Riddle me this :D (Conductive pen)

[@rt]

I want my money back!

[Blastcap]

It might not be conductive in a wet state, wait for it to dry and try again.

[TheBay]

It might not be conductive in a wet state, wait for it to dry and try again.

Agreed!

It also looks like it needs a good shake to mix it.

[@rt]

Yes it want more than ten second shaking. It has a mixing ball.
It’s still set up, so we’ll see

[rrinker]

 Indeed, the conductive paint I use for resistor wheelsets for model trains is the same way, does not conduct until dry - the adhesive/ink component keeps the conductive components in suspension and not able to conduct. I install an SMD resistor and use the conductive paint to complete the circuit. I then set the wheelset aside on a test track I have clipped to a meter and after it sits there long enough I see the reading start to drift down to the nominal resistor value (10K in my case) as the paint dries. It also takes longer than expected - the first few I though I messed up because even after the expected 15-20 minutes they were still showing infinite. So I stopped and went back and carefully checked each one and they all looked fine - now an additional 15 minutes or so had gone by and - hey, wait, they work!

[rsjsouza]

While I was watching the clip I was wondering if the conductive ink had a moderate resistance of a few tens or hundreds of ohms.

[rrinker]

 I suppose it matters what the conductive material is. I've seen ones that use powdered carbon which do result in noticeable resistance in the lines. The silver bearing paint I use, my train wheelsets come out to within the tolerances of the resistors I use. If the traces do add resistance, I must not have hit a resistor that was at the top end of the tolerance for the extra to push it over. But I'm also measuring on an old Fluke 8012A, I haven't tried with any of my new meter purchases.

[AndyC_772]

RTFM. That stuff is made up of conductive silver particles suspended in a liquid which is not conductive. It only conducts when fully dry.

[ataradov]

You should not apply it under voltage.

And yes, check the actual resistance.

[TheBay]

Indeed, the conductive paint I use for resistor wheelsets for model trains is the same way, does not conduct until dry - the adhesive/ink component keeps the conductive components in suspension and not able to conduct. I install an SMD resistor and use the conductive paint to complete the circuit. I then set the wheelset aside on a test track I have clipped to a meter and after it sits there long enough I see the reading start to drift down to the nominal resistor value (10K in my case) as the paint dries. It also takes longer than expected - the first few I though I messed up because even after the expected 15-20 minutes they were still showing infinite. So I stopped and went back and carefully checked each one and they all looked fine - now an additional 15 minutes or so had gone by and - hey, wait, they work!

I just looked resistor wheel sets up, quite interesting I must say!

[rrinker]

 I'm using different brand wheels next time. The ones I use have plastic axles, and it's that slippery kind of plastic nothing sticks to. So to get the silver paint to stick, I have to use a Dremel to rough a pathway across. The resistor gets stuck on with a dot of CA, that sticks to anything. ANd it has to be a TINY dot - if it gets on the metal end caps of the resistor, you've just insulated it! I had a very high success rate though, considering it was my first attempt. Next time I will use a different brand of wheel, which has a metal axle, and just a small insulated bushing on one side. Resistor goes diagonal across the bushing and the paint connects the end of the resistor to the wheel on one side and the axle on the other, much easier.  And I was using 18% silver paint, I may step up to 36% - the primary use of the paint I got is for scanning electron microscopes, amazingly enough.

[@rt]

In a dramatic turn of events, the LED was lit this morning!