## eCircuit Center – Spice Schematics

“The goal is a site where the learning of electronics is hands-on and fun. And the SPICE circuit simulator is a great software tool to achieve that goal. It hit me the first time I used SPICE – simulating is fun! And because it’s easy to use, I’ve spent a lot of time building and exploring circuits.” – Rick

eCircuit Center – Spice Schematics

SPICE is capable of performing both AC (frequency) Analysis and Transient (time) Analysis. SPICE also performs a number of other analyses like DC, Sensitivity, Noise and Distortion.

SPICE Basics, SPICE Commands, Circuit Collection

“At the core of the function generator is a triangle wave generator. How do you generate a triangle wave? The most common way is to get a capacitor and then alternate charging it and discharging it. But how to you get a nice linear ramp across the capacitor?”

Triangle and Square-Wave Generator

Simulation Circuit Examples –

• Programmable Gain Amplifier (PGA) Op Amp
• Single-Supply AC Inverting Amplifier
• Instrumentation Amp (3 Op Amp)
• Sensor Bridge with Current Bias
• The PID Controller
• Pulse Width Modulation
• Precision Half-Wave Rectifier

## Learn Digital Logic Gates Operation

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.

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

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.

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.

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.