# Tagged Questions

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.

97 views

### Stability of Constant Current circuit

we are developing constant current circuit with "High" current rate, about 3A. We are testing the second prototype, the circuit is this: Behaviour its ok, but we have observed, when we set high ...
45 views

### Battery Charger From DC Motor

So long story short I'm attempting to build a charger for batteries using a DC motor. The batteries I'm planning on charging are old smartphone batteries at 3.7V and 1000mAh. The DC motor that I am ...
49 views

### Question on Current Sensing Resistor in Lead Acid Battery Charger

I was reading several threads on Lead Acid Battery chargers and encountered a circuit diagram given by Russell McMahon here http://electronics.stackexchange.com/a/152641/93631 First of all, I would ...
75 views

### Circuit for Current Injection and Voltage Reading

I am developing a sensor based on the principle of EIT (Electrical Impedance Tomography). For the project, I need to inject into the material I am using, a constant current between two electrodes ...
89 views

### LiFePO4 Constant Current charging circuit with micro controller

I made a small off-grid solar station a few years ago, that was relying on lead acid batteries. I am now planning to change it for a 12v 8Ah LiFePO4 battery, because of it's low weight, space needed, ...
49 views

### Source of DC offset in circuit

I am trying to inject a 1 mA current pulse (10% duty cycle) at a frequency of 10 Hz, across a ball of gel(20 cm in diameter) through rubber electrode pads, using a constant current source (built in ...
129 views

### Capacitor across an ideal current source

How long will the capacitor below charge? Given that both the current source and capacitor are ideal. If someone says the capacitor will be charging up to its capacity, what is the capacity of this ...
33 views

### Universal voltage input using depletion mode N-FET - Advice

In an attempt to idiot proof a device I am designing that needs both 24V DC and 120V AC inputs for logic, I set out to create an input system that could handle either voltage going to a simple 3.3V ...
109 views

### Microcontroller Adjustable 2A 24V Constant Current Source

I need to come up with a method to provide a microcontroller-adjustable, regulated current ranging from 0-2A at ~24V to a load in a closed-loop fashion. I have been researching this issue for awhile ...
50 views

### Commercial 1.5m / 5' LED light fitting parallel LED arrangement

I am reviewing LED light fittings for an industrial premises refit. As with most of the experienced users on this site I like to understand what I'm purchasing and have opened up a sample fitting to ...
60 views

### LED driver circuit with both analog and pwm control

I would like to design an LED driver circuit that allows for simultaneous analog and pwm control. That is, I would like to set the the LED current using an analog signal and then be able to switch ...
45 views

### constant current source circuit 1550e

I am trying to design current source of 20mA for LED 1550e(thorlabs).The circuit designed gives accurate result in proteus simulation that LED is giving a voltage drop of around 1.2V and drawing 20mA ...
88 views

### Constant Current, 1.5 amp, high voltage into variable load [closed]

I need to design a constant current 1.5 A circuit. Input: A 3.3 v, 3 mA, 1.5 millisec pulse. Load: Detonators, with total resistance starting at 80 ohms and increases to 160 ohms in 1.5 ms. ...
256 views

### Is it possible and safe to charge a NiMH battery with this circuit?

I am trying to design a circuit to charge NiMH battery packs from 2.4V to 9.6V and also single cells. From what I have read about charging NiMH batteries, it seems that all that needs to be done is to ...
63 views

### Programmable current laser drive circuit

I'm trying to design a circuit to programmably control the laser drive current from 0-200mA. The current needs to stable (<50uA variation) but with a settling time of <1us (faster if possible). ...
152 views

### 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 ...
236 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 ...
54 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 ...
158 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 ...
229 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 ...
54 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 ...
165 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 ...
77 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 ...
392 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 ...
572 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 ...
81 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 ...
335 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 ...
131 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 ...
98 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 ...
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 (...
128 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 ...
153 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 ...
58 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 ...
98 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 ...
612 views

### LM317 µA Constant Current source possibility?

I want to create an adjustable ÂµA 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 ...
67 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 ...
121 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 ...
289 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. ...
104 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 ...
68 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 "...
385 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 ...
89 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 ...
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 ...
398 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 ...
267 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 ...
83 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 ...
342 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, ...
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. ...