looking for 1 transitor led flasher circuit..that works!!!!!

[merlinb]

I'm curious - if the tranny is acting like a zener....then why not use a zener? (which bit have I not grasped!)

Needs to exhibit negative resistance. Ordinary zeners don't.

[Manny]

I'm glad to see that it's working. 

Arma, what hFE do your 2n2222a's have?
Or would this not make any difference?

I'm going to try with some different pots/caps tonight.

Manny

[deadastronaut]

nice one manny.....ive got to wait for snail mail...

[deadastronaut]

yay!!!!...i just got my trannies through the post.......im trying it now ok guys..

amazing, i only ordered em last night!..

[~arph]

There is a bunch of threads here on the negistor (That's what this is called)

Do a search on negistor and negistrem (a negistor tremolo)

http://www.diystompboxes.com/smfforum/index.php?topic=9685.0
http://www.diystompboxes.com/smfforum/index.php?topic=5764.0
http://www.diystompboxes.com/smfforum/index.php?topic=57183.0

There is a lot more

Also look at moosopotamus.net he has a tri-negister noise box

[deadastronaut]

@arnoud cheers...

just tried 10 2n2222a's...nope!...isnt working!...

[R.G.]

Like I said, the transistor characteristics which are not on the datasheet matter hugely as to whether this will work. Likewise, the available voltage to break over the transistor's B-E, which means the LED matters. The manufacturer matters, the date code matters, everything matters because the desired action is not specified as part of the device spec, so the manufacturers don't test for this aspect of the device physics.

If you want a transistor which works first time, every time, look at the 2N6027. Or use any NPN plus a PNP connected as an SCS.

[~arph]

@arnoud cheers...

just tried 10 2n2222a's...nope!...isnt working!...

For the record, I never got it working either.. really seems to depend on getting the right (or wrong) batch of trannies

[deadastronaut]

hmmmmm...

im getting.

1.27v at collector

9.11 at emitter....

and 1.64 at base which isnt used....

note: these are not the can type...

[~arph]

I tried both...

[deadastronaut]

I tried both...

weird...dunno how armando's works then?...strange...


that negitrem looks good btw..think i'll have a look at that!...cheers.

[~arph]

Well R.G explained that here:

Like I said, the transistor characteristics which are not on the datasheet matter hugely as to whether this will work. Likewise, the available voltage to break over the transistor's B-E, which means the LED matters. The manufacturer matters, the date code matters, everything matters because the desired action is not specified as part of the device spec, so the manufacturers don't test for this aspect of the device physics.

If you want a transistor which works first time, every time, look at the 2N6027. Or use any NPN plus a PNP connected as an SCS.

Order either the transistor he mentions. Or order 2222's from a bunch of different suppliers (even then..)

[deadastronaut]

yeah gotcha!...looks like a trip to craplins after all....

[Gurner]

Or keep adding PP3s in series into your supply until that pesky tranny does go into breakdown!

[deadastronaut]

yeah...i will...

[Manny]

Or keep adding PP3s in series into your supply until that pesky tranny does go into breakdown!

I've seen a few alternative circuits that use one transistor but at higher voltages. It looks as though whatever we try we'll be struggling against the fact that this is behaviour is not specified for transistors so is very hard to reproduce accurately and consistently. (as R.G pointed out)

I've got a variable voltage source that can deliver a range of voltages. Might get it out later and see if the proverbial "sweet spot" can be found for my 2N222A's.

[deadastronaut]

yeah thats my problem i'm using a 9v supply only.....maybe next xmas i'll get one 

[earthtonesaudio]

There is a bunch of threads here on the negistor (That's what this is called)

Do a search on negistor and negistrem (a negistor tremolo)

http://www.diystompboxes.com/smfforum/index.php?topic=9685.0
http://www.diystompboxes.com/smfforum/index.php?topic=5764.0
http://www.diystompboxes.com/smfforum/index.php?topic=57183.0

There is a lot more

Also look at moosopotamus.net he has a tri-negister noise box

Yep.  Keywords "Negistor" or "Negatron" turns up a fair bit of useful data.

http://www.diystompboxes.com/smfforum/index.php?topic=65423.0
http://www.google.com/search?q=negistor&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

It helps to have a handful of different NPNs to choose from, but most (not all) 2n2222 that I have tried worked.  Sometimes one would work at 12V but not at 9V.  None worked below 5V.

[arma61]

weird...dunno how armando's works then?...strange...

Hi, some voltage readings of my working unit

PSU = 8.86V
Pot lug 2 = swing from 8.01V to 8.16V
LED pos side = swing from 1.54 to 1.62
T1 is a metal can 2N2222A V2, manufacturer is something like CDIL or COIL
T1 HFE is 171


Cheers
Armando

[deadastronaut]

@alex..ah i see many others have had grief getting this (negistor/negistrem) going then!.glad its not just me!.....thats a handy tranny alternative but unfortunately it still didnt work on others i tried...
seems a very fussy little bugger!...