jgb@prism.gatech.EDU (James G. Baker) (11/07/90)
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?
Thanks for the input...
--
BAKER,JAMES G - Lab Technician, School of Electrical Engineering
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!jgb
Internet: jgb@prism.gatech.edurobin@uhunix1.uhcc.Hawaii.Edu (Robin Amano) (11/08/90)
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? This is a simple one: +5V DC O---------->|----------/\/\/\/----------| L1 R2 | | _________________| PROBE O------\/\/\/\_______|/ _________| R1 |\,_____|/ |\,________ Q1 | Q2 | GROUND O---------------------------------------| SYMBOL QTY DESCRIPTION Q1,Q2 2 npn silicon transistor R1 1 27K ohm, 1/2 W resistor R2 1 150 ohm, 1.2 W resistor L1 1 LED the commas on the transistors are where the arrows should be, remember npn. this is a simple led on = 1, led off = 0 here's another one: +5 V O | | | / \ / 150 K \ 1/8 W / 5 % \ | |\ | | \ | |------| O------| | | | / | | | |/ | output input >--|---------------------| |-------| | | |\ | led | | | | \ | | led glows if \ |------| O------| \ / input is logic / 100 K | / --- low \ 1/8 W |/ | / 5 % | \ | | ----- | |\ --- | | \ - | |-------| O------| | |\ | | / | | | \ | |/ | output |----------| O----| |------| | | / | |\ | led | | |/ | | \ | | led glows if | |-------| O------| \ / input is logic | | / --- high / |/ | \ 100 K | / 1/8 W | \ 5 % ----- / --- | inverters are CD 4009 - neither led glows | leds are MV 5020 open circuit | | | ----- --- - hope this helps!! -- ---------------------------------------------------------------- Robin Amano | Internet: robin@uhunix.uhcc.hawaii.edu UHCC | 2565 The Mall | Honolulu, HI 96822
Mike.McManus@FtCollins.NCR.com (Mike McManus) (11/09/90)
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
Mike.McManus@FtCollins.NCR.com (Mike McManus) (11/09/90)
In article <MIKE.MCMANUS.90Nov9112458@mustang.FtCollins.NCR.com> Mike.McManus@FtCollins.NCR.com (Mike McManus) writes: > 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)). Well, I *meant* to say 7404, but you could also use a 7400 :-). Incidently, if you don't care about fancy looks, just use some eletrical tape and/or hot glue and just stick the whole mess (chip, LED and nail) (in/on)to a regular pen! -- 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