Hewlett-Packard 5082-7415 LED Display from 1976
In this article we examine a five digit, seven-segment LED display from Hewlett-Packard, the 5082-7415:
We realise they’re most likely now pure unobtanium, but we like some old display p0rn so here you go.
2025 update – Tronixlabs in Australia has a limited quantity of new, old-stock four-digit QDSP6064 displays. Email john at tronixlabs dot com for more information.
According to the data sheet (HP 5082-series.pdf) and other research this was available for a period of time around 1976 and used with other 5082-series modules in other HP products. Such as the Hewlett-Packard 3x series of calculators, for example:
Using the display is very easy – kudos to the engineers at HP for making a simple design that could be reusable in many applications. The 5082-7415 is a common-cathode unit and wiring is very simple – there are the usual eight anodes for segments a~f and the decimal point, and the five cathodes.
As this module isn’t too easily replaceable, I was very conservative with the power supply – feeding just under 1.6V at 10mA to each of the anode pins. A quick test proved very promising:
Excellent – it worked! But now to get it displaying some sort of interesting way. Using the following hardware…
- an Arduino-compatible board
- Two 74HC595 shift registers
- Eight 560 ohm resistors
- Five 1k ohm resistors
- Five BC548 transistors
- A large solderless breadboard and plenty of wires
Don’t forget to use the data sheet (HP 5082-series.pdf). You don’t have to use Arduino – any microcontroller with the appropriate I/O can take care of this.
Here is a simple Arduino sketch that scrolls through the digits with and then without the decimal point:
// Arduino sketch to demonstrate HP 5082-7415 LED Display unit
// John Boxall, April 2012
int clockPin=6;
int latchPin=7;
int dataPin=8;
// array for cathodes - sent to second shift register
byte digits[]={
B10000000,
B01000000,
B00100000,
B00010000,
B00001000,
B11111000}; // use digits[6] to turn all on
// array for anodes (to display 0~0) - sent to first shift register
byte numbers[]={
B11111100,
B01100000,
B11011010,
B11110010,
B01100110,
B10110110,
B10111110,
B11100000,
B11111110,
B11110110};
void setup()
{
pinMode(clockPin, OUTPUT);
pinMode(latchPin, OUTPUT);
pinMode(dataPin, OUTPUT);
}
void loop()
{
int i;
for ( i=0 ; i<10; i++ )
{
digitalWrite(latchPin, LOW);
shiftOut(dataPin, clockPin, LSBFIRST, digits[6]);
shiftOut(dataPin, clockPin, LSBFIRST, numbers[i]);
digitalWrite(latchPin, HIGH);
delay(250);
}
// now repeat with decimal point
for ( i=0 ; i<10; i++ )
{
digitalWrite(latchPin, LOW);
shiftOut(dataPin, clockPin, LSBFIRST, digits[6]);
shiftOut(dataPin, clockPin, LSBFIRST, numbers[i]+1);
digitalWrite(latchPin, HIGH);
delay(250);
}
}
And the results:
Now for something more useful. Here is a function that sends a single digit to a position on the display with the option of turning the decimal point on or off:
void displayDigit(int value, int posit, boolean decPoint)
// displays integer value at digit position posit with decimal point on/off
{
digitalWrite(latchPin, LOW);
shiftOut(dataPin, clockPin, LSBFIRST, digits[posit]);
if (decPoint==true)
{
shiftOut(dataPin, clockPin, LSBFIRST, numbers[value]+1);
}
else
{
shiftOut(dataPin, clockPin, LSBFIRST, numbers[value]);
}
digitalWrite(latchPin, HIGH);
}
So if you wanted to display the number three in the fourth digit, with the decimal point – use
displayDigit(3,3,true);
with the following result:
We make use of the displayDigit() function in our next sketch. We introduce a new function:
displayInteger(number,cycles);
It accepts a long integer between zero and 99999 (number) and displays it on the module for cycles times:
// Arduino sketch to demonstrate HP 5082-7415 LED Display unit
// Displays numbers on request
// John Boxall, April 2012
int clockPin=6;
int latchPin=7;
int dataPin=8;
// array for cathodes - sent to second shift register
byte digits[]={
B10000000,
B01000000,
B00100000,
B00010000,
B00001000,
B11111000}; // use digits[6] to turn all on
// array for anodes (to display 0~0) - sent to first shift register
byte numbers[]={
B11111100,
B01100000,
B11011010,
B11110010,
B01100110,
B10110110,
B10111110,
B11100000,
B11111110,
B11110110};
void setup()
{
pinMode(clockPin, OUTPUT);
pinMode(latchPin, OUTPUT);
pinMode(dataPin, OUTPUT);
randomSeed(analogRead(0));
}
void clearDisplay()
// turns off all digits
{
digitalWrite(latchPin, LOW);
shiftOut(dataPin, clockPin, LSBFIRST, 0);
shiftOut(dataPin, clockPin, LSBFIRST, 0);
digitalWrite(latchPin, HIGH);
}
void displayDigit(int value, int posit, boolean decPoint)
// displays integer value at digit position posit with decimal point on/off
{
digitalWrite(latchPin, LOW);
shiftOut(dataPin, clockPin, LSBFIRST, digits[posit]);
if (decPoint==true)
{
shiftOut(dataPin, clockPin, LSBFIRST, numbers[value]+1);
}
else
{
shiftOut(dataPin, clockPin, LSBFIRST, numbers[value]);
}
digitalWrite(latchPin, HIGH);
}
void displayInteger(long number,int cycles)
// displays a number 'number' on the HP display.
{
long i,j,k,l,z;
float f;
clearDisplay();
for (z=0; z
void loop()
{
long l2;
l2=random(0,100001);
displayInteger(l2,400);
}
For demonstration purposes the sketch displays random numbers, as shown in the video below:
Update – four-digit versions…
They worked very nicely and can be driven in the same method as the 5082-7415s described earlier. In the following video we have run the same sketches with the new displays:
In the meanwhile, I hope you found this article of interest. Thanks to the Vintage Technology Association website and the Museum of HP Calculators for background information.
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And as always, have fun and make something.
