I want to make this schematic here: http://www.micro-examples.com/public/microex-navig/doc/090-ultrasonic-ranger.html

But I don't have a 330uH inductor. Is it possible to make one ?

Second, how can I test an inductor how many uH (microhenry) does it have using an oscilloscope ?

 

I don't know how you can build it cheaper than this:

http://www.mouser.com/ProductDetail...EpiMZZMueR%2blcXtRMwTF/yJ2D16pKf%2bKhmFdK/N0=

To test it with a scope you can put a small fixed capacito of known value in parallel with the inductor to make a tuned circuit. Use a signal generator to feed a variable frequency to the LC circuit. When you see a resonant peak note the frequency. From that you can easily determine the inductance.

If you really want to wind your own, Google comes back with a googol of hits.

 

Making inductors is very easy. I have a basic one in this project...

CMOS 555 Long Duration LED Flyback Flasher

The hard part is measuring them.

I've addressed this several times without reaching an answer I like. I did break down and buy an LC meter, but I would like to come up with a good project for beginners to measure them.

There is a procedure in Flyback Converters for Dummies.

http://www.dos4ever.com/flyback/flyback.html

I also have several threads on the subject that are fairly unresolved. Do a search for threads started by me on the subject, some of the other guys had some good ideas on the subject.

Don't forget toroid inductors. They are pretty predictable and have nice characteristics. I don't have time right now to get in depth, but this will get you started on your reading.

The web is full of inductor calculators, it is another good place to start.

 

I bought an LC meter, too. Elenco. 1 year warranty. It disassembled at 370 days, and I rarely used it. (Whine!) A hundred bucks buys junk nowadays. So grateful I put out big bucks for a scope when I was making good money. That and a signal generator will do the job...slow, but effective.

 

You can order a kit and build an LC meter.

http://www.electronics-diy.com/store.php?sel=kits

 

Thanks everyone for all your input on this.

I will try it first with a function generator and an Oscilloscope. I will probably ask more questions at that time (right now I'm at work).

You can order a kit and build an LC meter.

http://www.electronics-diy.com/store.php?sel=kits

This looks nice, I have all the parts except the "82uH Inductor". Also I did not see where is the source code for the PIC ?

 

below Link is similar project with the source code for the PIC
http://ironbark.bendigo.latrobe.edu.au/~rice/lc/index2.html

 

I should have mentioned, code in C... the code there is in ASM and I don't know ASM.

I wanted to have code because I wanted to modify the code for my needs (i.e. to use PIC16F88 instead of PIC16F628)

 

Just make sure that the inductor core material, is correct in respect to the frequency you will use in your application. You may also take a look at the inductor section in this document
https://www1.elfa.se/data1/wwwroot/webroot/Z_STATIC/en/pdf/fakta55.pdf
@Bill I have been doodling with the plans of building a LCR meter using a sound card and the same technique that are used. In The lock-in amplifier, synchronous demodulation. It is still in my head. The problem is calibration.

 

You can buy an off the shelf cheap LC meter too. I had a thread about it not to long ago...

My newest toy...

 

Alternate choice beside pic/avr lc meter , I will suggest 2005(QST/QEX) LMS impedance bridge. it use sound card with stereo line input +lm358+ few resistors. You can download the program and documents from the link http://wb6dhw.com/RLC_Meter.html
I did the project using perforated board with good result except sometime the program no respond and need to force out(under win7).Compatible with pic lc meter accuracy(approaching to 1 percent accuracy or better than),and plus showing Rs, Xs,D,Q,angle, Z.

 

Microchip also have an AN on this topic using MCU with something named CTMU
http://ww1.microchip.com/downloads/en/AppNotes/01375a.pdf

 

If you are going to try to make your own inductor, you will need to use suitable core material. Toroidal cores are quite popular for use as inductors and transformers, but you'll need to do a good bit of research to get a suitable core; and the resulting inductor will be much larger than the Mouser inductor that Jaguarjoe suggested in the 1st reply to your thread.

You would not want to try to make an air core coil for 330uH, as you would need quite a bit of wire, and the resulting inductor will be a good bit larger than one wound on a toroid.

The "Mini Ring Core Calculator" is quite handy, and available to download for free here:
http://www.dl5swb.de/html/mini_ring_core_calculator.htm
For an inductor of that size, you could probably use a FT50 ferrite core. There are quite a few selections for ferrite types; and also for iron powder cores (the iron powder cores would require far too many turns).

But, you'll wind up having to do a good bit of fiddling around to get it close to correct.

 

I got some toroidal cores from a broken PC power supply. But those inductors have really thick wire.

Does the wire thickness matter ?

I am thinking to open a small adapter that I don't use anymore, and use the wire from one of the 2 coils.

One problem with toroidal core (that I can see) is that I have to pre-cut the wire to the needed length, and then do the wound-ing (hmm how do you say this?). That means somehow I have to pre-calculate the length of the wire before I start wound-ing.

 

You could a core from a PC supply. That mini-ring calculator will help you to figure out how many turns you will need to get the right inductance.

You'll pull off all of the old wire, as you can wind on small gauge magnet wire instead. If you try to go smaller than around AWG-30, the wire becomes pretty easily broken.

To figure out what the AL value of the core is, you start by winding on 20 turns (you can try just 10 turns, but it's not as accurate), measure the inductance, and feed the numbers into the "unknown cores" portion - use Tools, then "AL and Permeability". Fill in at minimum the number of turns you wound on the toroid (1 turn = 1 pass through the center of the toroid) and the inductance that you measured. If you want it to calculate the maximum wire gauge and length of wire you'll need, supply the toroid dimensions as well.

For an example, I just plugged into the AL tool 20 for # of turns and 50uH, giving me an AL value of 125nH/n^2.
Then I selected the "Unknown cores" tab, typed in 330uH for desired inductance, and for AL, I clicked "Copy AL from Tool" and it told me I'd need 51 turns.

Then you can go to the dark green block and enter 51 turns; it'll tell you more precisely what the uH value should be. Unless you need a closely tuned value, it should be good enough.