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- Newsgroups: comp.sys.cbm
- Path: sparky!uunet!leafusa!hal
- From: hal@HQ.Ileaf.COM (Hal Wadleigh)
- Subject: Re: User Port Hardware Question
- Message-ID: <1992Aug14.141352.2793@HQ.Ileaf.COM>
- Summary: Simpler solution
- Keywords: User port switching photoresistors specifications
- Reply-To: hal@HQ.Ileaf.COM (Hal Wadleigh)
- Organization: Interleaf, Inc.
- References: <1992Aug8.165804.16276@usenet.ins.cwru.edu> <1992Aug10.153011.394@HQ.Ileaf.COM> <1992Aug12.215509.26875@ccu.umanitoba.ca>
- Date: Fri, 14 Aug 92 14:13:52 GMT
- Expires: 9/14/92
- Lines: 7
-
- Actually, the circuit is simple. Put a photoresistor inline between a data
- bit and the port ground. When the resistor is lighted, the circuit is
- closed, giving you a zero bit. When the resistor is in shadow, the circuit
- is open, giving you a one bit.
- What I need to know is the spec that describes a photoresistor that switches
- at "normal" room light (say down to 5 lux) for a TTL logic line (5v, 100 mA).
-
-