6 ms·

For those of you who are unfamiliar with what a memristor is, as I was, HP has an easy-to-understand analogy on its FAQ page about memristors: "A common analog

by jawns 12y ago

For those of you who are unfamiliar with what a memristor is, as I was, HP has an easy-to-understand analogy on its FAQ page about memristors: "A common analogy for a resistor is a pipe that carries water. The water itself is analogous to electrical charge, the pressure at the input of the pipe is similar to voltage, and the rate of flow of the water through the pipe is like electrical current. Just as with an electrical resistor, the flow of water through the pipe is faster if the pipe is shorter and/or it has a larger diameter. An analogy for a memristor is an interesting kind of pipe that expands or shrinks when water flows through it. If water flows through the pipe in one direction, the diameter of the pipe increases, thus enabling the water to flow faster. If water flows through the pipe in the opposite direction, the diameter of the pipe decreases, thus slowing down the flow of water. If the water pressure is turned off, the pipe will retain it most recent diameter until the water is turned back on. Thus, the pipe does not store water like a bucket (or a capacitor) – it remembers how much water flowed through it." Source: http://www.hpl.hp.com/news/2008/apr-jun/memristor_faq.html http://www.hpl.hp.com/news/2008/apr-jun/memristor_faq.html

boyaka 12y ago
That made me think of a chinese finger trap.
deleted 12y ago
[deleted]
frik 12y ago
Conceptual symmetry between the resistor, capacitor, inductor, and the memristor: http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-terminal_non-linear_circuit_elements.svg http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-... The scales fell from my eyes. Now the electronics math makes sense - Memristor was the missing puzzle piece.
- swimfar 12y ago
  That reminds me of the missing mechanical equivalent of the capacitor, the inerter, which McLaren secretly began using on their formula one cars in 2005. But does this mean there's potentially another missing suspension component? http://personal.strath.ac.uk/yixiang.xu/talk_HUST_2008_Chen.pdf http://personal.strath.ac.uk/yixiang.xu/talk_HUST_2008_Chen.... edit: Assuming a Force-Current, Velocity-Voltage equivalence, I get the mechanical memristor behavior to be: dx=M.F.dt, with M being a property of the memristor(memdamper?). Or in other words, v=M.F; velocity is proportional to the force. (The dots are multiplication. Asterisks italicize the text)
  - jacquesm 12y ago
    v = M.F => that's regular inertia isn't it? In the case of the inerter presumably constrained by the stroke of the device. It's like a 'two stroke flywheel' in a nice package.
    - jessaustin 12y ago
      As explained at http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf, mass with respect to the inertial frame is equivalent to a grounded capacitor. However, the single "pole" limited the sorts of mechanical systems that could be designed. The inerter allows a system to be optimized with respect to the difference between accelerations, not simply an absolute acceleration. I think that two accelerations could also be related with levers, but the quantities involved might make that not so feasible as a suspension component.
- andrewcooke 12y ago
  what an awful diagram. it implies there's some kind of symmetry that relates all four, but when you look at the details there are asymmetries. if you think it was helpful look at it again and explain why di appears in two quarants but dq and dv appear once each.
  - dnautics 12y ago
    are you sure you're looking on both sides of the equations?
  - oofabz 12y ago
    You can rearrange the inductor equation to get di = (1/L) dϕ. Then the quadrants are perfectly symmetrical except for the ugly 1/L. But that's just an arbitrary unit created by humans, you could fix that by defining the unit of inductance as the inverse of what we use now.
    - andrewcooke 12y ago
      ah, thank-you. that makes more sense.
- jacquesm 12y ago
  I can't help but notice that the region occupied by the memristor is what would be best described as a 'flux-capacitor'. You really can't make this stuff up.
- rbanffy 12y ago
  It's great material for a T-shirt.
danielweber 12y ago
Are they teaching memristors in college these days as a fundamental component, or is it still too new?
- valarauca1 12y ago
  They are in higher level classes. My EE friends knew what they were instantly
danmaz74 12y ago
I read this analogy and immediately started thinking how complicated it would be to use this effect if the diameter is always changing, every time you make your water flow. Then I watched the video posted by achille [1]. If I understood the video correctly, the analogy should specify a fundamental thing: The diameter of the pipe only increases or decreases if the pressure differential is very high. You can make your water flow at low pressure without affecting the diameter in any measurable way. This should make using memristors practically much easier. [1] https://www.youtube.com/watch?v=bKGhvKyjgLY https://www.youtube.com/watch?v=bKGhvKyjgLY
jacquesm 12y ago
Interesting tidbit: a while ago, I was talking about memristors with a physics trained person. And he told me something that really stuck: It is impossible to make an inductor (coil) without resistance and without capacitance. It is impossible to make a capacitor without some inductance and a little bit of leakage. It is impossible to create a resistor that does not have self-inductance or a bit of capacitance. If you followed all that and you agree with it (because you've done some electronics) or you've heard of 'parasitic capacitors' and such, then you can see that it must somehow follow that parasitic mem-resistance must have been with us all along, but is such a small effect that we simply failed to notice it. No resistors, capacitors or coils that we normally use exhibits this effect in such a way that we adapt our designs to it to minimize it. That's in part the reason why it took so long to manifest in a usable form, if the effect would be as devastating as resistance on powerlines, as capacitance on wiring, as induction on large capacitors then we'd have exploited it long ago. So it's going to be something exceedingly subtle when and if it comes to market.
- danmaz74 12y ago
  Interestingly, this is exactly what the chief of HP labs said in this video [1]: That lots of papers noted the effect and talked about anomalies, but no-one made the connection to the memristors before them. He also says that the effect is only really noticeable at nano scales (because it needs incredibly high electric fields). EDIT: on second thought, that's not the case, because the HP memristor is not a memristor in the sense of the of the original paper describing it - it has nothing to do with the magnetic flux. It can only be described with the same set of equations, so, it behaves like a memristor, but is not "actually" a memristor that completes the set [2]. That is, if I understood the video correctly (but I think I did, as the speaker himself talked about a "trick" in the beginning of the video). [1] https://www.youtube.com/watch?v=bKGhvKyjgLY https://www.youtube.com/watch?v=bKGhvKyjgLY [2] http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-terminal_non-linear_circuit_elements.svg http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-...
  - jacquesm 12y ago
    Nice to see confirmation of that theory from that high up. It seemed extremely logical to me when I heard it the first time and like everything else, in retrospect it is blindingly obvious. I'd hate to see a memristor dropped into a circuit design and being handed the task of 'fixing' spice to produce the correct output. But by the looks of it the usefulness of individual memristors will be quite limited.
trumbitta2 12y ago
Always thought water increases its speed when you shrink the pipe, not the other way around
- brownbat 12y ago
  Ah, yeah, this could be more carefully stated. At a bottleneck, the water that gets through is moving faster, but the total volume of water going through is lower. It's a classic EE analogy, so people tend to shorthand it. One good and thorough explanation of the full bit is here: http://science.howstuffworks.com/environmental/energy/question501.htm http://science.howstuffworks.com/environmental/energy/questi... What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow. Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose. This is like decreasing the resistance in an electrical system, which increases the current flow.
  - davyjones 12y ago
    > At a bottleneck, the water that gets through is moving faster, but the total volume of water going through is lower. This is incorrect because the volume of water will be the same under I3 flow (called I-cube flow: Incompressible, Inviscid and Irrotational). Due to conservation of mass, we have mass = density x volume = density x area x speed x time Measuring the amount of volume for the same time with changing area, the only quantity that can change is the speed (recall that we have fixed the time and already assumed incompressible flow, hence density does not change). So, more area means lower speed and vice versa. But the volume always is the same under stated assumptions.
- danudey 12y ago
  Perhaps they meant flow rate?
- deleted 12y ago
  [deleted]
- 12y ago

by jawns 12y ago

boyaka 12y ago

That made me think of a chinese finger trap.

deleted 12y ago

[deleted]

frik 12y ago

Conceptual symmetry between the resistor, capacitor, inductor, and the memristor: http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-terminal_non-linear_circuit_elements.svg http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-... The scales fell from my eyes. Now the electronics math makes sense - Memristor was the missing puzzle piece.

swimfar 12y ago
That reminds me of the missing mechanical equivalent of the capacitor, the inerter, which McLaren secretly began using on their formula one cars in 2005. But does this mean there's potentially another missing suspension component? http://personal.strath.ac.uk/yixiang.xu/talk_HUST_2008_Chen.pdf http://personal.strath.ac.uk/yixiang.xu/talk_HUST_2008_Chen.... edit: Assuming a Force-Current, Velocity-Voltage equivalence, I get the mechanical memristor behavior to be: dx=M.F.dt, with M being a property of the memristor(memdamper?). Or in other words, v=M.F; velocity is proportional to the force. (The dots are multiplication. Asterisks italicize the text)
- jacquesm 12y ago
  v = M.F => that's regular inertia isn't it? In the case of the inerter presumably constrained by the stroke of the device. It's like a 'two stroke flywheel' in a nice package.
  - jessaustin 12y ago
    As explained at http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf, mass with respect to the inertial frame is equivalent to a grounded capacitor. However, the single "pole" limited the sorts of mechanical systems that could be designed. The inerter allows a system to be optimized with respect to the difference between accelerations, not simply an absolute acceleration. I think that two accelerations could also be related with levers, but the quantities involved might make that not so feasible as a suspension component.
andrewcooke 12y ago
what an awful diagram. it implies there's some kind of symmetry that relates all four, but when you look at the details there are asymmetries. if you think it was helpful look at it again and explain why di appears in two quarants but dq and dv appear once each.
- dnautics 12y ago
  are you sure you're looking on both sides of the equations?
- oofabz 12y ago
  You can rearrange the inductor equation to get di = (1/L) dϕ. Then the quadrants are perfectly symmetrical except for the ugly 1/L. But that's just an arbitrary unit created by humans, you could fix that by defining the unit of inductance as the inverse of what we use now.
  - andrewcooke 12y ago
    ah, thank-you. that makes more sense.
jacquesm 12y ago
I can't help but notice that the region occupied by the memristor is what would be best described as a 'flux-capacitor'. You really can't make this stuff up.
rbanffy 12y ago
It's great material for a T-shirt.

danielweber 12y ago

Are they teaching memristors in college these days as a fundamental component, or is it still too new?

valarauca1 12y ago
They are in higher level classes. My EE friends knew what they were instantly

danmaz74 12y ago

I read this analogy and immediately started thinking how complicated it would be to use this effect if the diameter is always changing, every time you make your water flow. Then I watched the video posted by achille [1]. If I understood the video correctly, the analogy should specify a fundamental thing: The diameter of the pipe only increases or decreases if the pressure differential is very high. You can make your water flow at low pressure without affecting the diameter in any measurable way. This should make using memristors practically much easier. [1] https://www.youtube.com/watch?v=bKGhvKyjgLY https://www.youtube.com/watch?v=bKGhvKyjgLY

jacquesm 12y ago

Interesting tidbit: a while ago, I was talking about memristors with a physics trained person. And he told me something that really stuck: It is impossible to make an inductor (coil) without resistance and without capacitance. It is impossible to make a capacitor without some inductance and a little bit of leakage. It is impossible to create a resistor that does not have self-inductance or a bit of capacitance. If you followed all that and you agree with it (because you've done some electronics) or you've heard of 'parasitic capacitors' and such, then you can see that it must somehow follow that parasitic mem-resistance must have been with us all along, but is such a small effect that we simply failed to notice it. No resistors, capacitors or coils that we normally use exhibits this effect in such a way that we adapt our designs to it to minimize it. That's in part the reason why it took so long to manifest in a usable form, if the effect would be as devastating as resistance on powerlines, as capacitance on wiring, as induction on large capacitors then we'd have exploited it long ago. So it's going to be something exceedingly subtle when and if it comes to market.

danmaz74 12y ago
Interestingly, this is exactly what the chief of HP labs said in this video [1]: That lots of papers noted the effect and talked about anomalies, but no-one made the connection to the memristors before them. He also says that the effect is only really noticeable at nano scales (because it needs incredibly high electric fields). EDIT: on second thought, that's not the case, because the HP memristor is not a memristor in the sense of the of the original paper describing it - it has nothing to do with the magnetic flux. It can only be described with the same set of equations, so, it behaves like a memristor, but is not "actually" a memristor that completes the set [2]. That is, if I understood the video correctly (but I think I did, as the speaker himself talked about a "trick" in the beginning of the video). [1] https://www.youtube.com/watch?v=bKGhvKyjgLY https://www.youtube.com/watch?v=bKGhvKyjgLY [2] http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-terminal_non-linear_circuit_elements.svg http://en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-...
- jacquesm 12y ago
  Nice to see confirmation of that theory from that high up. It seemed extremely logical to me when I heard it the first time and like everything else, in retrospect it is blindingly obvious. I'd hate to see a memristor dropped into a circuit design and being handed the task of 'fixing' spice to produce the correct output. But by the looks of it the usefulness of individual memristors will be quite limited.

trumbitta2 12y ago

Always thought water increases its speed when you shrink the pipe, not the other way around

brownbat 12y ago
Ah, yeah, this could be more carefully stated. At a bottleneck, the water that gets through is moving faster, but the total volume of water going through is lower. It's a classic EE analogy, so people tend to shorthand it. One good and thorough explanation of the full bit is here: http://science.howstuffworks.com/environmental/energy/question501.htm http://science.howstuffworks.com/environmental/energy/questi... What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow. Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose. This is like decreasing the resistance in an electrical system, which increases the current flow.
- davyjones 12y ago
  > At a bottleneck, the water that gets through is moving faster, but the total volume of water going through is lower. This is incorrect because the volume of water will be the same under I3 flow (called I-cube flow: Incompressible, Inviscid and Irrotational). Due to conservation of mass, we have mass = density x volume = density x area x speed x time Measuring the amount of volume for the same time with changing area, the only quantity that can change is the speed (recall that we have fixed the time and already assumed incompressible flow, hence density does not change). So, more area means lower speed and vice versa. But the volume always is the same under stated assumptions.
danudey 12y ago
Perhaps they meant flow rate?
deleted 12y ago
[deleted]
12y ago