Bi-color red/green LEDs: Disk II read/write????

Bi-color red/green LEDs: Disk II read/write????

Post by stephen e bugg » Sun, 15 Mar 1998 04:00:00



A store is clearing out bi-color LEDs red/green.   These LEDs have three
wires:  black (negative), red (red +), green (green +).

I want to add the bi-color LED to my Disk II drives, so that it will glow
GREEN for READ, and RED for WRITE.   I already have an AE 3.5" 800K drive
that does this, and it looks nice.   This will be a third enhancement to
Disk II --- "Super Bugg-Drive."

First, what value of resistor should be added?  The ad says these are 2
volt LEDs, and that 20 milliamps should flow through the LED.

Will the 20 milliamps affect the read/write performance of the drive in
any way?

Not sure where in the analog board to connect the LEDs.  Could I attach
the black lead to a ground point, then touch various analog card points
while the disk is reading vs. writing?

Will other components be needed besides the bi-color LED and its padding
resistors?

Would it be simpler to just reconnect the red LED to a point on the analog
board, and then to install a second separate LED to denote WRITE?


 
 
 

Bi-color red/green LEDs: Disk II read/write????

Post by Rubywan » Sun, 15 Mar 1998 04:00:00


stephen e buggie writes ...

Quote:

> A store is clearing out bi-color LEDs red/green.   These LEDs have three
> wires:  black (negative), red (red +), green (green +).

> I want to add the bi-color LED to my Disk II drives, so that it will glow
> GREEN for READ, and RED for WRITE.   I already have an AE 3.5" 800K drive
> that does this, and it looks nice.   This will be a third enhancement to
> Disk II --- "Super Bugg-Drive."

> First, what value of resistor should be added?  The ad says these are 2
> volt LEDs, and that 20 milliamps should flow through the LED.

> Will the 20 milliamps affect the read/write performance of the drive in
> any way?

     Since you would be sticking a 20ma load onto a 74LSxxx TTL output
in each case, the odds are pretty good that Read and Write data would be
screwed up.

     One idea is to use a couple general purpose PNP transistors. The
LED GND lead goes to GND. The Red lead goes through a 150 or so Ohm
resistor to the Collector of the "Write Transistor". The Green lead goes
through a 150 or so Ohm resistor to the Collector of the "Read
Transistor". Each transistor's Emitter goes to +5V.

     The Base of each transistor has a 1k or so Ohm resistor attached.
The resistor connected to each Base is the Input for that LED. This
should take care of driving the LEDs. When an Input goes Low (e.g. to
GND), the corresponding LED should light. If you feel brightness is too
high, increase the Base R value.

     The rest of the circuit depends upon the conditions you choose for
lighting an LED and how many of what kinds of IC's you have in your
parts bin.

     For example, you could use the condition: when /Enable is low and
/WR-REQ is low then /WR-LED is low.  /WR-LED goes to the Write LED (Red)
Input. If /Enable is low and /WR-REQ is high then you assume a Read and
/RD-LED goes low to turn on the Read (Green) LED.

     A single quad dual input NOR IC, like a 74LS02, could handle the
logic. In the circuit below, "[ ]" numbers are Disk ][ Analog board
connector points and "( )" numbers refer to pins on a 74LS02.

  [10] /WR-REQ ------ (2)
                         NOR-1 (1)---- (5 & 6) NOR-2 (4)---- /WR-LED to
Red Input
  [14] /Enable -------(3)           |
           _________________________|
           |
           |
           |__________(11)
                         NOR-3 (13)--- (8 & 9) NOR-4 (10)--- /RD-LED to
Green Input
  [14] /Enable -------(12)

  (7)  to GND
  (14) to +5V

     In the above, when /Enable is low, one of the LED's will light. If
/WR-REQ is low, the Red LED will light; if /WR-REQ is high, the Green
LED will light. (Some fiddling with resistor values may be required to
settle on the right ON brightness levels.)  One advantage of this
circuit is that you always have a 'drive ON' indicator and, so, do not
need to drill a hole for another LED.

     An alternative circuit could monitor actual Read [16] and Write
[18] activity using /Enable [14] to enable inputs to a dual 1-Shot IC.
Write transitions would fire the Write 1-Shot; Read transitions would
fire the Read 1-Shot. The /Q output from a 1-shot would connect to the
desired Red or Green Input. Pulse time for each 1-Shot could be
something like 1/5 second in order to guarantee a stable, bright
display.  

Rubywand

 
 
 

Bi-color red/green LEDs: Disk II read/write????

Post by David Wils » Wed, 18 Mar 1998 04:00:00



>A store is clearing out bi-color LEDs red/green.   These LEDs have three
>wires:  black (negative), red (red +), green (green +).
>I want to add the bi-color LED to my Disk II drives, so that it will glow
>GREEN for READ, and RED for WRITE.   I already have an AE 3.5" 800K drive
>that does this, and it looks nice.   This will be a third enhancement to
>Disk II --- "Super Bugg-Drive."
>First, what value of resistor should be added?  The ad says these are 2
>volt LEDs, and that 20 milliamps should flow through the LED.
>Will the 20 milliamps affect the read/write performance of the drive in
>any way?
>Not sure where in the analog board to connect the LEDs.  Could I attach
>the black lead to a ground point, then touch various analog card points
>while the disk is reading vs. writing?
>Will other components be needed besides the bi-color LED and its padding
>resistors?
>Would it be simpler to just reconnect the red LED to a point on the analog
>board, and then to install a second separate LED to denote WRITE?


I have been looking through my copy of Apple's DOS manual with the circuit
diagram of the Disk ][ analog card and Jim Sather's Inside the Apple II and
think it can be done.

The existing LED circuit is:

                           560ohm       Red LED
        +12v switched ----/\/\/\/----B --|>|-- 2---Gnd       current =

As a Red/Green LED can do 3 colours (Green, Orange and Red) but we cannot
do only Green or Red (as one LED will be run from the existing Enable while
the 2nd will illuminate when writing is also occurring), I would recommend
the following:

                           560ohm
        +12v switched ----/\/\/\/----B  --|>|---+    Green LED
                                                |
                                Gnd--2  --------+
                                                |
        ULN2003 (D4-10) --/\/\/\/---------|>|---+    Red LED
                           180ohm

This way you get Green for reading and Orange for writing. This immediately
tells you that the drive has been modified and the contrast between green
and orange is higher than between red and orange.

I do not know if the write signal is actually long enough to see (formatting
a disk should be no problem but normal writes may not keep the red LED on
long enough to see). If this is the case, additional circuitry would be needed
to stretch the write pulse to the LED.

Note, this has not been tried, I make no guarantee that this will work.
Try it on scratch disks first.

To calculate LED currents, use the following formula:

        Iled = (Vsupply - Vled) / R

so for the original circuit:

        I = (12 - 2) / 560
          = 10/560
          = 17.86mA

The output of pin 10 of the ULN2003 is clamped to a maximum of 5 volts by
a diode so:

        I = (5 - 2) / 180
          = 3/180
          = 16.67mA
--

 
 
 

Bi-color red/green LEDs: Disk II read/write????

Post by Rubywan » Sat, 21 Mar 1998 04:00:00


stephen e buggie writes ...

Quote:

> A store is clearing out bi-color LEDs red/green.   These LEDs have three
> wires:  black (negative), red (red +), green (green +).

> I want to add the bi-color LED to my Disk II drives, so that it will glow
> GREEN for READ, and RED for WRITE.   I already have an AE 3.5" 800K drive
> that does this, and it looks nice.   This will be a third enhancement to
> Disk II --- "Super Bugg-Drive."
> ....

     Since the last post, there was a chance to do some experimentation.
The circuit below seems to work well ...

NPN transistor Collector to Bi-color LED center
NPN Emitter to GND
NPN Base to two 3300 Ohm resistors
    One resistor goes to GND
    The other resistor goes ULN2003 pin 15 (connect to R2 at point
      closest to ULN2003)

LED Red (lead has right-angle at LED) to 150 Ohm resistor
    Resistor goes to pin 6 (Q output) of a 74121 One-Shot IC

LED Green (lead has slant-angle at LED) to 150 Ohm resistor
    Resistor goes to pin 1 (/Q output) of 74121 IC

74121 IC pin 7 goes to GND
         pin 14 goes to +5V
         pin 3 goes to 74LS125 pin 8 (connect to R16 at point
           farthest from ULN2003)
        (pin 1 goes to resistor to LED Green)
        (pin 6 goes to resistor to LED Red)
         pin 11 goes to + end of mini 10uF capacitor
         pin 12 goes to - end of the mini 10uF capacitor; and
         pin 12 goes to a 22000 Ohm resistor
           Resistor goes to +5V (can connect to 74121 pin 14)

     The NPN transistor can be any general purpose NPN type (e.g. a
2N2222, etc.).  It's input (Base) is driven by the /Enable after it has
been inverted by a gate of the ULN2003. When /Enable goes low to select
the Drive, the signal at the Base goes high. This connects the LED
common lead to GND through the transistor.

     If the Drive is selected (Enabled) and there is no Write operation,
the Green LED will get a + voltage through its 150 Ohm resistor from the
74121 /Q output. So; the Green LED will light when the Drive is enabled
(e.g. during boots and for any READs).

     If the Drive is selected (Enabled) 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. 120ms pulse at output Q. For the duration of the pulse, +V
goes to the Red LED through its 150 Ohm resistor. The Red LED lights.
(Meanwhile, /Q has gone low so that the Green LED turns OFF.)  

     Probably, the first circuit posted earlier will work, too; but, I'm
still not sure that Write Request is always long enough to be easily
visible. This is why the One-Shot IC circuit is used. (You can make the
pulse longer by using larger values for the capacitor or increasing the
value of the 22000 Ohm resistor.)

     Anyway, the circuit works well for showing Reads and Writes with a
standard bi-color LED. It's the one I installed on our Disk ][ drive.

     If you decide to try the NOR gates circuit posted earlier, the mod
below is a simpler version which should do the same thing
...              

In the circuit below, "[ ]" numbers are Disk ][ Analog board
connector points and "( )" numbers refer to pins on a 7402 Quad
dual-input NOR gate IC.

  [10*]/WR-REQ ------ (2)
                         NOR-1 (1)---- 150 Ohm Resistor to LED Red lead
  [14] /Enable -------(3)           |
           _________________________|
           |
           |
           |__________(11)
                         NOR-3 (13)--- 150 Ohm Resistor to LED Green
lead
  [14] /Enable -------(12)

  (7)  to GND
  (14) to +5V

*Note: To have the Write LED remain OFF when Write Protect is ON,
connect instead to 74LS125 pin 8 (connect to R16 at point farthest from
ULN2003)

LED middle lead goes to GND

     In both the One-Shot and the NOR gates circuit the IC is driving
LEDs. This is why 74xxx instead of 74LSxxx or CMOS IC's are specified.
Should you use a higher-current bi-color LED, it may be necessary to add
the driver transistors included in the original circuit.

     By the way, it turns out that the WR Data signal is frequently
active (with pulses) even when a Write is not in progress. This pretty
well makes it useless as a way to monitor Writes.

Rubywand

 
 
 

Bi-color red/green LEDs: Disk II read/write????

Post by Rubywan » Tue, 24 Mar 1998 04:00:00



> stephen e buggie writes ...

> > A store is clearing out bi-color LEDs red/green.   These LEDs have three
> > wires:  black (negative), red (red +), green (green +).

> > I want to add the bi-color LED to my Disk II drives, so that it will glow
> > GREEN for READ, and RED for WRITE. ....

>      Since the last post, there was a chance to do some experimentation.
> The circuit below seems to work well ...
> ....

     Below are a few additional notes for experimenters interested in
building the circuit.

Note: A good point for GND is pin 1 on the ribbon cable socket near the
back, left of the Disk ][ Analog Board. Pin 11-- the 6th pin on the
socket counting pin 1 as first-- is a good source for +5V. The pins--
actually, the bare leads from the socket going to the circuit board--
are shown below as viewed from the front of the Disk ][.

   1  3  5  7  9  11 13 15 17 19

   o  o  o  o  o  o  o  o  o  o

   |              |
  GND            +5V

Note: The new bi-color LED is installed in the hole left by removing the
old LED. (I just left the old LED connected.)   The mounting ring which
held the old LED did not fit well and tends to press the new LED's leads
together. I did not use the mounting ring. Epoxy (added from the back
after the LED is inserted) works well for holding the new LED in place.

Note: The 74121 IC was mounted on its back using epoxy in an open space
above the square cut-out in the circuit board. (Double-sided tape also
works well for 'dead-bug' mounting an IC.)  Pin 1 was marked with a dab
of white-out on the IC.

Rubywand

 
 
 

Bi-color red/green LEDs: Disk II read/write????

Post by Rubywan » Thu, 14 May 1998 04:00:00


There was a recent opportunity to do the two-color LED mod to some
Disk II drives-- i.e. A bi-color LED is swapped in for the old red "in
Use" LED. It shows Green for Reads and Red for Writes.

     Additional testing during the recent work led to an improved
circuit and the discovery of an error in my description of the earlier
circuit.

     First the correction. My earlier post says ...
....

Quote:>          pin 11 goes to + end of mini 10uF capacitor
>          pin 12 goes to - end of the mini 10uF capacitor; and
>          pin 12 goes to a 22000 Ohm resistor

....

There is no connection to pin 12 of the 74121. The above should have
read ...

Quote:>          pin 10 goes to + end of mini 10uF capacitor
>          pin 11 goes to - end of the mini 10uF capacitor; and
>          pin 11 goes to a 22000 Ohm resistor

     The original circuit works fairly well (if you figure out that the
directions contain an error); but, breadboard tests indicate that the
74121 can not adequately source many LEDs which might be employed.

     The new circuit uses transistors to drive the LED sections. By
getting LED power from the +12V line switched by power transistor Q1 in
response to /Drive Enable, the transistor used for this purpose in the
old circuit is eliminated. So, the new circuit needs only two
transistors-- just one more than before-- and drives the Green/Red LED
at higher brightness.

     As in the original design, the new circuit shows Green for Drive
Enabled + no Write and Red for Drive Enabled + 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-*
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 to secure LED in place
.

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.

Rubywand

 
 
 

1. Info Sought: Bi-color read/write LED for Disk II

I am building "Super Disk II" ----   a Disk II loaded with all hackable
features.

Someone wrote that instructions appear in a book, "Understanding the
Apple II" (approximate title), in how to install a two-color LED to
identify read vs. write fuinctions.

I already have a bi-color LED on my AE 3.5" drive, and it looks great.,

Ifd anyone can find this chapter, could you photocopy it to me, snail mail?

I understand that it works with an IC soldered toi the Disk II analog board.

I( hope to brag/show off "Super Disk II" at KansasFest this July; reades
who attend will get to see it!   (Autograph signing will be available.....)

BTW, its other features so far are:

DB-19 round cable
Front-panel write protect override switch (normal/always write/
                                           always protect)
Front-panel vernier speed-control knob

Steve Buggie
200 College Rd
Gallup, NM  87301

2. RHIDE - reports multiple definitions

3. BI-COLOR LED on Disk II Drive: Info needed

4. Epson Stylus 800 will not init.

5. WANTED: Docs red-green LED on Disk II

6. where is ResEdit 3.0?

7. Bi-color LED 5.25 analog boards: plug-and-play $7.00

8. Printer definition for Adobe PS driver needed

9. New! Bugg-Drive Plus; red-green read-write LED

10. DISK ][ HACKING: "Write" indicator LED: connect points??

11. reading/writing Apple II disks in a PC?

12. Reading/writing Apple II disks on other machines

13. Disk Drinve card for apple2 can read/write IBM-PC disks & Prodos