Digital-Design (Page 2)

This is a Gadget Tutorial for this Article LED Running lights CD4017 – Live Gadget Page.

Red Button Powers LED Running Lights, 555 Clock is counted by CD4017. Adjust R2, See ToolTips. This Demo shows LM555 running a CD4017 Counter to drive Ten Leds sequentially.

Press the Red button below to turn on the circuit press it again to turn off, i have put a new battery and did the wiring for you. The Red LED will flash according to the state of the 555 output at pin 3. The decade counter-divider CD4017 has 10 outputs, for every low to high transition, rising edge, the counter advances one LED. After going one full circle the the first LED lights again and it goes on…..

LED Running lights CD4017

The 10 outputs have 10 green LEDs. The current thru the LED is limited by R1, the current can be calculated like this (9V – 1.6V) / 1K = 7.4mA this is within 20mA which is the danger limit of the CMOS output. You want it to be bright use transistors for every output.


The CD4093B consists of four Schmitt-trigger circuits. Each circuit functions as a 2-input NAND gate with Schmitt-trigger action on both inputs. The gate switches at different points for positive and negative-going signals.

CD4093 – Quad 2-Input NAND Schmitt Trigger

The difference be-tween the positive (VTa) and the negative voltage (VTb)isdefined as hysteresis voltage (VH). All outputs have equal source and sink currents and con-form to standard B-series output drive.

CD4093 Quad NAND Schmitt Trigger

CD4093 is a very useful chip, as it has a Schmitt-trigger and it is a nand, cmos, low power.  It can be even made to function like an amp in some configurations. It was used in debouncing circuits, oscillator circuits and input signal conditioning of digital circuits.

DMM range and AC-DC mode Logic

If you had a train of square pulses from a magnetic sensor or proximity sensor. You could use this as a monostable or singleshot to reject noise and get a clean square wave from a messy input.

“There is a long gap between engineering college and mid career in a non-engineering position, but technology marches on so a simple method of keeping abreast with the latest developments is required. This application note starts with an overview of the basic laws of physics, progresses through circuits 1 and 2, and explains op amp operation through the use of feedback principles.”

Basic Analog for Digital Designers – Application Note

Basic Analog for Digital Designers

AN9510.2 October 19, 2004 – This is an Analog Reference for the Embedded Engineer. An Application Note from Intersil Tech Reference.

  1. Basic Physics Laws, Circuit Theorems and Analysis
  2. Ohm’s and Kirchoff’s Laws
  3. Voltage and Current Dividers
  4. Thevenin’s and Norton’s Theorems
  5. Networks in the Feedback Path
  6. Types of Opamp Configurations
  7. Video Amplifiers


Some algebra, the basic laws of physics, and the basic circuit laws are adequate to gain an understanding of op amp circuits. By applying these tools to various circuit configurations it is possible to predict performance. Further in-depth knowledge is required to do op amp design, and there are many sources where this knowledge can be obtained. Don’t hesitate to try some of these tricks on your local circuit design engineer, but be aware that it may result in a long lecture about circuit design.

CD74HCT373 – High Speed CMOS Logic Octal Transparent Latches with 3-State Outputs

The ‘HCT373 devices are octal transparent D-type latches. When the latch-enable (LE) input is high, the Q outputs follow the data (D) inputs. When LE is low, the Q outputs are latched at the logic levels of the D inputs.

From – 74HCT373 Texas Instruments

What it can do ?

This is like a Byte of Memory, A Byte means 8 Bits. A Bit Means one Input or Output Pin of an IC, Which understands Logic 1 is High and Logic 0 is Low.

74HCT373 Octal transparent D-type latches

The HCT works well with old TTL and CMOS families. This takes very less Power (battery lasts longer). It switches very fast (the computation is done faster). Its got good symmetrical output drive. Means Source and Sink both nice.

When you run out of ports I/O in your favorite uC, This guy will come to your rescue. Simple way is to Put four of this and Interconnect or Bus their Data inputs D0-D7. Then Connect this Bus to 8 Ports of our uC Chip. Enable the Output of all of them. Use 4 ports from your uC to latch each one with the data you want to be outputted. Now you have 8×4 32 Bits output. This comes at a small cost, the clock time, but negligible. In the same way you can enhance the Input ports, use the 373, the other way around with OE.

This all means more Keys, Sensors, Motors, Relays can be accommodated. By Multiplexing Matrix even more can be achieved. You can also expand Analog Inputs using Analog Multiplexers. Try CD4051 or even FETs.