4 Digit Hewlett Packard HDSP Clock Soldering Kit, now with USB-C!

Description

By popular demand, a soldering kit for the Hewlett Packard HDSP series displays. This kit is an updated version of the Includes everything needed to make your clock except the HDSP displays. You won’t find any micro controller in this circuit. The time is kept using 7400 and 4000 series digital logic IC’s that were state of the art technology when these HDSP series displays were common. These HDSP series displays were some of the first numerical LED displays ever made. They are unique because the logic die, LED dies, and bond wires are all plainly visible under a thin sheet of glass.

This kit is compatible with all of the 8 pin DIP HDSP series displays. You will have to consult the datasheet for your exact displays to double check the pinout. Some of these displays brightness can be controlled by the blanking input on pin 4, and others have a decimal point on pin 4. This clock will work with either version.

These HDSP displays run really HOT. This seems to be normal, however to help with the heat a low impedance resistor (R1-R4) is placed in series with the VCC pins in the circuit. If you’re using an HDSP display that has blanking control on pin 4, a 555 timer is built into the circuit to adjust the brightness with a 1.5KHZ pulse width modulated square wave. If your displays do not have this capability, this PWM circuit will adjust the brightness of the decimals.

This Clock does not have a separate page with assembly instructions, but assembly is straightforward. Simply place each component in it’s place that corresponds to it’s part number and solder them in place. No surface mount soldering required. You will need a power supply, HDSP displays, solder and a soldering iron. The crystal oscillator’s case needs to be glued to the PCB for accurate timekeeping.

You can find the open source design for this clock on our open source design page.

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