Questions tagged [constant-current]

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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66 views

Create specific resistances across a constant current source

I'd like to emulate the controls on a garage door circuit programmatically. As far as I can tell the circuit acts like a constant current source and sends out 10mA to the wall console. I'd like the ...
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63 views

Question on LED usage for constant current LED driver

I am a beginning electronics hobbyist interested in robotics, who started about ~1,5 year ago, and with much to learn. I've got a question on using a constant current PMIC on a PCB project that I am ...
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Designing a PID control with plant controlled using relays

I am working on a project to design a Controlled (Constant Current) DC Battery Charger. The charger has a variable transformer (Plant). The output of which is fed to the batteries to charge them via a ...
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57 views

(ARC WELDING) Why does voltage DROP with increasing current?

I hope I'm asking in the right place! I worked with automated TIG (GTAW) welding equipment. I'm confused about how the welding power supply controls the current applied through the work piece. If the ...
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2answers
127 views

Is it better to use discrete components or voltage regulators for a variable power supply? [duplicate]

I'm a recent graduate EE student and this is my attempt to gain experience and strengthen my resume so I'm eager to figure this out. I'm designing a dual channel floating output bench power supply ...
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112 views

Calculate voltage drop across Linear MOSFET in saturation region

Considering the below schematic, how is the voltage drop across the MOSFET calculated when it is operated in the saturation region? I am trying to calculate the power dissipated by the MOSFET so that ...
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2answers
104 views

Chrome plating current control

I am an electronics hobbyist and this is my first attempt at an analog circuit of this type. Mostly I stick to arduino and LED stuff or just wiring up kits, etc. This is my first attempt at designing ...
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1answer
32 views

Want to understand the led series/parallel and parallel/Series combination circuit

I'm Working on LED load design circuit which is up-to 64V@1.2A. I thought of giving LED's in series and parallel combination with switches to control the voltage but while searching I found one ...
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25 views

Effect of op-amp's input offset voltage on stability of constant current load

I'm designing a simple circuit to have a constant current load with good short term stability. The exact current value is not important, as long as it's stable short-term (10 seconds). R1 is the load -...
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54 views

Inductor as current source

In this schematic for an induction heater, there are two inductors used for current sources. My question is what happens if I increase/decrease the inductance? For example, what would happen if I ...
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1answer
38 views

Can I parallel two constant-current power supplies to drive 1 bulb?

I have a piece of historic equipment that HAS to have an incandescent bulb.* The preferred-voltage bulb (64V) is no longer available, so I'm forced to use 32V bulbs. This one wants 8.4 amps at full ...
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Circuit for OpAmp-MOSFET based constant current source for 0.2 - 1.5A

I'm a beginner in electronic circuit design and have designed my first Voltage based constant current source using OpAmp driven MOSFET (based on this). The intended current output needs to be ...
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74 views

Can the voltage drop of an LED driven at a constant current be higher than the supply voltage?

So I've been working on a constant current LED driver project, and I've run into a weird situation. I'm driving 3 parallel rows of 8 LEDs in series (Luxeon 2835 color, green) using a Sparkfun picobuck ...
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55 views

Fixed current source

Thank you for reading this question and forgive me if I sound naive. I am working with a device that uses 4-20mA as set-point, I need 3 fixed values to work with this device: (4mA, 12mA, 20mA) The ...
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55 views

What's the best way to control DC current in a circuit from 1mA-20mA at 15-30V input with a microcontroller?

I’m trying to create a circuit for iontophoresis that I can control the current of with a raspberry pi or eventually a microcontroller. What would be the best way to control the current? ...
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1answer
53 views

LM317 adjustable constant current source - Why is the voltage between Output and Adj pins is not always 1.25V?

I am trying to create an adjustable constant current circuit using LM317 to drive LEDs of different colors. More specifically, I want the brightness of the LEDs to be the same, therefore, the ...
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34 views

Current decreasing while measuring the current through a constant current source resistor

My Circuit : The above is my circuit. The Forward drop of LEDs is typically 2.8V and a maximum of 3.15V. I designed the current through the string to be around 21mA, so the emitter resistor is ...
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51 views

Yet another constant current LED driver design, almost

I am about to design a constant current LED driver, with the following requirements: The LED string is fed with 24 V The FPGA interface is 3.3 V The system consist of 8 LEDs in a row, with ...
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38 views

Problem with wide voltage range CC sinking

I want to sink ~10 mA of constant current at wide range of voltages even lower voltages like 10 mV, below circuit suggested to me in one of my older questions: simulate this circuit – Schematic ...
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2answers
29 views

Constant-current driving with LED Driver and Boost DC/DC converter

Novice here, sorry if I'm missing something obvious. I'm trying to drive 4 strips of 6 low-power RGB LEDs each (APF3236LSEEZGKQBKC) on a 3.3V battery. I have a 12-channel LED Driver (TLC6C5912) which ...
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1answer
37 views

Understanding the application of a switching regulator as a constant current LED driver

There is an application note from ON-semiconductors which provides a few diagrams to use a well known MC34063 switching regulator as LED driver. it's around the idea of setting the 1.25v feedback ...
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What are some practical examples of a constant current source?

Please don't state the obvious that nothing is a perfect constant current source. And please do not give examples of how to create them from components. I looked at this SE Q/A which stated the ...
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first order circuits

I solved this circuit for the current in the 3 ohm resistor and I thought that the current would be continuous but it's not. The circuit is first at stable state, then we turn the switch off and the ...
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36 views

Help needed for driving 160 nos - 1.5W RGB SMD LEDs (5074 footprint)

I'm a planted aquarium hobbyist and have been making DIY led lights with 3W LED chips (white and other colour leds in 4 separate channels) driven with meanwell LDD dimmed with arduino. However ...
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2answers
143 views

Building a DeWalt Charging Circuit - Getting out of my depth - Help?

Problem: I'm working on a project that will require a 60V DC (mobile) power source. I'd like to use DeWalt 20V 5Ah batteries to supply this power, 3 in series x 3 in parallel (9 total). Part of ...
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1answer
42 views

Circuit Analysis with constant current and voltage sources

This is a homework question of sorts. I am supposed to find the voltage across AB. I know that the answer is 24 volts by traversing from B to D to C to A adding up voltages of resistors, but should I ...
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1answer
55 views

BJT Constant Current LED Driver - Inverted behavior?

I'm trying to use build a constant current Led driver, using two BJTs (BC338 and BC547). The idea is to be controlled by Arduino's PWM, for dimming. I'm using the circuit bellow. The led is a white ...
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1answer
36 views

Limiting the Current of a Constant Current LED Driver which is Driving a Halogen Bulb

I am powering a 12V, 35W halogen bulb with a MeanWell HLG-100H-20B constant current power supply. The "B" version of this power supply has a really neat dimming control system which lets one control ...
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1answer
119 views

LM317 VS AMS1117 as Constant Current Limiter for LED SMD Boards

i need to design some board like this: each led is SMD 5730 type with current max 150mA in three line and input voltage almost 3.2×7~23V, to create some SMD led board like this: so i have seen this ...
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2answers
58 views

Constant current density

I am reading an article that says ... constant current density of \$−1.0\,\mathrm{A \cdot cm^{-2}}\$ Let's say that I have material that's \$2\,\mathrm{cm^{2}}\$, how would I calculate what's the ...
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171 views

Constant current sink circuit for battery load simulating, microamp current draw

I need to create a constant current sink circuit such that I can simulate current draws from a battery, and analyze the battery behavior. I'll be testing a battery that is 3.1V with 12mAh capacity. I ...
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4answers
50 views

AL8860 Led Driver: inductor placement

I have two questions concerning the placement of the inductor in an led driver circuit using the AL8860 by Diodes Inc.. I'm refering to the typical application circuit below: In their layout ...
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1answer
43 views

L5973 (step down) used in constant current oscillates

For a couple of days i'am playing with a L5973 dc - dc converter whith I want to convert to a constant current driver for 5 or 10W LED's. It kind of works but I get some oscillations in audible range. ...
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1answer
80 views

SMPS Constant Current Source only works with low resistance loads

I'm looking for any advice that can be given to solve this issue. I followed the design idea from here: buck regulator to CC source and it appears to work pretty well until I started raising the load ...
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65 views

Having a non constant current in a constant-current LED driver

I am using the TPS92511 LED driver as follows : It is not on a PCB but a veroboard with wires so it is not a perfect circuit. I have chosen Riadj to 4.9 kΩ which should give me something ...
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2answers
57 views

variation in source votlage is allowed in a constant current circuit?

Reference question: understanding constant current source circuit With respect to the linked question, I am seeing a variation in the load current as I change the voltage \$V_2\$ to and fro from \$...
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1answer
54 views

Opamp Burn up in constant current circuit

I designed a programmable constant current power supply to control two solenoids(electromagnetic).For the solenoid to open and close proportionally(it can move between fully open to fully closed and ...
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2answers
230 views

How to calculate the tolerance of this constant current circuit?

I am using the circuit below to provide constant current to th LEDs. I request your suggestion on how to calculate the tolerance of current (minimum and maximum variation of set current) due to ...
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46 views

Current Sink with OP184

I got a question. I'm building a current sink for a project and below you can see what i came up with. I modified the Linear Tech. circuit (LT1492) because i wanted to have lower Vos. I also added 3 ...
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4answers
104 views

Powering LEDs, dim LED in parallel

I want to build an light fixture for my aquarium and decided to use LEDs, almost everywhere it's suggested to wire the LEDs in series. but that will need a high voltage for many high power LEDs. also ...
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57 views

HowTo create an accurate constant-current dummy load using immersion heaters controlled by Arduino?

Given: variable sized nominal 3.2V LI/LFP battery cells, from little 18650 / 26650 cylindrical A123s up to large prismatics from CALB / Winston etc. the desire to capacity-test them off grid (no ...
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52 views

Setting gain on Improved Howland current source (best practice)

I understand that you can set the gain of an improved Howland by setting the the ratio of resistors \$R_2\$ and \$R_1\$ and/or the value of \$R_{\text{set}}\$. Is it better to leave the ratio of \$...
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1answer
54 views

Howland source, MAX current output?

How would one determine the maximum current output you could achieve from an improved Howland source given a specific Op-Amp? ie. What do I need to look at in the Opamps datasheet? (I am using a ...
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4answers
167 views

What's wrong with this PWM-controlled constant current sink?

T10 gets very hot and starts melting within 30s, even with a heat sink and values way below its rated 15A. Edit: I know it is not a true PWM controlled constant current, but that what I can do with ...
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59 views

Do I need a laser diode driver for this? (noobegginner)

I have a blue laser diode, with max specs of: 2.4w 2.2A 5.2V Currently, im using a ion power bank with a skinned usb wire to power it. The maximum current I measured from it is only 1.4A, and voltage ...
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40 views

Offset Voltage at Op Amp Inverting Terminal

I'm using ADA4350 as a transimpedance amplifier with various gains for feedback paths (30 ohms,3k,300k and 3 mega ohms respectively). When I give a constant current source of about 23mA as input to it,...
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2answers
56 views

Current limiter low voltage drop

I'm trying to understand the function of the constant current regulator CCR and the zener diode 1N5338. I do have more questions but these two components is probably a good start. I understand that a ...
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1answer
89 views

High Power LED Circuit Design & Constant Current Source Question/Feedback

I'm trying to design a dimmable LED circuit board. It's controlled by Arduino with its PWM signals. I'm new to electronics so I have some question regarding my design and knowledge on it. I've ...
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2answers
117 views

26 Led Array Component Identification and Failure Cause

I have the following LED lights. These lights keep failing on me. I'm suspecting that the DPAK(U1) component is failing but I have no clue what it is. The markings on the DPAK reads 5ZYl8GF6D. I'm ...
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111 views

What happens when transistor operates in saturation region for constant current source

I am learning about the constant current sources and I found this video What I dont understand is that, when the forward voltage of the LED is increased from 1.7V to 3.3V, and our Emitter voltage is ...

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