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sheilded cable & socket question — Parallax Forums

sheilded cable & socket question

yarisboyyarisboy Posts: 245
edited 2010-02-24 04:36 in Propeller 1
I purchased a temperature/humidity sensor from Gadgetganster.com and it is in the mail. The spec sheets recommend a shielded cable for remote sensor use. I looked at using RJ11, RJ-26, and RJ45 board connectors but don't have enough room left on my layout for them. A socket that will fit is for USB-B and fire-wire use. The part numbers are AMP 787780-1, Digikey 787780-1-ND, and Mouser 292304-1. Does the fire wire cable have a ground shield in it? I really wouldn't have to run a high clock frequency just to read temperature and humidity. Since I'm running this project in an automobile with a twisted pair CAN-buss (OEM) noise immunity could be a concern. I've got a bunch of old fire-wire cables in the junk drawer. I could cut into one and see how they are build. Good advice gratefully accepted.
scloyd

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MOORE'S LAW: The capabilities of electronics shall double every 18 months.
cloyd's corollary: Hardware is easy, software is hard.

Comments

  • WBA ConsultingWBA Consulting Posts: 2,935
    edited 2010-02-24 04:36
    You can find a good picture of the cross section of firewire on this Wikipedia page: en.wikipedia.org/wiki/Coding_system_of_FireWire. Link #2 in the references section is a PDF with the cross section on page 2. Each twisted pair is shielded and the full cable is shielded.

    Even though shielded cable is best, the connectors can be unshielded in the environment you describe. As long as the traces on the PCB are not close to other noisy sources, you should be fine. I have used the SHT11 with unshielded cable up to 20 feet long and have not had any issues. The environment was not as noisy as a car is, but it does show that the SHT11 is fairly durable.

    Since you can clock the SHT11 as slow as you want, you can also handle noise by slowing down the communication.

    For use with Cat5, see the post on this thread where I used the SHT11 with 208 feet of Cat5. I explain the best way to pair the lines using twisted pair cable. It's the post dated 12/16/2007.

    ps. thanks for buying my module!

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    Andrew Williams
    WBA Consulting
    WBA-TH1M Sensirion SHT11 Module
    Special Olympics Polar Bear Plunge, Mar 20, 2010
    Propeller-Based Reverse Geo-Cache Birthday Present Project
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