Stupid Question on Inductors

GeoffMillar

Hello from Oz

I have a 'Jantzen' 1.2mH air coil inductor (18 AWG) which I need to convert into 1.0mH for a project; unfortunately, I don't have any measuring equipment. The build won't happen for while, but I'm doing an audit of the BoM to see what's needed.

Would someone be able to 'guesstimate' how many turns would be needed to unwind it to get near enough to 1.0mH, please?

Thank you!

Geoff

Wolf

Shouldn't be more than 3 turns. Check the dcr.

GeoffMillar

Thanks Wolf

I don't have a thingy to measure the DCR, so will try 3 turns

Geoff

Wolf

No ohm meter? As in VOM, or multimeter?

GeoffMillar

@Wolf said:
No ohm meter? As in VOM, or multimeter?

No, would you believe I've never had to use one!

I've always built other peoples' designs.

Geoff

Steve_Lee

Where is the head-slap smilie?

Wolf

I don't just use it for speakers. It's a priceless tool to have for multiple reasons.

GeoffMillar

@Wolf said:

It's a priceless tool to have for multiple reasons.

I guess it could be, but I've never had cause to use one as I don't trust myself with things electrical.

However, your comment has got me interested in looking at what I could do with one: is this the sort of thing you use for speakers?

https://www.jaycar.com.au/true-rms-inductance-capacitance-dmm/p/QM1552

Thanks

Geoff

kenrhodes

Geoff, that meter might be fine. However it's not where I would start. There are a lot of verified, cheaper autoranging meters that would be a good place to start.
AliExpress work in Oz?

GeoffMillar

Thanks Ken,

Unfortunately things electrical are more expensive here than in the States; AliExpress posts here, but the shipping costs are prohibitive compared to the cost of the item(s).

"The Tyranny of Distance", as a famous historian once put it.

There are other meters from the same store, I'll check them out. I'm not sure what I should be looking for in terms of features - this one is the cheapest from that store, which is within walking distance:

https://www.jaycar.com.au/economy-catiii-multimeter-with-data-hold/p/QM1517

Geoff

kenrhodes

Autoranging is a nice place for starters. Higher count means more accuracy. I love having a low Z option and frequency. Most multimeters that offer capacitance have a limited range, but typically will cover the range needed for speaker design.
You could get all the measurements you need with a limp jig. I would start there.
A lot of cheap multimeters will work fine for a beginner. Still I would recommend ok knowing your goals before buying one.

GeoffMillar

Thanks Ken

Geoff

Silver1omo

https://www.eevblog.com/store/
That should be closer to you and should be good products.

Billet

I think it is nice that you have a brick and mortar store within walking distance where you can buy a multimeter. I would definitely favor them over some online seller.

GeoffMillar

Thank you all for your ideas, I'll trot up to Jaycar and have a look at what they have.

Geoff

6thplanet

Jaycar is such a cool place. Kinda an Australian Parts Express.

GeoffMillar

@6thplanet said:
Jaycar is such a cool place. Kinda an Australian Parts Express.

Yes, although it only has a very small range of speaker parts now.

Some years ago they used to sell Vifa drivers and a really good MTM kit with the D25 tweeter and P17 woofer; it didn't sell well so it was thrown out for about $120 pair, with cabinets! Jaycar then sold off the P17s for about $10 and the tweeters for $12!

Their house brand 'Response' drivers aren't that good, unfortunately.

Geoff