Control Circuits, Schematics or Electronic Diagrams

Control Circuits

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Last Updated: June 02, 2021 01:44 PM

Circuits Designed by Dave Johnson, P.E.

Freeze AlarmI chose an accurate thermistor from Keystone as the temperature sensor for this circuit. This device has a very specific resistance at a particular temperature. According to the data sheet for the thermistor, the device will have a resistance of 361K at zero degrees C, which is the freezing point of water. The thermistor is wired into a simple bridge circuit, which uses 1% resistors. The bridge is connected to a very low power voltage comparator. The circuit forms a switch circuit, which changes state, when the resistance of the thermistor reaches a certain value. At zero degrees C the voltage at the non-inverting input of the comparator exceedsCircuit Solution by David Johnson P.E.-May, 2006

Freezer Over-Temperature AlarmThis circuit turns on a beeper whenever the inside temperature of a freezer is greater than zero degrees Centigrade. The circuit draws only a few microamps from a 9 volt battery. It uses a glass bead thermistor accurate to 1 degree C.. . . Circuit by Dave Johnson P.E.-November, 2014

Freezing Temperature AlarmThe circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C (32F). A 9v battery powers the circuit. The average 9ua current is so low that the battery should last for many years.. . . Circuit by David Johnson P.E.-November, 2014

Links to electronic circuits, electronic schematics and designs for engineers, hobbyists, students & inventors:

Four-Watt AF Amplifer - I have recently included a page about AF amplifers for use with Homebrew rigs. In this I mentioned that I may include a practical one-watt circuit, complete with PCB foil and layout. Here it is, but I have taken the liberty of engineering it to provide 4-watts of AF output and with a frequency response almost suitable for Hi-Fi applications __ Designed by Harry Lythall-SM0VPO

Four-way remote control uses series transmission - 01/18/01 EDN-Design Ideas A simultaneous fourway remote-control system adheres to size, cost, and reduced-complexity constraints and uses a series transmission to drive parallel loads (Figure 1). You can use. PDF has several circuits, scroll down. Design by JM Terrade, Clermont-Ferrand, France

FOXBOX Transmitter Controller - This FOX-BOX is based on a single CMOS 555 timer and uses an ISD1000 chip to store the transmit ID. __ Designed by Joe Leggio WB2HOL

FPGA Memory Controller Links Embedded µP to Cache-Enhanced DRA - 01/19/95 EDN-Design Ideas DRAM chips often lack the performance that embedded systems require. Also, SRAM takes up too much space and is too expensive for any application using over 1 Mbyte of memory. But designers have another option: a memory built with DRAM enhanced with an on- Design by James Joseph and Charles Brown, Ramtron International Corp, Intel Corp

Freeze Alarm - I chose an accurate thermistor from Keystone as the temperature sensor for this circuit. This device has a very specific resistance at a particular temperature. According to the data sheet for the thermistor, the device will have a resistance of 361K at zero degrees C, which is the freezing point of water. The thermistor is wired into a simple bridge circuit, which uses 1% resistors. The bridge is connected to a very low power voltage comparator. The circuit forms a switch circuit, which changes state, when the resistance of the thermistor reaches a certain value. At zero degrees C the voltage at the non-inverting input of the comparator exceedsCircuit Solution by David Johnson P.E.-May, 2006

Freezer Over-Temperature Alarm - This circuit turns on a beeper whenever the inside temperature of a freezer is greater than zero degrees Centigrade. The circuit draws only a few microamps from a 9 volt battery. It uses a glass bead thermistor accurate to 1 degree C.. . . Circuit by Dave Johnson P.E.-November, 2014

Freezing Temperature Alarm - The circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C (32F). A 9v battery powers the circuit. The average 9ua current is so low that the battery should last for many years.. . . Circuit by David Johnson P.E.-November, 2014

Fridge Door Alarm - This fridge door alarm is using a 3V battery supply should be placed (in a small box) in the fridge near the lamp or close to the opening. With the door closed the photo resistor R2 presents a high resistance (>200K) thus clamping IC1 by holding C1 fully charged across R1 and D1. When a beam of light enters from the opening, __ Designed by Popescu Marian

Fridge door Alarm - Beeps if you leave open the door over 20 seconds; 3V battery operation, simple circuitry __ Contact: Flavio Dellepiane, fladello @ tin.it

Fridge door Alarm (2nd Version) - Alternative version of the popular circuit; 3V battery supplyStill operating at 1.3V __ Contact: Flavio Dellepiane, fladello @ tin.it

Fridge Saver - This circuit waits 5 minutes before re-applying the power to a refrigerator to prevent it from having to start up under pressure after a brief power outage. This is highly stressful for the compressor and the thermal cut-out switch built into the compress __ Designed by Andrew R. Morris

Frost Alarm - The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees celsius. A suitable bead type thermistor is found in the Maplin catalogue. The 100k pot allows this circuit to trigger over a wide range of temperatures. A slight amount of hysteresis is provided by inclusion of the 270k resistor. This prevents relay chatter when temperature is near the switching threshold of this circuit __ Designed by Andy Collison

Full bridge for motor control - Before trying to understand a full bridge circuit, you may care to read up on PWM controllers, which page also describes how a half-bridge circuit works. Most full bridge motor controllers also use pwm! Designing a full-bridge PWM circuit that is reliable and 'user-proof' is actually quite difficult! 4QD released our first such controller in 1992: it was probably not the first but was certainly early in the race. __ Designed by Richard Torrens

Full Color USB LED-Controller - Microcontroller : Microchip PIC18F2550 Sensor : DS18S20 temperature sensor Video: Temperature based color control CPU load based color control Screen based color control License: The source code of this work is licensed under a __ Designed by Steffen Schütte

Full-featured Dual Hbridge - Dueal non-shortin H-bridge with brake

Full-Wave Active Rectifier Requires No Diodes - A full-wave rectifier can be built without using any diodes. It exploits the fact that the output voltage of certain single- supply op amps is effectively clamped to ground (0 V) when the input signal goes negative. __ Designed by Anthony H. Smith

Full-wave rectifier has programmable gain - 11/09/00 EDN-Design Ideas The traditional approach to the design of a full-wave rectifier(Figure 1) is to set the gains of IC1 and IC2 to 1 and use the. PDF contains multiple circuits, scroll to find the one of interest Design by Chuck and Chris Wojslaw, Xicor Inc, Milpitas, CA

Fuzzy Set Point Controller-Act - 03/16/95 EDN-Design Ideas This is the third and final installment of our fuzzy design example. We are designing a simple, fuzzy controller that charges a capacitor through a resistor/inductor series combination. The controller senses proportional (P), differential (D), and integral (I) values of the error and processes them with two fuzzy rulebases, one for the P and D terms, Design by David Brubaker, Fuzzy-Logic Contributing Editor

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Control Circuits: #'s - A B - C D - G H - L M - P Q - S T - U V - Z