Testers or Instruments Electronic Circuits, beginning with Q-R

Tester or Instrumentation Circuits, Page 11
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Last Updated on: Friday, March 12, 2010 12:07 PM

Circuits Designed by Dave Johnson, P.E. :

RS232 Data Bus Status Indicator
This circuit indicates TXD and RXD activity. The thresholds are set at plus 3 volts and minus 3 volts. (added 12/04)

RS232 Serial Interface Status Indicator
I designed this circuit many years ago and have used it several times since. It uses a single logic IC to indicate the TXD and RXD line activity of a typical RS-232 serial data communications link. The thresholds are set at plus 3 volts and minus 3 volts. Two dual color LEDs are used as indicator lights.

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

Quartz Crystal Test Circuits - (electronic design added 6/07)

Quickly estimate an Electronic System's cooling requirements - 05/12/05 EDN-Design Ideas: Evaluate fan capacity versus thermal load.....(design idea added 10/05)

Quickly find PC board shorts with low cost tracer technique - 11/25/04 EDN-Design Ideas: A predominant failure mechanism for production pc boards is shorted traces. Finding hidden shorts is often time-consuming and frustrating. Typical techniques of cutting traces, lifting pads, and "blowing" shorts are, at best, questionable because they may affect the reliability of the circuit, and the ever-decreasing geometries and lower voltage ICs make these practices tricky and risky.....(design idea added

Radar Speedometer - This circuit is a Digital Radar Speedometer. It allows us to evaluate the speed of any object moving, especially cars and other vehicles. The speed is calculated in kilometers per hour (KPH). Its display has three digits. This radar works with the laser reflexion. It sends laser radiation to the object and this object reflects the laser radiation ….(circuit design added 08/08)

Radiation Design Test Data for Advanced CMOS Product - National Semiconductor Application Note (app note added 2/06)

Radio Spectrum Monitor - This is an experimental project to analyze radio band in FFT. (added 6/06)

Rain Detector (Aaron Cake) - This circuit uses a sensor made of a small piece of etched PC board and a simple SCR circuit to detect rain and sound a buzzer. The SCR could also be used to activate a relay, turn on a lamp, or send a signal to a security system. (circuit / design added 8/03)

Rainbow LED indicates voltage with color - 12/07/04 EDN-Design Ideas: Meters that indicate analog levels via a moving-pointer meter, a numeric display, or a column of LEDs typically occupy considerable panel area and require more than a casual glance to read. An indicator lamp or LED takes little space but indicates only an on or off condition. However, an unobtrusive LED that changes color as a function of a measured value would enable an observer to easily asse.....(design idea added 1/05)

Ramp Generator - (schematic added 8/03)

RCA WA-44C AF sine/square wave generator manual w/schematic - (design added 07/07/07)

RCA WV-510A "Master VoltOhmyst" manual w/schematic - (circuit design added 07/07/07)

RCA WV-98A "Senior VoltOhmyst" manual w/schematic - (circuit design added 07/07/07)

RCA WV-98C "Senior VoltOhmyst" manual w/schematic - (circuit design added 07/07/07)

Real world power tests model FPGA’s thermal characteristics - 04/12/07 EDN-Design Ideas: Applying forward bias to parasitic diodes smokes out those pesky thermal parameters.....(design idea added 9/08)

Reference Board Design ADE7755 - ADE7755 Analog Devices Application Notes (app note added 6/06) In Gerber Format

Reference Board Design in Gerber Format AD7751 - AD7751 Analog Devices Application Notes (app note added 6/06)

Regulator Monitors Its Input Voltage - 09/12/97 EDN-Design Ideas: (design idea added 6/06)

Remote Control Transmitter - Although ready-made remote controls are easy to get, with this project we show how to build on at home. Features are impressive, with 6 radio channels and long battery life. Complete with PCB layout. (electronic design added 6/07)

Remote control using telephone - Here is a tele-remote circuit which enables switching "on" and "off" of appliances through Telephone lines. The circuit described here can be used to switch up to nine appliances (corresponding to the digits1 through 9 of DTMF the Telephone key-pad). The Telephone can be used to switch ....(added 5/02)

Remote Humidity Sensor needs no Battery - 04/04/02 EDN-Design Ideas: Using ac-line power sources and batteries for remote humidity sensors is undesirable because these sources can be troublesome if you mount them in inaccessible points, such as smokestacks, cold-storage chambers, or darkrooms, where maintenance is difficult.....(design idea added 1/05)

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