Consider PWM signal
When using microcontroller and want to drive motor control or control led intensity you can use DAC to generate analog output voltage. But there is an easier way of doing this. You can use digital output to reach same results. This technique is known as PWM – Pulse Width Modulation.
In this picture you can see 50% duty cycle square wave form. The width of “1” is equal to “0” level, this means if signal amplitude is 5V, then average voltage over one cycle is 2.5V. It is as though of hawing constant 2.5V voltage.
If you have 10% duty cycle, then your average voltage would be 0.5V.
You should use low pass filter to convert pulses to analog voltage:
This is like digital to analog converter without DAC.
You can use PWM to drive LED to change light intensities. Also it can be used to generate audio by changing frequency of duty cycle. DC motors can also be controlled effectively by PWM.
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June 6th, 2006 at 11:26 pm
I am hoping to use this idea for a project. I want to send a PWM signal from a microprocessor, and, through the duty cycle, create a corresponding analog voltage. This is straight out of the article. The problem is, this analog voltage has to be a constant voltage, it cannot be varying (ie from your example of a 50% duty cycle and a 5V amplitude we would see an average 2.5V analog voltage, but i need this 2.5V to be effectively constant instead of just averaged). I dont know if the low pass filters can effectively achieve this or what. Any help would be greatly appreciated!
June 7th, 2006 at 12:59 pm
You may try to look at so called
Buck-Converter
And of course Wikipedia
I hope this gives some idea…
February 6th, 2008 at 8:17 pm
Hi,
if i want to generate analogue waveform (sin of frequency f) then what is the value of C and R required to get undistorted output.