RESET circuit

-

One thing I had to add was a power-up RESET circuit, which is just a 10uF cap and 1K resistor in series across the 5v supply. The RESET pin on the counters are connected to where the resistor and cap meet so that at power up, the cap is effectively a short to 5+. This causes a logic HI on the RESET lines to set the counters to zero. After the capacitor has charged up, it no longer looks like a short to 5+, so the only path left is through the resistor back to ground. That presents a logic LOW on the RESET pin, which allows the counter to count up or down.

Comments

Post a Comment

Popular posts from this blog

Pboard

-
Image
Pboard  Project Pboard (short for "P-channel board") is the working nickname of a new driver board that I plan to use with the next version RLbC.  Whereas RLbC 2 only featured output relays, Pboard will make use of  Adafruit's PCA9853 based servo-driver board to provide PWM signals to the outputs via P-channel MOSFETS.  Doing so will allow for fading the lights. Why use P-channel Mosfets? I chose to use  FQP27P06 P-channel MOSFETS over the more commonly accepted easier to wire N-channel logic-level MOSFETS out there simply because I wanted high-side switching.  Call me weird or old-fashioned, but I have always designed my low-level voltage systems with Common tied to the "negative" side of a supply (split or dual-tap not withstanding). However, going to P-channel switching does make the design a little more complex. Buffering is required since I can not directly tie the output of a PCA9685 to Vss (12VDC) otherwise it will be damaged.   Invert
Read more

GarageBox Project

-
Image
GarageBox After a year long hiatus, I've begun to finish my Olimex ESP8266DEV based project so that I can control my garage door and also a set of Christmas lights via WiFi.  Below is the current state of construction. The large orange board on the left is an Olimex-ESP3266EVB development board.  It is actually two boards in one:  If you look at the upper left , you'll notice a smaller PCB with is the actual ESP3266 wifi module.  It sits atop a larger board that provides power, a programming port and a single control relay.  The relay on this board is what I will use to open & close the garage door. In the lower right (black board) is a solid-state relay.  I plan to use this to control a string of lights hung above the garage door. In the upper right (green board) is a 5VDC power supply. Door Sensor Below is the sensor that checks whether or not the garage door is closed.  It is an infra-red proximity sensor with an open collector output (E18-D80NK). 
Read more