Alt-BEAM Archive
Message #12708
To: beam@sgiblab.sgi.com beam@sgiblab.sgi.com
From: Sathe Dilip sathe_dilip@bah.com
Date: Thursday, March 30, 2000 3:59 AM
Subject: Re: RC walker! (was : Feelers or Sensors)
>That's good news. However, the piezo elements can generate high
>voltages (certainly higher than what a 555 can withstand) depending on
>how much you flex them. The current however is very small. Its
>probably the potential divider made of three (5K ohm?) resistors
>(internal to the 555) that is loading the transducer and protecting the
>555. The internal circuitry of 555 may be capable to withstand some
>abuse but just as a good design precaution, I would suggest adding a
>zener in parallel to the piezo. Choose the zener value at about the
>supply voltage. This should provide adequate protection.
>
>Dilip
>------------------------------------------------
>
>Andrew Hooper wrote:
>>
>> Hi All,
>>
>> Well im proud to announce that the first test WORKED :)
>>
>> I built a simple 555 circut, replaced the cap with the pezio transducer
>> added a 1m resistor, soldered a wisker on to the pezio and used
>> a logic probe to check pin 3 :)
>>
>> When the wisker was touched or flexed pin 3 would drop low then return
>> to a high state :).
>>
>> Got even funkier when i droped the resistance to 5k and added a 1k
>> between pin 8 & 7 on the 555, got a sort of scratchy sound when the
>> wisker was flexed.
>
>----------------------------------------------------------------------
>The early bird may get the worm, but the second mouse gets the cheese.
>----------------------------------------------------------------------
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