Disk ][ LED fun

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macnoyd's picture
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Disk ][ LED fun

I took a little time today to get my hardware fix and decided to draw up a schematic to the bi-color LED circuit published so long ago buy Fabien Bénattou.

Disclaimer by me:  I did not design this.  I only drew it to show it's simplicity.  Very clever design that most with a little electtronics experience can build.

With a little more circuitry, you can see how this can be an insert directly to the Disk ]['s ribbon cable rather than something wired onto the analog board.

All signal designations shown are attached to the Disk ]['s Analog board.  Hope you like the design.  Maybe make your own?  :-D   Enjoy!

 

Footnote:  A kit for this is available from ReactiveMicro:  https://www.reactivemicro.com/product/disk-assembled-or-kit/

 

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Already published in the CSA2 Apple II FAQ

Just to be accurate, this circuit was described a long time ago in the official CSA2 (comp.sys.apple2) Usenet newsgroup Apple II FAQ.

 

Quote:
Floppy Disk Drives

 001- How do I add a write-protect On-Off switch?
 002- How do I add external speed adjustment to my Disk ][ drive?
 003- How can I adjust my 5.25" drive for optimum performance?
 004- How do I clean my disk drive R/W head(s)?
 005- What is the pinout for a duodisk drive connecting cable?
 006- What DuoDisk mods are necessary?
 007- Will a Duodisk function correctly on my ROM 3 GS?
 008- How do I fix a false Write Protect?
 009- My 3.5 Disk Drives don't work! What should I try?
 010- I added SCSI; now, my 3.5" drives often fail to work. Why?
 011- Both of my Disk ]['s come on when booting! Is there a fix?
 012- In connecting a Disk II I misaligned the connectors. A fix?
 013- A sound like a shotgun going off came from my drive. A fix?
 014- Uni-disk and Laser drives: neither works with my IIc. Why?
 015- How do I replace a 3.5" drive mechanism with one from a Mac?
 016- I have one 5.25" drive. Sys6 shows two icons!? Is there a fix?
 017- How can I tell a 13 from a 16-sector Disk ][ controller card?
 018- Can a Disk ][ Drive be used on a IIc or GS smartport?
 019- How do I install a bi-color LED R/W indicator in my Disk ][?
 020- What's the scoop on the 3.5" High Density drive?
 021- What is a "UniDisk"?
 022- What is a "RAM disk"; and, how do I create one on my IIgs?
 023- Which 3.5" drive/interface combinations work on a IIe?
 024- How can I boot from my /RAM5 RAM disk?
 025- My 5.25" drive ruins every disk I insert. How can I fix it?
 026- Incorrect 'Disk Full' error on a 3.5" UniDisk drive. Why?

 

From: Rubywand

019- I would like to add a Read/Write indicator to my Disk ][
     drive. How can I do this with a bi-color LED?

     The circuit described below works well. It shows Red for Drive Enabled +
Write and Green for Drive Enabled + not Write. That is, a Read is assumed if
the drive is ON and no Write is occurring. The advantage of this approach is
that you always have a lighted LED 'drive ON' indicator and, so, there is no
need to drill a new hole in your drive panel. The new LED can use the hole
occupied by the old "in Use" indicator LED.
 

Parts

IC-     74121 or 74LS121 1-Shot multi-vibrator
Qgreen- 2N2222A gen purpose NPN transistor
Qred-   2N2222A gen purpose NPN transistor
Rcath-  120 Ohm 5% 1/4 watt resistor
Rgreen- 3.3k 5% 1/8 watt resistor
Rred-   3.3k 5% 1/8 watt resistor
Rp-     20k 5% 1/8 watt resistor
Cp-     10uF/10v 10% "dipped tantalum" capacitor
LED-    2.2V 20ma 3-lead (common cathode) Green/Red bi-color LED
 

Building the Circuit

IC- locate pin-1 and mark it on bottom side with white-out.
 'Dead-bug' mount the IC using epoxy in the open area near
  top-middle of board with pin-1 end pointing to the right.

connect Rcath to solder pad at - (minus) end of C2
connect #20 wire from IC pin-7 to solder pat at - end of C2

connect Rp from IC pin-11 to IC pin-14
connect Cp + to IC pin-10 and Cp - to IC pin-11

connect #20 wire from IC pin-14 to solder pat at + end of C4

connect a wire from IC pin-3 to end of R16 closest to 74LS125

connect Rgreen to IC pin-1 (74121 "/Q" output)
connect Rred to IC pin-6 (74121 "Q" output)

solder transistor Qred Collector to Q1 power transistor Collector
 (solder pad area at left front of circuit board just to left of
  the power transistor). Position toward left edge of pad.

solder transistor Qgreen Collector to Q1 power transistor Collector
  solder pad to the right of Qred.

LED- connect a 3-wire 11" cable to the LED (black to center, red to
  to lead with right-angle bend, green to lead with slant bend).

Old "in Use" LED- pop off the retainer ring and push through the
  LED. Leave the LED mount in the hole. Cut off the LED, spread
  cable ends and tab over with cellophane tape. (Put old LED and
  ring into parts box.

Spread apart retainer 'leaves' of LED mount (at back side of panel)
  to permit easier insertion of new 3-lead LED.

Run LED + cable over back of board and along bottom toward the
  hole in the front panel. Push through hole. (If hole is too small,
  use a Dremel tool and steel 'bulb bit' to slightly enlarge front
  part of hole.)

connect LED cable black to free end of Rcath
connect LED cable green to Emitter of Qgreen (right transistor)
connect LED cable red to Emitter of Qred.

position old LED cable beneath new LED cable.

connect a wire from the free end or Rgreen (on IC pin-1) to the
  Base lead of transistor Qgreen.

connect a wire from the free end or Rred (on IC pin-6) to the
  Base lead of transistor Qred.

Add epoxy to the back of the LED and holder to secure the LED.
 
 

How it Works

     When /Enable goes low to select the Drive, the power transistor (Q1)
switches ON and supplies +12V at its Collector. If there is no Write, 74121
output /Q is high, Qgreen conducts, and the LED shows Green. That is: the Green
LED will light during boots and for any READs.

     If the Drive is selected (/Enabled is low) and there is a Write operation
and Write Protect is not ON, then, the /Write Request signal at 74LS125 pin 8
will go low. This triggers the 74121 One-Shot (at pin 3) producing an aprox.
160ms pulse at 74121 output Q. For the duration of the pulse, /Q is low and Q
is high. Qred conducts, and the LED shows RED to indicate WRITE.

 

 

macnoyd's picture
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Yes, saw that ...

I found that, but a schematic for it was never made, which is why I decided draw it.  :-)

To be even more accurate, I was careful to NOT take credit for anything but the schematic itself and made note of that.  Enjoy! 

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Well, timewise and moneywise , it would have been better for me to just buy one of Henry's kits for $30.00. :-)    

 

However, this was a very cool learning experience using DIPTRACE to layout the board and actually send it off for production.   I had 10 of these made and assembled the first one this morning and it actually worked!!!   

 

Thank you macnoyd for doing the schematic and thank you "anonymous" for the original post.   This came out pretty nice.  I know that it could have been made more visially appealing and optimized, but this is my first crack and using DIPTRACE and I just used the built in defaults for routing and layout.  

 

I think I am going to fool around to see if I can optimize this and may try one more run.   It was fun and a great learning experience!!!!

 

Thanks,

Jay 

 

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Great job Jay!

Keep me on your list if you want to share a few of those boaards, plus some expense.  Nice work indeed!

It's good to see folks actually put efforts like this into making actual projects.  Makes it all worth it.

 

Now if i can only get that WildCard elite card I've been looking for ...  :)

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Hey macnoyd...

Hey macnoyd...

 

if you share me with a picture of the top and bottom pcb layers, I can probably make a new layout as done for the APU card.

 

have fun...

Torsten

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Hi Torsten, If you look st the Schematic ...

Hi Torsten, If you look st the Schematic, you can lay it out exactly like that.  The only trace that needs to "cross" (so to speak) is the voltage that feeds the LED driver.

The lines that go to the resistors can pass between the . 0.1" spacing connector pads.  Easy-peasy.

You could actually make this 1-sided with a single jumper.

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Hi Bob,

Hi Bob,

 

I'm talking about the Wildcard you've mentioned above ;-)

 

Torsten

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Bob, 

Bob, 

 

I knew he was talking about the WildCard too. Heck  I'll give anyone that wants a copy a copy of the gerbers and even the DIPTrace project if you want it.   :-)  LOL! 

 

Thanks,


Jay

 

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Hi Jay,

Hi Jay,

 

I do have interest in getting the Gerber for the Wildcard elite. Would be great if you can sent them via PM.

 

Greetings Torsten

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jwg1962 wrote: Well, timewise

jwg1962 wrote:

 

Well, timewise and moneywise , it would have been better for me to just buy one of Henry's kits for $30.00. :-)    

 

However, this was a very cool learning experience using DIPTRACE to layout the board and actually send it off for production.   I had 10 of these made and assembled the first one this morning and it actually worked!!!   

 

Thank you macnoyd for doing the schematic and thank you "anonymous" for the original post.   This came out pretty nice.  I know that it could have been made more visially appealing and optimized, but this is my first crack and using DIPTRACE and I just used the built in defaults for routing and layout.  

 

I think I am going to fool around to see if I can optimize this and may try one more run.   It was fun and a great learning experience!!!!

 

Thanks,

Jay 

 

 

You probably can try to build a SMD version... just to learn this, too ;-)

 

Greetings Torsten

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Whoops.  My bad. I wasn't too

Whoops.  My bad. I wasn't too clear in my message.  I meant Gerbers and files for the LED project.   I think I will try an SMD version. Good idea! 

 

Jay 

 

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Has anyone tried hitching one

Has anyone tried hitching one of these things up to a half height clone drive?

 

A

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