Dilshan R Jayakody’s Web Log

At the beginning of 2018, we developed the first version of the 6-channel speaker selector using PIC16F88 MCU and ULN2803 Darlington transistor array. In this new design, we redesign it with low-cost MCU and Darlington transistor arrays. This design also provides the same functionality as the 6-channel speaker selector switch we designed earlier. This new speaker selector uses STC15W201 MCU. This MCU is a low-cost 8051 MCU designed by STC micro . At the time of this writing, the STC15W201 can obtain for less than US$ 0.8. To drive the seven segments and to control the relays, this design uses the popular 74HC595 8-bit shift register ICs. PCB of the 6-channel speaker selector. To select each speaker channel, we use pair of 12V DPDT relays. These relays interface to 74HC595 through a ULN2001D 3-channel Darlington transistor array IC. This 3-channel Darlington driver IC is functionally equivalent to the famous 8-channel ULN2003 IC. This ULN2001D version is an 8-pin IC and is av...

This is an AT89S2051 base 8bit bus monitoring utility. This module indicates bus values using hexadecimal numbering format and notify value changes by the beep. This utility is design to work with any 5V compatible TTL/CMOS - data/address buses. This 8bit bus monitor requires 5V external power supply. In the idle mode this unit draws 15mA of current and in working mode (when inputs get change) this may raise up to 20mA – 30mA. Due to this low power profile, this system can also attach into the PSU of the "testing system". This module is release as an open hardware project and it is covered with Creative Commons Attribution-ShareAlike 3.0 license . All the project related resources are available at Open Hardware Hub .