One of my friend bought 12 volt 4.2 amp DC fan and bought 125 AH battery to get a longer backup. LM317 has internal thermal and short circuit protection so most probably it might be still OK, but if it's a duplicate IC then the results could get seriously affected. actually 6 of those led at once. input current does not matter, neither will the output consumption, it's the input voltage that must not exceed 35V, rest everything is internally protected for these ICs. Comparar. But in practice I still am unable to replicate the current using NI Multisim. ?If so, how can it be done???? say, if i need to drive those led at 10v and 500mA, what i need to do? yes that's correct, it should be done as suggested in the previous comment. Hai, thanks for the calculation. Vista Rápida . I think I am not understanding Vref. Copyright © 2021 Newhaven Display International, Inc. All Rights Reserved. I tried turning my pot up to 28v on the input and that just reduced my current to the load but kept the voltage on the load at 19.7 volts.Do you have any pointers?Thanks for your help. A shunt is supposed to short the power supply rails on overload. Great now that all makes sense. Making a current controlled LED tubelight. 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? Since I need 2.5 amp for a battery charger I removed above 2.2 ohm resister. Supply is 24 volt 5amp. Connecting the adaptor to LM7808 to obtain constant 8v, 1.5A. Also, if i’m running LM196 at current limiting mode, is the main heat dissipation from the chip itself or from the resistor? Hi, you can try the second last circuit from this article; https://www.homemade-circuits.com/ic-lm338-application-circuits-explained/. Your understanding is correct but won’t be as efficient as including T2 would be. A 12v festoon filament bulb of 15w, (car interior bulb) should have 1 ohm cold and 10 ohms hot (it draws 1 amp normally). What can i do? If the input is a 12V supply then you can connect the LEDs in parallel across the output of the first circuit, with a 24V input you will need to connect the LEDs in series and connect their ends with the output of the first circuit. Dave, you can try applying the second last design by upgrading the MOSFET with 5 to 6nos of IRF540 in parallel. & also will the circuit be the same for 1-led ? By the way input should be adequately rated with the amp capacity, meaning it should be rated much higher than the required specs of the load. The input supply will need to be 7V higher than the final result obtained in the above software. So as long as I have the correct current it should be okay because my supply can easily supply enough voltage (Vf). Hi sir can you tell me what is current generator circuit & current limiter circuit? So, to power a 12V LED, should I use a minimum of 15V power supply? LM317 will not work, since parallel connection of the LEDs will require 650 x 6 = 3.9 amps. Here, I is the current limit in amps as required by the application. I have selected most of the components of the suggested circuit for a trial run. I have deleted your previous comment to avoid duplication. of high power leds of 5W,12v.Will be driving it by pc smps 12v rail. The bulb will light up as soon as the output is shorted. I want to used 1 watt LED in 7 no series and 14 no line in parallel total 98 no LED's. How can I achieve the full 5 amps I designed it for? On a side note, I had some 1n4007 diodes, anyways they can be used? 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. How to convert that to 13.5v 700mA DC? If they are incandescent lamps then definitely the PNPs are not limiting current, they are probably used as switches. In my project I need a 10A current limiter, thus LM196 would be the right choice. LM338 capable of giving max output of giving 5A. Salida 24-48Vcd. So for the IC LM317, LM338, LM196, the input Amphere can be anything. In stead of load-resistance (R2 here), can we put some current mirror circuit for soft control? Does the value of R1 or the setting of the P1 pot matter? What will be the values of the two resistors?? 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. Connected two strings in parallel. 7805 will not supply 10 watt at 3.3V so it cannot be used. Writing it again. Hi Shane, if the voltage is not going above 19V without the LED connected, there could be something wrong with the IC again or the wiring, if it's happening with the LED connected, remove it and check the same without any load, it should increase to 24V, and that could be considered as normal. I’ve bought a similar current controlled circuit but it’s minimum of 4 volts and I need the smaller battery size. This current controller circuit features a Darlington pair T2/T3 coupled with T1 to implement a negative feedback loop. I want to make a 7w bulb using Edison 0.5w,5630 led. Will the same circuit run from a 9V power source? The figure shows a variable resistor for setting the current control, however R1 can be replaced with a fixed resistor by calculating it using the following formula: Current may be different for different LEDs and can be calculated by dividing the optimal forward voltage with its wattage, for example for a 1watt LED, the current would be 1/3.3 = 0.3amps or 300 ma, current for other LEDs may be calculated in similar fashion. i want to use LM317T IC instead mentioned one. ?Supply voltage is 12V 3 amps. I have a programmable PSU to deliver the supply voltage, so this can be increased as needed. Is Vref always 1.25. how did you measure the output current? But for the lamps in the series with REC, TAPE MON, etc, I don’t understand how the RC circuits affect the voltage, so I can’t spec the lamp. If you find the IC heating up, you can try using LM338. so the output from each resistor will be 6.6v, 350mA. I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. Let's say the input supply the source current I starts rising due to high consumption by the load for some reason. Any ideas? Previously, perhaps the LM317 had shut down due to overheating. A 11 watts CFL bulb require 240v AC, 2. The resistor is calculated in the following way: Yes, I was not understanding the maths. FOR CREE LED XML 3.3v,3A what will be the input voltage and resistor value? If we have: Power Source: 12v..(from car battery) Power leds 10Wx3( 10V, 0.8A each one) Can you give some sugestion about the diagram and the configuration and wiring? Ok got it work with a different IC. I think this will be a constant output. each LED series will require a 25 ohm resistor, not a 6ohm….may be all your LED sgot damaged and could have become weak. Can u tell me what resistor value I can replace with that existing resistor?? multiply 1.25 by the amps that must not exceed. 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. Images can be sent by uploading to a free image hosting site and providing the link here. Much appreciated. I am not sure why I was limited to 19.7 volts as I would like to drive the led a bit harder. R = 1.25/5 = 0.25 ohms, wattage = 1.25 x 5 = 6.25 watts. I would like to create a circuit which is similar to the one above but uses a MOSFET. An LED system is itself the most economical lighting option available to date, it cannot be further modified in any manner for getting more than what its been specified at. A specialized current limiter becomes crucial only for those LEDs that are rated with over 100mA current and have the tendency of becoming hot themselves. Am using 13.5v smps adaptor. Also the LM317 became very hot when I was measuring the current only. No problem Brian, please see the configuration presented in the following concept, you can replicate the MOSFET/BJT section for your specific application, https://www.homemade-circuits.com/0-300v-variable-voltage-current/, The current can be calculated by the formula 0.6 / 3 = 0.2 ohms 2 watt. my question is how we can improve illumination & is it required current limiter circuit in above article in this application. you can use the following software for calculating R1, R2 values precisely: https://www.homemade-circuits.com/lm317-lm338-lm396-calculator-software/. Thanls again! Its nice to read your knowledgable blog, I'm a Street Vendor in Delhi have 7 Outlets as of now and in search of a lighting system for the vending counters. easy-electronic-circuits.blogspot.in/2012/03/deriving-high-current-from-7805-7812.html. I have used the IC myself plenty of times and have never faced this issue, if this would be the case the manufacturer would have clearly mentioned it in the datasheet. I thought maybe ohms law fixed current and resistance locked the voltage at that level but then I remembered leds don't abide by ohms law.????? Hi Swagatam, Many thanks for the prompt response, the actual PD across the load is required to be approx 16.5 volts. My load resistor is set to .0001 ohms. you can simply feed the 12V at the input of the first circuit, and use the output to power the Arduino lamp. Oh well.Thanks for all your help. I don't think a simulation would be necessary, simulators are not always correct, it's better to build the circuit and verify the results using a digital multimeter, that would enable you to understand the design practically, tweak it personally and also confirm the final results. T2 does two things, it saves power and also enables a complete shut down of power to the load on over-current. Also can I use a small car bulb as this resistor (the shunt or emitter follower resistor)? Dear sir, Good day to you Kindly help me How do I connect one 10 watts LED through a LM338? with a 12V/1.5amps output, it can accommodate not moire than 9nosof 1 watt leds, made by connecting 3 strings of 3 leds each in parallel. and if possible Please, where should I connect the ammeter safely so that it works correctly, thank you very much for your attention, I await a reply please through by e-mail to HNF1975@gmail.com. that can be used up to 40 watts which can be used instead of mcb …..as in our market we didn't get the mcb that can meet our requirement (that trip in 40 watts)….I would be grateful if you help me in this project. Even if your battery is rated at 1000 Ah still a 12V load would work without any issues.” My question:-Just now ,I am makeing ca. A classic example is illustrated below, which can be easily modified as per the requirements and LED specs. Thanks by advance. The current increased till it hit 24v and started decreasing above 24v. Sir, I have a proublem. because below 1 ohm thr is no resistor available in local market. Fantastic!! yes it may be done, provided your 13.5V is almost constant and the ambient heat does not rise by too much. A 40 watts LED panel require 26 v DC. Do I need to build the current limiter for each of the output that will be connected to the handsets? ? I connected 2 x 5watt LED in parallel to a LM317. Use this formula for calculating the resistor, R = Us minus total LED drop divided by led amp. Th supply voltage can be increased to approx 24 volts. Hi Sir,How U??? We strive to help elementary and middle school students as well as hobbyists, through STEM education, strengthen their hands-on practices and problem-solving abilities عات نایاب، سهم بزرگی از بازار الکترونیک ایران را در اختیار بگیرد. Newhaven Display partners with distributors worldwide to bring you the best in display products and design services, no matter where you’re working from. Hi Swagatam, I didn’t want to say too much on an open forum but what I need is a way to control current so I can connect multiple LEDs to the same microchip IC output without needing a resistor for each individual LED. Seeeduino V4.2 is an Arduino-compatible board, which is based on ATmega328P MCU, Arduino UNO bootloader, and with an ATMEGA16U2 as a UART-to-USB converter. 10 LEDs of 1 watt each connected in parallel which require 3.3v, 3.5 A. which of the above two will be more energy efficient? suppose in the above circuit, the input is 12v 1A and the output is 12v 700mA by fixing the R1 as 1.78 ohms. Can I send a pic of the schematic? I’d like to use the circuit above but the steps for calculate the component values (mainly resistance), are not clear for me. Is the LM317 burnt out???P.S. Hai, Can u tell me that how u calculated the R1 should be 0.5 ohms, 2 watt in which u replied for Vinu subash?? You can read the following article for getting further details about the connections and the calculations: https://www.homemade-circuits.com/how-to-calculate-and-connect-leds-in/. Required fields are marked *. To prevent battery overheating during charging, we want to do current limiting to 40A on a leg of the circuit. i want to make 1 watt led light (3.3v, 300ma) driven from my old mobile phone charger (5.8v, 500ma). i want to run some high watt led. To 12V DC Adaptor power supply? And both the resistor is conected to An IC.. yes R1 is connected to the LEd so it's irrelevant, try R2 or R10, experiment a bit with the two and adjust until the required output is found. Hi, each string will consume 350mA, not 700mA, the total will be 700mA. Good afternone Sir! which of the above two will be energy efficient? Transformer out put current after 10amp bridge rectifier is 7amp.when directly connected to DMM. It must be done by connecting the ammeter in series with the LEDs, if you connect the meter probes directly to the output terminals then the IC will get shorted and heat up. I connected 3 x 0.5ohm resistors @ 5W. 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. Also, to further reduce the dissipation on the MOSFET and the limiting resistor you can use the 24 V in pulsed form. 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. ... 10 LEDs of 1 watt each connected in series which require 33v, 350 mA, 2. i have a collection of 50’s/60’s model trains which work fine until i try to use a modern transformer/controller 0 to 12 v dc @ 2.5 amps. for your application you can add one current control stage for each LED. Not as simple as yours though! R1 and R2 are interdependent, and R2 has to be set to match the load voltage specs. First of all, congratulations for the help that you give us. Fuente Driver Para Led De 8-12W Voltaje De Entrada 85-265Vca. This will result in an increase in the potential across R3, causing the T1 base/emitter potential to rise and a conduction across its collector emitter. 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. but still i dont get sufficient illumination. R2 or R10??imgur.com/12SdCvSimgur.com/dFKArEo. Reason being the light shave to stay on with full power for around 7 Hours. (-20 to +70c), CH x CW = 4.75mm x 2.95mm, RoHS. Ashoke, use three 1 ohms in parallel, that will give 0.3 ohms almost. So need a clarification on calculation.And am having another two doubts…Q1:- 1. So, from calculation I(LED) =0.4A each.The resistance value= 1.25/0.8= 1.56 ohms. You will need an LM338 with the first circuit configuration.For R1 you can use 0.4 ohms, 1 watt resistorthe leds can be connected in parallel at the output, and the input of the IC can be connected with the 12V /5 amp supply. I'm Not able to find possible solution to my Problem, would be great if you could help. Voltage and current rating of 10W LED is 9-11V and 1050mA respectively. Am I correct in thinking that I can replace them with a voltage divider configuration? If I use the last circuit, will there be any difference between high side and low side current limiting? Even if your battery is rated at 1000 Ah still a 12V load would work without any issues. 3500 mA. i made a small observation in the second diagram in the smp you wrote 12amp and 5amp, i think the 12 should be voltage value and not current, am i write? if 13.5v drops down there won't be a problem but it must not rise upto 14V or 15V. The above BJT based current limit circuit can be improved by replacing T1 with a mosfet as shown below: The calculations will remain the same as discussed above for the BJT version. So the LED bank need 6.6v, 1.4A. Hi Jennifer, sorry, I was actually referring to the first transistorized circuit using two transistors, the one which shows the big square LED. you can try the last circuit persented in the following article: https://homemade-circuits.com/2013/04/1-watt-led-emergency-lamp-circuit-using.html. yes even with an output short circuit the current should be limited, not sure how it was showing 2.3 amps, anyway it's good to know that it's working now. hello swag i used the above circuit with 30 watt led .all going well but i couldn,t find 0.7ohm 7watt resister.. so i used 2 resisters of ( 0.33ohm 5watt + 0.33ohm 5watt )in series . It may be due to the current limitation of 2A. I found winding the input voltage from 20 volts up to 28 volts the output voltage driving the led remained the same at 19.7 volts. I Don't have electricity available on the streets hence have to rely completely on BattteriesI'm Currentlky using 80 Watts 1 watt LED Strips that operate with 12 V Battery, But want to increase the lighting to around 400 Watts with minimum powerc onsumption of battery Power. In this blog we have studied a few versatile work horse ICs such as LM317, LM338, LM196 etc which are attributed with many outstanding power regulating capabilities. the controller “see’s” a large inrush current and before the locomotive can move and trips the overload circuit in the controller. I have 24 volt 5 amp supply & 1 watt LED in series 7 no so is it necessary to use current generator or limiter after supply? Many thanks, from the “0-300V Adjustable MOSFeT Transformer-less Power Supply” Circuit diagram, as directed i will ignore the bridge rectifier (D1) and the reservoir capacitor (C1). how to connect the battery to the below link circuit and what are the modification do i need to obtain 13.5v as output? which resistor i have to change to obtain 13.5v?? Your LED burnt due to heat, and thermal runaway. : My power is 12.3V & 3A. I took the readings from the point where I connect the LED. The series resistor connected with the three LEDs is calculated by using the following formula: R = (supply voltage – Total LED forward voltage) / LED current, R watts = V x A = (12-9.9) x 3 = 2.1 x 3 = 6.3 watts. 10 LEDs of 1 watt each connected in series which require 33v, 350 mA, 2. ?https://homemade-circuits.com/2013/06/universal-ic-555-buck-boost-circuit.html, These are the images of the 12v adapter. Comparar. Really appreciated. Hi Brian, you can try the following software for calculating the resistors. A vintage way is the LM3909, a chip from 1975 that can flash an LED for a year from a single flashlight battery. I have connected 30x1w leds….3 leds in a string totally 10 strings…..my input voltage is 12v 5amps…..how should i wire up these led arrays to the input source…..aim of the circuit: led should glow at full brightness, less heat generation. I=3.78A R=0.36ohms.Left to right pin out of IC (writing to front) Adj, Vout, Vin.Resistor connected between Vout and Adj.As a variation I also tried a 0.8ohm, 0.33ohm and no resistor and get exactly the same values on Vout across the load (100 watt 24v led) as I do with the 0.36 ohm resistor.The values I get is 19.7 volts and 3.7 amps. Keep the battery connected with the solar panel through a high value resistor, this will keep the floating charge always on. but Led burned due to excess of current so i red about LM338 and i found that it allows 5A current,, all i need is 3A & 3.37V. Due to this the current increase would get countered and restricted through the load. 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. I hope that explains it better. I have used 32 volt supply 0.36 ohms connected between Vout and adj.I figure this would give me approx. Our standard Character display designs range from 1-line by 8-characters to 4-lines by 40-characters. Everything will abide by Ohm's law, only the way to understand it could change as per the specifications of the particular component.
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