My young son has just been building a two transistor bistable (set/reset) flip-flop and the standard two transistor astable flip-flop (flasher) with a couple of LEDS in each. All as first steps into electronics.
His question now is how to make a bistable flip flop with only one switch as input that toggles on/off each time the switch is pressed. Obvious question but it has stumped me.
Years ago I did this by using two flip flops wired as a master and slave but this solution required many transistors and I'm not sure I could reproduce the thing anyway having hacked it on the fly at the time.
I have seen toggle flip flops built with two transistors, caps accross the base resistors and a parallel switch resistor connecting the emitters to ground (as here http://ourworld.compuserve.com/homepages/Bill_Bowden/page9.htm) Fine but I would prefer the input to go into some more normal place rather than brute forcing the negative rail up and down. Also we loose 1 volt from the suply.
So the challenge is, does any one have any nice discrete transistor toggle circuits that:
a) Use minimal components as my sons patients for building things is a bit short at the moment.
b) Uses a more "logical" input method.
c) Runs from a 5 to 6 volt supply, dictated by our rechargeable battery pack.
b) Can be easily understood by a 12 year old beginner. (Or me for that matter)
Extra caps and diodes allowed.
Cheers all.
His question now is how to make a bistable flip flop with only one switch as input that toggles on/off each time the switch is pressed. Obvious question but it has stumped me.
Years ago I did this by using two flip flops wired as a master and slave but this solution required many transistors and I'm not sure I could reproduce the thing anyway having hacked it on the fly at the time.
I have seen toggle flip flops built with two transistors, caps accross the base resistors and a parallel switch resistor connecting the emitters to ground (as here http://ourworld.compuserve.com/homepages/Bill_Bowden/page9.htm) Fine but I would prefer the input to go into some more normal place rather than brute forcing the negative rail up and down. Also we loose 1 volt from the suply.
So the challenge is, does any one have any nice discrete transistor toggle circuits that:
a) Use minimal components as my sons patients for building things is a bit short at the moment.
b) Uses a more "logical" input method.
c) Runs from a 5 to 6 volt supply, dictated by our rechargeable battery pack.
b) Can be easily understood by a 12 year old beginner. (Or me for that matter)
Extra caps and diodes allowed.
Cheers all.
Hello DIYAudio,
funny this thread should exist, as I am currently looking to build nearly the same component.
I unfortunately have no idea what to do with a .asc.txt file, but I did look at heater's circuit:
I have to say, wow, that's a lot of components.
Isn't there any easier (read, cheaper & smaller) way to build this circuit?
I don't really care if it uses transistors or relays, the important things are low cost, and hopefully also low power draw.
I found a circuit using three 4x relays, however those alone would cost about 21€, and seeing as I'm looking to build 5 flip-flops, 105€ is really too expensive for me.
Are there any cheaper ideas?
funny this thread should exist, as I am currently looking to build nearly the same component.
I unfortunately have no idea what to do with a .asc.txt file, but I did look at heater's circuit:
An externally hosted image should be here but it was not working when we last tested it.
I have to say, wow, that's a lot of components.
Isn't there any easier (read, cheaper & smaller) way to build this circuit?
I don't really care if it uses transistors or relays, the important things are low cost, and hopefully also low power draw.
I found a circuit using three 4x relays, however those alone would cost about 21€, and seeing as I'm looking to build 5 flip-flops, 105€ is really too expensive for me.
Are there any cheaper ideas?
If all you need is cheap, small and low power, just use two FF's in an IC -- 74hc74 or what was it again. Or even a 555.
Concerning discrete, how about this one:
Bistable Multivibrators or Flip-flops
Concerning discrete, how about this one:
Bistable Multivibrators or Flip-flops
The circuits shown will not actually work as the OP wants: they require debouncing and fast, clean edges.
Some more components would be required to make them work.
This circuit will actually work, and it is not more complicated.
As a bonus, one more based on a SCR:
Attachments
I recall that "Wave Generation and Shaping" by Strauss (amazon link) had a Tflop built out of two NPNs and a lot of discretes. Maybe I can find my copy somewhere.
What are you referring to that you recall Mark? Please post . The flip flop I posted I designed in the 90's.
Here is a link to the rest of the dtl switching I cropped that from.
https://hackaday.io/projects/hacker/1205951
I am referring to one of my textbooks from uni, written by Leonard Strauss -- (here is a review of the book). I have a memory that it contains a toggle flipflop made of a bunch of discretes and 2 transistors -- and we had to build it and demonstrate its operation in the lab. Maybe I can find my copy of that book, if so I will attempt to find that page, and if I do, post an image here. But don't hold your breath.
Wolf13 has stirred a 9 year old thread.
On a problem that I believe was well solved well before 1960. 1950s engineers were inclined to treat a good F-F plan as confidential because with bad Germanium a good plan could support million dollar computer contracts. But by 1960 G-E was exposing their thoughts in a book sold in all radio/TV repair distributors.
https://steampoweredradio.com/pdf/ge transistor manual/GE Transistor Manual Circa 1960 1.pdfhttps://worldradiohistory.com/BOOKSHELF-ARH/GE-Books/GE-Transistor-Manual-1964.pdf
On a problem that I believe was well solved well before 1960. 1950s engineers were inclined to treat a good F-F plan as confidential because with bad Germanium a good plan could support million dollar computer contracts. But by 1960 G-E was exposing their thoughts in a book sold in all radio/TV repair distributors.
https://steampoweredradio.com/pdf/ge transistor manual/GE Transistor Manual Circa 1960 1.pdfhttps://worldradiohistory.com/BOOKSHELF-ARH/GE-Books/GE-Transistor-Manual-1964.pdf
Hello PBR
Your right they did do a good job . 60 years since a discrete component flip flop was released ? This one is a little different in some situations less parts are needed. The switching is done at the diodes. Very fast switching. Minimal parts. And expandable to multiple switch 3 way 6 way whatever you like.
Your right they did do a good job . 60 years since a discrete component flip flop was released ? This one is a little different in some situations less parts are needed. The switching is done at the diodes. Very fast switching. Minimal parts. And expandable to multiple switch 3 way 6 way whatever you like.
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