Help with current filtering on controller of brush-less DC motor (BLDC)

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Current filter , Can u help ?

Hi everyone

I have a problem of current filtering with my controller of brushless dc motor (BLDC).



the problem that the current is PWM and i want to read it and show a fixed value like the multimeter process.

so what's the filter that can be used to prevent this problem , or specially what's is the filter inside the multimeter ( i know that a Low Pass Filter!!).
 

Re: Current filter , Can u help ?

You can use shunt resistor in feedback path and apply that signal to LM324.By Feed this signal to Microcontroller it may be possible to read the value.
 

Re: Current filter , Can u help ?

Mr phoenix

the problem is not how to read .

the problem how to filter the crazy oscillations in the signal generated by the current

this is my conditioning circuit in these 2 pictures






i think the idea is to use digital filter ?

or can anyone help what's is the filter used to measure dc current or dc voltage in multimeter ??

please let me know
 

Re: Current filter , Can u help ?

Your capacitor C23 needs to be a large enough value, that it will hold a charge during idle gaps in the waveform.

Example, if you are reading pulsed DC at a frequency of 50 Hz, then a suitable value is 100 uF. This will give you reasonably smooth output for measuring.
 

Re: Current filter , Can u help ?

Hi Mr BradtheRad

if this true why the multimeter can read the value without any problem and without delay !!

i don't know what the filter inside looks like !?

thanx
 

Re: Current filter , Can u help ?

There is the analog type of meter. It averages the waveforms automatically, due to inertia of the needle movement.

I'm not sure about digital meters. I choose the AC range on mine and it gives a stable reading of AC. I believe it averages the readings. Perhaps then it has a smoothing capacitor at the input.

However my digital meter gives inconsistent readings when I apply varying DC, on the DC range. Evidently it samples the voltage just a few times a second, briefly. I think it has no smoothing capacitor at the input then.
 

Re: Current filter , Can u help ?

Hi
thanx Mr BradtheRad

has anyone another answer ??



thanx in advance
 

Current filter Can u help

You can try changing the filter to inlist2:current_user,supervisor

Here is an example:
supervisor = "steve,mike"
current_user = "steve"
?inlist2current_user,supervisor
= .t.
 

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