A simple do-it-yourself low pass filter

Good day, dear readers! Today we will focus on building a simple low pass filter. But despite its simplicity, the quality of the filter is not inferior to store counterparts. So, let's get started!

The main characteristics of the filter

  • The cutoff frequency is 300 Hz, the higher frequencies are cut off
  • 30 Volt;
  • Consumes a 7 mA filter.

Circuit

The filter diagram is shown in the following figure:
Simple low-pass filter with your own hands
List of details:
  • DD1 - BA4558;
  • VD1 - D814B;
  • C1, C2 - 10 μF;
  • C3 = 0.033 μF;
  • C4-220 nf;
  • C5 - 100 nf;
  • C6 - 100 microfarads;
  • C7 - 10 microfarads;
  • C8 is 100 nf;
  • R1, R2 is 15 kΩ;
  • R3, R4 is 100 kΩ; / li>
  • R5 - 47 kΩ;
  • R6, R7 - 10 kΩ;
  • R8 - 1 kΩ;
  • R9 - 100 kΩ - variable;
  • R10 - 100 kΩ;
  • R11 - 2 kΩ

Manufacturing a low-pass filter

A voltage stabilizing unit is assembled at resistor R11, capacitor C6 and zener diode VD1.
Simple do-it-yourself low pass filter
If the supply voltage is less than 15 volts,then R11 should be excluded. On the components R1, R2, C1, C2 the adder of input signals is assembled.
A simple do-it-yourself low pass filter
It can be excluded if a mono signal is input. The signal source should be connected directly to the second pin of the chip. DD1.1 amplifies the input signal, and the filter itself is assembled on DD1.2.
Simple do-it-yourself low pass filter
The C7 capacitor filters the output signal, the R9, R10, C8 has a sound control, you can also exclude it and remove the signal from the C7 negative foot. figured out the scheme, now let's move on to the manufacture of printed circuit boards. To do this, we need a 2 x 4 cm glass fiber sheet. Low Pass Filter Card File:
A simple low pass filter with your own hands
Grind to shine with fine-grained emery paper, degrease the surface with alcohol. We print this drawing, transfer it to the textolite using LUT method.
A simple low pass filterhands
 A simple low pass filter with your own hands
If necessary, we paint the track with varnish. Now we need to prepare a solution for etching: dissolve 1 part citric acid in three parts of hydrogen peroxide (1: 3 ratio, respectively). We add a pinch of salt to the solution, it is a catalyst and does not participate in the etching process. We immerse the prepared solution in the prepared solution. We are waiting for the excess copper to dissolve from its surface. process t We get our fee, wash it with running water and remove the toner with acetone.
 A simple low pass filter with your own hands
Solder the components, focusing on this photo:
 Simple do-it-yourself low pass filter
In the first version of the figure I did not make a hole under R4, so I soldered it from below, in the document for downloading this flaw was eliminated. You must solder the jumper onboard the motherboard:
 A simple low-pass filter with your own hands
The assembled circuit worked when it was first turned on and does not need to be adjusted.If there is no sound at the output, roll up the variable resistor and check all the connections on the board. This is where my article comes to an end.


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