An electronic component that sources current - if it sinks current it is called a current sink but both devices (sinks and sources) can be called sources. An IDEAL current source will supply current , maintain high voltage compliance (i.e. adapt it's output voltage to match the network it is ...
4
votes
1answer
106 views
How to build a voltage-controlled current sink / voltage-controlled resistor
I am trying to control a current through several current-mirror device (specifically the IREF pin on the TLC5940) using a single potentiometer. I've tried using a ...
0
votes
0answers
49 views
can power source damage electronics? [duplicate]
I think that this is a noob question but I just can't figure it out:
I have 2 devices :
First device working on 5V / 50A
Second device working on 5V/ 30A
I want to power them with power source : ...
3
votes
1answer
100 views
Temperature current source using a LM35
Anyone care to explain how this piece of circuit work?
I already build it and it works wonders but I can't figure it out.
4
votes
1answer
93 views
Measuring very small changes in resistor network using current source
I am trying measure a very small change in resistance (approximately .400 Ohms), due to the the effects of connecting a large resistance in parallel with a network of smaller resistors essentially ...
0
votes
1answer
99 views
Are these LEDs glowing due to leakage current? How to prevent it?
I've been trying to develop this circuit for a multiplexed display with two seven segment digits and five SMD LEDs. For simplicity, I've only shown one digit (LEDS 1 through 7) and two SMD LEDs (8 and ...
0
votes
1answer
129 views
Adjustable constant current source using a lm317
I am looking to provide constant current source, I am using a LM317 right now and it seems to be doing the job just fine. however I need to switch it between 2 or 3 different current levels. I can not ...
4
votes
2answers
124 views
buck converter for high current LED
My first question here:
I want to make a simple adjustable current supply for some LEDs I have (approx 3 V and up to 3 amps). I've decided against just using a single FET to control current as it ...
-4
votes
1answer
113 views
How to find the current and Resistance?
Ok Everyone DownVoted! i am sorry about the diagram! So i Updated it
this is my new diagram:
simulate this circuit – Schematic created using CircuitLab
Then Now how to find I1? what is ...
2
votes
2answers
103 views
Can a too powerful battery damage a circuit? [duplicate]
I have an IOIO board, a 13V 10A Battery (when I tested with my multimeter). For the IOIO board, 5-15V, ~10mA is enough. Can a 13V 10A Battery do wrong to the board or is it okay?
5
votes
4answers
322 views
Why does this current limiter circuit oscillate?
I'm trying to make a 0-25 mA current limiter. I want to take a control voltage of 0-5 V as input and have it control a current of 0-25 mA through a restive load (the restive load may vary between ...
0
votes
3answers
57 views
Finding source voltage, v1, and I1 in a circuit with a current source
simulate this circuit – Schematic created using CircuitLab
*Can anyone tell me why this circuit would be considered parallel instead of series?
2
votes
2answers
140 views
How does a real current source change its pd to keep constant current
An ideal current source is able to change its potential difference at the output to keep the same current at the output regardless of the load imepedance there. Real current sources are able to do ...
1
vote
1answer
67 views
Create circuit from current–voltage characteristic 2
Why is there a need for a current source in an electric circuit? As we know without voltage there will be no current flow then why do we call it current source? Why we do not use voltage in place of ...
0
votes
2answers
130 views
Format Approach to NODAL ANALYSIS
SITUATION:
Nodal Analysis is nothing more than applying KCL and is very powerful. I'm working on developing a more clearer perspective of two approaches in Nodal Analysis "GENERAL & FORMAT". Mesh ...
1
vote
1answer
157 views
How does current split in a circuit?
I'm redesigning a board that has a lot of peripherals attached to a SOC. These all use different voltages. Board is powered with 12V,1A
Most peripherals are connected like this:
RJ45 <-> GigE phy ...
2
votes
2answers
113 views
Sinking and Sourcing Current to and from a PIC24F Output Pin
Sinking and sourcing current refers to current going into and out of the MCU (respectively), right? If you configure a GPIO pin as an output, why would current ever go into the pin (since it's ...
0
votes
1answer
178 views
What all do i need to build LED bulb
I'm thinking of using few of the CREE LEDs but wondering what all would i need to build
a bulb from scratch.
Here's what I've got:
LEDs (of course)
LED high current drivers
some sort of rectifier ...
6
votes
2answers
189 views
How should I select the resistors for this constant-current application for a 317?
Over at OnSemi, they have a little doc about using a 317 voltage-reg as a current source:
http://www.onsemi.com/pub_link/Collateral/AND8109-D.PDF
Their final example, providing constant current to an ...
2
votes
3answers
441 views
MOSFET - OPAMP circuit
I was looking for a voltage controlled current source see here , and I stumbled upon this circuit with description here :
Now I am having difficulty figuring out how this works - I made a model of ...
0
votes
1answer
134 views
When to use Nodal Anaylsis / Mesh / Superposition?
I'm studying these three methods and i'm confused on exactly which one is used when. This is a very broad question. Therefore, could some explain in general terms the difference of the three methods ...
0
votes
3answers
163 views
Node Analysis - current calculation
I have a cicuit here that's giving me trouble when finding out what V1 and V2 equal.The book says that I1 is traveling through the 8 ohm resistor (R1) towards ground. But when I build the circuit on ...
3
votes
2answers
329 views
Micro-controller controlled current source
I am trying to design a programmable current source that can go up to 5 A. I have a few designs in mind but none of them really seem to be best solution. I would appreciate if any one has any good ...
1
vote
1answer
79 views
KCL Node Analysis
I can do mesh analysis with KVL no problem however trying to switch over and to KCL with Node analysis I cannot understand.
How do you determine current coming in to the node? I don't understand how ...
0
votes
1answer
100 views
Circuit Simulator is being funky
This circuit simulator called "iCircuit" for mac users is showing some weird readings. It's showing a reading of 2.4mA and i'm getting 6mA in my calculations for this circuit I threw up. Am I missing ...
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 ...
5
votes
3answers
341 views
Constant current source
In my other topic i asked on how to create a sawtooth signal and guys on the forum gave me an excelent anwser. But! I cannot fully understand the first part of a circuit which is supposed to be an ...
3
votes
1answer
385 views
Why is my constant current source (LED driver) pulsing?
I bought a current source to try to power some high brightness LEDs. The LEDs take 350mA so I found a current source on digikey that matches that and ordered it:
...
2
votes
1answer
188 views
Current source with no voltage drop
I'm designing a device with 3.6V Vcc and RGB LED. Blue part of an LED has the voltage drop in the range of 3.2..3.6V and i have to drive it with current limited to 30..50mA. This gives a restriction ...
5
votes
2answers
449 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 ...
3
votes
1answer
143 views
Role of current source in comparator
I have this schematic of a quarter of the internals of an LM339 from this site
I want to know what the purpose of the four current sources are in this circuit, and how might they be implemented?
I ...
7
votes
4answers
412 views
Why would you attach a Diode to the base of a BJT?
I was looking at a DC BJT setup for sourcing current and came accross this
I have never seen a diode attached to the base of BJTs before and was wondering what it might be used for? I believe it ...
4
votes
1answer
362 views
Increase 74LS TTL gate's output current to drive multiple high-power LEDs
If have several 1 watt LEDs that I want to drive off of a TTL gate's ouput. What can I do to increase a 74LS TTL logic chip's output fan-out (current) to be able to produce a true 5 V output that is ...
0
votes
0answers
98 views
Peltier power driver [closed]
I need to control a 15VDC@26A Thermoelectric device, i have troubles finding a power driver for it, is it suitable to design my own, or anybody knows a place to buy one?, best regards.
Arturo ...
1
vote
1answer
613 views
how do i create a current source
I have a problem designing a current source.
Basicalyy I need to drive this I->P converter which needs a 4-20mA input. If I understand well the datasheet the resistance inside the component is 500ohms ...
2
votes
2answers
411 views
application of current source and current sink concepts
current source and current sink implies the direction of current flows. for source circuit, there is a "switch" connected between positive terminal and load, where it source the current through the ...
0
votes
1answer
169 views
Need help designing a current controlled source in PSpice?
The image below shows an electrical network with 8 elements, a current controlled source, a bunch of resistors, one current source and a voltage source.
Although I haven't labeled them, there are 5 ...
0
votes
2answers
145 views
How to implement an isolated connection matrix
I need to implement a circuit for a researcher, which looks a little bit like this:
Description of the circuit:
There are two or more fully isolated biphasic current drivers, and N output pins. ...
4
votes
1answer
2k views
Voltage regulator for linear constant-current (1.5A) LED driver?
I am considering building my own driver for a ~1.5A LED to power a microscope for my research.
For this application, efficiency isn't critical, but because exposure times to the camera can be short ...
0
votes
2answers
363 views
What is meant by relative voltage?
Suppose you have a circuit
,you are told that the voltage at point 2 relative to point 1 is -90V, the voltage across R2 is -30V and V0 is 200V.
What is the meaning of voltage at 2 relative to 1? ...
5
votes
3answers
595 views
Measuring Resistance of a Wire With an ADC
I'm trying to design a circuit which can measure small resistances down to 0.1 Ohm and a max. of 10 Ohms. I won't be measuring actual resistors but rather large coil of wires, upto 500 m (as you can ...
4
votes
2answers
190 views
Why don't my coil work?
I disassembled my old Niko RC car today. Thought I could play around with the parts.
But what I can't seem to understand is the coil. The powersource of the rc car is a 7.2v NiCd 620mAh battery. And ...
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%)
...
5
votes
3answers
2k views
How to drive high powered LEDs as efficiently as possible
I have come across some very high powered LEDs.
Datasheet for LEDs
http://www.cree.com/led-components-and-modules/products/xlamp/arrays-nondirectional/xlamp-cxa2011
My question is: for these high ...
6
votes
3answers
271 views
Voltage controlled AC current source
I have been tasked to build a heater for an industrial application. The heater uses resistance to heat the liquid and the application needs very precise control of temperature (+/- 1 degree). Existing ...
10
votes
4answers
3k views
What exactly is a current source?
What I understood from the definition of current sources is that it is a source which supplies a constant current across a load no matter how the other parameters (like resistances for example) in the ...
-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 ...
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 ...
2
votes
2answers
76 views
Shorting the output ports which have nominal bandgap voltages of 1.24V
I am using LED drivers (TLC5940) which allow one to fix the operating current \$I_c\$ flowing through LEDs. This is accomplished by connecting a resistor (of the desired value) between an output port, ...
1
vote
1answer
441 views
Alternative to REF200 Current Source [closed]
I'm using TI's REF200 as a 200uA current source but need something cheaper with similar precision (temperature stability, accuracy, etc). I'm using this in conjunction with an INA337 Inst. Amplifier, ...
