a low voltage minimal parts clock runs 1Mhz.

I'd dig out my 2N2646 which were sitting in my part drawer for so many years, and try it out on a breadboard. I'll reduce the frequency to around 100KHz and use it as a time base for my dividers.

Allen

 

What is the actual difference between an old UJT such as 2N4852 and the new 2N6207 UJT/Thyristor?

2n2222A is probably what I tried to get and could not find - i was working from radio shack forrest-mims-iii hobby guides

2N6207 is programmable (better stated it has modes of operation depending on how used) ... i can't tell you for sure if i hit the programming window correctly

if i remember correctly i tried the diag. in post #4. I got some erratic blinking while with tuning resistors (extremely touchy window) but it was un-reliable enough i couldn't say if it was an action of the 2N6207 or just circuit fluctuations (i'd have needed an oscope, knowing not much, to say)

 

With a PUT oscillator, a LED is not a great load as it does not allow C to discharge fully to ground. Adding a resistor from cathode to common
usually corrects the problem, maybe 1k or less. Just a few weeks ago I pulled some out for a frequency divider. I was wondering if a common gate bias could be used for several PUTs & discovered that when triggered the gate fell to ground with a nice clean neg. square pulse with same width as K + pulse.

thanks. i was just doing example circuits from forrest mims III - any i could do with parts i had. if i do any analysis like that it would be for (say, at least an ardiuno (or some gpio) project. haven't got that far really.)

that's interesting - do capacitors work better near ground operation than saturation? why is it better if it fully grounds (assuming curves of the PUT are met either way - which i shouldn't assume)?

 

@Bordodynov I see an additional resistor (R5) not in @AlbertHall's link. That's the only difference I'm seeing in the two diagrams,

i see a 2n2646 added

as i said - i was interested in 2n222 but using 2n6027 until assured by papabravo that using a UJT as a "digitally switched blinking LED" would "not be a good project for me". i assume he predicted i would need to do allot of curve matching (at best) to hit the window and that for a blinking LED - not worth it. some of the forest mims III projects do require a little tinkering to get working (need tuning) - but this one seems to be up there with the worst?

 

I still have a fist full of old TO-3 2N2222As but just about any of the TO-92 marked 2N2222 are probably actually the A spec. I asked about the 2096 because I have an old John Lenk book circa ~1973 "Electronic Components and Circuits" that starts with UJT and then goes right to FET. Old out of production UJTs. I bought some 2N6027s to play with but lot more on my ToDo List before I get to them. I was just curious and didn't intend to step on your thread and apologize for doing so.

 

I am curious as to why the 2N6027 was made as UJT was pretty well outmoded by the BJT. Is it to use to replace non-working legacy UJTs? Or does it have a legitimate modern use?

 

I am curious as to why the 2N6027 was made as UJT was pretty well outmoded by the BJT. Is it to use to replace non-working legacy UJTs? Or does it have a legitimate modern use?

An analogue in the case for surface mounting is actively sold: