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Constant Current Circuits

#'s - C       DQ      R - S
 

Last Updated: November 21, 2017 05:45 AM

Circuits Designed by Dave Johnson, P.E.

 

Test UL Ground ResistanceUL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.   This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001

Tests UL Ground ResistanceUL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.  This resistance must be tested with actual line current in excess or 10 amps.  The circuit shown uses a couple of LEDs to indicate if in fact the resistance is less than 0.1ohmsmodified on july 10, 2006 . . . Hobby Circuit designed by Dave Johnson P.E.-April, 2001

UL Ground Resistance TesterUL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.   This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001


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Reduced Power Infra-Red Diode Driver -  Infra-Red LEDs can be used as continuously operating beams of light.  Sensing a break in the path of light between the source and a photodiode receiver is often used in safety and alarm systems.  To extend the run-time of the light source, the diode conducts the minimum current necessary, in this case 10mA.  Controlling the duty __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Shunt Constant Current Source -  This extremely simple circuit works well and may be just the thing in certain situations.  Output current is approximately 600mV divided by R2. __ Designed by Andrew R. Morris

Signal Sources Conditioners & Powerry -  AN98 Eighteen circuits are presented in this compilation.  Signal sources include a voltage controlled current source, an amplitude/frequency stabilized sine wave oscillator, a versatile, 0V to 50V wideband level shift and four sub-nanosecond pulse generators with risetimes as low as 20ps.  Five signal conditioners appear; a unique, __ Linear Technology/Analog Devices

Simple Circuit Dual Constant-Current Load Tests Low-Current Power Supplies -  06/21/07  EDN-Design Ideas You can use a simple 9V-battery-powered constant-current load to test small power supplies at various loads__ Circuit Design by John S Lo Giudice, STMicroelectronics, Schaumburg, IL

Simple Circuit LED Constant Current Lighting -  There is a lot of effort going on to improve the technology of LED (Light Emitting Diode) lighting. The reason is that LEDs are much more efficient than standard incandescent or CFL light bulbs.  They also last longer than either of the alternatives and don’t have issues with disposal like CFL bulbs.  LED lighting has a lot going for it except one thing. It is still pretty expensive __ Designed by Gary C. Sutcliffe

Simple Circuit LED Constant Current Source -  Chip manufacturers are always coming up with ever more sophisticated constant current driver chips for LEDs.  We have included this design for those of you who prefer a more cheap and cheerful solutionmust register on this site __ Designed by Published in Elecktor July/Augu, 2010

Simple Circuit provides Motor feed control -  07/25/02 EDN-Design Ideas Linear power driver works from single supplyBecause we needed a small grinding machine, we modified an old milling machine that lacked a control system.  The table of the grinding machine needed only to move back and forth with__ Circuit Design by Jean-Bernard Guiot

Simple Circuit Variable Voltage Source -  The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency.  For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage.  The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1ohm) equalizing resistors (1volt at 10 amps) , so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage __ Designed by Bill Bowden

Simple Constant Current Source -  This simple constant current source uses an LM317 regulator IC.  N.  B.  The pin-outs of the IC are not a mistake, the output is taken from the adjustment pin.  I found this circuit to charge all my NiCad batteries, and I use a Kambrook mechanical light-timer (or equiv.) for 110vac to time the charge __ Designed by John Nooyen

Switchmode Constant Current Source -  Operating a stepper motor using a fixed (constant) voltage supply results in poor torque at high speeds.  In fact, stepper motors tend to stall at fairly low speeds under such conditions.  Several approaches can be used to overcome this problem, one of which is to use a constant current supply in place of the more __

Test UL Ground Resistance -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.   This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001

Tests UL Ground Resistance -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.  This resistance must be tested with actual line current in excess or 10 amps.  The circuit shown uses a couple of LEDs to indicate if in fact the resistance is less than 0.1ohmsmodified on july 10, 2006 . . . Hobby Circuit designed by Dave Johnson P.E.-April, 2001

Thermally Controlled NiCad Charger -  A voltage controlled current (maximum of 1A) is used to charge a NiCd battery.  The control voltage is derived from the temperature difference between the battery and the ambient air.  The charge current is reduced as the battery heats up. __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Three-transistor current source covers wide range -  05/31/14  EDN-Design Ideas This Design Idea is a two-wire current regulator that strikes a good balance between performance and parts count.  Employing three transistors, three resistors, and one LED, it achieves good regulation   (better than 1% over most of the voltage range), lower operating voltage   (1.2V typical), and better tempco   (0.07%/K) than other circuits of similar complexity.  It is designed to operate in a range of currents from tens of milliamperes to several amps.  It does not use any hard to find parts; for example: an LM10 can be used to make an even higher performance circuit, but this IC is not multi-sourced and is likely to be discontinued.  __ Circuit Design by Einar Abell0

Two Terminal 1A Current Source -  The LT3080 linear regulator can easily be configured as a two terminal current source __ Linear Technology/Analog Devices App Note, Mar 24th 2010

Two Terminal 3A Current Source -  The LT3083 is a 3A low dropout linear regulator that can be paralleled to increase output current or spread heat on surface mounted boards.  Architected as a precision current source and voltage follower, this new regulator finds use in many applications requiring high current, adjustability to zero, and no heat sink.  The device __ Linear Technology/Analog Devices App Note, Mar 9th 2011

Two Terminal 500mA Current Source -  The LT3085 linear regulator can easily be configured as a two terminal current source __ Linear Technology/Analog Devices App Note, Mar 24th 2010

Two Terminal Current Regulator (LT1635) -  The LT1635 combines an op amp with a 200mV reference.  Scaling this reference voltage to a potential across resistor R3 forces a controlled amount of current to flow from the +terminal to the –terminal.  Power is taken from the loop. __ Linear Technology/Analog Devices App Note, Mar 31, 2010

Two Terminal Current Source -  The opamp buffers the upper potential of a shunt regulator to set a voltage drop on R1 equal to the reference.  The net current to RL is the programmed R1 current plus the quiescent supply current of the opamp passing through the reference. ___ Linear Technology/Analog Devices App Note, Jun 21, 2011

UL Ground Resistance Tester -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.   This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001

Variable Digital LoA - D -  This can also be used as a constant current source. __ Contact: Jameco Electronics

Variable Voltage Source -  The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency.  For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage.  The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1ohm) equalizing resistors (1volt at 10 amps) , so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage __ Designed by Bill Bowden

Voltage Controlled Current Source -  Adding a current sense amplifier in the feedback loop of an adjustable low dropout voltage regulator creates a simple voltage controlled current source.  The range of output current sourced by the circuit is set only by the current capability of the voltage regulator.  The current sense amplifier senses the output current and __ Linear Technology/Analog Devices App Note, Mar 31, 2010

Voltage Controlled Current Source with Ground Referred Input & Output -  A flying capacitor device such as the LTC1043 can produce a precision voltage differential over a wide common mode range.  Here it converts a ground referred input voltage directly to a differential voltage across a fixed resistor which then forces a precise current sourced at the circuit output. __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Zener oscillators -  These two circuits are interesting from an academic point of view.  Their practical implementation is rather critical and it is not easy to get steady operation.  Circuit (a) requires a "cooked" zener: connect it first to a constant current generator, then increase the current __


Constant Current Circuits:  #'s - C       DQ      R - S


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