74HC14 inductance meter

191

01:43:04

If anyone know how to do it as properly work version in EveryCircuit please HELP ME.
Simple circuit for inductance meassure. But I can't setting this for properly work of relaxation oscillator like in the HC14 datasheet. How to do emulate of Schmitt trigger... Also I see RC filter doesn't work properly (all the time voltage going UP !(???)
===========================
Normal it work: about 260 kHZ signal from relaxation oscillator separated and formed by second gate. Sawtooth signal going on the 3rd gate and otput 3rd gate forming square (from possitive peak of coil) with over 90% plus duty. Last gate reverse phase signal from 3rd gate we have square with less than 10% duty. At the end RC fiter get the average voltage from square vawe of 4th gate and precission is here 10mV/1uH. Voltage level is proportional to inductance. Range from 500 nH to 50uH
=============================
THANKS TO GREAT hurz HELP who helped build the schmitt trigger and explaining the rules he wrote:
=============================
Schmitt trigger gate model surrounded by switches 3 gates and some resistors to emulate a single 74HC14 gate
Hysteresis is about 1V like the original on according to Philips spec. This is to any timing/frequency calculation very important.
Input resistance is 10MOhm which should be for most cases high enough.

Since EC and its propagation delay, keep an eye on delay parameter to get it right for your simulation speed!
=========================

published 6 years ago

hurz

6 years ago

Unfortunately everycircuit does not provide schmitt trigger behaviour as option, and since propagation delay was implemented its not easy to adapt gates to your need, anyway check this as workaround but it needs 3 gates to simulate a single 74HC14 gate ! http://everycircuit.com/circuit/6520088709824512

hurz

6 years ago

To the RC filter, let the pulse be 5% on and 95% off what is the voltage you expect in average for 5V HC logic gates? 5%, right? 1% is 50mV and 5% is 250mV and this takes some time from zero volt. 34kOhm × 100nF × 4 = about 13ms (4 tau to get it stable) 13ms at a periode of 260kHz takes more then 3500 cycles to simulate. You need a lot of time to see a final result. Built it, test it and see what it does in reality. Simulation in transient mode cant help you for any problems.

wegi1

6 years ago

Next time kindly thanks to you for valuable help. This fine emulator with support of community is fantastic ! I'd build this circuit. https://easyeda.com/wegi1/Arduino_shield_L_meter-246969ce713941938d50377ced4407c3 As arduino shield. Working fine, I want check this on simulation.

wegi1

6 years ago

added Schmitt trigger after hurz help - thanks again

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.