Testers or Instruments Electronic Circuits, beginning with Q-R


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Tester or Instrumentation Circuits, Page 22
Testers: #'s A-B C D E F-G H-K L M-O P Q-R S T V-Z
Last Updated on: Friday, August 29, 2008 02:34 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 schematics, circuits, designs or diagrams for engineers, hobbyists, students & inventors:

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

Quickly find PC board shorts with Low cost tracer technique: 11/25/04 EDN Design Ideas / (added 1/05) 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.

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)

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 / (added 6/06)

Remote Control Tester: (electronic circuit added 10/05)

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 on or switch off the appliances also while being used for normal conversation. (added 5/02)

Remote humidity sensor needs no Battery: 04/04/02 EDN Design Ideas / (added 1/05) 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 and inconvenient. Figure 1 shows a simple way to remove the power source from the humidity-sensor circuit. ...

Remote Monitoring System Sends E-mail via SMS: App Note 3297: Maxim IC (application note added6/06)

Resistance, DC Current, AC Current, Frequency and Period Measurement Errors in DMMs (5988-5512EN): Aligent Application Note (added 4/08)

Testers Next Q-R's

Testers: #'s A-B C D E F-G H-K L M-O P Q-R S T V-Z