3 ms·
I built one from discrete transistors in a lab class in college, on a breadboard. Fun times debugging and getting it to work. Then I flashed an led with it righ
by reader9274 8mo ago
I built one from discrete transistors in a lab class in college, on a breadboard. Fun times debugging and getting it to work. Then I flashed an led with it right next to another led flashed from a 555 chip. With the same discrete timer caps, the flashing frequencies were different due to the extra parasitics in the breadboard discrete 555 version. So had to compensate the caps to make the flashes match each other's frequency.
- jacquesm 8mo agoThat's a great exercise. The hard part is always that in chips you can pull stuff that is rather tricky discretely, for instance, a multi-emitter transistor. So you can't always do a 1:1 conversion but for a 555 it is still doable. I saw this a while ago: https://www.instructables.com/Designing-a-555-Timer-on-Discrete-Elements/ https://www.instructables.com/Designing-a-555-Timer-on-Discr...
- direwolf20 8mo agoOnly because odd components aren't marketable. There used to be 4-terminal MOSFETs, they weren't sold after ICs became normal. Never heard of a multi emitter transistor being sold discretely but it's possible.
- jacquesm 8mo agoI use dual gate FETs frequently for all kinds of tricks and they're super useful. Is that what you had in mind?
- squarefoot 8mo agoDual gate mosfets were a godsend when building RF/IF mixers or preamps. Luckily I have a small stash as they're almost unobtanium and costly these days, but for most uses such as mixers and preamps they can be swapped with a pair or normal jfets in a cascode configuration like this one: https://i.stack.imgur.com/6Nyhg.gif https://i.stack.imgur.com/6Nyhg.gif
- cbdevidal 8mo agoToday I learned you can build an entire freaking CPU out of 555s lol https://hackaday.com/2011/08/05/building-a-computer-out-of-555-chips/ https://hackaday.com/2011/08/05/building-a-computer-out-of-5...
- jacquesm 8mo ago> Dual gate mosfets were a godsend when building RF/IF mixers or preamps. exactly :) BF901 FTW.
- analog31 8mo agoCoincidentally, there were vacuum tubes with dual grids for mixer and AGC applications.
- buescher 8mo agoAnd there's someone with a stash of those too. Dual-gate mosfets are one of the ways you know something's been in the back catalog way too long.
- Zardoz84 8mo agoOmg... and thinking that my mother throws a huge stash of components like that. my father was an electrical engineer and ham radio. At least, I managed to save a stash of electronic valves and some analog equipment like an old oscilloscope that could be in a museum (I saw a similar model in a museum).
- gus_massa 8mo agoDo you still have a video saved somewhere?
- morninglight 8mo agoReal men use Unijunction Transistors like the 2N2646. https://en.wikipedia.org/wiki/Unijunction_transistor https://en.wikipedia.org/wiki/Unijunction_transistor
- buescher 8mo agoOne of the books I first tried to learn from was _Miniature Projects for Electronic Hobbyists_ by one Ken W. Sessions. It was really a unijunction transistor project book. You know how some people will say you'll learn maybe not the best mental models for electronics from Forrest Mims' books? (I don't get it, they seem OK to me) Well, Forrest has nothing on Ken W. Sessions. The circuits worked, though.