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If Tracy says you can/should ground the sensor leads then you don't need a resistor. It all depends on whether a pin is driven to logic 1 (generally 5 volts), if it is and you ground it without a resistor, you can burn the that pin's circuitry rendering it useless and perhaps damaging the entire chip. IF however, the pin is set for input only and is never driven to logic 1 by the code in the chip then it will not have voltage on the pin and grounding it will not harm the pin. Tracy is probably using the analog input pins on the chip and they are made for accepting an analog voltage (say from a sensor).
When I don't know the pin set up, I always use a resistor to be on the safe side.
Ed
----- Original Message ----- From: "Bill Schertz" <wschertz@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, June 24, 2006 12:12 AM
Subject: [FlyRotary] Re: Radio noise
Ed, that is a worthwhile suggestion. I am going to pick up some resistors tomorrow. I note that the sensors are 10 to 180 ohms for temp and pressure, was there a reason for the suggestion of 20K?
Thanks.
Bill Schertz
KIS Cruiser # 4045
----- Original Message ----- From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, June 23, 2006 9:07 PM
Subject: [FlyRotary] Re: Radio noise
Just a WAG, Bill. Could it be the oscillator of the microchip in the EM2 generating the nose because some of the pins (tied to the sensors) are not a complete circuit. Might try just hooking up some 20K ohm resistors between your sensor leads and ground just to see. Either that or perhaps getting feed back from the chip on your power lines suggesting a low value .01uf capacitor.
Ed
----- Original Message ----- From: "Bill Schertz" <wschertz@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, June 23, 2006 6:42 PM
Subject: [FlyRotary] Radio noise
I am in the process of wiring up and testing each piece of electronic equipment before putting the top on my plane which will make it much harder to get access.
I have an SL-30 NAV/COM and SL-40 COM. The COM works, but when I turn on the EM-2 I get a bunch of hash (white noise). Any suggestions on diagonstics? The EM-2 is not connected to 'all' sensors yet.
Bill Schertz
KIS Cruiser # 4045
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