Dilshan R Jayakody’s Web Log

HD-1410 is quite popular iambic keyer which is manufactured around the 1970s by Heathkit . The original HD-1410 keyer is designed using 5 commonly available 74LS series TTL ICs and 8 transistors. Other than iambic operation it has an option to adjust sidetone frequency and support for (external) single-paddle key unit. In this project, we redesign the original HD-1410 electronic keyer with today's commonly available components. In this new design, the key components which we replace are transistors, diodes, and power supply section of the original HD-1410 circuit. Most of the NPN transistors in original design are replaced with KSP42 and KSP10 transistors, and all the PNP transistors are replaced with KSP92 transistors. To keep everything simple we also use the same TTL chip-set with this new design. PCB of modified Heathkit HD-1410 electronic keyer. Tested PCB layout for this new keyer is available in the project archive and this PCB layout is based on standard through-...

This is a simple electronic project which we implemented for some local event to guide audience automatically with some prerecorded voice messages. The core component of this unit is ISD1820PY voice record/playback chip which is manufactured by Nuvoton Technologies . Except for ISD1820PY, this unit use commonly available low power LASER and LDR assembly to detect people. To drive the loudspeaker we use popular LM386 audio power amplifier. Thanks to ISD1820PY and LM386 this system can be implemented on a breadboard or on stripboard with a minimum number of external components. This circuit is designed to drive using 6V or 9V DC battery but it can also drive with 6V or 9V DC regulated power supply. To get 3.3V we use an LD1117V33 voltage regulator, but this can also be replaced with some commonly available 3.3V regulators such as LD33V, MC33269-3.3, etc. For the speaker, we use 4-inch 8Ω full-range speaker. A prototype version of electronic voice messenger. This unit can be u...