3 ms·

When I read the title, my first thought was about the cryotron: "Tantalum in superconducting state can carry large amount of current as compared to its normal s

by 13of40 5y ago

When I read the title, my first thought was about the cryotron: "Tantalum in superconducting state can carry large amount of current as compared to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire." https://en.wikipedia.org/wiki/Cryotron https://en.wikipedia.org/wiki/Cryotron

kens 5y ago
I actually mentioned the Cryotron in the original draft of this article, but there wasn't room for it. Some of the other forgotten computing technologies of the 1960s are tunnel diodes, microwave oscillators (Parametron), and electroluminescent photoconductors.
- stevespang 5y ago
- IndrekR 5y ago
  Did a design with a tunnel diode in 2011. Around 300 devices were made and sourcing the diodes was not easy — but still possible.
  - ncmncm 5y ago
    Care to explain why a tunnel diode was the right thing for the purpose? And, if you had been unable to source them, what you would have done instead?
    - IndrekR 5y ago
      It was an experiment set for International Physics Olympiad. There was a black box with a tunnel diode, inductor and capacitor inside. If the diode would have been impossible to source, another set-up for the black box would have been used instead. Experiment is described here: http://hedgehog.ee/ipho http://hedgehog.ee/ipho
klyrs 5y ago
As far as I can understand superconductivity, the devices are similar but opposite. Superconductors have a both a critical current (in the absence of a field), and a critical magnetic field (in the absence of a current). So, cranking the control line raises the field, which squelches current capacity to zero (and/or since there's an excess of either/both, superconductivity is lost).

by 13of40 5y ago

kens 5y ago

I actually mentioned the Cryotron in the original draft of this article, but there wasn't room for it. Some of the other forgotten computing technologies of the 1960s are tunnel diodes, microwave oscillators (Parametron), and electroluminescent photoconductors.

stevespang 5y ago
IndrekR 5y ago
Did a design with a tunnel diode in 2011. Around 300 devices were made and sourcing the diodes was not easy — but still possible.
- ncmncm 5y ago
  Care to explain why a tunnel diode was the right thing for the purpose? And, if you had been unable to source them, what you would have done instead?
  - IndrekR 5y ago
    It was an experiment set for International Physics Olympiad. There was a black box with a tunnel diode, inductor and capacitor inside. If the diode would have been impossible to source, another set-up for the black box would have been used instead. Experiment is described here: http://hedgehog.ee/ipho http://hedgehog.ee/ipho

klyrs 5y ago

As far as I can understand superconductivity, the devices are similar but opposite. Superconductors have a both a critical current (in the absence of a field), and a critical magnetic field (in the absence of a current). So, cranking the control line raises the field, which squelches current capacity to zero (and/or since there's an excess of either/both, superconductivity is lost).