Monday, November 16, 2009

Printed Inductors

Today I started experimenting with Printed Inductors, which is something that I have always wanted to try. The idea is to print and etch inductors directly on the PCB, many commercial products and some kits use this technique.

For my first experiment I created a 25.5 Turn Inductor with a single 5mil spiral trace, 12mil centre-to-centre spacing, within a 1 inch diameter. The tuning capacitors are soldered to the upper two pads.

 A Tuned Tank Circuit

Note: it is difficult to see the spiral with the naked eye, it is just a blur of shiny copper.


This is the Centre of the Spiral Conductor

My goal was to resonate at my favourite QRSS frequency of 10.140mHz. With the help of a 47pF cap and a parallel 4-50pF trimmer, resonates was obtained on the desired frequency.

I thought the distributed capacitance of the spiral and of the 32mil double sided PCB would kill the Q of the circuit, but it seems to do well as indicated on an AIM-4170B Analyser. But, this will need more investigation.

Scale = 8 to 12mHz

I may have to plan a project using this technique for the tuned inductors.

As I have time, more experiments and information on Printed Inductors will follow!

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4 comments:

  1. Hello Mr.Brown,

    Can you please tell me the tool which you used to design this spiral inductor?

    With Regards,
    Avinash

    ReplyDelete
  2. I used Inkscape to design the spiral inductor, Inkscape has a nice utility to design spirals and other odd shapes.

    ReplyDelete
  3. Hello Mr.Brown,

    Thanks a lot . I basically want to design a PCB Inductor like this :
    http://www.ti.com/tool/ldc1000evm . I wanted to design an inductor similar to the one shown in the figure of the EVM module. So the trace width is extremely small(4mil) similar to your coil. Once I design it, how can I etch it on a copper board i.e., did you do the etching yourself ?

    With Regards,
    Avinash

    ReplyDelete
  4. Hello Mr.Brown,

    After some careful study, I now know that I can etch the spiral myself on a copper board, using the usual techniques. In the spiral which you have created, the trace width is 5mils and the gap between the spirals is 12 mils, am I right ? Can you please tell me how I can specify the gap between the spirals in inkspace?

    With Regards,
    Avinash

    ReplyDelete