PWM question

hello forum,how can i take PWM (0.500v 102 Hz)from arduino ?thank you

Setting PWM frequency PWM-Frequency

I don't know if you can get exactly 102Hz. If the PWM output is going to a high impedance input a voltage divider might work to get to 0 to 0.5V.

Sounds like the XYproblem

Please tell us why do you need that particular value ?

-Maahar

:slight_smile: hello my friend i want to test the low speed of fan in a peugeot 407

102 Hz is certainly slow enough to generate the pulse in software with a millis() or micros() timer.

The half a volt requirement is unusual. What exactly are you trying to drive with the pulse?

cattledog:
102 Hz is certainly slow enough to generate the pulse in software with a millis() or micros() timer.

The half a volt requirement is unusual. What exactly are you trying to drive with the pulse?

i want to test the low speed of fan in a peugeot 407

i want to test the low speed of fan in a peugeot 407

The voltage that you are trying to output still seems strange. How did you determine that value ?

i want to test the low speed of fan in a peugeot 407

You can not be driving the fan directly from the Arduino, so the .5v must be going to a fan controller, relay, transistor, mosfet, etc.

As UKHeliBob indicates, please provide additional information about what you are doing.

cattledog:
You can not be driving the fan directly from the Arduino, so the .5v must be going to a fan controller, relay, transistor, mosfet, etc.

As UKHeliBob indicates, please provide additional information about what you are doing.

the fan has a controller and when the a/c working the PCM gives 0.500v for the low speed,i saw it with the oscillator

the fan has a controller

Can you provide any technical documentation about that fan controller.

when the a/c working

a/c = air conditioning??

the PCM gives 0.500v for the low speed

What is a PCM?

i saw it with the oscillator

You saw a square wave signal with an oscilloscope -- 0 low .5 v high, at 102Hz? --as the input to the fan controller at low speed?

cattledog:
Can you provide any technical documentation about that fan controller.
a/c = air conditioning??

What is a PCM?

You saw a square wave signal with an oscilloscope -- 0 low .5 v high, at 102Hz? --as the input to the fan controller at low speed?

a/c is airconticion
pcm is the power control module (ECU)
{{{{{You saw a square wave signal with an oscilloscope -- 0 low .5 v high, at 102Hz? --as the input to the fan controller at low speed?}}}}yes!!no 0 low 5 high,just 0.500v

{{{{{You saw a square wave signal with an oscilloscope -- 0 low .5 v high, at 102Hz? --as the input to the fan controller at low speed?}}}}yes!!no 0 low 5 high,just 0.500v

I'm sorry for the language difficulties. To confirm, you saw a high/low signal at 102HZ, and the high signal level was only .500v?

cattledog:
I'm sorry for the language difficulties. To confirm, you saw a high/low signal at 102HZ, and the high signal level was only .500v?

yes my friend

I think there are two ways to get the signal you want.

I think that you could be able to use a high frequency 0/5v pwm signal at 10% duty cycle which is passed through a low pass filter to generate the analog output of .500 v. Then, The underlying pwm signal is turned on and off at 102 Hz. Unfortunately, I do no don't know the best values of pwm frequency, R and C to design for .500v output at 102 Hz. Some of the hardware design will depend on how clean of a signal the fan controller requires.

Alternativey, you could use a DAC (digital to analog converter) like this one MCP4725 Breakout Board - 12-Bit DAC w/I2C Interface : ID 935 : $4.95 : Adafruit Industries, Unique & fun DIY electronics and kits and pulse the output at 102Hz.

Or use a resistive divider - that requires knowing the input impedance of the load though...