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Mike:

Is there a way to track the number of turns the VVC has made and, when it reaches a certain count, it won't advance the stepper any further? It might get a little messy with micro-stepping, but it should be doable.

Jack, W8TEE

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From: Michael Hagen <motdog@...>
To: [email protected]
Sent: Tuesday, October 3, 2017 10:21 AM
Subject: Re: [BITX20] Yet another magnetic loop antenna

These Stepper Drivers are used a lot for 3D printers.? I got spares, but never have blow one up.

They are real inexpensive on eBay.

The is a lot bigger problem driving a Vacuum Variable on the Loop Ant than a Capacitor.

I am wondering how to come up with some "end stops" for turning the shaft.? They take about 18 or so turns end to end.

In fact mine feels like is is coming apart at the end in one direction, gets loose feeling.

And this stuff is near the RF field of the loop.? You sure don't want a bunch of metal stuff there.

Right now I just have to reach over and peak it for noise during receive since I have it near the BitX.

I turn the volume up and peak it.? I am going to put a piece of wood dowel on it temporarily.

Maybe it is not a real problem since if it stays tuned it never goes near the ends.

I am just worried about the stepper taking off and hitting the ends.

I wish it had a clutch arrangement built into it, but it feel like it is coming apart when I get near one end.

I have thought about a small belt to a 10 Turn pot, then it could be like a Servo and be driven to a pot position?

This is the first Vac Variable I have had in over 50 years of Hamming.? Its Cool!

Mike, WA6ISP

On 10/3/2017 6:24 AM, Jack Purdum via Groups.Io wrote:

I've used both the EasyDriver and this one from Polulu:

I found the Polulu to be a more robust driver.

Jack, W8TEE

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From: "paul@..." <paul@...>
To: [email protected]
Sent: Tuesday, October 3, 2017 5:40 AM
Subject: Re: [BITX20] Yet another magnetic loop antenna

Excellent write up. I've recently finished building an air variable cap and the next project is integrating the stepper and building a controller.?

Could you use relays to control your driver micro stepping with the Arduino? Also, you might want to look at the Sparkfun EasyDriver. It has logic pins broken out that can set the stepping from full to 1/8 and also an enable/disable pin. I also have a Chinese EasyDriver clone which was a fraction of the price of the original but I haven't tested either yet.?

Regards,

Paul
KG6QGE

Virus-free.

-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...

-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...

-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...