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Tag Archives: Digital-Design

Two Stage Sequential Timer Docs

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The circuit is a two stage sequential timer with auto reset. It can turn a Solenoid On/Off after a Sequence of delays that are preset. This is also a basic example of timer usage in automation.

Design Documents

Source Files Orcad Format

All Timers are 1 – 30 Secs Analog with Presets to adjust with a screwdriver. The Switch, Solenoids and Power supply has to be via terminal blocks or plug-jacks. The PCB may be upto six Square Inches for standard DIP components but with SMD it may be smaller.

Block Diagram :

Sequential Timer Specs

The PCB has to be tested to conform with the circuit, this has to be Meticulous. The Circuit is for the Battery and Solenoid Specified and will have to be modified if battery and solenoid are different. D1 to D4 can be replaced by a 300V 3A Bridge Rectifier Module. F1 fuse could be 2A – 3A Slow Blow depends on Solenoid inrush current. Presets can be with some graduations if possible for ease of adjustments. LED resistors can be a bit lower if more brightness is required.

Learn Digital Logic Gates Operation

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The Gate is a digital component that is used to compute an output for certain inputs, the inputs and outputs have two states high-1 and low- 0. Let us assume high is 5V and low is 0V (like in CMOS). On a high level the LED will light up and on a low level the LED is off. Now let us see what Logic means.

Learn Digital Logic Gates Operation

Th pages listed belwow requires images and javascript to be enabled to try out the demos of the gates.

 

Digital Logic Gates

Gates are what make many of ICs, the two popular families are the 40xx CMOS and the 74xx TTL . Now 40xx come in 74HCT40xx flavors which approach the quality of an ideal gate. Entire circuits with Gates can also be also be burnt into PLDs, FPGAs and CPLDs just like you burn your CDROM. Gates can also be implemented in assembly language which a microcontroller like 8051 will understand and execute.

Hardware gate circuit will operate in real time, nano seconds delay will be there due to propagation delay, gate capacitance and FET switching times etc. Software or microcontroller gates code working will depend on both propagation delay and the CPU clock speed.

Gates can be combined to make combinational or sequential logic circuits. combinational circuits are a complex network of gates interconnected to evaluate a pattern of output for patterns of input. Sequential circuits use memory elements hence output patterns depend both on input patterns and the memory of history of events. An example of combinational logic circuit is a seven segment display decoder CD4511 and and example for a sequential logic circuit is CD4029 up-down counter.

The CD40xx CMOS family can work at even 3V-9V-12V DC and consume low power. The speed is not as fast as 74xx TTL family. It is good for simple portable battery powered circuits. The 74HCTxx series is good for low power and high speed but will work at 5V. When you have problems interfacing CMOS and TTL use 74HCTxx family.

Three Point Preset Counter

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This is a prototype of a Preset Counter. It is built with ICM7217. The cabinet is ABS Plastic DIN 96-96. The Panel is Engraved on Acrylic.

I don’t remember for which application it was used. It has three thumbwheel settings, when the proximity switch counts upto the set-value, the corresponding relay turns ON, with a State Indicating LED on front panel.

Three Point Preset Counter

These can be configured sequentially or to work synchronously, this depends on what customer wants. Both modes may give the same result. In sequential operation, Some of these counters-timers may need to wait for an external trigger or feedback from a limit switch or another process like pressure alarm. Then more Input options may have to be provided.

Basic Electronic Digital Circuits

Counters, timers, analog-process and its interconnectivity makes up the various process loops or chain-reactions in Machine control. The various types of sensors for measurement and feedback of analog and event parameters, monitor the mechanical system and communicate the data to the process instruments.

The below circuit is a reference, i used the old intersil hot ideas book. There was no internet then. Databooks were valuable reference material. In the below timer circuit replace the clock with a schmitt trigger signal conditioning, it becomes a event counter or preset counter with thumbwheel input. See photograph above.

ICM7217 Timer and Counter

The Actuators like Drives, Solenoids, Pumps, Valves and Heaters act in accordance to the commands of the control system. This regulates and manages the process or machine to deliver consistent and repeatable yield of the end product.

LED Running lights CD4017

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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.

 

CD4093 Quad NAND Schmitt Trigger

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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.

Basic Analog for Digital Designers

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“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

Conclusion

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.

74HCT373 Octal transparent D-type latches

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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.