Jump to content
Sign in to follow this  
abc

Embedded for a 10 year old?

Recommended Posts

Again you are not reading what I have written  "I did not indicate that conductive thread was a viable solution,"

 

I also did not indicate to use the stainless thread.  I said "If you want better resistance then sew with larger AWG wire."  I was referring to sewing with copper wire, not stainless thread.

Share this post


Link to post
Share on other sites

You seem to have missed the entire point of this this thread: making embedded/electronics accessible to 10 year olds.

 

OP mentioned conductive paint/glue because it is commonly touted as being an enabling technology for youngsters in electronics.

 

While the concept certainly shows promise for the future what is available today is not viable.  Furthermore, the people promoting it exemplify my biggest peeve in the "maker movement" -- selling an expensive item at a ridiculous markup under the guise of helping introduce people to the hobby that is almost certain to make them unhappy and frustrated.  I could rant on at length about this, so I'll just stop here.

 

Conductive thread *is* often used by people with limited electronics knowledge to make things (most commonly LED clothing) and this is most certainly a viable use.  I am certainly making no argument here, largely because there are no other solutions.

 

However, by mentioning it in this thread, you are making an *implication* that it is appropriate to the discussion.  Bringing up the price of tea in china would be about as appropriate in this discussion.

 

But, if you *are* going to bring it up, at least get your facts straight.

Share this post


Link to post
Share on other sites

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. 

Someone had told me that servos are more sparky than steppers and thus require more circuitry, is that true? I don't mind it over the long run, but it's nice to start with something simple.

 

Someone had recommended me Polymorph plastic (very strong and durable plastic that becomes soft and pliable at 60 c). I am fascinated with this stuff, but it's $1/lb, and that probably means smaller robots. (Though I've also read that a cheaper alternative is glue from some hot glue sticks - but I wonder if they are as safe, etc.) 

 

Is there a place on this forum or elsewhere for discussing the mechanics of robotics? 

Share this post


Link to post
Share on other sites

What do you mean by "more sparky?"

 

IMO, if you want to keep things as simple and as cheap as possible, you want to be using R/C servos.

 

I don't know if there is a servo library in Energia, but oPossum5150 has posted code here that will let you drive 8 servos from even the most basic of MSP430 parts.

 

I have never used polymorph, but I have heard good things about it.  $1/lb actually sounds absurdly cheap to me -- are you sure that is the correct price?

Share this post


Link to post
Share on other sites

Servos have the circuitry internally. No spark issues unless you are in a flamable atmosphere. generally no elecrronic noise issues, either.

 

Typically, you want a separate (5 to 6 volt) supply for the servos due to the high current draw, as well as the issue with 3.3V controllers that most servos need at least 4.5V to operate reliably at all. Little noise is fed back via the control (PWM) input, and I have never had a problem. Most, but not all, are fine with a 3V control input, even with 5V power. Do check that your choice of servo isn't pulling the PWM input high to its power supply voltage though. That can damage a 3.3V microcontroller if isolation isn't used.

Share this post


Link to post
Share on other sites

What do you mean by "more sparky?"

 

I mean, generates more voltage spikes? I've heard that a 5V servo can create a 100V spike, is that true? I understand that's why servos require a couple of diods and maybe a capacitor, to get rid of the spike?

 

I meant $1/oz for Polymorph, not $1/lb of course. I've also read somewhere that one can use hot glue for the same purpose, has anyone tried that?

Share this post


Link to post
Share on other sites

I have not used the low temp molding plastics like polymorph, but have read good reviews and know a few people that love them, despite the price.

 

I have, in the distant past, used castable resins-- epoxy, acrylic, and polyesther-- and not had issues. I have not used the low heat-softening materials. I am not sure I would want a 10yr old using a material that needs to be worked at 60C or higher (references I have seen say 80 to 90 is better.... see sparkfun site, for example), but it does depend on the 10yr old. I cooked my own dinner, soldered, cast lead, used a grinder, etc at about that age.

 

I will note that is also  a pretty low temp limit for anything that needs to maintain strength and shape. Not a very high temp around electronics.

 

Hot glue as glue is a different beast, as there is minimum risk of skin damage if touched, and a small heat load. Most are pretty soft, flexible, and not very strong. They tend to be optimized for melt temp and adhesion. Strength in bulk not so much. If it is going to be worked to shape, same concerns about temp and burns working with it.

 

 If casting is a possibility, I would go with a standard castable. Not reusable, but permanent. Gotta be sure to use a true castable, tho, as there is a difference between these and the resins intended for fibreglas or other coating purposes once you are filling a large volume. I used to make patterns from wood and plasicene, one shot molds from plaster of paris. Today, I would probably paint the resin on to make the mold, then cut it apart, coat the inside with release for a one shot. For duplicate parts, use two part silicone designed for the purpose. Caulk in a tube is NOT a substitute. It will NOT work (yes, I found out the hard way in the days before the web. I was involved in several threads on rec.arts.fine about this back in the day)

 

For most things these days, when I am nor running it in ABS on the printer at work or machining/welding in metal, I use styrene or ABS. Available in sheet and rod in various dimension from both hobby suppliers and industrial suppliers 9McMaster and MSC, for example) pretty cheap. Easy to cut and work with hand tools, joins with cement or heat weld (harbour freight welder isn't bad. I friction weld using a rod of similar material in a die grinder or dremel. A temp controlled soldering iron may work, but I have never tried) ABS is what legos are made of. Most kids toys, and many other 'plastic' products are ABS or straight styrene. Good source of material. Amazes my students, and coworkers, sometimes, when I weld lego pieces to kids toys and make something in 5 min they have struggled weeks to do.

Share this post


Link to post
Share on other sites

Wow! This topic has got legs but it sure ain't about Energia anymore.

 

 

Maybe a site editor could move this topic to a more suitable location so they can carry on and on and on and on....?

;-)

Share this post


Link to post
Share on other sites

Bought this: 

 

http://www.ebay.com/itm/181409484752?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

10pcs 6mm 2 phase 4 wire micro-stepping motor Canon with a small plastic gear for $2.58 

 

Figured, at this price, we might use them for something. What are they good for? Could one make a robot (a tiny "creature") out of these, with a little Polymorph or 3D printing? It does not specify the torque, I expect it to be tiny.

 

BTW, I've read more about Polymorph and am in love with it. 

 

I'd buy servos if I saw them at this price. Still looking. Suggestions would be greatly appreciated.

Share this post


Link to post
Share on other sites

*Any* motor or solenoid can generate inductive spikes if it doesn't have a proper snubber network.  An R/C servo should have one internally.

 

Hobby King is a good source for inexpensive servos:

 

http://www.hobbyking.com/hobbyking/store/__287__189__Servos_Parts-Micro_Servo_5_10g.html

 

Be sure to order from one of the US warehouses.  Many people have had bad experiences ordering from the International warehouse.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×