Krystaldetektor
En krystaldetektor, krystalensretter eller krystaldiode er en antik elektronisk komponent og ensretterdiode, der består af en tynd fjedrende metaltråd som let rører et mineral af halvledende krystal (sædvanligvis blyglans) med formålet at fungere som en grov punktkontaktdiode. Det krævede noget tålmodighed at finde et egnet sted på krystallet.
Den diodeensrettende effekt på blyglans blev opdaget af den tyske fysiker Karl Ferdinand Braun i 1874[1] – og videreudviklet af radioforskerne Jagadish Chandra Bose, G. W. Pickard[2] og andre.
Krystaldetektoren blev anvendt som en detektor i de tidlige krystalradioer, fra omkring 1906 og til 2. verdenskrig. Krystaldetektoren gav denne type af radiomodtager sit navn. Krystaldetektoren var den første type af en halvlederdiode – og faktisk den første halvlederkomponent. Krystaldetektoren er forældet og anvendes kun i antikke eller antikke reproduktioner af radioer.
Det karakteristiske for krystaldetektorer er, at de kun har en lille parasitisk kondensatorvirkning over sig – og kan kun tåle en lav strøm gennem sig. Den lille kondensatorvirkning gør dem netop egnet til højfrekvensdetektorer.
Formentlig er eksperimenter med krystaldioder af karborundum (SiC) og en strømkilde årsagen til, at en lysdiodevirkning blev opdaget i 1907 af H.J. Round.
Formentlig er eksperimenter med krystaldioder og en strømkilde årsagen til, at dioder med negativ differentiel modstand blev opdaget bl.a. 1908, 1910 - og bredt offentliggjort omkring 1923 af flere. [3] [4] [5] [6] [7] Disse "sære" dioder kan med den rette justering og kredsløb få et krystalapparat til at fungere som en superregenerativ modtager, radiosender eller en standard krystalmodtager. Fuldt menneskelavede elektroniske komponenter med negativ differentiel modstand blev lavet/opdaget af Leo Esaki omkring 1957 og hans komponent kaldes en tunneldiode eller esaki-diode.
Kilder/referencer
- ^ computerhistory.org: 1874 – Semiconductor Point-Contact Rectifier Effect is Discovered
- ^ G. W. Pickard, "How I Invented the Crystal Detector". Electrical Experimenter, vol. VII, no. 4, p. 325, Aug. 1919 Citat: "...In 1898, when my work in Radio-communication began, there was but one detector—the coherer...In the period 1902 to 1906, I tested many different minerals and combinations, including magnetite, pyrite, galena, molybdenite, silicon and zincite. Much development was also required on holders for these minerals...31,250 Crystal Detectors Invented. A list of the several thousand materials I have tested would make dry reading. Suffice it to say that I have found some tzvo hundred and fifty minerals and furnace products which make operative detectors, cither against metallic contacts, or in combination with other minerals. The possible combinations of these two hundred and fifty substances amounting to some 31,250, pairs, have all been tested by me, or by my assistants, and many hundred useful pairs have been found...", backup
- ^ God information om anvendelse af dimser med negativ modstandskarakteristikker, før de blev opdaget i tunneldioder i 1957: Cristadyne: Semiconductor archaeology or tribute to unknown precursors Arkiveret 17. marts 2013 hos Wayback Machine Citat: "...In 1923, Oleg Losev [O. V. Lossev, Lossew] (1903-1942) ( See link below ) managed to make a high frequency generator using such a detector. But it was polarized. This indicates that this diode had a characteristic curve in which a negative slope was present. And this makes one think of the tunnel effect diode invented a half a century later...These layouts where part of what one called CRYSTADYNE [eller Cristadyne, Crystodyne ] systems. But in those days, the technical performance and industrial ease of the new increasing valve technology made these layouts to be ignored, and then forgotten..."
- ^ The Wireless World and Radio Review. October 1, 1924 and October 8, 1924: "The Crystal As A Generator And Amplifier" by Victor Gabel.
- ^ earlyradiohistory.us: Radio News, September, 1924, pages 294-295, 431: The Crystodyne Principle Citat: "...SEVERAL experimenters have observed that some contacts, such as crystal and metal or crystal and carbon generally employed as detectors may produce undamped oscillations of any frequency, exactly as the vacuum tube oscillator. The same contact may also be utilized as an amplifier. Oscillating crystals are not new since they were investigated as far back as 1906 by well known engineers, but it was not until lately that a Russian engineer, Mr. O. V. Lossev, succeeded in finding some interesting uses for oscillating crystals..."
- ^ earlyradiohistory.us: Radio News, September, 1924, page 291: A Sensational Radio Invention By HUGO GERNSBACK Citat: "...Stated in a few words, the invention encompasses an oscillating crystal...In other words, THE CRYSTAL NOW ACTUALLY REPLACES THE VACUUM TUBE. That this is a revolutionary radio invention need be emphasized no further. [Her var Hugo Gernsback dog langt forud for sin tid]...We can not only detect with the crystal, but we can also amplify with it...we can now also transmit with the Crystodyne, and, as a matter of fact, a number of students in Russia have actually sent messages with such sets over distances of more than three-quarters of a mile during the past few months..."
- ^ beatriceco.com: Bell Labs – The Transistor – Other Claims to the Invention Arkiveret 21. december 2013 hos Wayback Machine Citat: "...This effect, he stated, was discovered by Dr W. H. Eccles in 1910, and remarked: “It is hard to realize that it took about ten years for practical active crystal-diode circuits to appear, in spite of Ditcham's reminder—circuits that included both RF and AF amplification...Most of the credit for creating practical devices [of this kind] goes to O. V. Lossev of Russia, whether or not he knew of Eccles' pioneer work a decade earlier..."
- Patenter
- U.S. Patent 836.531 – Means for receiving intelligence communicated by electric waves (silicon detector), Greenleaf Whittier Pickard, 1906
- U.S. Patent 837.616 – Wireless telegraph system (silicon carbide detector), Henry H.C. Dunwoody, 1906
- U.S. Patent 906.991 – Oscillation detector (multiple metallic sulfide detectors), Clifford D. Babcock, 1908
- U.S. Patent 912.613 – Oscillation detector and rectifier ("plated" silicon carbide detector with DC bias), G.W. Pickard, 1909
- U.S. Patent 912.726 – Oscillation receiver (fractured surface red zinc oxide (zincite) detector), G.W. Pickard, 1909
- U.S. Patent 933.263 – Oscillation device (iron pyrite detector), G.W. Pickard, 1909
- U.S. Patent 1.118.228 – Oscillation detectors (paired dissimilar minerals), G.W. Pickard, 1914
Se også
- Punktkontakttransistor
Eksterne henvisninger
 | Wikimedia Commons har medier relateret til: |
- Crystal and Solid Contact Rectifiers 1909 publication describes experiments to determine the means of rectification (PDF file)
- Radio Detector Development from 1917 The Electrical Experimenter
- The Crystal Experimenters Handbook 1922 London publication devoted to point contact diode detectors. (PDF file courtesy of Lorne Clark via earlywireless.com)
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A precision crystal detector (sometimes called a cat's whisker detector) from around 1914, an obsolete radio component used in unamplified crystal radio receivers. This type was a professional unit used in sensitive receivers in wireless telegraphy stations. The vertical needle on the right gently touches the face of a crystal of iron pyrite (iron sulfide, FeS2, Fool's gold) contained in the cylindrical metal capsule below it, forming a diode which is used to rectify the received radio signal. Only certain sites on the crystal's face functioned as rectifying junctions, so the device had to be adjusted by trial and error to find a "sweet spot" before each use. The crude device was very sensitive to the contact between needle and crystal, so the spring loaded micrometer screw on the left can be used to adjust the pressure precisely.
Forfatter/Opretter: JA.Davidson, Licens: Copyrighted free use
A galena cat's-whisker detector, an early radio wave detector used in crystal radio receivers from about 1905 to the 1940s. The fine metal wire attached to the adjustable arm touches the face of a natural semiconducting crystal of galena (lead sulfide) in the capsule at right. The contact forms a PN junction making a crude semiconductor diode. In a crystal radio its function is to rectify the alternating current radio signal, extracting the audio (sound) signal from the radio frequency carrier wave. Only certain sites on the crystal surface function as rectifying junctions, so the device had to be adjusted before each use by dragging the wire across the crystal to find a "sweet spot".