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abc

Embedded for a 10 year old?

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You'd have to find something to fit that shaft, which I think is 5mm / 3/16" across the major axis, the rounded ends- not the flat sides, with a set screw or compression coupler to lock it down.

 

There are bell-cranks and other things that may be useful, depending on what you're trying to accomplish.

 

Hobby shops are often decent places to find things like that.

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If you want to build a creature on the cheap, forget about the steppers and go with servos.  9 gram servos are three bucks a pop, they are dead simple to drive, provide absolute positioning, and only require one I/O pin each. 

 

The steppers I linked to are $12 for a 5-pack. As for simplicity, I am a bit confused, because I've just read this:

 

Servo Motors

 

Fast, high torque, accurate rotation within a limited angle

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That is actually a very good deal for the stepper+driver setup.  The only thing to be aware of is that you have no absolute position setting (or maintenance) with the steppers.  Driving a stepper with a uln2003 is actually quite a bit more complicated than driving a servo.  Driving steppers is only easier when you have an intelligent controller, which the uln2003 is not.

 

However, with the appropriate software driver library, all of those complexities are abstracted away.   The availability of that driver library is, to a large part, going to determine where you can use them.  Unless, of course, you plan to write/port your own.

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This is getting more and more OT, but.. what do people think of electric ink and electric glue? Seems like a good idea, but its popularity seems pretty low, why?

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I would rather go with conductive thread and other fabric based components before I would go the conductive paint/epoxy. As mentioned, pricey, high resistance, joining standard parts to existing materials.  Conductive thread, sneak your wife's sewing machine, get some cheap fabric and sew your parts on a fabric circuit board, I guess that would be an FCB.

 

Check out Adafruit, they have lots of fabric based components.  

 

Thanks

 

Joe

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Thank you all so much for the wealth of info! 

 

Do we need an anti-static wrist band? I am thinking probably not, with hardwood floors and humid climate. Am I right?

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@@abc - nearly 20 years working on cell sites' RF and prime power paths and not once have I put on a wristband, nor have I popped anything because of that. And other cell-techs I've spoken with haven't had an issue. We touch the 'grounded' door to get into the site, touch the 'grounded' chassis enclosing the equipment, and even the air registers / vents are grounded, so the air should be grounded. ;)

 

I await the replies.

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On a few topics...

 

Conductive thread usually has appreciative resistance -- on the order of 10-30 ohms per foot -- and doesn't address the connectivity issue.  In fact, connecting it can be a real PITA.  It is fine for LEDs where you can factor in the resistance instead of using a dropping resistor, but otherwise I don't see much use for it.

 

Just because your MOS part hasn't failed outright doesn't mean you haven't damaged it or altered its characteristics.  Every time you discharge through the gate you are punching a tiny hole in it.  A few tiny holes will not make much of a difference but the effect is cumulative.  This can make circuit debugging a nightmare down the road.

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@@rockets4kids,

 

The OP asked about use of conductive paint/epoxy,  I did not indicate that conductive thread was a viable solution,  I indicated I would use conductive before I would use conductive paint.

 

But doing a bit more research,  The Adafruit web site indicates that a 3 ply stranded stainless steel thread has the following specs:

 

Measures 0.25mm thick, 3 ply thread, 0.83 ohm per inch

 

If you look at the AWG chart at http://www.engineersedge.com/copper_wire.htm

 

These specs are right in line with stranded 30 AWG wire and for 1000 feet the resistance is 103.00 ohms.

 

The 3 ply stranded stainless thread has better resistance than 30 AWG copper wire.  If you want better resistance then sew with larger AWG wire.

 

Watch some of the videos at the Adafruit web site,  working with conductive thread is not as bad as one might think.

 

Cheers

 

Joe

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Joe writes:

 

 

> The OP asked about use of conductive paint/epoxy,  I did not indicate that conductive thread was a viable solution,  I indicated I would use conductive before I would use conductive paint.

 

Maybe you would, but I sure wouldn't.  It has all the disadvantages of conductive paint (expensive, high resistance) and yet at the same time is more difficult to use thanstandard copper wire.

 

> But doing a bit more research,  The Adafruit web site indicates that a 3 ply stranded stainless steel thread has the following specs:

> Measures 0.25mm thick, 3 ply thread, 0.83 ohm per inch

>

> If you look at the AWG chart at http://www.engineersedge.com/copper_wire.htm

> These specs are right in line with stranded 30 AWG wire and for 1000 feet the resistance is 103.00 ohms.

 

 

You are reading that chart incorrectly.  30 ga copper wire has a resistance of 103 milli-ohms per foot vs 9.96 (0.83 * 12) ohms per foot for the conductive thread.

 

Also, have you ever tried soldering to stainless steel before?  It is *not* fun.

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