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I think you need to elaborate a bit because I can't decipher what you've posted.Hi my friends
i have a sensor with pwm output(38khz). i want convert it to voltage.
i used rc filter but it does not have a real time response!!!
what should i do?????
I think you need to elaborate a bit because I can't decipher what you've posted.
Chris
Take a look at the typical app circuit on page 2 and read page 3.
http://pdf1.alldatasheet.com/datasheet-pdf/view/26556/VISHAY/TSOP1138.html
Chris
Reading this again has me wondering if we're misinterpreting you. Do you want to filter the signal or obtain a DC level from it?i have a sensor with pwm output(38khz). i want convert it to voltage.
If he wants a DC voltage I think it's going to require more than a Diode and Cap because of that very high value collector resistor. Especially if the output signal is going to be split in two. One being the PWM signal and the second.. DC. He's probably going to need a high Z input buffer driving a rectifier diode and filter cap. Not doing so, by hanging a diode and filter cap directly on that 80KΩ output, will certainly swamp out the PWM signal.I think he want's a D.C voltage. That's how I take it. Let me see if I can come up with something.
Adam
Yeah, I think a common single ended LM324 in voltage follower config should suffice. On the other hand we're assuming we understand what he wants. I've been down that rocky road to many times to admit how many!I'm thinking a little op-amp circuit personally.
Adam
Adam, I'm a bit confused with this circuit. I didn't sim it but it would seem to me that R1 * C1 would more likely transform an (above zero) square or rectangular wave to something that resembles an above zero sinusoidal-(esc) wave. Am I missing something?Here is a very crude circuit which will produce a voltage from a PWM signal. 1 us pulse produces approx. 300 mV and 25 us produces approx. 4.8 Volts. If that's what the OP wants.
Adam
View attachment 20753
Isn't that the same when it comes to PWM?Do you want to filter the signal or obtain a DC level from it?
Well perhaps if the high time is 100%.Isn't that the same when it comes to PWM?