Gallery – Hobbybotics PCF8574A I2C I/O Expander

The Hobbybotics I2C I/O Expander is based on the Philips PCF8574A.  The PCF8574A provides eight bits of I/O with the use of only two micro-controller pins.  Included are pictures of the first version of the PCB.  Go here and check out the pictures.


Project – Hobbybotics Photo Interrupter V1.0

The Hobbybotics Photo Interrupter is based on the Panasonic CNZ1120.  A photo interrupter sensor is composed of an infrared emitter on one side and a shielded infrared detector on the other.  By emitting a beam of infrared light from one side to the other, the sensor can detect when an object passes between them, breaking the beam.  Such sensors are used as optical limit switches for CNC applications or position sensors in robotics, for example.  Being a version 1 design, I made a few mistakes when I created the PCB.  Originally, I added a LED for on-board visual indication however, I routed the trace wrong.  No big deal as I corrected it by not installing one on the PCB.  Easy enough fix and it should be obvious if the circuit is working correctly, right?  The second error, while not really an error in the end, is I swapped the PCB footprint pins when I created the CNZ1120 photo interrupter part in ExpressPCB.  This turned out to be a better fit in the end as it allowed me to place the component on the opposite side of the board away from the other components.  I did update the schematic and board files to reflect the corrections.  So, go here and check out the project and, if you decide to build from my project files, remember that I have made corrections.

Gallery – Hobbybotics Photo Interrupter V1.0

I uploaded pictures to the gallery of version 1 of the Hobbybotics Photo Interrupter based on the CNZ1120. I screwed up a bit when I designed this board as I created the footprint for the CNZ1120 photo interrupter backwards. It still worked out in the end and I actually like it this way as it allows me to place the interrupter on one side of the board with the rest on the components on the opposite side.  I also screwed up a bit in the schematic with the placement of the LED.  This little mistake was fixed by simply removing the LED and associated resistor from the final board.  In the end, it still works!

View it here.

Project – Hobbybotics Optoisolated Relay Controller

I have added a project detailing my design for an optoisolated relay controller.  I was looking for a simple way of switching high current DC and AC loads without the added expense of SCRs.  I can use this board to switch on/off lamps, a spindle motor for a CNC machine, or the heating elements on the toaster oven I am using for my re-flow oven project (more on this later).  Excited?  No? Well, go and check out the project anyway as you might learn something or, in the very least, find something that I screwed up on.  If you find the later, please let me know.

Check out the project here or the gallery here.