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Printable RC Filter

by CafeT, published

Printable RC Filter by CafeT May 5, 2010

Description

In line with my desire for a 3D printer like the CupCake that uses conductive build material, here is a printable RC filter. The two spirals are a resistor and a capacitor. As you might have noticed, one of the spirals is continuous (the resistor) and the other has a gap in the center (the capacitor). Use of the circuit is just a matter of attaching power or a signal across the two thicker terminals perpendicular to the line formed by the spirals. This kind of circuit could probably be printed with traces on a PCB. Made in Inkscape and Blender.

http://makezine.com/go/makerbot

Recent Comments

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20% carbon black (by mass) into PLA (or PLC) yields a very conductive polymer (~0.09 Ohm/meter through 3mm filament), printed as an RLC resonant tank will be most interesting... any guess at this R(L)C behavior is suspect at best. Experimenters hoe!

I made a much longer resistor at thingiverse.com/thing:3029 with resistance calculations.
I didn't calculate the values. I just know from experience the sort of effects you get from PCB traces.

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Instructions

This is a 2D design extruded so it has volume. The block underneath is just to support the thinner sections. Ideally, the block would be dielectric/plastic while the design on top would be conductive.

<p>20% carbon black (by mass) into PLA (or PLC) yields a very conductive polymer (~0.09 Ohm/meter through 3mm filament), printed as an RLC resonant tank will be most interesting... any guess at this R(L)C behavior is suspect at best. Experimenters hoe!</p>

<p></p>

<p>If you print it in copper R will be a fraction of an ohm and C will be only 10's of pF. That would give a time constant of the order of 1ps. At those sorts of frequencies the parasitic inductance and transition line effects would dominate.</p>

<p>I don't see any practical use for this.</p>

<p>How did you calculate resistance and capacitance? I was going to make it parametric (wrt these values) anyway, and that would help a lot.</p>

<p>I didn't calculate the values. I just know from experience the sort of effects you get from PCB traces.</p>

<p>I made a much longer resistor at http://www.thingiverse.com/thing:3029 with resistance calculations.</p>

Printable Resistor
by CafeT

<p>I didn't make this with a a scale in mind. Thanks goes to clothbot for doing that. I was just demonstrating creation of components and hoping someone else would be able to do more of the electronic engineering to make it useful. :)</p>

<p>Also, parallel plates in 3D is an obvious capacitor building method...</p>

<p>Neat idea!</p>

<p>The STL came out empty for me so I converted the SVG to DXF and whipped up an OpenSCAD wrapper to make something scalable to test later: http://www.thingiverse.com/thing:2982&lt;/p&gt;

<p>You can't print conductive material yet, but there's nothing to stop you using the squeegee method to fill the trace with something that is!</p>

Printable RC Filter Redux

<p>Now we just need someone to make a software that can determine the values of R and C with a given geometry and material, so we can print the filters we actually need... ;)</p>

<p>Have you considered this approach:</p>

<p>http://www.chem.utoronto.ca/staff/WHEELER/Papers/OnDemand.pdf&lt;/p&gt;

<p>This paper is about microfluidic applications, but if you want to print circuitry that's where I'd start... We used a colour printer to print a mask (using regular inks) directly onto copper sheet and then etch. Passing the copper sheet through the printer seems a bit...counterintuitive...but we didn't have any problems (YMMV, always possible it could blow up or injure you so be careful ) :)</p>

CafeT - in reply to MarkU

<p>Good suggestion, thanks for pointing that out. I like how they can control thickness, too, have to read the paper in full later. If I had that I'd have been more careful about calculations, practicality, etc.</p>

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