Double-T-Filter

[martinvicanek]

Here is a little excercise inspired by BobF: a digital implementation of a double-T-filter. In the analog days this was a popular notch filter, primarily for its robustness wrt component tolerances.

Doppel-T-Filter.png (5.64 KiB) Viewed 31118 times

The schematic below is a direct implementation of the corresponding nodal equations using an explicit Euler scheme. Nothing of a big deal really, but I thought I'd share it anyway.

[BobF]

Hi Martin,

Very cool! It came out quite nice. I think I have even learned something new!

After playing with this for a few hours (too many), can I change the resistors and capacitors to any value that would work in the hardware world or are there high and low limits on this one? If I can change values does dt also need changing? What is dt for, damping or ?

Thank you!

Later then, BobF......

[DigiTonix]

Bravo!!! Martin... I like this Thanx for sharing!

[martinvicanek]

can I change the resistors and capacitors to any value that would work in the hardware world or are there high and low limits on this one? If I can change values does dt also need changing? What is dt for, damping or ?

dt denotes the time step and is a constant equal to 1/samplerate. You can try out other resistor capacitor values as long as the RC time constant is large compared to dt. You could stretch it a bit further by replacing Euler with a more sophisticated ODE solver but if the system characteristic frequencies exceed Nyquist the only remedy is a smaller time step (oversampling).

[DigiTonix]

When we talk about filters, we are talking about magnetude ... I want to learn more, you can simulate resistors сомpression ?

Filter Compression.png (23.35 KiB) Viewed 31079 times

[KG_is_back]

very interesting. I always wondered how to simulate electric circuits but never had a clue...

[BobF]

Hello gang,

I thought this was rather cool and shows another side of Flowstone's power. So how about a challenge for any of you good at coding(code, asm, or ruby). See if you can create some more resistor/capacitor circuits and maybe even other analog devices. Like transistors, fet's, diodes, and so on.
I would really like to join in on this, but I am not at all good at coding.

That's it then! Really hope to see more here soon. Good luck!

Later then, BobF.....

[DigiTonix]

Hey ... BobF thinking right ...
I also want the different components of the flow !, different diodes, lamps, resistors, and other ...

Martin, is this possible? to make different types of chain links (I'm talking about analog circuits) ...

(Sorry my bad English, if you do not understand written)