Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!rochester!uhura.cc.rochester.edu!ub!zaphod.mps.ohio-state.edu!samsung!uunet!ncrlnk!ncr-mpd!Mike.McManus From: Mike.McManus@FtCollins.NCR.com (Mike McManus) Newsgroups: sci.electronics Subject: Re: TTL Logic Probe Message-ID: Date: 9 Nov 90 11:24:58 GMT References: <16525@hydra.gatech.EDU> Sender: news@ncr-mpd.FtCollins.NCR.COM Organization: NCR Microelectronic Products, Ft. Collins, CO Lines: 36 In-reply-to: jgb@prism.gatech.EDU's message of 6 Nov 90 19:36:21 GMT In article <16525@hydra.gatech.EDU> jgb@prism.gatech.EDU (James G. Baker) writes: > Anyone out there have schematics or suggestions for building a TTL (only) > logic probe. I took one of the little hand-held probes apart and found > a terrifying amount of capacitors, resistors and unknown DIP chips. Can > I make one simply by using a few latches, etc? You want quick and dirty? Here's what I built: +----|>|----+ <-- tri-color LED (red/green) |\ | | +--| >O---+ +----+ | |/ | | | | +----|<|----+ | probe tip (nail) | | | | | V +--------------------------+--/\/\/----||====> OK, I *said* dirty... This probe *WILL* load your circuit, it won't catch glitches (unless you have great eyes :-), and it doesn't have a latch. But if your circuits are simple TTL, this works pretty well. The tri-color LED lights red for logic 0, green for logic 1, and yellow for high freq signals. It's small and easy to build (I clipped the leads off the 7400 and soldered directly to the tabs, stuffed the thing inside an old pen (the extra fat kind)). I'd welcome any ideas for a more complex version of this, especially one to isolate the probe tip from the circuit. I do like the tri-color part. -- Disclaimer: All spelling and/or grammar in this document are guaranteed to be correct; any exseptions is the is wurk uv intter-net deemuns,. Mike McManus Mike.McManus@FtCollins.NCR.COM, or NCR Microelectronics ncr-mpd!mikemc@ncr-sd.sandiego.ncr.com, or 2001 Danfield Ct. uunet!ncrlnk!ncr-mpd!garage!mikemc Ft. Collins, Colorado (303) 223-5100 Ext. 378