I have absolutely no idea if this will pay out, but working on impractical projects keeps me (mostly) sane, and these trying times require even wackier distractions.
Teaser image (work in progress):
(https://i.imgur.com/CSKg55gl.jpg)
ooh, detector diodes!!
they have like a Vf of 0,2 right? and a relatively high ESR
i love it, i think i want to try it out myself, but with smaller pieces of steel and carbon due to size restraints of the candy cans i use.
no socket on the IC?? not afraid of frying her i see.
im out of the running until monday, when ill try the diode type out.
Stand well back! Eric's already spark eroded those razors and he hasn't even switched it on yet.
are you going to do carbon arcs w/ those pencils, as well? [there was someone showed a pic of gear w/ selenium rectifiers visible in recently, wonder where that was.]
Quote from: duck_arse on April 02, 2020, 11:36:25 AM
are you going to do carbon arcs w/ those pencils, as well? [there was someone showed a pic of gear w/ selenium rectifiers visible in recently, wonder where that was.]
The pencil points will eventually rest on the oxidized portion of the blades as point contacts to complete the diodes. I've also been told that phosphor bronze guitar string scraps might work in that role. I'll probably give it a try.
Quote from: duck_arse on April 02, 2020, 11:36:25 AM
are you going to do carbon arcs w/ those pencils, as well? [there was someone showed a pic of gear w/ selenium rectifiers visible in recently, wonder where that was.]
Selenium rectifiers as clippers? The thought never occurred to me. I don't think I have any, but I've trashed a few over the years, working on old gear. What is their Vf like?
Quote from: willienillie on April 03, 2020, 05:04:21 AM
Quote from: duck_arse on April 02, 2020, 11:36:25 AM
are you going to do carbon arcs w/ those pencils, as well? [there was someone showed a pic of gear w/ selenium rectifiers visible in recently, wonder where that was.]
Selenium rectifiers as clippers? The thought never occurred to me. I don't think I have any, but I've trashed a few over the years, working on old gear. What is their Vf like?
there is a company, I don't know how I found their website, but they still custom manuf them in stacks and post specs. but I wasn't paying too much attention at the time. cehco or cougar, maybe.
Quote from: duck_arse on April 03, 2020, 09:16:43 AM
Quote from: willienillie on April 03, 2020, 05:04:21 AM
Quote from: duck_arse on April 02, 2020, 11:36:25 AM
are you going to do carbon arcs w/ those pencils, as well? [there was someone showed a pic of gear w/ selenium rectifiers visible in recently, wonder where that was.]
Selenium rectifiers as clippers? The thought never occurred to me. I don't think I have any, but I've trashed a few over the years, working on old gear. What is their Vf like?
there is a company, I don't know how I found their website, but they still custom manuf them in stacks and post specs. but I wasn't paying too much attention at the time. cehco or cougar, maybe.
thsi website?
https://cougarelectronics.com/power-conversion-components/selenium-rectifier-suppressor/
Suppressors, eh? I got a couple 1N5657 TVS diodes in a random assortment recently. Now I am wondering how they "sound". :icon_lol:
Next project, perhaps. They look cool, anyway (admittedly not anywhere near as cool as selenium though):
(https://i.imgur.com/sUDgs4Cm.jpg)
just add some fins, Eric.
think i have some selenium diodes in a bridge configuration i replaced with a proper bridge.... i also have a ziplock full of trashed 2n3055s i planned to use as clipping diodes... maybe i can find an old enclosure to build a team fuzz in....
Feel free to show off any unusual clipping diodes in this thread. Bonus points for building anything rediculously impractical for a guitar pedal. Got a diode larger than a shoebox? Let's see it and hear it! :icon_twisted:
Quote from: EBK on April 03, 2020, 11:34:57 AM
Feel free to show off any unusual clipping diodes in this thread. Bonus points for building anything rediculously impractical for a guitar pedal. Got a diode larger than a shoebox? Let's see it and hear it! :icon_twisted:
there is some sort of rectifier in my old car battery charger, looks like selenium with those bigass fins.
i also have a nice collection of high power resistor diodes (made to be put in parallel) in a very inconvenient package, the anode is just a thick lead, but the cathode is a piece of M5 thread...
I've got a number of zener power diodes with the threaded stud. Some of the smaller ones aren't too ridiculously huge for pedals, but I've never tried them for clipping. As a side note, whatever the metal-can (RCA?) power rectifiers that Fender put in later silverface amps were, those sound quite good in a Tube Screamer. I have some of the red bullet-shaped ones that Traynor used, maybe I should try them too. I was digging around in a box of old bits last night, and found an NOS Raytheon 1N294, supposedly a 1N34A equivalent, it's red with a white band and looks cool as hell, but unfortunately I only have one.
A lot of those old battery chargers used centre tap secondary and only a pair of selenium diodes needed. Since they will have a common anode or cathode, you don't get a back to back pair *.
Doesn't stop you trying an asymmetric setup with another diode type and you do have an option to use the selenium as just one or both in parallel.
* You may be lucky and have a full-bridge. It can even be a full-bridge stack but only half used.
Anytime I see EBK started a thread I'm in. Looks great so far, looking forward to sound clips :)
Quote from: anotherjim on April 04, 2020, 03:59:16 AM
A lot of those old battery chargers used centre tap secondary and only a pair of selenium diodes needed. Since they will have a common anode or cathode, you don't get a back to back pair *.
Doesn't stop you trying an asymmetric setup with another diode type and you do have an option to use the selenium as just one or both in parallel.
* You may be lucky and have a full-bridge. It can even be a full-bridge stack but only half used.
im not planning on opening the charger up tho, it belonged to my grandpa and i use it to power projects that run 12V and high power. but when applying reverse voltage to the leads, it starts conducting at 3-ish volts, ill put some terminals on an enclosure to use it as a single sided clipping diode, i think ill use a (pair of) Led for the other side.
Quote from: EBK on April 03, 2020, 11:34:57 AM
Feel free to show off any unusual clipping diodes in this thread. Bonus points for building anything rediculously impractical for a guitar pedal. Got a diode larger than a shoebox? Let's see it and hear it! :icon_twisted:
is having to carry a 2Kg battery charger impractical enough for you, EBK?
I haven't posted a pic since the initial teaser. This is all wired up and soldered, except for the pencil point probes.
(https://i.imgur.com/SNZwBekl.jpg)
what is the schematic of the distortion you have here??
Quote from: iainpunk on April 08, 2020, 05:10:16 PM
what is the schematic of the distortion you have here??
It is 99% based on the MXR Distortion+. It is also based off of the layout at tagboardeffects:
http://tagboardeffects.blogspot.com/2010/07/mxr-dist.html
I have added a switch to accommodate an attenuated diode lift mode to allow for a better evaluation of the effect of the diodes.
When the slide switch is up, it has a series trimpot instead of the parallel diodes (just an attenuator). With the switch in the down position, the diodes are connected and have (at least until I start testing it and changing stuff) a saturation control ala Jack Orman.
If I haven't said it before, I have no idea if this will work or sound good. It is a starting point for having fun.
And, if you are interested, and can follow it, here is my layout:
(https://i.imgur.com/ALMjRQyl.jpg)
hey, i think i get it, just an mxr dist+ wit a pot in between the diodes and op amps.
i'm not really in to the whole stripboard/vero thing, i chose the pad per hole side in "the war of the prototype boards". :icon_lol: :icon_lol: :icon_lol:
i also think there is a good middle ground, which still gives you the possibility to make the circuits compact, but also has the ease of use of vero (ignore the arrow)
(https://i.postimg.cc/PLjwd7K4/Corner-Pattern-Perf-Board.jpg) (https://postimg.cc/PLjwd7K4)
Have you seen this page?
http://www.sparkbangbuzz.com/ (http://www.sparkbangbuzz.com/)
http://sparkbangbuzz.com/zinc-oxide-diode/zinc-oxide-diode.htm (http://sparkbangbuzz.com/zinc-oxide-diode/zinc-oxide-diode.htm)
Quote from: Gus on April 09, 2020, 05:30:40 PM
Have you seen this page?
http://www.sparkbangbuzz.com/ (http://www.sparkbangbuzz.com/)
http://sparkbangbuzz.com/zinc-oxide-diode/zinc-oxide-diode.htm (http://sparkbangbuzz.com/zinc-oxide-diode/zinc-oxide-diode.htm)
Interesting. Thanks for sharing! I have to melt some pennies now to try this zinc blob diode.
Or these:
http://halestrom.net/darksleep/blog/011_copper_diodes/
https://hackaday.com/2016/05/01/home-made-diodes-from-copper-oxide/
https://www.instructables.com/id/How-to-make-a-copper-oxide-diode/
I have many other links but they're on another computer. (includes the ones Gus posted)
Last year I spent countless hours trying to replicate some of the experiments to use them in a distortion pedal.
But I had a real hard time getting them to work. Really frustrating.
At one point I found myself oxidizing and 'blueing' every kind and piece of metal I could find around the house.
Eventually the wife gave me 'that' look. Made me feel like a 10 year old. :-[
Some kinda seemed to work but were still behaving weird:
-it clipped in both directions, I did not need two diodes. ???
-it needed quite a bit of current and even a just little too much current destroyed the diode or 'contact point'.
This evening, I did some quick tests to see if my DCA55 would believe I had a diode. Depending on the spot the pencil touched, I got one of three results on the screen:
1) No device
2) Unknown/faulty device
3) Depletion mode P-channel MOSFET (source and drain terminals)
I'm guessing that third result, if any, is probably indicative of the diode operation. I would've guessed it would report it as a Schottky diode though....
(https://i.imgur.com/D9QxIWfl.jpg)
No clipping yet.
(https://i.imgur.com/I3Ky4K7l.jpg)
Not giving up.
have you tried the blade edge as yet? not for shaving. obvs, but for diode-ing. [perhaps stand the blades cutting edge up, w/ pencils wrinting points down.]
Here's a classic galena detector with variable arm position to find the best point:
(https://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Kristallradio_%283%29.jpg/200px-Kristallradio_%283%29.jpg)
This used to be a standard for crystal radios. As well as these, Philmore used to make crystal radios with the cat's whisker contact already placed in the best position and sealed under a glass dome:
(https://web.eecs.umich.edu/~srs/Antiques/Radios/Philmore_Crystal_Radio.jpg)
This gives you a better view of the dome:
(https://www.radiomuseum.org/images/radio/philmore_mfg_co_new/super_little_giant_supertone_336_52326.jpg)
I've started experimenting with a new probe made out of an old acoustic guitar string (phosphor bronze). The winding is the whisker, and the stiff core provides an adjustable spring.
(https://i.imgur.com/atRgUdsl.jpg)
Again, no idea if what I am doing makes sense.
I think I need to clean and retorch the blade. There is a lot of pencil graphite on it from moving the pencil probe about a thousand times.
I'm glad I found this thread because I'm looking into making this very thing. It was looking for real measurement data that brought me here to this thread. The fact that Erik EBK put the picture of the o-scope was exactly what I was looking for. Thanks for that. But, I can assume that since it's 4 or 5 years later that this never really got working. I think I understand why.
The blue steel carbon pencil detector from a foxhole radio is a point-contact diode. Looking for the characteristics of that pointed me to an electrical engineering site that compared point-contact diode to PN junction and Schottky diodes https://www.eeeguide.com/what-is-schottky-diode/ (https://www.eeeguide.com/what-is-schottky-diode/). There's a graph towards the end that shows the behavior. It's not like it reaches a threshold forward voltage and then current flows, it's much more gradual. In fact, it resembles a much more gradual parabolic curve
I = (C2*V + C1)*V + C0
If I had experimental measurements for the forward voltage (V) and current (I), I could compute coefficients for it.
Anyway, it's not going to hard clip the way "normal" diodes do with a forward voltage. In reverse... maybe, but then you would have to set a bias voltage on the opposite side for the signal to push through. Curious to see if anything came out this project in the past few years.
Bill