| ??? 01/27/08 11:50 Read: times |
#149979 - Another sensor and schematic using 555 Responding to: ???'s previous message |
Hello Charles,
A common technique is to use the sensor capacitance as the frequency determining part of an oscillator. If you use a relaxation oscillator you can transmit the square wave output of significant distances. The CMOS version of the 555 timer will do for a start. The humidity sensor from Humirel, HS1101 seems close to the sensor you have mentioned, their data sheet has complete implementation details using the 555. You can find it here: http://www.humirel.com/product/f...HS1100.pdf I have used them, the only pain is calibrating individual sensors. http://www.sensirion.com/ if I recall, they have digital output (I think some form of SPI). Again, if I recall, they have a thingy that gives you both temp and humidity I have purchased the above sensors for my new products, but not yet implemented, calibration may not be required, comes with a temperature sensor, it also has a built in heater to check the humidity sensor and you can purchase a plastic filter to go with the sensor. Regards, John. |
