how conductive is conductive filament can a chep cube become a resistor
let's find out on today's filament friday
this video is sponsored by pcbway.com this video is also brought to you by the generous donations
of these patreon supporters you can get conductive filament pretty much anywhere but i've had a spool
of protopasta for a while so i figured i'd use that to make conductive pla they just mix plastic
with carbon the same stuff that they use to make resistors so really it's just resistive material
so how resistive is conductive pla the specs are specified as resistance per centimeter so in x
and y direction 30 ohms per centimeter and a z direction 115 ohms per centimeter but i'm not
really sure how they measure it so i just decided to do my own measurements on my own 3d prints
i searched around for some conductive test prints but i couldn't find any good ones so i just
thought why not just do some strips and measure with an ohm meter so i decided to just go into
tinkercad and make some strips of my own the first one is one millimeter wide by one millimeter tall
the next one is two millimeters wide by one millimeter tall and then i made a three millimeter
wide a four millimeter wide and a five millimeter wide and all of them are 100 millimeters long
i brought that into cura and realized i could change the thickness just by adjusting the z
height without uniform scaling i can go right up to five millimeters so i could make five
millimeter by five millimeter blocks and then i realized i probably need a special profile
to slice this so i made a conductive profile based on my good profile at a point two layer height i'm
only going to use one wall for this print and i'm also going to do no top or bottom layers i'm going
to use 100 infill with lines and then i'm going to rotate them 90 degrees to each other so they cross
and connect each other like wires this filament also requires a little higher temperature so i'm
going to use 215 degrees i slice it and it says 13 minutes to print the one millimeter tall version
if we look at the preview you can see it's going to print lines horizontally and the next layer is
going to print short little lines perpendicular to it to connect those lines the thought is it will
make connections from side to side wire to wire so everything is connected as one piece of conductive
plastic all the way across the 3d print i wanted to measure 20 millimeter wide cross sections for
resistance so to be consistent i made a jig to hold my probes back to tinkercad i made a plate
with two 9.5 millimeter holes this should fit the probes and they're exactly 20 millimeters apart
so just group this together and print it out and here it is and it fits perfectly first try
i did five different prints this one's the four millimeter tall i did a one two
three four and five so i'm testing the five millimeter wide strip by just pressing hard
to get rid of contact resistance 570 ohms four millimeters wide is 606 ohms three millimeters
wide is around 800 ohms two millimeters wide measures 900 ohms and one millimeters wide is
like 1.5 k i did it multiple times and took the averages and then i plotted them and this is the
result the heights are in color one two three four and five at the top is the colored lines
and in the bottom is the width and the side is the resistance and you can see as the cross-sectional
area gets bigger five by five is the least amount of resistance one by one is the highest
now resistance is actually measuring how hard it is for electrons to get through the conductor
now electrically it makes sense that the bigger cross area would reduce the resistance think of
it this way one millimeter by one millimeter is like one ticket booth at a sporting event
if everyone had to go through that one ticket booth there'd be a lot of resistance would be
a lot of backup of people trying to squeeze through there but if instead you spread it
out so you have five ticket booths just like five millimeters now more people can get through faster
what if you put one or five ticket boost on every level of a five-story parking garage
five by five that's 25 ticket booths people are going to get through much easier and then
you're going to reach a point where you've got so many ticket booths that there's not enough people
to go through and that's the same thing with electrons there's only so many free electrons
and they'll go through and then it's going to level off which is kind of what we saw at the
four to five millimeter square cross section since i'm probing at 20 millimeters i wondered what a
20 millimeter by 20 millimeter by 20 millimeter print would be in resistance well that's a check
cube so let's print a chep cube in conductive filament and see how much resistance it is i
load the chep cube into cura and i'm going to use that same conductive profile to slice it and it
said it would take 42 minutes to print again 100 percent infill and here it is the lines are going
to cross back and forth all the way through you can see back and forth so it printed pretty nicely
so now we can actually probe this thing and see how much resistance it is i'm going to do that on
the bottom so here's my probe i touch it and i'm getting about 1k but it's dropping it's going to
level out to about 850 ohms if you want to light an led you typically need a series resistance
to limit the current if you're running at 5 volts you tend to use a 300 or 330 ohm resistor
if you're running at 12 volts you need about 800 to 1k so since this measured about that range
let's see if we can use this as a resistor to light an led so i made the simple breadboard
circuit current's going to flow through the led across the check cube and then back to ground
i got the power supply set to 12 volts i got two probes to hold the check cube
so i'll put the chap cube on top and look at that led lights here's a close-up i touch it the led
lights i take it off the led goes off i added a post so i could just rest the chep cube on
it because contact resistance can affect things so here it is resting there the harder i press
i reduce the contact resistance and the led gets brighter now what would you use this for well you
could make your own stylus now this is a small one so the resistance is going to be higher and
i can draw a little bit once in a while something appears on my phone but to really get it to work
consistently i need the bigger one which has less resistance so five by five now i can actually draw
right on my phone so could you use this conductive filament to make a circuit board
no i wouldn't recommend it for that i recommend pcbway.com pcbway.com is a great place to get
circuit boards i use them all the time you can get 10 pieces for only five dollars plus shipping
or if you want assembly you can get assembly services for a low cost and it doesn't stop
there they offer cnc machining 3d printing sheet metal fabrication and injection molding
ordering circuit boards is easy just upload your gerber files and then go through their selection
menu and you can just go with the defaults or you can do things like change the board color
and then you order them they'll ship them out to you top quality i highly recommend pcbway.com
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