SIMPLE, cheap latching circuit - one transistor?

2

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  • Ah...

    Just use a sot23 20c micro ;)
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  • Tracy AllenTracy Allen Posts: 6,139
    edited December 2017 Vote Up0Vote Down
    Okay, insane as it is today, say you disallow a package with gazillion transistors, but you allow a package with up to two transistors, and no internal voltage or current sources. Here is an article that covers a lot of ground...

    http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1085599
    IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS, VOL. CAS-32, NO. 1, JANUARY 1985
    Bipolar- JFET-MOSFET Negative Resistance Devices
    LEON 0. CHUA, FELLOW, IEEE, JUEBANG YU, AND YOUYING YU
    Abstract -A systematic method is given for generating negative-resistance
    circuits made of 2 transistors and linear positive resistors only. The 2
    transistors may be bipolar (n-p-n or p-n-p), JFET (n-channel or p-channel),
    MOSFET (n-channel or p-channel), or their combinations. Since the
    circuits do not require an internal power supply, they are paassive and can
    be integrated as a two-terminal device in monolithic form.
    Two algorithms are given for generating a negative-resistance device
    which exhibits either a type- N V-I characteristic similar to that of a tunnel
    diode, or a type-S V-I characteristic similar to that of a four-layered
    pn-pn diode.
    Hundreds of new and potentially useful negative resistance devices have
    been discovered. A selected catalog of many such prototype negative-resistance
    devices is included for future applications.


    It might be said too that all of these have potential as three-terminal devices as well.
  • Heater.Heater. Posts: 20,075
    edited December 2017 Vote Up0Vote Down
    I was just now fiddling with an LDR that's been hanging around my desk wait for a use for years. Of course I though of this thread and "why not use the LDR as the feed back for the single transistor latch?"

    Of course it's all been done before. For example this nice demo:



    A useless expensive way to create a latch, unless you happen to need such a light actuated gizmo.

    I think it's also a great way for folks to get a feel for transistor behavior.

    Now, can this be done using a LED or LEDs as the photo reciever? That would be neat as people don't have LDR's lying around so much.

    Tracy, Back in the 1970's I built an oscillator that made use of the negative resistance region of a P and N channel FET in series with and LC tank. Just for fun. Fascinating.
  • Heater. wrote: »
    Wow, amazing paper from back in the day.

    I'm struck by how all the circuits in there are encrusted with diodes, capacitors and voltage sources.

    I get the impression that in the modern world it's cheaper and faster to just use a bunch of transistors for such latches and flip flops.
    In the not too distant future people will talk about how microprocessors were made up of millions of transistors when they could have just used one of these. 'One of these' is something we haven't thought of yet.
    Infantryman's Axiom; Always cheat, always win.
  • xanatos wrote: »
    Cool info guys, thanks. The UJT thought really brought the idea back - it was indeed a UJT I had seen used in this capacity before.

    Such parts like SCRs and UJT can trigger/hold, but they are somewhat less friendly in the conditions they require for SET and UNSET.
    Often, a lot more parts are needed, to create those conditions !

    That's why CMOS gates sell in much higher volumes these days than UJT.

    You can get SOT23 sized package single-gate logic, with S-R logic, that has very easy interface.
  • Heater. wrote: »
    That would be neat as people don't have LDR's lying around so much.

    I'm doing my part to nudge people towards hoarding LDRs! http://forums.parallax.com/discussion/161210/bulk-4-cent-photocells-what-shall-we-make

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • What about using the venerable 555, or did I miss it?
    My Prop boards: P8XBlade2, RamBlade, CpuBlade, TriBlade
    Prop OS (also see Sphinx, PropDos, PropCmd, Spinix)
    Website: www.clusos.com
    Prop Tools (Index) , Emulators (Index) , ZiCog (Z80)
  • A 555 has too many pins :)
  • I'm just learning at this level, but isn't a ujt expensive compare to an SR latch?
    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • Before before the µP, the '555, or the LED, we had the glow of the NE-2, its negative resistance latching action...
    576 x 461 - 88K
    576 x 461 - 97K
  • Ooo... I have done that back in the day.

    My friend made a weird techno, sculpture, tree like thing using a dozen neon lamps and capacitors and a 90v tube radio battery. It was quite, err, shocking.



  • I've used the attached circuit with a small SCR on a BS1 which is too busy to look for a brief occasional switch closure (a very slow wheel encoder). Instead of going directly into a BS1 pin, the switch triggers and latches the SCR, which can be read at the BS1's leisure by any input pin. Afterward, the SCR is reset (turned off) by briefly making the BS1 pin high, then making it an input again to repeat.

    SCRfun2.jpg
    400 x 600 - 17K
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Peter JakackiPeter Jakacki Posts: 6,776
    edited December 2017 Vote Up0Vote Down
    erco wrote: »
    I've used the attached circuit with a small SCR on a BS1 which is too busy to look for a brief occasional switch closure (a very slow wheel encoder). Instead of going directly into a BS1 pin, the switch triggers and latches the SCR, which can be read at the BS1's leisure by any input pin. Afterward, the SCR is reset (turned off) by briefly making the BS1 pin high, then making it an input again to repeat.

    SCRfun2.jpg

    What a sneaky circuit and a novel use for an SCR (but probably one good reason not to bother with a BS1!). Have you tried a simple forward diode into a small cap connected to the I/O?. A brief pulse charges the cap, the diode blocks it from discharging, and then the BS1 reads a logic high and simply discharges the cap. A current limit resistor is optional on the I/O pin as the cap only needs to be around 1,000pf.

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  • Even better! Love your cap/diode idea, surely that's some type of early computer memory! Reminds me of Tracy's very clever Stamp tester: http://forums.parallax.com/discussion/comment/930555/#Comment_930555
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Anyone who wants a RARE LASCR better buy these before I do.

    https://www.ebay.com/itm/Archer-Light-Activated-SCR-MRD920-P-N-276-1095A-NOS/302560727749
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Wow, it's really sad to think that I was once able to walk a couple blocks to buy stuff like that off the shelf. But no more...

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • erco wrote: »
    Anyone who wants a RARE LASCR better buy these before I do.

    https://www.ebay.com/itm/Archer-Light-Activated-SCR-MRD920-P-N-276-1095A-NOS/302560727749

    It's like a trip back to radio shack '81. Did you see this linked listing?
    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • ercoerco Posts: 18,647
    edited December 2017 Vote Up0Vote Down
    As long as we're strolling down DIY electronic memory lane with our checkbooks open...

    https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=unbuilt+heathkit&_sop=16

    Be sure to sign your check with this: https://www.ebay.com/itm/182062555151

    Edit: Same seller has a picture tube brightener. Hurry, won't last!

    https://www.ebay.com/itm/302531437560
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Checkbooks? I think I remember checkbooks. Went out of fashion in 1996 or so.

  • erco wrote: »
    Did you see this linked listing?

    Mercury tilt switches are still widely available from China (they're happy to ship you all the toxic waste you want). At 8 cents each, there's a poor man's IMU in there somewhere.

    https://www.ebay.com/itm/10PCS-3MM-Mercury-Switch-Tilt-Switch-Tilt-Sensor-for-Arduino-ESCA/222723178920
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • ercoerco Posts: 18,647
    edited December 2017 Vote Up0Vote Down
    Did you see this linked listing?

    Mercury tilt switches are still widely available from China (they're happy to ship you all the toxic waste you want). At 8 cents each, there's a poor man's IMU in there somewhere.

    https://www.ebay.com/itm/10PCS-3MM-Mercury-Switch-Tilt-Switch-Tilt-Sensor-for-Arduino-ESCA/222723178920



    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • erco wrote: »
    Did you see this linked listing?

    Mercury tilt switches are still widely available from China (they're happy to ship you all the toxic waste you want). At 8 cents each, there's a poor man's IMU in there somewhere.

    https://www.ebay.com/itm/10PCS-3MM-Mercury-Switch-Tilt-Switch-Tilt-Sensor-for-Arduino-ESCA/222723178920

    I'll go up to a dime for a cheap IMU, but that's just my two cents :D
    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • erco wrote: »
    I've used the attached circuit with a small SCR on a BS1 which is too busy to look for a brief occasional switch closure (a very slow wheel encoder). Instead of going directly into a BS1 pin, the switch triggers and latches the SCR, which can be read at the BS1's leisure by any input pin. Afterward, the SCR is reset (turned off) by briefly making the BS1 pin high, then making it an input again to repeat.

    SCRfun2.jpg

    This is a neat circuit.
    Hope it's not too far off topic but can an SR latch be made with a single transistor in a similar way?
    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • Heater.Heater. Posts: 20,075
    edited December 2017 Vote Up0Vote Down
    mikeologist,
    I'll go up to a dime for a cheap IMU https://www.alibaba.com/product-detail/Smart-Bes-GY-85-Sensor-module_60469624641.html but that's just my two cents.
    What on Earth is that? A 6DOF IMU sensor. An 9DOF IMU sensor?

    No wait, it says "pressure sensor".

    No wait, it says "Ultrasonic Sensor".

    WTF?

    But the GY-85 should be a 9 DOF IMU chip.

    Whatever it is, its good to know that I can order 500 Kilogram/Kilograms of them per Month!

    Bah, give me a simple mercury switch.


  • Heater. wrote: »
    mikeologist,
    I'll go up to a dime for a cheap IMU https://www.alibaba.com/product-detail/Smart-Bes-GY-85-Sensor-module_60469624641.html but that's just my two cents.
    What on Earth is that? A 6DOF IMU sensor. An 9DOF IMU sensor?

    No wait, it says "pressure sensor".

    No wait, it says "Ultrasonic Sensor".

    WTF?

    But the GY-85 should be a 9 DOF IMU chip.

    Whatever it is, its good to know that I can order 500 Kilogram/Kilograms of them per Month!

    Bah, give me a simple mercury switch.


    Yea, the cheapest listings always have bad titles. I just look at the pictures.

    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • Yes but, did you ever order anything from sellers with such pages of gibberish?

    What did you actually get?

    OK, for 1 cent who cares?

    Still, I'm curious.

  • Heater. wrote: »
    Yes but, did you ever order anything from sellers with such pages of gibberish?

    What did you actually get?

    OK, for 1 cent who cares?

    Still, I'm curious.

    Oh yea, they are the best to order from. I used to buy those pocket game systems that played emulators before ipod went touch and phones were still dumb. I usually got them for about $4, but every once in a while I'd get a box of relays or LED matrices. Didn't matter because the profit margin was over 1000% and it all went up on ebay.
    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • So where can we buy mercury now a days?

    As a young kid, I used to collect it from broken thermometers. Great fun to play with. Wondrous and magical stuff.

    In high school we had jugs of it slopping around the place for various science experiments and demos. I even tried to make my own mercury switch with whatever glass blowing skills I had (Did not work for long).

    Now I realize I have not actually seen any mercury, face to face, for 45 years?




  • Heater. wrote: »
    So where can we buy mercury now a days?

    As a young kid, I used to collect it from broken thermometers. Great fun to play with. Wondrous and magical stuff.

    In high school we had jugs of it slopping around the place for various science experiments and demos. I even tried to make my own mercury switch with whatever glass blowing skills I had (Did not work for long).

    Now I realize I have not actually seen any mercury, face to face, for 45 years?

    These guys have a pound for $131
    Any com port in a storm.
    Floating point numbers will be our downfall; count on it.
    Imagine a world without hypothetical situations.
  • You'd be surprised how little a pound of mercury is. I had a neighbor once who had done mining in Alaska. A byproduct of the smelting was mercury, and he had a small flask full of it. I was shocked how heavy it was.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
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