Inductors for passive EQs...

[CJ]

no, thats cool.
it makes your measurements that much better, since you would probably get a more constant core constant if you meausred all three taps at the same freq.
you might try that, just for the heck of it.

also, if you have a junk core, try some super glue in the gap.
i wonder if that would do the trick as far as holding the gap constant.
the core companies sell an adhesive, be we are "off the shelf diy freaks" , right?

hold on, i have junk core and glue here.....

stay utned...

 

[alk509]

CJ, did you get a chance to test that glued core? Or did you start sniffing the glue and forgot about the core? :razz:

I re-measured the coil (two days after winding) and it is a little off, but still within a few percent of what it was originally. I wound another one, and it came pretty close to the first one (my digital camera's batteries are dead and recharging, so no pics until tomorrow). I put some threadlock on the screws, which should help keep them nice and tight.

Pics and measurements sometime tomorrow. Nighty-night!

Peace,
Al.

 

[alk509]

Specs for coil B:

Peace,
Al.

 

[CJ]

Cool.
The super glue works great!
But you only get one shot at it.
Maybe best if used in conjunction with tuning slug, iotherwise, inductance is fixed.
cj

 

[alk509]

So it's been a while since I wound my inductors, and I've been "aging" them on my bench... Today I re-measured them, and they've drifted a little. Here are my measurements:

Original coils: 1640mH, with taps at 490mH and 820mH.

Coil A:

• Tap 1: L = 463mH (-5.5%). DCR = 5.6R.

• Tap 2: L = 798mH (-2.7%). DCR = 7.4R

• End-to-end: L = 1580mH (-3.6%). DCR = 10.7R

Coil B:

• Tap 1: L = 481mH (-1.8%). DCR = 5.5R.

• Tap 2: L = 803mH (-2.1%). DCR = 7.2R

• End-to-end: L = 1605mH (-2.1%). DCR = 10.4R

I'm still going to leave them out for a while to let them settle. I wonder how low they will go? :?

It's my birthday tomorrow (yay! :green so I'll be a little busy, but I'll try to wind at least one more of these through the weekend. I have some 3019 cores coming in from Amidon next week for the mid-band inductor. That one has three taps instead of two, so it'll be even more of a pain in the nuts to wind... The hi-band coil will go on an 1811 core - no taps on that one!

Peace,
Al.

 

[triodemike]

Inductor B is in all likelyhood close enough. Did the potcores from Amidon come with bobbins or did you need to get them seperately? You used #29 wire in your coils? I would like to build a Passive EQ and will want to wind my own inductors.

 

[alk509]

[quote author="triodemike"]Inductor B is in all likelyhood close enough.[/quote]

Anything within 10% is close enough, as far as I'm concerned! :green:

[quote author="triodemike"]Did the potcores from Amidon come with bobbins or did you need to get them seperately?[/quote]

Everything's included (except the metal screw).

[quote author="triodemike"]You used #29 wire in your coils? I would like to build a Passive EQ and will want to wind my own inductors.[/quote]

You need to figure out what inductance you need, and then use the wire gauge vs. number of turns chart on Amidon's website to estimate what size core/wire gauge you need for your specific application.

Oh, and welcome to the Lab! :thumb:

Peace,
Al.

 

[alk509]

Coil C is done:

Notice the lower inductance despite higher turns count... I did this one pretty much all scatter-wound, and not as tight as Coil A (about the same tightness as coil B). I think that's the reason...

I only have one big core left, which I hope to wind soon... three down, one to go!

Peace,
Al.

 

[CJ]

Looks like fun and happy celebrations!
tempeture might be a factor, if you have your core p/n, you can scrounge up the curves off the net.

 

[SUPERMAGOO]

http://groupdiy.twin-x.com/displayimage.php?album=40&pos=10
http://groupdiy.twin-x.com/displayimage.php?album=40&pos=8
http://groupdiy.twin-x.com/displayimage.php?album=40&pos=60

 

[CJ]

Tears of joy run down my cheek....

 

[synthetic]

Wow, the calculator plus key is used as a counter? Fun! :guinness:

 

[alk509]

I think it's the '=' key, actually...

That's really cool, Christian! :thumb:

Peace,
Al.

 

[alk509]

Mid-band cores are here!!!

Pics at 11.

Peace,
Al.

 

[AnalogPackrat]

Cool, Al! Man, I am itching to work on a NYDave passive EQ, but I have my queue so stuffed already... I'll just have to wind vicariously through my Hand-Winders-Anonymous brethren.

A P

 

[CJ]

Good deal. I wanna beat you to that Redd 47 thing.
Give me a weekend.

 

[alk509]

Just measured all three inductors again... Coil A is still all over the place everytime I measure it (within reason: greatest deviation from original has been -5.5% so far, but today it's within 3% of original)...

So here's a tip for you: Coil B and Coil C are a little more consistent (+.61/-1.8% of original). The only difference between A and B and C, is that on B and C I applied liberal amounts of crazy glue directly to the coil after winding each tap, wrapped the whole thing in tape and then put in the core. So the super glue appears to keep things tight and consistent.

I haven't done anything with the new cores I got yet, but I might get my winding on later tonight... stay tuned.

Peace,
Al.

 

[CJ]

If you really wanna have fun in your kitchen on a sat nite, put those suckers in the oven at 200 and see what they measure.
Then the fridge.
We used to do temp work this way before the chamber, don't tell anyone!

Freezers look weird with wires coming out of them.
I tackled my fridge one morning becuase I thought it was a suicide bomber.
Then the coffee.


You guys finish a project, and thats it.
When we finish a circuit, the fun is just starting.
That darn temp work is a pain.

Put your SSL in an oven and freezer and try to tweak it so you get 1 percent accuracy all over the temp band.
Good luck!


Pass the NTC's, will ya?

Run wires to your bridge so you can actually watch the inductance ramp up and dpon as the core reaches tempeture.

 

[Svart]

how did this turn out anyway?

It seems that I will need to wind some big EQ cores myself since I am having trouble finding what I want.

 

[AnalogPackrat]

Yeah, I'm curious, too. But I think Al is out with his RC sailplanes (or maybe if the weather sucks he's sniffing glue and building more of them).

Svart--Amidon is pretty cool to deal with. I bought a bunch of pot cores from them last month for my project. Check their web page--they have a nice graph for figuring how many turns of various gauges of wire you can get on each size bobbin. That and the Al value for the core that goes with the bobbin gives you what you need to figure out each inductor.

A P