More Fun With Electricity!

I finally got around to a bit more guided testing of my conductive ABS plastic this week, thanks to some direction from /u/eb86 and /u/SaffellBot from Reddit.  They suggested to simply measure the resistance of the conductive filament rather than the voltage drop.  Eb86 also gave me more direction on measuring the voltage drop with the filaments in series and the multimeter in parallel -- haven't gotten to this yet, but I will soon.

If you haven't read my previous blogs on this subject I'll repeat the disclaimer that I'm a horrible dabbler with electronics.  I've no issues with admitting my amateur status at anything (it's a pretty good approach for learning stuff, you know) and I love it if my dabbling inspires other people, but remember -- everyone's responsible for not burning down his or her own house.

This one's a pretty safe experiment.  Same 3D printed conductive block that I described in this blog.  This time I simply plugged the multimeter directly into the block to measure the resistance.  The reading was a pretty steady 143k ohms.  That's a heck of a lot more than the 330 ohm resistors that I normally use with my LEDs; I'm surprised the LED lights up at all with the conductive filament in the circuit.

Simple result: while this arrangement does conduct electricity, the resistance is pretty high.  (Sounds like I could be describing a marriage at times, huh?)

Appropriate music suggestion: Muse, "The Resistance."

Yesterday's experiment also resulted in a mystery*.  When my 3D printed block is in the circuit without a resistor the LED doesn't light at all.  Logic suggests that the resistor and block together would increase the resistance, but no one ever said that logic is key to science, right?

The logical next step (to me) is to print some different configurations of the conductive filament and figure out which offers the least resistance.  I've already got this latest one at 90% infill, is the resistance higher or lower with more dense infill?  Is the diameter of "wire" a contributing factor?  Like a circuit board, perhaps a very thin layer of conductive plastic is better than the wire I have now -- say, .1mm or .2mm as opposed to ten times larger.

More to come...but after I've finished more of my actual work for Film Tycoons.

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*By "mystery" I mean, "I don't know the answer to this, though it's very likely that someone with more knowledge of this subject probably sees my mystery as a basic fundamental concept.  You can laugh, but you know who you're coming to when you're trying to figure out a SQL database, don't you?

I Have No Job, But I Have A 3D Printer

(I thought that was a bit catchier title than, "Conductive Filament Part 2."  At least it gets fewer conflicting hits on Google, right?)

I meant to post this earlier in the week but as the title subtly hints, I was laid off on Monday.  That took a bit of wind out of my blogging sails this week.  Ironic, given that I've abruptly had time on my hands.  On the plus side, I'm interspersing my job search time with 3D tinkering and helping get the new 3D printers set up at my daughter's school, so...let's do some more filament testing.

In Part 1 of this subject I started testing the actual conductivity of STAR Alchement's Conductive ABS Filament.  In technical terms, the results were middlin'.  While my printed coupler did conduct electricity, it dropped the 8V output from my battery to just over 4V.  I decided to change a few things on the next attempt.

I was out of bananas, so I used a penny for scale.

The coupler in this experiment is regular ABS (Hatchbox Gold, not to be confused with the awesome double album, ABBA Gold) while the inside is Alchement's Conductive.  The sockets are the same size cones described in the first blog; the wires pressure fit snugly into the ends of the block.  Each cone tapers down to a 2mm diameter cylinder, and the entire arrangement is 40mm long.

One other key change -- I separated the processes and used different infill densities.  The gold box is 25% infill, same thing I use for most prints.  The conductive part, however, is at 90% infill. 

Similar test to before.  Measure the battery output alone, then add the coupler to the circuit and measure again.  No need for a "before" shot this time, it's pretty much the same as the first time.  (It's the same battery, same battery clip, and I promise I haven't been running my Walkman off it in the intervening week.) 

You can see the results below. Although the voltage still isn't at the full 8V the battery was putting out before, it's much higher at 6.26 than the 4V from the first piece that I printed.  It was also quite steady.  Once the wires were seated firmly the reading hardly budged.  The obvious conclusion is that the 90% infill made the major difference. 

Next steps will be trying a few more variations of the "wire."  The connecting wire here is 2mm diameter over 20mm (each of the sockets is 10mm deep) and perhaps that volume causes more diffusion.  (Mike Patterson, if you're reading this, stop laughing.  My line is business intelligence, not electrical engineering.)  After a visit to PAX South this weekend I'm going to print more models with 1mm or .5mm wires and see if I get any noticeably different results. 

First Test of the Conductive 3D Filament

One of my favorite things about 3D printing as a hobby is that new capabilities are developing almost daily.  It seems like a new type of filament is on the market every day, or someone has assembled a new extruder to do anything from create edible cake decorations to pouring concrete housing.  A while ago I ordered [STAR] Alchement's Conductive ABS filament and this week I started testing it out.  The significance of this as a printing capability is pretty obvious.  If you've also got an interest in electronics, it's possible to simply print some circuitry as opposed to leaving cavities for electronic parts in your prints.  My dual extruder printer should be particularly well suited for this -- print regular ABS from one extruder for the main print, and conductive from the other to make "wires" through the print.

Of course, this all depends on whether or not the conductive filament is truly conductive.

The Amazon reviews aren't promising.  To date there's one question asked: is the filament truly conductive?  One person has answered, and he rather vehemently says no, it's not conductive at all.  Likewise, the sole review gave the filament three stars and claims that it's not conductive "by any means." 

Well, I've got a roll and I like Alchement's other filaments, so let's give it a try.  Here's my disclaimer: I've only run one test so far.  I'm going to modify some of the prints to see if I can improve the results.  I wouldn't claim that this first bit of data is conclusive.

For a simple conductivity test I printed a little connector, pictured to the right.  It's just a rectangle of filament, 40mm long, 2mm sides.  The final 10mm at each end is a hollowed out cone, 1mm wide at the very end, narrowing down to .4mm.  Hence, a jumper wire or the leg of an LED or resistor pressure fits into the socket and there are 20mm of "solid" filament between the two sockets.  (Quotes around "solid" because I printed this at 50% infill.  One of the next things I'll toy with is printing the "wire" at 100% infill.)

Quick printing specs: because I'm dealing with a pretty small part and want the sockets to work well I changed my primary layer height to .1mm.  The bed is set at 105C and the extruder at 230C.  It printed quite nicely at these settings and given how small the part is, it took about 10 minutes.)

Time for some measurements.  The picture on the left is the multimeter hooked up directly to the 9V battery.  Not surprising, I'm getting just under 8V.  (It's a veteran battery.)  On the right, I've gone from the battery to my filament connector, then a jumper wire to the multimeter probe.  Noticeable drop in voltage, down to 4V, but it IS conductive.

Some immediate thoughts: it's possible that my socket design isn't the best.  The wires are all plugged in pretty tight; they won't fall out of the sockets without a good tug.  It's worth looking at, though.  Also, the aforementioned infill of the wire.  In the current configuration (no pun intended) my "wire" is 4 square mm with 50% infill.  When printing this as a wire inside another model I plan on making the wire a 1mm cylinder at 90% or 100% infill. 

Of course, the multimeter is good for testing but not really a fun application.  Here's a little more visual evidence of the difference, using an LED to demonstrate.  Again, straight hookup on the left, conductive filament socket in the mix on the right.

Early conclusion: hell yeah, it's conducting electricity!  No disappointment here, it's time for more experimentation.  :)

Organized Resistance

One of the guys at the Fort Worth Library Panther Lab Maker Space recently showed off a very cool method of storing the resistors in his electronics supplies.  He uses a sewing kit with an array of small, individual boxes which close securely, one box for each size resistor(For the uninitiated, those plastic boxes with "configurable" compartments are terrible for electronic parts.  The walls are never flush to the bottom of the box, so whenever you pick it up stuff slides beneath walls and gets all mixed up.)

I scoured the sewing stores nearby but couldn't find the same organizer.  Merry picked up some clearance fabric, but that wasn't really in the success criteria for the mission.  I did find those storage systems on Amazon but they were over $50.  I didn't want to pay that and wait two days for shipping when I could design my own solution and, well, wait two days for it to print.

I had these plastic test tubes (okay, they're pin holders, but "test tube" sounds more technical) and decided to build a rack that could organize them.  First step was a single rack, modeled in OpenSCAD.  Couple of key criteria: first, the seat at the bottom and the collar slightly above needed to hold the tube in place when turned vertically, yet the collar has to be low enough that the tube can tilt and be extracted even when there's a row above.  Second, I needed enough space for my fat fingers to get hold of these things.  And third, I want to be able to connect any number of holders to accommodate whatever size box I find for them.

I did make a 5-holder version once I was happy with the single.  It's pretty easy in OpenSCAD; there's a module for a single holder.  Call that module five times with a few translate tatements and you're good to go.

The connector holes are 2mm diameter, so the knobs on the connector straps are slightly smaller -- 9.25mm at the base and 9mm at the tip.  (The width of the strap is also a pressure fit, since the recess is 10mm wide and the strap itself is 10mm wide.  Yeah, probably should have made the strap just a tad more narrow, but hey -- it pressure fits.)

Next step, of course, is to find or print a box to carry these in, or perhaps print something to mount them on the wall in the electronics lab/office/game room.

Here's the Thingiverse link for anyone interested in printing their own.