constant current or constant voltage?

Hello, I'm looking into driving about five separate piezo ultrasonic water misters and one of them have the rough requirement of 24 volts. my question is if i wanted to drive all five at the same time I'm thinking I would want a 24 volt constant voltage source, is this accurate? Bonus question: what dictates whether a constant current or a constant voltage source is needed?

Question by waldosan 1 year ago  |  last reply 1 year ago


Constant voltage AND constant current? Answered

Hi, smart people of the internet :) Is there a power supply or a converter that can be set on a specific voltage and current, and keep both constant at the same time? I looked at ebay converters like B3606, DPS5015, BST400 and the like. They all have constant voltage (CV) and constant current (CC) settings, but they can't do both at the same time. If for example the current being drawn is too high, the unit switches from CV to CC and drops the voltage as much as needed to keep the current constant. Is a simultaneous CC CV power supply even a thing? Thanks!

Question by Morgantao 1 year ago  |  last reply 1 year ago


What is a constant current source?

I had some questions: What is a constant current source? How does a constant current source work? Do i need a cc supply for an led or would a cv supply work? Thanks :)

Question by qwerty156 7 years ago  |  last reply 7 years ago


Too much voltage or will the current limit it?

According to the circuit I need about 6 volts input to run a luxeon star LED. As I understand it, the regulator takes about 3v leaving 3v for the LED and will will provide a fixed current of 320ma which is just fine. My question is, can I use a higher input voltage such as 12v without affecting the luxeon star? Although the current output is fixed, will the output voltage rise as the input voltage rises and burn out the LED?Image reference http://led.linear1.org/a-cheap-current-regulated-luxeon-star-driver-design/1/TIARichard:)

Topic by Richard21 11 years ago  |  last reply 10 years ago


Overdriving constant current led panel

Having trouble locating a 250ma constant current 100w led driver and was wondering if anyone has had experience overdriving led strip panels. Smallest i can find at that wattage seems to be 350ma

Question by Kirkus77 10 months ago


Constant current power supply, will this work? Answered

Hi,  i found some parts in an old computer, since i could not get my hands on an lm317 This is what i used, 1 x L7805cv voltage regulator ( from an old computer) 2 x 660nm 3 watt each running at 2.2v 0.700mA 1 x 10ohm resistor connect to ground and output 1 x 12v 1.5a power supply I can run 1 or 2 leds and they are pretty bright, only the L7805 gets hot but i assume thats normal. What do you think of this setup, will it last? See pictures Greets JB

Question by MistaMasta 6 years ago  |  last reply 6 years ago


Looking for some clarity on 1w led power

I am having a hard time working the math and figuring out exactly what I need so I thought a question to others might help. I am trying to determine the best way to power a led light.  Here is what I am trying to accomplish.   I have 12"x12" box that will hold 4 round circuit boards.  Each board has positions for 9 1w leds.  3 for red, 3 for green, and 3 for blue.  Each color is in series.  My goal is to use a 12v power supply for each box.  So we are talking about trying to power 36 1w leds all together but they may or may not be all on at the same time.  The box will be dmx controlled by a computer so that I can adjust the 3 leds in each color on each board.  So its possible that I might only have 1 color on 1 board on for example.  Or I could have one color on all 4 boards on (12 leds) at any given time.  Or they could all be on. My led specs Red (610-630nm):DC Forward Voltage:2.2V~2.6V  Forward Current: 350mA green (510-530nm):DC Forward Voltage:3.2V~3.6V Forward Current: 350mA blue (460-465nm):DC Forward Voltage:3.2V~3.6V Forward Current: 350mA  So a couple things that I am having trouble with.  I know that I can power this with 12v using a high amp (15) source but then I need different resistors with high wattage ratings for different colors I would think?  That seems like a lot of power wasted.  So then I can go with a constant current driver but I can't seem to find one that would apower that many leds at once.  Do I need to do two constant current drivers?  Is there a better way?  and what about the fact that each color on each board may be on or off at various times?  Basically using the dmx controller to colorwash the different corners of the 12 x 12 box.  Will that affect the power drawn and change the supply that I need? Thanks

Topic by joecolafrancesco 4 years ago  |  last reply 4 years ago


Inductance and resistance question help

Hi folks I'm new to this I was wondering if someone can help me with these questions I've answered them but I would like one of you expert folks to tell me if they are correct or where I'm going wrong Or if I have the correct formulas its just a question for an exam revision which I have soon. A coil of inductance 4H and resistance of 80Ω is connected in parallel with a 200Ω of resistor of negligible inductance across a 200v dc supply. The switch connecting these to the supply is then opened; the coil and resistor remain connected together. State in each case one for immediately before and one for immediately after opening the switch; The current Through the resistor Switch closed 200v/200Ω =1a Switch open 200v/80Ω =2.5a The current through the coil Switch Closed 200v/80Ω = 2.5a Switch open 200v/(200ohm +80Ω) = 0.714a The e.m.f induced in the coil Switch closed (2.5a*80Ω)/200v = 0v Switch Open 2.5a *(200Ω + 80Ω) = 700v The voltage across the coil Switch closed 200v/1a = 200v Switch open 2.5a * 200Ω = 500v

Topic by Andrew187 6 years ago  |  last reply 6 years ago


Variable Constant current in micro-amp range? Answered

Would like help with finding a IC that can be controlled directly or indirectly using an arduino.  It needs to go from 10 microamps to about 200 microamps. I have a 5 volt power supply. Is there an IC for this, or how should I do it. I couldn't find anything on google that i understood. Thanks.

Question by headslant 2 years ago  |  last reply 2 years ago


Time constants of batteries ?

Hi,I'm trying to figure out the way solar battery charger work and I'm a bit confused about the following point.I read that for batteries you could consider the PWM voltage to be equivalent to DC. This I understand well for average voltage (obviously it's the same), but what about the dynamics ?If your PWM frequency is something like 100 kHz, that's a 10 µs period. Does the battery has time to follow and make big voltage and current peaks or does it just averages all that to more decent values ?One way to put it is : Are the battery time constants indeed much bigger than the PWM period ?Thanks for any idea on that topic !

Topic by Emmanuel2015 7 months ago  |  last reply 7 months ago


constant 4.5 V supply using batteries?

how may i get a constant power supply of 4.5 Volt using batteries? -------------------------------------------------------------- WHAT I FOUND SO FAR googling and visiting several discussion groups i found related advice ... - e.g. using 1 more than the required batteries in combination with e.g. a voltage regulator, diode, resistor, DAC - if i use 4 instead of 3 aa batteries and the voltage drops after a while - would a voltage regulator, resistor, DAC still provide 4.5V from the remaining voltage? may i ask you what you would recommend? -------------------------------------------------------------- WHAT I NEED IT FOR i am using rf sender/receiver modules with my picaxe 08m microcontrollers & found, that they (and the connected antennas) work best at a constant voltage of 4.5 V

Topic by marc_is_curious 7 years ago


constant 4.5 V supply using batteries? Answered

How may i get a constant power supply of 4.5 Voltusing batteries? --------------------------------------------------------------WHAT I FOUND SO FAR googling and visiting several discussion groupsi found related advice ... - e.g. using 1 more than the required batteriesin combination with e.g. a voltage regulator, diode, resistor, DAC - if i use 4 instead of 3 aa batteriesand the voltage drops after a while - would a voltage regulator, resistor, DACstill provide 4.5V from the remaining voltage? may i ask you what you would recommend? --------------------------------------------------------------WHAT I NEED IT FOR i am using rf sender/receiver modules with my picaxe 08m microcontrollers & found, that they (and the connected antennas) work best at a constant voltage of 4.5 V

Question by marc_is_curious 7 years ago  |  last reply 6 years ago


Different collor high powered 3 watt led strings on one constant current power supply? Answered

Greets, Can i connect 3 different collored led strings to one constant current power supply? This is my power source, gives min 9v and a max of 48v @ 700mA Mean Well LPC-35-700 https://www.meanwell-web.com/product_info.php/products_id/LPC-35-700 My leds all 3 watt 6 x 630nm red - 2.5v/3v - 750mA 2 x 660nm deep red - 2.2v - 700mA 2 x 460nm blue - 3.4/4v - 750mA Can i create these string? 1 string with 6 x 630nm = 18v @ 700mA, should have no problem to run, right? 1 string with 2 x 660nm = 4.4v  (9v min from power) 9v - 4.4v = 4.6v / 0.7mA= 6.57 ohm resistor i should add to this string, correct? 1 string with 2 x 460nm = 6.8v (9v min from power) 9v - 6.8v = 2.2v / 0.7mA = 3.14ohm resistor i should add to this string, correct? Can my power supply handle this? Since it changes voltage. If i can use this, which watt resistors would i need? I would also for example like to add 1 potentiometer for the 460nm blue leds And add 1 potentiometer for the 660nm deep red leds Am i asking to much here or can this be done? Thnx JB

Question by MistaMasta 6 years ago  |  last reply 6 years ago


How to Make a Constant Current Lithium Ion Charger

Hi Guys! I have a bunch of 18650 lithium ion batteries that can handle a charge rate of 5C. Each one is 3,000 milli-amp hours, and I would like to build a charger for them as my project. I understand the mechanics of charging lithium ion batteries, and that they need to be charged at a constant current up until that current reaches 4.2 volts, than switch over to constant voltage. The constant voltage charging makes up about 20% of the battery capacity, and I am willing to forgo that amount. What I am trying to build is a constant current charger for it that would  charge at a current of 1C, and shut off when it reaches 4.2 volts, and I would like some help as to how I would do this. I was thinking that I would have some sort of current source that supplied 3 amps and then have a relay that would shut off the current as soon as a voltage detector reached 4.2. I do not know much about current sources, so I am asking here for some help. Thank You for Your Help!

Topic by merlinj 2 years ago  |  last reply 2 years ago


How to wire and power LEDS with a constant current driver?

I want to light up 6 leds, one each of red, orange, yellow, green, blue, purple.   The specs for red, orange, and yellow are: 20 mA, 2 V.  Green, blue purple are 20 mA, 3 V. I ordered these constant current drivers http://lighthouseleds.com/20ma-led-current-limiter-driver.html 20mA (+/- 3) Constant Current Output Voltage Varied (constant current) Input Voltage 2-45V Across Limiter Now, how do I wire the leds and what type of battery do I use?  On the current driver website it shows 3 leds in series with the driver and battery.  I was thinking of using a 9 volt battery.  But placing my 6 leds in series would add up to a total of 15 volts, and wouldn't work, correct?  So, do I need to wire 2 or 3 leds in series, then put those groups in parallel?  Do I need another current driver? Thanks in advance.

Question by rachl009 3 years ago  |  last reply 3 years ago


Selecting one or many LEDs for constant-current driver?

I'd like to build a flashlight with several LEDs, perhaps different colors, perhaps different beam characteristics, and allow the user to select one or more of them to be active at once.With primitive electronics, this is simple: Each LED gets its own current-limiting resistor in series with it, and then all the LEDs with individual switches go in parallel across the power bus.But I'd like to use a constant-current driver (buckpuck or similar) for better efficiency and stability across varying input voltages. This means the LEDs should be in series. To take one out of the circuit, I'd simply short across it, bypassing it so the current still flows through the other(s). This is pretty simple with two LEDs, as I could use a center-off toggle switch to short A, neither, or B. But if I try for three LEDs in series, the logic of allowing any combination to be bypassed *except* all of them (because a dead short would damage the driver circuit) quickly gets complicated.Is there something simple I'm overlooking? Or do people simply avoid doing it this way for this reason? (The obvious solution is to use a constant-current circuit for each LED and run them all in parallel, but that gets expensive in a hurry!)

Topic by Myself 12 years ago  |  last reply 11 years ago


Matching 700mA constant current driver to 20mA LEDs? Answered

Hello all: Ultimately I'm trying to drive upwards of 100 3mm white LEDs in an art project with dimming and a connection to 120v AC power (this is for a chandelier). I've been playing around with some constant current IC driver like the Supertex CL2 as well as 5 and 12v power supplies but I've been looking for a dimmable solution with a small form factor. I picked up a Robertson constant current LED driver but it outputs at 700mA, I assume because it's intended for 1W or 3W LEDs needing the higher current. Is there a circuit design that I can use like a current divider to drive smaller loads with this supply? My current thinking is as follows: 1) I could simply load 35 parallel strings of LEDs since 700/20 = 35 (of an appropriate voltage drop probably between 9v-15v) and rely on the equivalent resistance of each string to act as a defacto current divider. 2) I could do the same thing but with an in series resistor of some value for each string, the constraint being that increasing the resistor will reduce the number of parallel strings and I may need relatively high wattage resistors if I'm driving 9+volts of LEDs on each string. 3) I could do a smaller parallel current divider, but I'm not confident in my math analyzing the ratios of the resistors to achieve this (for instance if I had only two parallel loads and one was drawing 20mA and the other the balance of 680mA the resistors would have to have the same (inverted) relationship i.e. 34:1...to say nothing of the wattage through the 680mA line, which might be as high as 6-8 watts depending on voltage. Is that right? Are there any other clever solutions I'm not thinking of? Obviously I could buy a lower current driver (and I may ultimately)  but even the lower current options are at 350mA, so the same problem will exist at a smaller scale. Thanks everybody for thinking about this, I look forward to seeing your thoughts!

Question by michael.pokorny.54 4 years ago  |  last reply 4 years ago



analog circuit to mimic constant resistance load? Answered

I unfortunately do not have many big resistors that can dissipate lots of power, and would like to make a dummy load to test and parameterize batteries and power supplies. I want constant power, constant current, and constant resistance load, I do have lots of opamps and a few N and P channel enhancement mode MOSFETs as well as many 2N3055s and a couple MJE2955's. I think constant current is the easiest, since all I need to do is make a closed loop controller that will turn off the transistor as the current is exceeded, and turn it on as the current falls. Constant power might be more tricky, as I need a device that controls the bias on a transistor as a function of the product of the voltage and current, since P=IE or W=AV, and similarly, constant resistance, I need a thing that will divide voltage across the pass element by the current through it. I don't want to use a "slow" microcontroller for this, I like nice continuous analog control system, if that is possible.

Question by -max- 3 years ago  |  last reply 2 years ago


PSU design (major revisions): Transformer calculations help?

Recently I have attempting to design a proper dual-rail power supply that will allow me to set a voltage as low as +-1V up to +-30V in 0.1V increments at (hopefully) 3 significant digits (at least for the lower voltage settings). Anyway, this supply is also going to be current limited to up to 5A,again, it can be set to just about anything. I plan on using an Arduino micro-controller to set the output. In order to do this, I plan on using the analogWrite functions, or better yet, a legit DAC. There will be 4 outputs from the Arduino that will set the power supply output by applying a 0-5V voltage on the input of the 2 current limits and 2 voltage sets. (one for the negative rail, one for the positive). However, I have kept running into the same problem: how do I plan on driving this linear power supply with up to 200W*? My first idea was to use a a MOT, due to their high-power capabilities, and re wind the secondary with the right number of turns to achieve this output. However, I have heard that these transformers are not optimal for continuous running due to their poor and cheap design. (losses are very high). My second idea was to search around for a 250VA transformer. However, even until now, the VA rating confuses me. How does VA compare to W? I know this has something to due with reactive power, real power, and apparent power. However, I have no intuition of any of these 'powers.' How would I go about calculating the correct size transformer for the job, also, I am going to assume this linear power supply has the properties of a resistive load, since it is rectified and smoothed with a filter capacitor, so practically nothing should react with the AC power. (unless there is something more to the full-bridge rectifier setup I am considering.) This is when I came across unwound toroidal cores found on eBay for $25, the perfect price range! However, this has raised more questions! to start off, beyond turns ratio, I do not know now many turns I need for the AC side of things. I know intuitively and from experience, mains-frequency transformers do not work with only one (or even few) winding(s). I think this has to do with saturation, but I'm no expert by any means. and the inductive reactance of the transformer's primary. How do I calculate losses, inductance, and other important parameters of a homemade transformer like this? Things get very nasty when I look back at rewinding an old transformer. Now I have all these questions about inductive reactance, power, currents, magnetic flux and saturation, but also, about determining the original power rating of something like a very old small welding transformer or one from a large 10A car-battery charger. Is it possible to approximate the power by measuring the dimensions of the core? How close will this approximation be?  After getting frustrated with this, I considered alternative approaches. What if I purchased 2 ~20V ~6A SMPS (switch mode power supplies) connected them in series, and connect the center tap of my linear supply to the joining point between the 2 SWPS's? Would this be unstable and be bad for the SMPS if a load was connected between the 'outputs' of this new center tapped supply? Would any sort of balancing be required? Also, a bigger problem includes how this will be connected to my linear PSU design. With a low voltage @ high currents, I would be wasting a LOT of power, power that has to be dissipated away from the transistors. This heat can approach 200W, which is company unreasonable! Anyway, I would them have to either a switching preregulator, or modify the SMPS's so the voltage can be controlled easily and varied between, say, 3V to 20V. absolute accuracy is not required, close enough, and rest of my PSU should handle it. This becomes seemingly impractical too, and many other considerations need to be made. What should I do? what are the calculations and factors I need to know? i do not have an LCR meter to measure inductance, so trial and error is out. Does anyone here have experience at this? Help would be greatly appreciated! *The 200W figure was calculated by taking 40V, (What I believe would be a safe to allow some slack for +-5V voltage drop across my 2 shunts and transistors) and multiplying it to 5A of current for the maximum power output. ------------------------------------------------------------------------------------------------------------------- I have added an image of my current design, and I have modularized it the best I could. The YELLOW is all my current power-management circuitry. Currently just a transformer with many taps, going to a currently-undesigned switch box that will change the voltage on the output, which is then rectified and enters a filtering capacitor, finally entering the circuit.  The GREEN field is the voltage set. It is the most major part of the PID feedback loop, along with the ORANGE field. It works simply by feeding a voltage to the positive of a op amp configured as a comparator, and with negative feedback from the output. It then outputs a signal to the transistor, turning it either more ON, or more OFF depending on how the output voltage compares to the +Vset. The negative portion is largely the same, but the input voltage needs to be inverted so the output voltage is set negative properly. I was not able to use less than 2 op amps for this portion, unfortunately. The ORANGE field is current set. It works by measuring the voltage drop across the shunt resistor, and outputting a unity voltage that is referenced to ground, instead of to the positive rail. (It took me forever to finalize and perfect that!!!) Anyway, this voltage is then fed into a op-amp configured as a comparator to drive the transistor. The BLUE field is my switching regulation topology, which is controlled by both the ORANGE and GREEN fields. Do you like my use of diodes as a super-simple voltage or current selection switch? the op amp that outputs a lower voltage is the one that gets 'listened to' by the transistors. This way, current and voltage mode enable properly. This does add a small problem when it comes to powering the op amps, all of them have to be powered off of slightly higher voltages to swing the full range due to the voltage drops of those diodes. In the PINK field is simply a single-transistor solution to a constant current load. This allows the regulator to be regulated even at very low voltage set levels. This is why I am able to achieve a +-0.5V on the output (at least within LTspice) Finally, and most unimportantly, the light PURPLE fields have a simple ultra high-gain difference amplifiers that will detect if the output current and current set are the same, and turn On or OFF the respective LEDs. The green LEDs are voltage-mode indicators, and the red LEDs are to show when current-limiting mode comes on.

Question by -max- 5 years ago  |  last reply 5 years ago


How to modify a constant current LED driver 700mA into 350mA?

Is it possible to modify a constant current LED driver 700mA 5W (230V input) to use with 4x1,2W 350mA Diods??

Question by Allecc 6 years ago  |  last reply 6 years ago


Current Consumtion by a DC Motor?

 I am asking few questions EV related, more current related. Let a consider a dc motor rated 4hp at 24v and 2hp at 12v. So is there a way to calculate ampere draw of the motor at various loads.(like no load, full load, or any load). And if we know the full load current of the dc motor then can we calculate the max load for the dc motor. Next as the dc motor is 2hp at 12v then will this value be constant or will the motor be able to produce 4hp at 12v even rather than at 24v. And will a battery eg 50ah be able to supply more then 50amp.

Topic by flyingdutchmen1659 6 years ago  |  last reply 3 years ago


i want an High power LED constant current ckt?

Question by kiranvaka 6 years ago  |  last reply 6 years ago


Need help wiring 10w leds and constant current drivers. Answered

I have a 12v 16amp power supply and i need to hook up 6 10w leds together along with cooling fans/heatsinks and constant current drivers.Its my understanding that i need 6 constant current drivers. one for each led to prevent overheating.i can hook up one no problem but how do i connect all 6 together with the 12v 16amp power supply in parallel?if i was using a resistor it would only have to connect it to the positive side of the power supply in parallel but as u can seen in the pic the cc driver have neg/pos on both sides. im making an aquarium light.I have 6 heatsinks and fans 12v6 10W Constant Current LED Driver DC9-24V to DC8-11V 850mA for 10W High Power LED6 10w ledsSpecification(10w)Model Type: High Power Integrated Chip lamp Beads Integrated approach:3 Series 3 Paralleling Forward Voltage: 9-12V(if use DC 12,Recommended Series a about 1.50 ohm resistor to use) Forward current: 900mA Luminous Flux: 90-120LM/W Color-rendering index: 60-85 Beam Angle: 120 degrees Working Temperature: -20 centigrade to 60 centigrade Color Temperature: Warm White: 3000-3200K

Question by monopolymoney 1 year ago  |  last reply 1 year ago


Circuit Design for DC to DC Buck-Boost Converter

Sir, I am Anand from india, I will made a project based on bicycle. I have take 5 to 80v From my Bicycle pedals. Generator power is in AC 3-Phase. I want to made next step. in this I want to this 3-Phase AC 5 to 80V are constant At 48V DC. I put the 4 batteries in series. 12V 20Ah battery I use. I want to charge this batteries please help me. Thank you.

Topic by AnandC10 2 years ago  |  last reply 2 years ago


Required voltage and current for Knathal wire? Answered

Hi, i want to heat a Tungsten rod by using the Kanthal Wire(36 Awg). I want to know what is the required voltage and current to reach the 1300 deg Celsius. I am planned to make the constant current (like 3 amp) and increase the voltage. So help me to control the temperature at 900 to 1300 deg by changing the power supply.

Question by Gnanak 3 years ago  |  last reply 3 years ago


What do I need to make a constant current driver for a 5w LED?

I have a Vollong 5w 350 lumen LED. I was told i have to use a constant current driver for it to work. I looked at some instructions on here of how to build your own, but it was for a 1w and he had 200mA of current. I am needing somewhere around 700mA and a voltage of 7v. Can anyone explain what parts i need to substitute to get this made? I'd like to just make one myself instead of waiting 3 weeks for one to come in. Any help would be appreciated. Thanks!

Question by MattATC 7 years ago  |  last reply 3 years ago


Ho do I pick an LED driver?

I bought a few cree XP-E LEDs and I'm very confused as to what drivers I should buy. This is my first electronic project so I'm a bit confused. I do know that for high powered LEDs, constant current is the only way to go but I have no idea how much I need. These are the LEDs I bought: http://www.ebay.com/itm/CREE-XP-E-XPE2-12W-4-Leds-Colorful-Red-White-Green-Blue-LED-Light-20MM-6V-12V-/221887486794?var=520780573872

Question by iron_cupcakes 3 years ago  |  last reply 3 years ago


LED Lamp current X DRIVER

Hello very good people, 1. Someone told me that I can connect a 3.8A led lamp to 100w driver 3A (constant current) because the driver will dimmer the lamp. Is this correct? 2. Is the driver that operates according to the capacity of the bulb (3.8A) or is the lamp that operates according to the capacity of the driver (3A)? The current of which one acts according to the other? Thank You

Question by logoaki 4 years ago  |  last reply 4 years ago


Help 170 leds in series parallel

5 leds in series, way too many resistors can I use constant current? If so how many strings of 5 could be connected with 12 to 14.7 volt supply?

Question by bdexter 9 years ago  |  last reply 9 years ago


what makes collector current to be beeta(current amplification factor) times base current?

What makes collector current to be beeta(current amplification factor) times base current? Is it because of shape of the transistor or doping? or Why it is acting as constant current source? or Why the collector current is independent on collector resistor and Vcc(voltage across collector and emitter)?

Question by deepakmurali 7 years ago  |  last reply 7 years ago


How do I make a reasonably efficient constant current power supply for 6.5A at up to 400W?

For charging 6-module packs of NiMh Prius batteries (43.2v) at 1C.

Question by nedfunnell 10 years ago


How to drive a 10W RGB LED with 12v PWM? Answered

Hi all, I'd like to drive a 10W RGB LED, much like these ones found in the RGB LED floodlights. I want to strip all of the internal circuitry and control it with 12V PWM signals such as the ones that come from these controllers.  They all seem to provide around 4A/channel. My understanding is that each colour (Red, Green and Blue) needs around ~300ma, so I could use resistors, but as this is a fairly high power situation, there will be a large amount of power loss, and low efficiency. Is there another way ie with constant current drivers specifically for RGB chips that accept 12v RGB PWM input?  Thanks Joe 

Question by joearkay 2 years ago  |  last reply 2 years ago


how can i control the current flow to the motor of a toy car using arduino?

I need the codes for arduino and its setup. i want the remote controlled toy car to have constant current in its motor  even after i dont push the control button. i am new and never used arduino before. thanks

Question by marufbillah 6 years ago  |  last reply 6 years ago


LED driving and wiring question? Answered

I have read and read and read, and am still confused no where seems to be able to give me a straight answer, so i've come to the instructables forum for help.  I am planing on wiring 16 leds in series driven by a driver. The constant current driver's specs are' in   -  85-277V, 50/60Hz, 0.5A MAx  out -  650mA, 30-60V, 40W The 3W leds run at 750mA, 3.2-4.0V so each led circut should require 52.1v-65.5v,  and 48W. I was hoping to under drive them to increase their lifespan, as i had a different project fail when one led blew and killed the entire line.   My questions are; 1) can i run 3 of these circuits off of one standard north american  plug 125V?  2) will this work? and did i miss anything?  3) can anyone recommend any simple improvements? I've done as much research as i can, but i never have been good at electronics and circuits. and half of the things i find are contradictory. That's why i went into chemistry.  Thank you for reading this, and thank you for responding and helping me!

Question by ninjutsu 2 years ago  |  last reply 2 years ago


LED lamp voltage X DRIVER

Hello my friends, What about the voltage, Is the driver that operates according to the voltage capacity of the bulb (20-26v) or is the lamp that operates according to the capacity of the driver (20-36v)? The voltage of which one acts according to the other? Can I use a lamp of any voltage since this voltage is understood the ability of the driver (20-36)? the driver is the same amparage and constant current. Thank you a lot.

Question by logoaki 4 years ago  |  last reply 4 years ago


Overdriving led panels

Having trouble finding a 250ma 100w constant current led driver, has anyone had experience overdriving led panels, i was thinking of trying a 350ma

Question by Kirkus77 10 months ago


Fried 3 leds - 5 x 3 watt LEDs and mean well lpc 35watt 700ma constant current driver Answered

Hi, I have 5 leds all of 3 watt each, i used the Mean Well LPC-35-700 constant current driver I hooked up all the leds to the driver in series, but as soon as i turned it on it fried 3 leds 1x 660nm, 1 x 450, and one 630nm led, but the last 2 leds are stil working. Could anybody let me know what did wrong, if you need more specs i can  give you

Question by MistaMasta 6 years ago  |  last reply 6 years ago


How to get constant 5.2V from ~1-7 Volts?

I have multiple solar panels (3V, 6V). I want to build a charger for bicycle, to keep my battery powered lamps (DIY) battery alive. Currently, I use my DIY lamp with a USB Power bank (5,2V , approx. 50k mAh), but my lamp contains 39 LEDs, and they are ultra-bright LEDs, so they drains the battery fast. So I thought if I connect some solar panels to it, I can charge power bank during daytime.

Question by Sp1k33 2 years ago  |  last reply 2 years ago


How to power a High power laser diode?

If I build a 42A Constant Current PSU which can supply 1.2-6v, will the laser diode only draw 1.8-2V or will it try to draw to much voltage and damage its self? I have a 40W CCP CW Laser diode, here are some characteristics. Operating Voltage (V) <2.0 (1.8 typ.) Operating Current (A) <46 (42 typ.) I know that laser diodes will try to draw as much current as possible and suffer thermal runaway, so they need constant current power supply's. If anyone has any information on how to power high power laser diodes please let me know. All help will be greatly appreciated! 

Question by deltawars 4 years ago  |  last reply 4 years ago


What is the best way to power 25 red 3watt LED's and 5 blue 3watt LED's with a 100w LED constant current source driver? Answered

Please excuse me as my technical skills are not as good as I would want them to be :D So, I am trying to build a grow light with this setup: 1. 25 red 3Watt LED's - DC Forward Voltage (VF) : 2.2-2.8Vdc - DC Forward Currect (IF) : 700mA 2. 5 blue 3Watt LED's - DC Forward Voltage (VF) : 3.4-3.8Vdc - DC Forward Currect (IF) : 700mA 3.100W LED Constant Current Driver http://www.dx.com/p/waterproof-100w-led-constant-current-source-power-supply-driver-100-240v-146055#.VRh4f-HkWqg Power: 100W; Input voltage: AC 100~240V 50/60Hz; Output voltage: DC 8~12V; Output current: 8A (label on the box says: 12V 8A) What would be the best way to wire the LED's for maximum efficiency? I'm thinking somehow in parallel, but how exactly? Thank you.

Question by voltskaterzb 4 years ago  |  last reply 4 years ago


Using a 1500mA LED driver to power 1400mA of LEDs?

    I am building a light panel to grow lettuce indoors and need some help. I am relatively new to electronics and trying to learn. The LEDs are: Max. Forward Voltage: 3.0-3.6V Max. Forward Current: 700mA The LED driver: DC20-39V 1500mA +-5% I have done the calculations and will be using 20 LEDs in 2 strings with 10 LEDs in each resulting in 1400 mA at 36.0 VDC. So I bought the LED drivers stated above with the current knowledge i had. But after learning about Constant Current LED Driver, I'm not so sure anymore as the LEDs will not draw what they need, instead be supplied with a constant 1500mA. Am I correct to assume that the LEDs will be fried driven in this configuration? Is there a way to make it work or is the only option to buy a 1400ma LED driver? Many thanks!  

Question by Stumpe 3 years ago  |  last reply 3 years ago


Accurate Variable Current Sink? Differential Voltage Reference?

Some background: I have recently aquired a few really nice (and really heavy!!!) LAMBDA power supplies, The largest one supplies 24V, and up to 9A, but has annoying foldback current limiting, which causes the output shut off when even a short period overload (like inrush current) is detected. What I want: I would like to modify this power supply to give me (ideally) completly variable 0-15v dual rail voltages & 0-5A adjustable current limit, & I would like this to be controlled with arduino so that I can use a nice LCD display and control the supply remotely with a bluetooth or wifi app, and possibly do some data logging which could come in handy for energy measurements and stuff! My current PSU design: The schematic below is what I've currently built in LTspice. Both the voltage & current regulation work. The voltage across the (+) and (-) inputs of the current error amplifier should be the sum of the voltage drop across the shunt resistor and the voltage drop of a voltage reference, so when the voltage on the shunt resistor exceeds the voltage of that reference, the op amp will start to limit current by reducing the bias voltage on the pass transistor. This V_ref needs to be both variable and accurate, but since this V_ref is a differential voltage between the output of the pass transistor and the input of the error amp, I came up with the clever idea to use a resistor there and a variable constant current sink. That way the constant current through that resistor results in a fixed V_drop across it. With a bit of fudging around with it, I was able to make it work. However, I need to replace that "ideal" current sink with a real one. I tried using the classic NPN-based one, but it wasn't good enough. I then attempted to make the slightly improved version of that current sink with a spare op amp, although this worked, it would stop pulling current once the voltage fell below what was being maintained across the small resistor. The REAL question: Would anyone happen to know how to make a really accurate and variable current sink? Maybe if this is not such a great idea, what other methods can I use to generate a fixed differential voltage?

Question by -max- 3 years ago  |  last reply 3 years ago


Best Way of Boosting 7.4VDC to 12VDC? Answered

I need to power two stepper motors off of 7.4VDC, and am trying to figure out the best, most cost efficient way.  What type of DC booster circuit would be best for this application? Do I need any noise filter? If yes, what kind? If I understand correctly, Stepper motors need a constant current. Does this limit my selection of DC boosters/step up devices?

Question by RocketPenguin 2 years ago  |  last reply 2 years ago


Such a thing as a variable voltage/current overcharge protection?

I've had a couple of bad transformers in battery chargers in the last couple of months and I am thinking of building my own variable voltage/current battery charger with an ST Microelectronics L200. Figure #23 http://www.datasheetcatalog.com/datasheets_pdf/L/2/0/0/L200.shtml But I would like to have overcharge protection so I don't have to monitor the batteries charging once I set the volts and current for that battery. Something that would just shut off or switch to a trickle charge when the battery reaches the voltages I want or set. Also, another question - I am intending to use a salvaged transformer from an old chamberlain garage door opener for this project and need to know the best method for lowering the voltage from it to something the L200 can handle. It's a 1:3 and takes my 125v main to roughly 42v and the L200 is rated at a maximum of 40v input. I was figuring on just using a resistor, but I don't know how to calculate what I need since the current and voltage will be changing the load on a per battery basis. Also I think the transformer might be a little small for this project, it only measures about 2"x2", while most of the chargers transformers were twice the size or more. So I'm wondering if it might not be able to handle the constant power or heat requirements for charging. *Added a pick of the transformer. And since I've asked this many questions, I might as well add another. I was looking through the "how to get free electronic parts" pages and I didn't see any on solar cells. Does anyone know if any company does samples for cells the way they do for electronic parts? I am capable of following simple to moderate schematics and can solder well. But when it comes to making new circuits and such, I tend to just hobble together something I've seen or used before that works. When it comes to programming and calculating circuit load and all that I become bogged down pretty fast. If I can see it and experiment with it till I get it right, I am better off and maybe learn something. So the simpler the better.

Question by Dochide 7 years ago  |  last reply 7 years ago


Electronic timer circuit.

I have a 9vdc supplying 3ma constant current. I wish to switch polarity automatically every 5 minutes with a timer. How can I do that simply?

Question by rhhince 9 years ago


Does a current activated switch as small as an OR Gate exist?

I have a type of connector that has two wires. two on one side and two on the other. One of the "connectors/wires" is red with ~5V and the other is white with a varying current/voltage of ~10mV to 3.3V which goes in either direction. This connector is meant to be plugged in, in either direction. So at any given time, only one side is receiving current. The bottom of the connector if thought of as a box comes into contact with a grounding panel, which shorts out the connector, and it does not function. What I need is to have a sort of switch, that when activated by current, can "turn" off the bottom pins when plugged in one way, and then the other pins when plugged in another way. I have thought about it and I can use a simple OR Gate, for the constant 5V, but OR Gates will not work going in two directions or at a varying voltage of 10mV to 3.3V. I was thinking that perhaps a current activated switch would work, but it needs to be a very small chip, and relatively low cost. Anybody have any ideas? Sorry for the poor picture. I am not an artist. ;) Thanks, in Advance. -Sterling

Question by XP1 5 years ago  |  last reply 5 years ago


Help me designing charger for Li-ion 9.volt battery?

Hello all.... need help !! circuit diagram for making charger for my li-ion 9volt- 600ma battery ...  I want to charge at 60ma ... how to limit current here (constant current) (I have 12v  & 18v 1.5amp power adapter) in general how to limit current in Circuit? (which components to use ??) Thank you :)

Question by 60ma 3 years ago  |  last reply 3 years ago


Boost converter LED brightness?

Will a boost converter IC (such as the one from maxim) ever be able to power a high power LED as brightly as when the LED is powered with a constant current source?

Question by .Unknown. 8 years ago  |  last reply 8 years ago


How to connect 10x 10W Power LED?

I have 10x 10W LED, vf = 9V and fc=600mA. I planned to conect them 2 in a row and 5 rows in parallel. From this, i know that the overall row Vf = 18V and fc=600mA overall current drawn from the source = 3A (min) I plan to use 24V source to power this circuit, anyone can kindly advise me, 1. How I ensure the current into each row is constant at 600mA? 2. do I need voltage regulator or just a power resistor connect onto each row will do? anyone pls kindly advise.. Thanks a million PS: Happy new year to you all

Question by acidjc 8 years ago  |  last reply 8 years ago