The constant-current tag has no wiki summary.
3
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1answer
151 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
27 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
42 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 ...
10
votes
5answers
575 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 ...
2
votes
4answers
475 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% ...
-2
votes
1answer
188 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
210 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 ...
3
votes
2answers
390 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
562 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
76 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 ...
0
votes
0answers
44 views
iDAC + Current Mirror with 20V compliance
I want to create a 0-100uA constant current pulse with 20V compliance for use as portable biological stimulation device. I'm using a Cypres PSoC 3 as the MCU. I was originally planning to use an ...
2
votes
3answers
200 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
485 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
450 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
vote
1answer
376 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 ...
4
votes
3answers
527 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
320 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
308 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 ...
4
votes
3answers
195 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
votes
4answers
2k 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.
...
-3
votes
1answer
293 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
vote
2answers
514 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 ...
4
votes
1answer
348 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 ...
1
vote
4answers
4k views
LM317 to create constant current of 2mA?
I have a circuit where I want to have a constant current of 2mA through a variable resistor. I've been told that I could probably use a LM317 as a current regulator, with one resistor on the ouput. ...
2
votes
2answers
622 views
An LM350, can I have both constant current, and specific voltage?
I have a regulator such as in this setup to provide 1.2 Amps to a load that requires constant current:
R1 is set to 1 Ohm, which nicely brings the current within range (1.25A according to a small ...
3
votes
2answers
733 views
Beginner information related to constant current dummy loads
I am beginning an electronics design project to build a constant current load to drive testings for batteries, bench power supplies etc. I have been hard trying to locate some black-on-white ...
2
votes
2answers
2k views
Capacitor Discharge through Constant Current Source
I was just thnking of how to model the voltage decay from a fully charged capacitor through a constant current source (CCS). A good approximation to this would be to model the constant current source ...
1
vote
2answers
378 views
Low loss current sink
I'm working on a battery powered device that has 4 individual LED drivers. The output from the LEDs are controlled with separate PWM signals from a small MCU.
This has to be low cost, and a low cost ...
1
vote
1answer
639 views
Simple constant current source that doesn't die on voltage spikes
For testing various laser diodes, I need a constant current source, adjustable up to 150 ... 200 mA or so, down to... well, maybe 1 or 2 mA? (low enough to measure where is the lasing threshold where ...
0
votes
2answers
4k views
Voltage Controlled Current Source integrated circuit? Exists?
Does anyone know of a Voltage Controlled Current Source IC? Or do you know how I can build one with as few other components as possible taking up a minimal amount of space?
current range needed is ...
5
votes
4answers
3k views
Adjustable linear led driver? Linear, not PWM
I'm working on a product that requires an led to output currents varrying from 0mA to 350mA and as many possible levels in between (~1000 would be sufficient I suppose). I CANT output a PWM signal to ...
1
vote
4answers
510 views
Improving this current regulated LED driver circuit
In this here circuit the function generators at the left represent the digital output pins from a microcontroller. I happen to be using an Arduino Uno for that purpose at the moment and the relevant ...
2
votes
7answers
1k views
Controlling high output LED's with a microcontroller
I'd like to build a circuit to precisely control the current through a couple of (LED and laser) diodes. I would like to minimize the number of components if possible. Power consumption is not a ...
2
votes
2answers
509 views
Why is a laser supply so tricky?
I need to build supply for ~20 laser diodes (~150 mW each), and the question is why can't we just use a constant current power source for each of them?
A similar question for pulsed mode operation: ...
