I was interested so a little more googling shows that “Velostat pressure sensitive conductive sheet” is available from many places such as Tinkersphere $3.99 for 12” x 12” piece. Same stuff available directly from Adafruit, Digikey or Amazon for slightly more. Same properties as QTC???
As I remember from Match the only hitch in using this was getting it to stay at one setting. Need some kind of detent to hold the pressure steady.
Isn’t this possible to make yourself?
I mean like a piece of plastic sponge, soaked with graphite and latex mixture or something?
(i guess i should try that myself ?)
I tried some QTC and then gave it away because afaict it only works in single mode lights that are battery crushers (no spring above or below the battery).
I do not own any battery crusher lights…
All my lights have a spring, so the QTC would not work.
I’ve tried qtc before. I prefer the reliability and feel of infinitely variable control rings but those lights are bigger than qtc lights. I would like to try making a non-battery crush qtc host one day, just for the challenge of it
I did that with a cooyoo 10180 light.
Separate battery compartment, the head twisted to compress the QTC pill onto a fixed stationary contact not the cell itself.
Yeah, I mean the light was stripped & heavily modified, just remembered it with pinks comment.
A slightly better way to implement QTC.
So you could have a sprung cell compartment and just the head or tail unit doing the variable thing without crushing the cell.
they have a 2 mode switch in the head, that is based on a domed metal disc that gets compressed to access the 2nd mode.
That defeated the QTC, which I wanted to use to get a moonlight mode… Instead the QTC would trigger the high mode. iow, the QTC needed more pressure to work, than the 2 mode switch, which is based on a springy piece of metal that would move with less pressure than the QTC needed…
waste of time
That is not to say that a heavily modified light could not be made… but the QTC definitely did not work for my intended purpose with a 10180 light… They come in many brands, they all work the same 2 mode spring switch…
I also tried it in a Fenix E01 and a Maratac, again hoping to create a sublument mode… Total Fail
Yeah, i replaced the springy triangular(ish) disc in mine for a tiny strip of metal.
Works much better, because that springy disc couldn’t be soldered properly to the PCB, causing problems…
And so the tiny strip will have to be removed again if i want to try a pressure sensitive resistor in stead.
I think it’s wise to sandwich the pressure sensitive medium between thin brass sheet discs or between the PCB and a thin disc, so it won’t deform or damage.
If the QTC is in the head then there is a compression and twisting motion being applied.
If it’s in the tail then it’s mostly just compression from the flat cell negative.
The cell positive is taking all the twisting force.
There have been various methods to protect the QTC like placing it between conductive plates, tape etc in head twisty applications.
I’ve found that method to give more flickering output, especially on lower pressures, the conductive surfaces oxidize etc.
QTC is fairly fragile and will split or wear out faster due to friction if you have it just making contact on the cell & head contact being compressed and twisted.
That’s what I think anyway.
You can see here how Fritz used three QTC pills between two brass plates to try to overcome some of these problems. I don’t know how successful it was as other parts were too damaged when I received this light.
This might be worth a shot for me at some point. Great resource here for QTC. I have gotten oddly fond of the 10180 lights, and they seem perfect for this.