My question is, how do you hook this up to the Arduino? I woul be making three of them, one for each color and using the LM with a 12V supply. Please guide me accordingly. Hi Garfield, for 10 watt LEDs the Arduino signals will need to be fed to transistor drivers, and the LEDs will need to be connected across the collectors for BJT , or drains for mosfets and the positive line…this positive line is supposed to come from the above current limiter stage….
I hope you got the plan. Firstly, wow, our names are quite similar. Secondly, I plan to connect about 15 pcs of 10w leds V,mA using a computer PSU 12V,20A , but I hear there's a risk of burning the leds out due to variable current and heat. Is there any way to implement your circuit to this application. Sorry, I'm a complete newcomer to this, so can't figure it out myself. Instead of the above explained LM design you can rather go for the following design and apply with each of the LEDs….
Even though I kinda got the basic concept of the circuit from the link you provided, I have no clue how to practically apply it, what components do I need to procure? Sattam, you will have to calculate the parts with the help of the formula as suggested in the article. Can i skip the current limiting section from the above ckt to drive n nos. Will be driving it by pc smps 12v rail. It is mandatory for all high watt LEDs.. Thanks Abba, glad you are learning from here…yes it seems like a printing mistake, but I am sure readers will understand and ignore it….
Hi Sir.! First of all, congratulations for the help that you give us. If we have: Power Source: 12v.. Thanks by advance. Thank you Fremin, actually if you use the first circuit with a proper limiting resistor, then the series resistor with the LED can be avoided. Writing it again. Not sure if previous question was posted properly because I cannot find it after post.
I need your help to limit high amp input. One of my friend bought 12 volt 4. I am sure something should be connected to limit the current. Can you please help me generating a schematic of a circuit that can limit the current for 4. Hi Saqib, all comments are held for moderation without any notice, so they will always reach me, no issues.
I have deleted your previous comment to avoid duplication. If your fan is rated at 12V, then the current would have not effect on its functioning because if the load and source voltages are correctly matched, current becomes immaterial. Even if your battery is rated at Ah still a 12V load would work without any issues. I am sure the fan is not rated for 12V operation or it might have had some other internal problems.
Make sure to add a 1. Your LED burnt due to heat, and thermal runaway. When an LED heats up it starts consuming more current, this causes more heating and the LED consumes even more current….. So it is not the current rather heat which destroys an LEd in the absence of cooling. But controlling through external cooling can be difficult, therefore it is better to have a current controlled input. You can employ both voltage and current control by applying the design shown in the following article:.
Good afternone Sir! If the above sentence is right,it means no need of current controling curcuit. Am I right? God bless you again and again! If it has the heating up tendency in that case a current controller will be required, otherwise the LED will start drawing more current as it heats up! Thank you for your response! Obviously, the heating up tendency will be controlled by the heatsink but I think that the absence of the current controller may lead to loose more current in the form of heat which economically is not efficient enough.
Is that true? Thanls again! I want max 4 amps as I am charging some current sensitive batteries with a 24v LED driver constant Voltage power supply. It has a hiccup current protection which I dont want and has kicked in at 4. Cheers, Dave, UK. All the designs shown above will work with 24V without any issues. So you can use any of them for your specific need by calculating the parameters accordingly.
Thanks very prompt. I may not have a IRF so the link was for the power nower transistor I will try and use. If I use a potentiometer of 10k instead of the zener will there be problems please? My pleasure! If you do not want to use a mosfet then you must try the second last design. Zener is required only for a mosfet not for BJTs.
Hello again I really want to adjust the current limit a little, so thought to feed T1 with a voltage divider a pot of 10k? For your case you could add a pot in series with R1. Make sure to calculate them correctly.
Not as simple as yours though! A filament bulb can be used in place of R2, but the the response of the bulb may not be as linear as a normal resistor. A 12v festoon filament bulb of 15w, car interior bulb should have 1 ohm cold and 10 ohms hot it draws 1 amp normally.
I wonder therefore if one uses this as the shunt resistor on the NPN emitter , and just use one BJT transistor my Power transistor I could then have a 10k pot entiometer feeding the base between the 24 power supply rails? A shunt is supposed to short the power supply rails on overload. Do you think dispensing with or leaving out T2 would work therefore as a current limiter if one uses a pot as a voltage divider on the base of the power transistor instead of T2 etc?
My understanding is that as the voltage across the emitter resistor, shunt or whatever rises the forward bias between the base and emitter will drop so I could have current adjustment using the pot? A Shunt is normally connected in parallel to the load, not in series.
T2 does two things, it saves power and also enables a complete shut down of power to the load on over-current. On the contrary if only a limiter resistor is used it will keep dissipating power at different levels regardless of the over current, and never allow a complete shut down of the supply on over current conditions.
If I use the last circuit, will there be any difference between high side and low side current limiting? As I could see the last circuit limits current on the low side, but in my application the current must be limited at the high side ie.
Sorry did not understand what you meant by high side low side current? You can set it at any desired threshold current. The only criterion is to select the mosfet appropriately for handling the specified amount of current.
Keep the battery connected with the solar panel through a high value resistor, this will keep the floating charge always on. Initially try a 1 K resistor and check whether it prevents the battery voltage from dropping from its fully charge level.
If it does, then try some other higher values like 4k7, 10K etc and see which highest value succeeds in preventing the battery voltage drop from the full charge value. Select this highest value. My choice on using a MOSFET is so that there is very little current drawn by the circuit other than that going through the load. The current passing through the load is required to be limited to 3A and the negative or ground side of the load is required to be connected to the ground or 0 volts.
The approximate voltage across the load Vload should be in the region of Will this be acceptable to your design. Hi Swagatam, Many thanks for the prompt response, the actual PD across the load is required to be approx I have a programmable PSU to deliver the supply voltage, so this can be increased as needed. Th supply voltage can be increased to approx 24 volts. Hi Brian, you can try the following software for calculating the resistors.
R2 is the ground side resistor. Many thanks, for your ongoing advice. I have selected most of the components of the suggested circuit for a trial run. What would you suggest? Hello sir please do you have a video on making the current limiter on a pcb or a breadboard on youtube? My load resistor is set to. Proteus circuit simulator shows my load drawing 3. Battery voltage is 8. How can I achieve the full 5 amps I designed it for?
Swagatam, i have a need to do DC current limiting on a much larger scale. Say we had a 24VDC system with capability of A continuous. To prevent battery overheating during charging, we want to do current limiting to 40A on a leg of the circuit. What is a commercial solution that we can apply? The idea should to slowly increase the voltage instead of applying it at once. Hello, I am looking to replace some indicator lamps in an old JVC A-X9 amplifier, but there are no specs in the service manual, so I am trying to figure out the circuit diagram.
There are two pnp transistors connected at their bases in parallel at the beginning of the light bulb circuits, and each transistor feeds a different circuit. Circuit one has 5 bulbs in series with various switches, and circuit two has 7 bulbs in series with various switches and also RC circuits. My question is would the pnp transistors act as current limiters for these circuits? I tried to build a simple model in iCircuit, and the current was always the same no matter what bulb characteristics I chose.
Hello, Without checking the schematic practically I cannot suggest much. If the LEDs are 20 mA type then current limiting can be done with series resistors, transistor current limiting is normally required only for power LEDs, with current higher than mA. The original circuit used incandescent bulbs, not LEDs. I would like to change to LEDs, so I am trying to figure out what the circuit will require for modification.
Can I send a pic of the schematic? If they are incandescent lamps then definitely the PNPs are not limiting current, they are probably used as switches. If you use 20 mA LEDs which will be much brighter compared to the incandescent lamps, then appropriate resistors can be used for the current limiting. Images can be sent by uploading to a free image hosting site and providing the link here. Can you determine the type of bulb from the schematic? My ultimate goal is to tell the gentleman who is building the LED replacements for me what the voltage of the bulbs being replaced is.
In my project I need a 10A current limiter, thus LM would be the right choice. So, what is the best IC in my case. Do you have any tip? Tks Eduardo. Great site. I need a simple current limiting circuit for a 12v solenoid valve on a sailboat hyrdraulic steering system. Cannot live with the power consumption of 2 amps to hold the solenoid open and it is not necessary. Any suggestions how to do that with LM?
I am thinking some sort of an RC network to control a mosfet that gives path to one resistor when first energized, then a path to the second resistor value when the capacitor voltage decays, but not sure how to approach that.
Hi, thanks, the following idea should accomplish the intended slow start current limit application:. The R3 develops the required switch ON voltage for the BC transistor base whenever the current limit exceeds the maximum tolerable threshold. But due to the presence of the uF cap, the BC is unable to trigger quickly allowing the full current to pass, at the onset.
However, as soon as the uF is fully charged, the BC activates and becomes functional for controlling the current limit…. For a maximum operating current limit after capacitor delay of 0. R1 and R2 are interdependent, and R2 has to be set to match the load voltage specs. Is the voltage drop always going to be too large to power LEDs with 3v forward voltage? Hi Jennifer, the transistorized circuits shown at the bottom section of the article will easily work with 3V supplies.
Thanks very much, so the one with the BJT 2N circuit at the bottom? If you want to fix the current to say 15mA what is the calculation for a fixed resistor rather than the variable one? And I would this be suitable for any number of LEDs off the output or is there an upper limit?
Hi Jennifer, sorry, I was actually referring to the first transistorized circuit using two transistors, the one which shows the big square LED. A specialized current limiter becomes crucial only for those LEDs that are rated with over mA current and have the tendency of becoming hot themselves. You can read the following article for getting further details about the connections and the calculations:. I have bought a tiny unit that does this with fixed mA output but it needs minimum of 4volts v and I wanted to know if it was possible to successfully run say 5 LEDs off a single IC output at only 3volts using a current control circuit with mA output.
It needs to be a small footprint so it can fit on a small PCB and a 3v battery. I hope that explains it better. At 3 mA each of the LEDs will look very dimly lit. Found the datasheet — is there an alternative to the 2N in a more standard small surface mount package? That BJT is too large and expensive for my application but the simple circuit is perfect.
You can easily do it by connecting the ammeter directly across the output of the limiter. However, remember doing this will heat up the current regulator, so you must take the readings quickly for the necessary calibration. Sir, I have a proublem. Transformer out put current after 10amp bridge rectifier is 7amp. I connected 2. But after lm voltage controler circuit, I am getting only 1.
Since I need 2. But current still reduced to 0. Please sir, solve my proublem. Thanking you sir, Leelesh. Leelesh, there can be only two reasons behind this issue, either your LM is a duplicate or faulty, or your connections are not fully correct. A good LM will produce a guaranteed 5 amps provided the input is rated higher than 5 amps and the IC is mounted on a large heatsink. How is this possible? Add a low value series resistor with the line, connect a suitable bulb across the resistor.
The bulb will light up as soon as the output is shorted. I have a 5V 18A desktop computer power supply and I want to build a multiple port charging station where more than 10 handsets phones can safely charge without over current issues. Do I need to build the current limiter for each of the output that will be connected to the handsets?
You can try the first concept from the above article for each channel separately, using IC LM If you find the IC heating up, you can try using LM Hi sir, Please clarify bit more under heading , Using Mosfet for current limiting , How to calculate R1,R2 values and Working ,how much current we can limit?
Hello Anushree, I have added the required information under the specified section! The calculations will be exactly similar to the previous versions in the article.
I want to drive some ma UV LEDs, though ten of them, intended to make a 30W nM lamp for curing photo-activated polyester and epoxy resins. Yes you can use BS in parallel without any further modifications to the shown design. Can you include the resistor power calculation in your article? I have BC and 2N transistors available. I also have AMS voltage regulator or a variable buck converter, if these would help. Hi Andrew, yes, for the transistorized circuit also current sensing resistors will be required, albeit with much lower wattage value compared to resistor without transistors.
I have added the wattage calculations formula in the relevant sections. Ah, yes I see now. How do I find value for Hfe? You use I have bc or 2n transistors. Which value do I use? In your transistors example there may be a mistake.
No problem Andrew, The R1 resistor is for the base of T1, but the actual current limiter is the resistor R2, at the base of T2. Actually the mistake was in the diagram, it is supposed to be a 35 V circuit example for controlling a watt 35V LED module. Acer Mini Tower. Navy Blue Mosaic Tile. It S Showtime Incredibles. Aisle Decorations.
Toby Keith Album Covers. Acer Mini Notebook. Pipe Clothing Rack. Liquid Look Leggings. Lm Amplifier. Breakfront Furniture. Corner Gas Log Fireplace. Windows Notifications Disable. This continues with the LED getting hotter and hotter and conducting more and more power that even without "moving to a new environment" your LED will eventually fail and burn out regardless of how precisely you've set the voltage.
LEDs can never be driven by constant voltage unless you want them to die an early death. Question 1 year ago on Step 5. I would like to obtain a current source around mA. My Power Supply is 21V. Could you help me? I don't understand. Depuis un ans je suis dessus pour un avion Beechcraft Question 2 years ago. In the constant current led driver circuit you do state that in step 6, the input voltage varies from 3 volts right up to 60 volts.
Is the input voltage dc or ac? I want to achieve it without opening the LED it without messing with the invite circuit. What is a good approach to do this? Would an nchannel power mosfet do the trick?
Thanks in advance! Question 3 years ago on Introduction. Question 3 years ago. Dan, thanks for this clear and simple explanation. I see only higher voltage values. Hi I'd like to make a high power led strobe. Something around lumens out put, can I use one of your designs to accomplish this task. Question 3 years ago on Step 1. Tip 3 years ago on Step 5. Concerning regulators, there are some very tiny regulators available online on eBay and Banggood.
I've tested them, and they work great. They are adjustable, but cannot provide much current so don't push them. I had so many bad experience with the existing LED driver in the market, and I want to know why. I am very fresh into electronics, please excuse my ignorance if I say something fundamentally wrong.
I did some study with the circuit and the part list. After some calculation, it seems that the only thing the MOSFET does is to stop the circuit with excessive current flow on the order of 10 to 50 times the running current , and does almost nothing to the small current fluctuation. Once again, I am very new to the electronic circuit design, and maybe I've interpret the datasheet incorrectly. I am hopefully I can get some insight from the experts like you concerning a little more detail about the calculation and the detail parts selection.
I am having some trouble following along with the full instructible and don't want to order parts I don't need. By dan MonkeyLectric Follow. More by the author:. About: Dan Goldwater is a co-founder of Instructables. Currently he operates MonkeyLectric where he develops revolutionary bike lighting products.
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