Saturday, October 26, 2013

Centralize power switch for PC arrays with power failure monitor

UPS system is a common peripheral in computer field. Now most of these UPSs are equipped with USB driven system shutdown software. But some of the cheap UPS system may not have software controlled PC shutdown systems and some of them had some limitations too (for example operating system compatibility issues, supporting for multiple nodes, etc.).

In this post we design power failure monitor with centralize power switch for array of PCs. Using this system administrators can turn on multiple PCs with single button press and all of these PCs get power down automatically at power failure. To reduce cross platform issues we design this interface to work with main-board power switch and because of this administrators may not need any special software for this system. Most important point of this system is its independence with UPS hardware.

Prototype of centralize power switch project

Main controller of this system is PIC10F200 - 8bit microcontroller. Thanks to its SOT-23 package we can limit this system into 86mm × 58mm PCB. This supplied PCB design is based on SMD parts but this can be build using non SMD parts also.

At the testing stages we test this with both Linux and Windows operating systems. Configuration steps for each operating system are available at bottom of this post.

This module is support up to 8 PC nodes and this can be extent into more nodes by adding counters (4017) and CMOS switches (4066) to the system.

Sunday, October 13, 2013

LMD18245 base Microstep Motor Driver

This article describe the LMD18245 and PIC16F877A base 16 step bipolar stepper motor driver which is design to work with 12V 18º bipolar stepper motors. In this design we use pair of LMD18245 DMOS full bridge motor drivers to control 2 phases of the stepper motor and PIC16F877A MCU is used as controller.

We test this driver with several stepper motors (including 1.8º - 12V stepper motors) and all of them provide excellent smooth output with this driver. The supplied firmware of this driver is design for 16 micro-steps but it can be easily change to full-step, half-step, 8, 32 or 40 micro-steps.

In this given design LMD18245 current sense resistor is calculated for 200mA and it can be extend to 3A by changing the value of R2 and R4 resistors. For more information refer the LMD18245 datasheet.

This project is released as open hardware project. Firmware of this project is released under the terms of MIT License and schematic is released under the terms of Creative Commons Attribution 3.0 Unported License. All the project schematics and firmware source codes (including compiled binaries) are available to download at