Xref: utzoo sci.electronics:15153 comp.sys.ibm.pc.hardware:2485 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!elroy.jpl.nasa.gov!news From: cyamamot@kilroy.jpl.nasa.gov (Cliff Yamamoto) Newsgroups: sci.electronics,comp.sys.ibm.pc.hardware Subject: Simple one evening project Summary: Probably too simplistic, but useful Keywords: IBM, PC, floppy drive, LED, in use, color, density Message-ID: <1990Oct23.162706.10585@elroy.jpl.nasa.gov> Date: 23 Oct 90 16:27:06 GMT Sender: news@elroy.jpl.nasa.gov (Usenet) Organization: Jet Propulsion Laboratory, Pasadena, CA Lines: 77 Originator: cyamamot@kilroy Nntp-Posting-Host: kilroy.jpl.nasa.gov (I'm cross-posting this to pc.hardware for those tinkerers over there) I've been an avid reader of Sci.electronics since my college days and it has always been so helpful. The wealth of information is staggering and I'd just thought I'd submit this simple one evening project for those interested. It's really too simple to be considered a significant project but I felt it was useful enough to make one myself half a year ago. For those who have played with Compaq computers, you'll note that they use interesting floppy drives whose in-use LED changes color depending on the density of the floppy. I thought this was pretty useful since I'm in such a rush, I rarely pay attention to the floppy label and rely on the LED color to determine the capacity. I liked this feature so much on my Compaq at work, I wanted to add it to my 386 at home. So here's an ASCII schematic of what I made: +5 VDC | 1/6 1/6 |\ LS04 |\ LS04 Reduced Write (pin 2) >-------| >o----+-----| >o-----+ |/ | |/ | NOTE: red and | V V green LEDs are Gnd - Red - Green actually a ____________ | | single bicolor Drive in Use >----/\/\/------+--------------+ LED. 220 ohm Red = Lo Density Green = Hi Density Figure 1 - New In Use LED circuit Notes: - Reduced Write (pin 2) is low when low density (360K/720K) - Reduced Write (pin 2) is high when high density (1.2M/1.44M) - Reduced Write is located on pin 2 of the 34 pin edge connector - Drive in Use on most floppy drives is active low and is connected DIRECTLY to the cathode of the original In-Use LED (see Fig. 2) - Power for +5 VDC can be obtained from pin 4 of the power connector - Ground can be obtained from pin 3 of the power connector - Most (if not *ALL*) bi-color LEDs have a common cathode - Tie all unused inverter inputs to +5 VDC or Gnd (ground) - You may not need the 220 ohm resistor if your floppy drive already has one ON THE CATHODE side. Most drives however are configured as: Red 220 ohm LED ____________ +5 VDC >----/\/\/---->|------> Drive in Use (often NAND gate output) Figure 2 - Circuit often found on most floppy drives I took a LS04 and snipped all the pins off leaving just the stubs on the sides of the chip. Soldered some long wire-wrap wire to it then wrapped the chip in some duct tape. Small enough to tuck somewhere on the floppy drive itself. Most of the parts can be found in your junk box or at Radio Shack. I don't know if they carry a bi-color LED though. I was lucky since I had just bought a Toshiba 1.2Mb floppy drive from SoftWarehouse (a fairly large computer store chain around the USA). This Toshiba had a bi-color LED built-in! But it was only there so the user could pick the LED color with a jumper.... permanently! A few cuts with an Xacto, some patch work to the circuit and that was it. I probably went overboard on the details, but what I appreciate about Sci.electronics are the folks here who don't assume everyone is an electronics wizard. We all had to start at the bottom sometime and I hope this little project will encourage other beginners to get their feet wet. Cheers! Cliff Yamamoto ------------------------------------------------------------------------------- USnail: Clifford K. Yamamoto - KA6JRG | Email: cyamamot@kilroy.jpl.nasa.gov Jet Propelled La-bore-atore-ee | cyamamot@grissom.jpl.nasa.gov 4800 Oak Grove Drive | cky@hydra.jpl.nasa.gov M/S 238-737, Section 333 | cyamamot@devvax.jpl.nasa.gov Pasadena, Calif. 91109 | cyamamot@jato.jpl.nasa.gov ---------------------------------------+--------------------------------------- MaBell: (818) 354-1242 - off. (818) 354-6042 - alt. (818) 354-6426 - lab.