no voltage you have a wrong connection or your firmware is not switching the right port pin.

Added after 56 seconds:

You may short-circuit the ULN2003 output to ground to confirm the buzzer is OK.

 

[pranam77]

unl2003a with pull up circuit

Hai shashavali_m
Can you please post the schematic here so that having a look at the circuit is better than guessing.

 

[shashavali_m]

uln2003 buzzer

Updated on this topic:

When i connected the input pin of ULN2003A to VDD by removing the Microcontroller as it is on base, the output of the ULN2003A is GND, which in turns switch ON the Buzzer and ceates a sound. But when i drive through the input of ULN2003A from microntroller, am unable to switch ON buzzer. I check the voltage on the input pin of ULN2003A, its around 0.13V, it means it is not able to drive UNL2003A.

Please help me why Microcontroller pin cant drive the ULN2003

 

[FFFFFF]

difference uln2003a uln2003an

test after connect a 10 k to 100k resistor to the microcontroller power suppply

i think output is open collector

FFFFFF

 

[asif_ts]

uln2003a

Hi,

I have connected (AT89c55) P1^7 port pin to ULN2003A and output of the ULN2003 is connected to a buzzer.
Problem is that am not able to switch on the Buzzer.

Please help me

Thanks in Advance..

i think u are not pullup with 10k sip
you also used for single I/O 10k/R

 

[GetDeviceInfo]

If you check your datasheets, you'll see that the required current to turn on the driver is higher than what your port can source.

You can flip your logic around so that you are continually sinking a pull up resistor that provides the appropriate drive capacity.

 

[pauloynski]

Can´t believe there is someone using this kind of garbage developed in the early´s 1975. Do a favour to yourself and change to an AVR.

 

[geobabu]

Take care abt the ULN, its have Current drain pins. make the connection according to it
Geo

 

[abo_obayd]

Hi,
Take care!
When selecting ULN2003, choose the ULN2003AN.
There's difference, i tried this beleive me!
You will probably find it manufactured by TI.
ULN2003AN.

may be it's not the problem in your case, just keep it in consideration.