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# Amplified the signal of PWM from PIC18

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#### boon1987

##### Newbie level 6
Hi,

I am working on a project related to ultrasonic transmitter. I get the PWM signal from PIC18f452 to ultrasonic sensor. The PWM signal can get 40kHz frequency but the voltage is from 0 to 5V only. My question how to make the PWM signal become peak to peak voltage from -10 V to 10 V?

My concern is generate a 40kHz signal with -10V to 10 V peak to peak voltage square wave to ultrasonic transmitter.Does anyone have any idea on it? It is on the robot, so cannot use signal genearator. I need to use some circuit or PIC to do this task. Please provide me assistance, thank.

Added after 4 hours 46 minutes:

Hi,

I found a schematic of Ultrasonic Circuit from internet. The person who design it using connect the output of PIC to RS232 chip. After that, the output of RS232 chip is connect to buzzer.

I understand that the PWM of the signal from PIC can achieve 5V. But I don't understand how they convert the PWM signal to peak to peak 20V(from -10 V to 10 V) square wave. Anybody can give me the explaination? Image of schematic is below. I circle the area with red pen.

They connect GP4 and GP5 to RS232 chip and connect both output of RS232 to ultrasonic transmitter N1076.

The RS232 chip is normally a MAX232 IC.

Can anyone help me on this. Thank.

Schematic

boon1987 said:
The PWM signal can get 40kHz frequency but the voltage is from 0 to 5V only. My question how to make the PWM signal become peak to peak voltage from -10 V to 10 V?
What you wish to achieve can be done with help of a transformer. One of the advantages of this approach is that you can get even greater voltage than 20Vpp.

boon1987 said:
... But I don't understand how they convert the PWM signal to peak to peak 20V(from -10 V to 10 V) square wave. Anybody can give me the explaination? [with MAX232]
Using MAX232 for as a driver for the ultrasonic transducer is a very clever hack. You should read the datasheet for MAX232 and the RS-232 specification.

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