[sdiy] touch-sensitive switches - how?

KA4HJH ka4hjh at gmail.com
Mon May 3 22:14:19 CEST 2021


> On May 2, 2021, at 9:08 PM, Benjamin Tremblay <btremblay at me.com> wrote:
> 
> I eat my crow.
> I should try that touch switch feature in my teensy.
> 
> 
>> On May 2, 2021, at 7:48 PM, KA4HJH via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>> 
>> How about a cold cathode thyratron (that just happens the be a lamp as well)?
>> 
>> http://www.industrialalchemy.org/articleview.php?item=1084 <http://www.industrialalchemy.org/articleview.php?item=1084>


Here's an inexpensive MTX-90 toy you can play around with (no assembly required)—cute "control modules" with five touch-sensitive pads:

https://www.ebay.com/itm/133725689779

Note that this is one of several variants available (white/gray panels, clear/orange lenses). Search the same category for "MTX-90". The orange lenses are cool but clear lenses will be brighter when lit.


Based on generic circuits for other cold cathode devices in old Russian data books, I'm guessing that the power supply was half-wave rectified 220V AC . There are a number of schematics online for real-world applications of the MTX-90, none of them as simple as this particular do-dad and/or "proper". I haven't puzzled it out yet as I'm waiting for someone in the neonixe-l group to hook one up and report back.


They came from out of nowhere. Several listings appeared on eBay over a few days. No one had ever seen them before and what the intended use was is still a mystery. And the asking prices have gone up since I haggled down two sellers.

There's a ton of surplus Soviet electronic parts on eBay, mostly from Ukraine. All of the cool stuff—Geiger-Mueller tubes, Nixies, Dekatrons, etc.—is steadily rising in price. I've missed out on some excellent investment opportunities in just the last two years. The Nixie clock craze has gotten steadily crazier. 

If you any B7971s lying around take good care of them.


Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com/

“...the book said something astonishing, a very big thought. The stars, it said, were suns but very far away. The Sun was a star but close up.”—Carl Sagan, "The Backbone Of Night", Cosmos, 1980


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