• 1 AMP CURRENT INJECTOR
  When you need to measure resistance down to a few micro ohms, this circuit works great. It is powered from two "C" cell batteries and is designed to inject a well-regulated one amp of current into the unknown resistance. By measuring the voltage drop across the resistor with a digital voltmeter, the resistance value can be accurately measured. The circuit also is equipped with a low battery monitor. Published in Popular Electronics, November 1992

• 120vac Under Voltage Tester
  Using a cheap 24vac transformer, this circuit can test a product under low 95vac conditions.  With the components show, it has a rating of 250 watts max.

• 20MHz VCSEL 3mW LASER TEST CIRCUIT
  This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL) that don’t require light output control circuits. The circuit shows how to drive the device from a single high speed CMOS IC. The circuit can easily be modified to transmit signals from kilohertz to about 50MHz.

• 40KHZ LED TEST SIGNAL GENERATOR
  This 40KHz crystal controlled oscillator circuit drives an infrared LED with powerful 40ma pulses.  The circuit can be used to test optical communications circuits, designed to receive 40KHz modulated light signals.

$5 junk box circuit determines phase sequence :  04/23/98 EDN-Design Ideas / (added 11/05) [Note:  File contains multiple circuits scroll to find this circuit.]  Have you ever wondered which way a blower motor is going to turn when you plug it into anor socket, or have you ever inherited  task of modifying three-phase wiring in your plant?  circuit in Figure 1 is a simple, approximately $5 phase ...

(9435) PCI Performance Measurements - Concepts and Practical Application:  Agilent Application Note   (app note added 6/06)

µC measures High-frequency signals :  03/02/98 EDN-Design Ideas  / (added 6/06)   

1 GHz Frequency Counter:  Used with transmitters, receivers in VHF/UHF band (16F84, SAB6456) (circuit added 8/06)

10 Hints for Making Better Network Analyzer Measurements:  Aligent App Note  (added 2/06)

10 Hints for using Your Power Supply to Decrease Test Time (5968-6359E):  Learn ten simple ways to improve your testing capabilities with your power supplies and electronic loads. Aligent Application Note (app note added 4/08)

10Hz - 100KHz D.D.S. Function Generator:  (electronic circuit added 05/07)

10Hz - 1300MHz Frequency Meter:  Universal VHF/ UHF frequency meter (circuit added 8/06)

16-Bit ADC Simplifies Current Measurements:  DN341  Design Notes (Linear Technology) (app note added 6/06)

1-Wire Humidity Sensor:  App Note 758: Maxim IC  (application note added6/06)

20MHz High Speed Function Generator:   High Speed Function Generator was published in  professional electronics section of  Aug 1996 issue of Electronics Australia, and has proven to be extremely popular.  kit is no longer available from any of  kit suppliers… (circuit added 8/06)

220 Volt Wiring Detector:  This circuit senses power lines behind walls  (added 9/04)

220/230VAC Input 12VAC Output 100VA Max Halogen Converter:  Fully Assembled and Tested demo board CD including datasheets, application notes and ballast design software Features: Short Circuit and Overload Protection, Fully dimmable with all dimmer types, Compensated Load Regulation, Over temperature shutdown, EMI Filter  (added 3/05)

24-Bit ADC Measures from DC to Daylight:  DN219  Design Notes (Linear Technology) (app note added 6/06)

25 k Volt Generator Tests Insulation:  06/04/98 EDN-Design Ideas  / (added 09/05) To generate high voltages with proper insulation between  "hot node" and  rest of  circuitry, a car ignition coil can function in place of a high-voltage transformer. se coils have voltage ratings of approximately 20 kV, so you can use m to produce voltages around this value. Because you know  turns ratio of  coil, you can make a stable high-voltage source using a well-controlled voltage at  primary side (Figure 1).

250mW HF CW Transmitter:  (circuit / schematic design added 6/06)

3 GHz Divide by 1000 Prescaler:  Converts 0.1

3 Level Audio Power Indicator #2:  Battery-operated Three LED display that connect it to loudspeaker output   (added 5/02)

3 Level Audio Power Indicator:  Battery-operated3 LED display that connect it to loudspeaker output   (added 9/04)

3.3V converter delivers 3W from Li-ION battery :  11/05/98 EDN-Design Ideas  / (added 6/06)   Lithium-ion batteries are rapidly gaining popularity in portable applications because of ir superior energy density, low self-discharge rate, and high cell voltage. When you use one Li-ion battery to power a 3.3V dc/dc converter; however, you encounter a problem, because  battery voltage can be higher or lower than 3.3V. When fully charged, a Li-ion cell has approximately 4.2V output; when fully discharged,  voltage is approximately 2.5V. refore, you cannot use a simple buck or boost topology with a single inductor to generate a regulated 3.3V output. Some designs boost  voltage to approximately 4.3V and n use a low-dropout regulator to produce  3.3V. This approach is inefficient, and efficiency is a crucial consideration in battery-powered applications.  circuit in Figure 1 offers a solution to  problem....

3.3V lithium cell supply requires one inductor:  08/05/99 EDN Design Ideas / (added 6/06) Because of  growing popularity of lithium-ion (Li-ion) batteries and 3.3V power supplies, portable-equipment designers must often create a 3.3V supply that a single Li-ion cell can power.  fact that  output of a Li-ion battery ranges above and below 3.3V during its discharge cycle complicates  design.

30 Meter QRP Transmitter for Morse Code:  (circuit / schematic design added 6/06)

300ma DC-to-AC Converter:  This circuit was used to provide battery backup to a device that had an AC (output) wall transformer. Due to  quasi-sine-wave output and imprecise 60Hz output frequency, some devices might not work properly. Peak output is  DC input voltage minus about 20 ohms drop. Use bigger output MOSFETS for more current output.  Designed by Andrew R. Morris  (added 6/06)

3-digit Volt / Amper Meter:  Based on CA3161, CA3162 ICs (circuit added 8/06)