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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1answer
45 views

200mA constant current @ 6V from 12V battery [on hold]

I have made a digital speedometer with a Hall-effect sensor, but while the battery is discharging, sensor output also changes. I need a circuit that consumes the entire battery capacity, that is, from ...
3
votes
1answer
57 views

Component usage in this constant-current source circuit

In the April 2014 edition of Elektor magazine, they present a circuit for a high-precision current source device (page 42). It allows the user to select a constant-current between 10nA and 20mA. They ...
0
votes
3answers
102 views

how to create a high current source?

I'm looking to observe magnetizing offsets of various current sensors. The idea is that when you pass a high current pulse (close to the rating of the device) through a current sensor and then return ...
0
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1answer
70 views

Constant current LED driver min / max current rating explanation

I currently have a 150-1500mA led driver that I sue to power a 30W LED. Driver has adjustable maximum current pins that I can use to change to match the maximum current. I have it set to 1050mA. I am ...
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votes
1answer
75 views

Back EMF and Source EMF, stabilizing current?

In a circuit where there is change in a magnetic flux, Back EMF is induced. When back EMF is increases it reduces the source EMF( or oppose it) and therefore, the current is reduced, in order to ...
0
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0answers
45 views

3x CAT4101 parallel with CREE LEDs

I've tested the LEDs with one CAT4101 and they work great, but now it's time to dial it up a notch. I've now got three CAT4101's wired up in parallel to give me 3A to drive two 10W CREE LEDs in ...
0
votes
1answer
96 views

Switched-mode constant current supply with Schmitt Trigger

I'm planning on building a small constant current power supply for charging lithium-ion batteries on the go. While they normally use constant current AND constant voltage, I've elected not to include ...
0
votes
2answers
50 views

How can I tell if my current is continuous in a first order DC circuit with a switch

Assuming this circuit has been running for a long time (switch SW1 is closed), and in t=0 the switch (SW1) opens, and I'm being asked about the current that runs through the inductor L1. I know that ...
4
votes
5answers
354 views

Constant current circuit

I'm back for another question, this time shorter than the wall of text I posted last time! Here is my question: How does the red (rot) LED at the input to the base provide a constant current to ...
3
votes
2answers
90 views

Standard current and discharge current

I've been looking into batterie's datasheets and don't understard what 2 of the specifications mean: continuous standard current and maximum continuous discharge current. Could someone explain this to ...
-1
votes
1answer
93 views

Is it possible to increase voltage without changing the current? [closed]

If we have a certain power applied to a circuit, and we would only like to increase the voltage applied by large factors... can this be done? Maybe by increasing only the resistance? Or maybe by ...
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votes
2answers
133 views

Constant current led drivers shared ground

I have 4 constant current led drivers with PWM. Here's 300-1500mA LED Driver datasheet. I want to use 3 of these drivers to power each color of a 90w rgb led. I was under assumption that I could ...
0
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0answers
59 views

Controlling a TLC5927 LED Driver

I am trying to control TLC5927, with no success. I have read the whole datasheet, but I still can't figure it out. I tried to simulate it, with no success too. Can someone draw me a timing diagram ...
0
votes
0answers
104 views

Keeping current constant during PWM dimming of a LED string

simulate this circuit – Schematic created using CircuitLab I'm looking for a good control method for PWM dimming a string of LEDs and keeping the current through the LEDs at a constant ...
0
votes
1answer
50 views

Differences between a LM317AHVT and a LM317T

Is there any practical difference between the LM317AHVT and LM317T vis-a-vis regulating a 900mA, 9-12V LED?
0
votes
1answer
103 views

Constant current driver LED over-voltage effects [duplicate]

I have a 90W RGB led. Voltage range is 32-34V for green and blue but it's 22-24v for red. To what extent does the voltage matter if the current output is limited to let's say 30W (max for single ...
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votes
2answers
90 views

Increasing current [closed]

Here an interesting challenge. You have a 3 volt 50uAh battery. How many would it take to create a device that can supply 3 volts at 1mAH. Would you connect them in parallel or series or a ...
3
votes
4answers
227 views

Ideal constant current source?

I've developing an LED fixture for my aquarium to grow plants. To do so, I've selected several high powered LED's. I'm currently considering driving them with LM317's because I know how to use those ...
0
votes
1answer
82 views

Can I use constant current LED driver as input to Buck regulator?

I have an 100W constant current LED driver that I bought in error but maybe I can use it in another way. I want to use 3 buck regulators to pwm control each individual color of 90W RGB LED. Can I ...
0
votes
1answer
89 views

Is there any benefit of making lamps with high wattage LEDs but low wattage driver circuits other than cost?

Over the past few years I have bought a number of GU10 mains voltage LED bulbs and have generally been disappointed with their brightness. The 9W LED bulbs I bought (supposedly 460-590 Lumen) produce ...
0
votes
1answer
278 views

Powering high power LED modules/plates (series parallel internally)?

I am trying to build a high power RGB LED light. I am looking for 50W-100W range for the LED (all colors combined). 100W RGB LED desn't seem to exist so I am left with 50W, 60W, or 90W options. I ...
1
vote
4answers
300 views

Does voltage matter when using constant current PSU?

Let's say I have 90W RGB LED module/plate (10 Series and 9 in Parallel internally). It has Voltages: R: 20~22V; G: 32~34V; B: 32~34V; Can I power all colors with 3 identical 30W constant current ...
2
votes
0answers
244 views

How to drive 400W of High-Powered LED's in parallel / series?

I want to create a luminaire (a lighting unit) comprised of the following: 5 Nichia LEDs running @ 70.2W / 39V / 1.8A 6 Cree LEDs running @ 2.2W / 3.2V / 700mA 14 Cree LEDs running @ 1.61W / 2.3V / ...
0
votes
1answer
355 views

Dimming multiple power LEDs with individual constant current PSUs from a single arduino?

Main question: how to individually dimm (PWM) multiple power LEDs that are each powered from a separate constant current power supply, and do this dimming from a single arduino? I have 10 LED ...
0
votes
2answers
1k views

Make adjustable mosfet constant current source

I want to modify this circuit below so the current can be trimmed. The problem is the variations in base-emitter voltage of the NPN transistor. According to datasheets, it is between 0.55V and 0.7V ...
2
votes
1answer
792 views

High-side MOSFET drive in current-limited power supply

As preamble, this is the typical schematic for an opamp constant-current load used for testing power supplies and what not. (Sorry for the terrible circuitlab MOSFET symbol; that's an N-enhancement ...
1
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2answers
151 views

Circuit to maintain a minimum current?

I bought a cheap USB battery pack to power a portable project. It works great, except it shuts itself down if there's a current draw lower than a certain amount (haven't pinned it down, but I think ...
3
votes
2answers
720 views

Why N-channel MOSFETs are better than P-channel MOSFETs?

Besides the reason that electron mobility is higher than hole mobility, what are the other reasons of preferring an N-channel over a P-channel MOSFET?
3
votes
1answer
813 views

Constant current source math - Using AD8276 differential Op-Amp

So I'm trying to implement a constant current source to conduct a specific measurement using a AD8276 differential amplifier. I'm trying got derive the equations my self for sanity check, and to give ...
0
votes
1answer
56 views

R-EXT connection on the STP16CP05MTR LED sink driver

I'm planning to use a STP16CP05MTR LED sink driver to drive some LEDs in a matrix. The STP16CP05MTR supports constant current by the use of an external resistor ...
1
vote
1answer
149 views

TLC5926 With No Load

I've read here that running the TLC5940 with no load can cause some issues with it drawing excessive power. The TLC5926 is a constant current driver rather than a PWM driver. It seems to me that since ...
11
votes
6answers
1k views

Usefulness of constant current limiting in bench power supply

I'm building a bench power supply as my introductory project to electronics. When it comes to adjustable voltage it's easy to see the usefulness of such feature but I can't figure out what is the ...
6
votes
4answers
2k views

Why does this buck converter output such low current?

I'm making my first attempt at building a buck converter, as a constant-current supply for a 700ma LED, from a 5V or 12V supply. I have it working with the parts I had on hand, at about 88% ...
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votes
1answer
455 views

Can I power a 3mA piezo buzzer with a lower than 3mA continuous current battery?

I want to power a self drive piezo buzzer with a rated current given as >3mA. http://www.microbuzzer.com/buzzer/spec/TE-HPS12C-H2.5.pdf I am looking for a small battery I can use to power the buzzer ...
2
votes
1answer
714 views

Constant current battery discharge

I'm simulating NiMH cell discharge from 1.5V to 1.0V. The circuit I drew is supposed to draw a constant current from the battery. I simulate a DC Sweep in circuit lab but somehow the current draw ...
4
votes
2answers
2k views

Efficient constant-current regulator for 700ma LEDs

I'm building a lamp with twelve 3x700ma RGB LEDs in it, that need to be individually PWM controlled (100-200Hz), so they can display different colours from each LED. To do this then, I think I need a ...
2
votes
1answer
3k views

Constant current circuit with transistors/MOSFETs design comparison

There are a few designs out there for constant current devices, but most of them use a certain chip. I was looking for a way to build my own constant current supply from parts that I have available. ...
5
votes
2answers
148 views

BCR402R - what is the purpose of Rext in this LED driver?

I'd like to know what is(are) the purpose(s) of Rext in the BCR402R LE driver circuit. The BCR402R is a 20 mA constant current LED driver. The application circuit (see below) shows an external ...
2
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3answers
343 views

What is a Low Drop Constant Current Driver (LDCCD)?

In this post, the gentleman describes this device but does not give any details about how it works. What's underneath the shrink tube? The easiest way to explain my Low Drop Constant Current ...
4
votes
2answers
1k views

How to dim an LED with constant current supply?

I have a power RGB led with 350 mA max per color. If I get 3x 300-350 mA constant power supplies will I be able to dim each individual color from 0 to 100% power with Arduino (with NPN transistors)? ...
5
votes
2answers
795 views

Using a TLC5940 to control LEDs with different forward voltages

I am trying to build an LED matrix (64x32) of RGB LEDs using a TLC5940 current sink LED driver. The forward voltages of the LED components for each RGB LED are: R: 1.8V G: 2.8V B: 2.8V The driver ...
1
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1answer
1k views

PWM LED dimming via constant current source

I have this idea to dimm LEDs and I'd like to get some opinions if it's feasible. Q1 and M1 form a constant current source, Q1 ensures a 0.7V drop across R2 by pulling M1 gate to ground. Q2 gets a ...
5
votes
3answers
1k views

What is causing the oscillation in the feedback loop of an SMPS?

I am trying to make a switching constant current regulator for a Ni-MH charger. It accepts a current set input from the microcontroller using a PWM DAC. I basically want to source 2000mA and 200mA for ...
4
votes
2answers
470 views

Powering RGB LED's and using a PWM chip; series or parallel?

I'm working on a hobby project where I will be using an Arduino board and a TLC 5940 to control 5 different groups of RGB LED's. The number of LED's in any particular group will not necessarily match ...
4
votes
2answers
593 views

Basic schematic help

I'm trying to design a lighting circuit for an indoor garden, and I'm not understanding things that seem like they're really basic, so I need some help. The schematic I'm referencing is: I have a ...
3
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3answers
301 views

Constant current “driver”

I need constant current 100mA source (120 channels of them) with as much low output tolerances as possible (so I don't want to use for example LM317 +resistors). I found Supertex CL7 chip (+- 5%) ...
2
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4answers
4k views

How do I get a constant current of 2mA; output voltage of 9V dc?

I need a device that can run on batteries (probably one or two 9V batteries) that will provide an output voltage of about 9V but, more importantly, is constant current of 2mA. This will be dc output. ...
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votes
1answer
461 views

What's the cheapest, quickest way to obtain an adjustable constant current source? [closed]

I need a simple adjustable constant current source that provides 0.1mA-5mA constant current from a 9V battery. Ideally it would show the output current on an analog or digital readout, but that's not ...
1
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2answers
854 views

Direct current measurement without circuit breaking

Is it possible to measure direct current without breaking the circuit? For AC parameters its no problem using current clamp. I would like to know if something like this is possible with direct current ...
5
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1answer
776 views

Current source vs current limiter

After reading the answers of two questions regarding the LM317, the answers made me think about whether I realy understand current source and current limiter. In this answer it says: The LM317 ...