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resistors' calculation

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Junior Member level 1
Sep 11, 2007
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i am designing a circuit connection using SRM400 module,LM555 timer and a buzzer on the breadboard.however,i do not sure about the value of the resistors used to make the buzzer works..the operation of these devices are:

1. LM555 timer(replacement for MCU) will generate an excitation pulses to pin1(I_O) of SRM400 IC,PW0268.
2.the transmitted pulse will be output at pin 11(DRIVER_O) to the ultrasonic transducer.
3.once the ultrasonic transducer detect there is a valid obstacles detected,the reflected signals(ECHO) will be route to pin10(ECHO)
4.then the reflected signals will go through internal processes within the PW0268 itself until the reflected signals output reach at pin1(I_O).
5.the buzzer will work as what i expected when the ultrasonic transducer detected obstacles.

this is the PW0268 circuit diagram:

i had connected the pin1(I_O) to the input of the connection of the buzzer of testpoint(TP) shown below:

i would like to know how to get the exact resistor's values?is there any calculations method to do it?

thank you very much:D
i am looking forward to your replies as soon as possible:D

resistors calculation

THE buzzer needs dc voltage.
I think you can use it in another configuration.
The purpose is just to supply the voltage needed only when needed. So the resistor is selected to make the transistor work in cut off or saturation modes.
Are you familier with these things?
If ues I suggest to select resistors and then by measuring V and I reach to the best value.
But you can do an easier configuration than that.
Let me know which to do and if you need help just ask

project using pw0268

hello u this is working but u can do this by using similar and different products

lm555 buzzer

to pouchito,
your method did work if i use it in another configuration for example if i connect it with the proximity detector,IRPD version 3.when the detector detects it will make the buzzer work.the buzzer works at a range of 4-8 Vdc.however, the problem is my SRM400 module cant work like what i mentioned in the first posted forum.if the SRM400 module cant work,the buzzer wont work.i am still trying hard to explore the problems:cry:maybe i can get some suggestions from you

thank you very much

method of calculation of resistors

therefore the problem is with the srm?
are you getting any output? what is the voltage?

ic - pw0268 with mcu

to pouchito,
therefore the problem is with the srm?
are you getting any output? what is the voltage?
i had gotten the same waveforms as the datasheet shown below:

the Vp-p=9.5Vdc,the Vavg=4.5Vdc with oscilloscope setting 5V/div and 500uSec/div

pw0268 calculations

ok let me know again what is going on.
step by steps problems can be solved.
Forget about the buzzer right now.
is there any signal coming to the IC?
is there a signal coming out of the IC?

Added after 9 minutes:

Do you have this?
this is the datasheet with clear images

14 pin ic calculation

to pouchito,

is there any signal coming to the IC?
yes-->at pin 1* of PW0268IC and there is a clock found at pin 16(CLK)

is there a signal coming out of the IC?
yes-->at pin 1* of PW0268IC

*since pin 1 is I_O pin

Do you have this?
this is the datasheet with clear images

yes,i have the datasheet.

conclusion:No difference in the echo pulse for different distance, when i adjusted the VR1 & VR2 from the SRM400 module.

resistor calculation for 9.5 to 5 volts

I will try to help you whan I get home

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