Workbench Pro electronic circuit simulator program.
Note: This circuit has been built and tested with descrete parts and simulated with EWB 5.12.
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| A capacitive type sensor circuit using the technology presented in U.S. Patent 3,869,676 | |||||||||||||||||||||
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| Data on this and other related pages will be up dated as time permits. Last up date:2-3-04 | |||||||||||||||||||||
| During the past few months, I have received quite a few emails about building working sensors using the information in my patents. Building the Hall effect sensors is not that easy because the correct magnets and Hall Effect sensor ICs are not sold through the average electronic part stores. What I will do is to add a few short articles to show how one can build a linear position sensor or rotary angle sensor using capacitance measuring circuit technology. There are several patents that are expired but can still be used to construct very good position sensors. U.S. Patent 3,869,676 is one such patent. The diode-quad bridge technology that was introduced in this patent was used to design several automotive sensors that were used starting about 1985. This capactive sensor technology is still being used today in rotary, linear, and pressure sensor design. All the components can be purchased at DigiKey or other electronic suppliers. Several examples will be presented. | |||||||||||||||||||||
| Click here to view U.S. Patent 3,869,676 on the USPTO Website. | |||||||||||||||||||||
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| If you do not see the patent, click on the USPTO HELP button for full screen imges. | |||||||||||||||||||||
| The diode-quad bridge circuit schematic shown below can be used with an Electronic Workbench Pro electronic circuit simulator program. |
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| The Vcap is a 5 to 55 pF variable capacitor. If the Vcap is adjusted from 5 to 55 pF , the output voltage will increase from .5 Volts to 7 Volts. A variable differential capacitor assembly can be designed to build either a rotary angle or linear position sensor. As an FYI, this circuit was adjusted for an output voltage of 5 Volts at +22C. The circuit was then placed in a freezer at -40C and the output voltage droped to 4.76 Volts. The circuit was then placed in an oven at +60C and the output increased to 5.21 Volts. So, some form of temperature compensation may be required for your application. Note: This circuit has been built and tested with descrete parts and simulated with EWB 5.12. |
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| Go To Capacitive Sensor Page 2 of 2 For additional info | |||||||||||||||||||||