Questions regarding Constant Current supplies, devices and applications. As opposed to Constant Voltage supplies. Voltage will vary while Current remains the same. Common in LED lighting applications.

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Two LM317 Based Voltage and Constant Current Regulator Circuit

I have read some articles on on the following circuit. I was wondering if I can create such a Voltage and Constant Current Regulator for my Power Supply or not. My Question is - is this circuit ...
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0answers
25 views

Can I connect the current sink pins of a linear LED driver?

I am designing a little battery powered LED necklace/button kind of device, which has a matrix of 42 LEDs. Each column of the matrix is driven by one CAT4002A to achieve a defined current and to allow ...
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4answers
145 views

How to limit current to LEDs

I have understood that this is a bad way to do it: Since some LED can draw more current than others. So lets say I would power some high powered LEDs, like say 10 x 3W LED with a DC forward ...
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1answer
48 views

Less noise when not following LED Driver datasheet

I designed a board which uses a LED driver (datasheet). It clearly states, DO NOT connect DIM- to Vin-: However, these are the waveforms I get on Analog DIM pin when they are disconnected, and ...
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2answers
127 views

Why do the inputs of this CC circuit op-amp need clamping?

I'm studying the constant current circuit of the HP E3610A DC Bench Power Supply. I'm building a supply of similar topology using surface mount components and the LF442 isn't available in a SOIC-8 ...
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0answers
9 views

Tradeoffs and solutions between low current transient responce and max. current in a lab power supply

Consider a CC/CV power supply implemented in a topology like the one in How to improve current control loop in power supply? Let's say it's designed for a high maximum current (like 5A) and includes ...
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0answers
53 views

Why has my constant current driver no voltage output?

I am trying to build a lamp from a 300mA/max. 20V constant current driver (the one left over from here) and two 350mA, 15-17V white LEDs. When I do not connect anything to the driver, I can measure ...
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0answers
35 views

simulation constant current discharge battery

Based on this topic: Constant current battery discharge I made a constant current discharge circuit in ltspice. But I can not see that the voltage drops from the battery, and that is the whole idea. ...
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1answer
155 views

Digitally-controlled 0-10A constant current source for driving LEDs

I'm looking to build a circuit to drive single high-power LEDs. The circuit will be controlled from a series of TTL pins: one for enable/disable, and ~4-6 to set brightness via current. The LEDs ...
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1answer
34 views

Cascading WS2803 LED drivers, each with different output current

I've decided on using WS2803 PWM constant current LED drivers. I'd like to cascade two of them and use the first one for 15mA output and the second one for 20mA output (each chip for driving different ...
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3answers
96 views

Is it OK to PWM a current source?

I want to control power RGB LEDs, for efficiency and safety they are better to be driven by a current source. I can use either linear or buck converters. I made a linear current source using ...
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3answers
67 views

Adding a dimming knob to a step up power supply

I am a ME student with little EE knowledge, and I currently have a setup which includes a 12V SLA battery, a 100W LED chip and a constant-current constant-voltage step up converter. The board can be ...
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5answers
270 views

Testing Chinese CR2032 Li-ion Battery Capacity

I recently bought a lot of cheap CR2032 batteries from aliexpress. Since there is no manufacturer stated on the package or the batteries, I would like to know if these batteries really have 220 mAh or ...
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2answers
252 views

AC constant-current source design

I want to provide a fairly constant current (say 10mA RMS, peak 20mA, of 60Hz AC, using a 120V supply) to a load of highly variable resistance. It doesn't have to be super-clean or precise, but ...
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1answer
57 views

Stabilising a constant current load opamp feedback loop

I designed a constant current load around the ACS712 Hall-effect current sensor (module from eBay). This module gives a voltage output of 185mV/A superimposed on VCC/2. Its current range is +-5A altho ...
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5answers
195 views

How to remove spikes from switching transistor?

I am building a steady current source which delivers steady current (0-20mA) to an LED. The brightness of the LED (current) is controlled through a potentiometer's voltage and a voltage follower as ...
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1answer
94 views

Constant Current Load ampere measurement

I have the following circuit that I am building, a constant current load): I am using a 9 volt battery and a 1.5 volt battery to power the circuit. My load under test is a AA battery. Based on this ...
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2answers
72 views

BSS138 mosfet not for level shifting

i want to build a constant current source to drive an LED like the one in the image below. I want to use a BSS138 N-mosfet transistor which is mainly used in logic level shifting. My question is if i ...
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2answers
1k views

What is the dual of a diode?

A diode has an exponential I-V curve. To a first approximation, it will pass whatever amount of current is required to keep the voltage across it constant. Is there a passive component that will ...
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2answers
105 views

Mixed forward voltage LEDs in series with constant current driver

I've been looking for answers for a few weeks, so now I'll actually voice my question! My plan is to power 109 LEDs in series off of one constant current driver. The goal is to create supplemental ...
6
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2answers
134 views

Probing with Oscilloscope Stops ADC Fluctuation

I've gone back to my constant current project to fix an annoying fluctuation in the required current display. See schematics below. The entire circuit consists of a CCS section with signal outs for ...
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1answer
48 views

Constant Current IC Driving a String of ICs

I have been having difficulty wrapping my head around the ideas of constant current and constant voltage. Basically I have assembled this circuit with an arduino. Now, imagine that I wanted to ...
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1answer
83 views

Multiple TLC5940s on PCB “dropping out” when many outputs turned on

I've designed a PCB to connect 12 TLC5940s to an 8x8x8 RGB LED cube through 3 64-pin headers, which I will include screenshots of below. I have a separate board for controlling the anodes for ...
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3answers
433 views

LM317 µA Constant Current source possibility?

I want to create an adjustable µA Constant Current source using a LM317. It is typically stated to have a 5mA to 10mA minimum current for proper regulation. The On-Semi version linked above shows a ...
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1answer
64 views

Buck controller MOSFET drive voltage

I am trying to design a switching regulator for LEDs, which uses the LM3405 as controller. This IC uses the BOOST pin to power the internal MOSFET driver, which controls an internal MOSFET. There are ...
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1answer
82 views

How to programme constant current of a LED Driver for various current levels?

I need to design a backlight unit that will change its duty cycle and constant LED current via a microcontroller. My supply is a SMPS with 12V - 20A output. I need to drive 16 * 16 = 256 LEDs(seperate ...
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2answers
151 views

Charging lead acid battery using boost/buck converter

I plan on permanently connecting a 12v lead acid battery to my home made wind turbine (dc). I already have a dc-dc buck/boost converter so I wonder if i can use that to charge the battery. ...
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1answer
97 views

Automatic switching of a constant current circuit

I'm running 14 ~3W (700mA) LEDs in series on a constant current LED Driver that handles between 36-65V output. The driver runs the LEDs at 600mA. The heatsinks I've attached are pretty small, and if ...
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1answer
43 views

Adjust the power of laser diode on both CW and pulsed mode

I am working on my graduation project to build a laser unit, i am supposed to control the power of laser diode when operating in pulsed mode and continuous mode. firstly, i had the pulses from ...
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1answer
270 views

How do I build the current regulator circuit referred to on the LM337 datasheet?

What I would like to accomplish: I am trying to add current regulators into a home built dual rail linear regulated power supply. I previously asked this question about transformer fusing and ...
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0answers
83 views

Constant current source - unexplained issues

I have been puzzling over this for days now, and cannot for the life of me figure it out... I have a constant current source set up to use as an analog dimmer for my LM3429 LED driver. I have made ...
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1answer
138 views

Is there a way to get dc out of a capacitor? [closed]

The voltage and current during discharge of a capacitor is describe with an e function. I assume that thus a separate component is necessary (since ...
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2answers
314 views

constant current source circuit

I am designing a constant current source(35mA) circuit using transistor.Thought of usingthis below circuit but the problem with that is my resistance R is fixed( 2.3 ohm ) which I could not change due ...
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1answer
148 views

How do “Inverter” or “IGBT” welders control CC and CV output?

I have a question on welding units. A lot of the newer units these days have "Dependable Fairchild or Infineon IGBT (non module)", "MOSFET design for Hobby use" and I can't tell if all of this stuff ...
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0answers
67 views

Designing Buck Converter with Adjustable Output Current and Output Voltage

I am currently attempting to design a buck converter where both the output current and output voltage can be simultaneously adjusted. I will be utilizing an Arduino for control. I figured some sort of ...
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2answers
221 views

How can I make a Fuse Blown Indication LED circuit with variable voltage input?

I'm creating a power supply with an input fuse and and output fuse, and I'd like to have blown fuse indicators. However, the circuits I have found typically have set voltages and thus set resistors, ...
2
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1answer
73 views

Mirroring constant current

I'm trying to draw a constant 60mA from a battery but I get a draw that is too high with the following setup. Does anyone know what I'm doing wrong? Regards EDIT: Sorry I added the wrong measures. ...
4
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2answers
121 views

Why sample current via lopsided resistive divider?

I'm studying the constant-current circuit of the Agilent E3610A 15V 30W DC Bench Power Supply. The entire schematic is at the end of the user manual, but I've redrawn the parts of interest here for ...
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3answers
230 views

High Side Constant Current Source

I am trying to create a constant current source of 100mA to charge a single cell Li-ion battery. I see the LM317 thrown around a lot as a solution, but I'm looking for something that does not require ...
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1answer
75 views

Instrumentation Amplifier output mysteriously increases upon connecting across a resistor, compared to connecting the same voltage directly across it

I am designing a simple resistance measurement circuit. Resistance range is from \$10m\Omega\$ to \$10k\Omega\$ and desired accuracy is 0.1%. The circuit provides constant current to the resistance ...
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2answers
171 views

Is it possible to build non-linear resistor using linear potentiometer

I have CAT4101 constant current LED driver and I need to control LED current. My idea is to use microcontroller and digital potentiometer (MCP41010) to control the current. While the potentiometer I ...
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1answer
240 views

7805 for 4-20mA current injector

I'm trying to setup a low cost current injector for testing certain I/O modules. I found a rather simple design for a current source using 7805. simulate this circuit – Schematic created ...
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1answer
213 views

MOSFET as constant current source?

This circuit is being called a constant current source, how can this be? Since the gate and the source are both connected together their isn't a potential difference between them. Doesn't' this mean ...
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1answer
62 views

Advice on driving the DRL leds

I'm going to be using 2 sets of three 12v 9W leds, purchased from that well known auction site so that's all the info I have, as daylight running lights. Obviously I could simply connect them up (in ...
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1answer
170 views

LED constant current driver

I need a constant current of 400-500mA for each color of a 10W rgb LED. Each color consists of 3 1W chip is series. for 3 LEDs in series I'll need about 11 Volts for blue and 8 volts for green. So far ...
2
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2answers
181 views

Puzzled with the result of LM317 constant current

So, LM317 can be used as a constant current regulator by adjusting the voltage in the Adj pin. The internal voltage reference is 1.25V, and so using a 1.25/0.900 ~= ...
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0answers
100 views

Overcharging LiPo with current source

What would happen if I charge a LiPo battery with a constant current source? I know that properly it should be charged constant-current until 4.2V and then constant-voltage mode, but what if I just ...
3
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1answer
117 views

Multiple power supplies in home-made circuit

I'm planning to build an ebb-and-flow hydroponic system (nope, not for weed) and as my electronics skills are close to zero, I'm trying to put things together before soldering anything. I'm a decent ...
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1answer
204 views

LM317 constant current load

Would this work as a constant current load since I don't have a high power pot? Is there a better way to do it? simulate this circuit – Schematic created using CircuitLab
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1answer
71 views

TPS40211 PWM LED driver topology

I've recently been trying to figure out an LED driver circuit for my 32V, 0.7A CoB emitter. I settled on the TPS40211, since it ticked all the boxed in terms of input voltage range, output, etc. I ...