How do you construct a low pass filter?

[WildStriker]

How do you specifically construct a low pass rc circuit? Like which terminals on each component do you need to connect the wires to?

Comments will be appreciated.

Thanks

 

[MrAl]

Hi,


You connect the resistor to the capacitor, that makes a junction and a free end of the resistor and free end of capacitor.
You connect the free end of the resistor to the input signal, and the free end of the capacitor to ground. The other lead of the input signal is also connected to ground. The output is taken from the junction formed previously, and ground is the reference so the output is taken across the junction and ground.

 

[WildStriker]

Hi,


You connect the resistor to the capacitor, that makes a junction and a free end of the resistor and free end of capacitor.
You connect the free end of the resistor to the input signal, and the free end of the capacitor to ground. The other lead of the input signal is also connected to ground. The output is taken from the junction formed previously, and ground is the reference so the output is taken across the junction and ground.

I'm aware that there are a number of terminals on the resistor and the capacitor. Is there a difference in these terminals on each component and which terminals do you connect the wires in from the resistor/capacitor to the onscilloscope and signal generator?

 

[Mikebits]

Simple Google answers your question.

Filter Circuits with Capacitors

 

[MrAl]

I'm aware that there are a number of terminals on the resistor and the capacitor. Is there a difference in these terminals on each component and which terminals do you connect the wires with from the resistor/capacitor to the onscilloscope and signal generator?

Hello again,


Oh ok, well it's hard to tell what someone wants to know from one post usually anyway.

With a resistor and capacitor it doesnt matter which terminal you choose. You can flip the resistor and it still works the same, and flip the cap and it still works the same.

There is one exception, and that is if you are using a type of capacitor called a "polarized" capacitor. One type of polarized capacitor is an electrolytic capacitor, and that has either a big plus sign (+) or a big minus sign (-) stamped on the case somewhere, and that indicates what terminal is positive and which terminal is negative.
Normally you connect the negative lead to ground and the positive lead to the resistor.
That means you connect the signal generator positive to the resistor and negative to ground, although if you were actually using a polarized capacitor you'd also have to make sure to apply seme DC offset because a sine wave usually goes both positive and negative. A polarized capacitor would only be used when an offset is available, either in the circuit or from the test generator.

You'll most likely be using a non polarized capacitor (no polarity) so you can use either lead of the capacitor any way you want without regard to which lead is which.

If you already have a capacitor and you dont know what kind it is, if you can post a picture we can take a look and advise. If not, perhaps a link to the catalog or data sheet and that will help too.

Most ceramic caps like 0.1uf, 0.01uf, etc., are non polarized, while larger values like 10uf and 100uf and up are usually polarized, and 1uf comes commonly as either type.
There are exceptions however, because you can in fact purchase larger values that are polarized too.

 

[Voltz]

Simple Google answers your question.

Filter Circuits with Capacitors

The link is informative but most likely incomprehensible to someone who doesn't understand how to make a Low Pass Filter in the first place unless they happen to know about dB and Angular Frequency etc...

 

[WildStriker]

Hello again,


Oh ok, well it's hard to tell what someone wants to know from one post usually anyway.

With a resistor and capacitor it doesnt matter which terminal you choose. You can flip the resistor and it still works the same, and flip the cap and it still works the same.

There is one exception, and that is if you are using a type of capacitor called a "polarized" capacitor. One type of polarized capacitor is an electrolytic capacitor, and that has either a big plus sign (+) or a big minus sign (-) stamped on the case somewhere, and that indicates what terminal is positive and which terminal is negative.
Normally you connect the negative lead to ground and the positive lead to the resistor.
That means you connect the signal generator positive to the resistor and negative to ground, although if you were actually using a polarized capacitor you'd also have to make sure to apply seme DC offset because a sine wave usually goes both positive and negative. A polarized capacitor would only be used when an offset is available, either in the circuit or from the test generator.

You'll most likely be using a non polarized capacitor (no polarity) so you can use either lead of the capacitor any way you want without regard to which lead is which.

If you already have a capacitor and you dont know what kind it is, if you can post a picture we can take a look and advise. If not, perhaps a link to the catalog or data sheet and that will help too.

Most ceramic caps like 0.1uf, 0.01uf, etc., are non polarized, while larger values like 10uf and 100uf and up are usually polarized, and 1uf comes commonly as either type.
There are exceptions however, because you can in fact purchase larger values that are polarized too.

Okay, thanks.

One last question, do you know which terminals of the signal generator do you connect the circuit to?

 

[MrAl]

Hi,

If you use a non polarized cap then you can connect either lead to the resistor and the remaining lead to ground, but usually you connect the positive output to the resistor, and ground (other) lead to ground.

Have you worked with schematics before at all?

Also, can i ask what you are trying to build?

 

[skypup]

Are you building an active or passive circuit?... Check Nigel Goodwin's thread above on 'Basic Opamp Circuits'.