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."

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.

*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.

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. 

Conduct Block 1.JPG