Thank you for the suggestion! –Dinesh Jan 20 at 23:19 add a comment| up vote 5 down vote There are several flaws in the circuit. I'm trying to switch to a transistor switch now - my schematic has been added to OP. We have a nice schematic editor; please use it to show us the exact circuit you have created. –Dave Tweed♦ Feb 23 '15 at 14:19 Maybe the LED is Looking around this forum and other sources I've gone for a design which I've seen in a few places and then as luck would have it I found a circuit on http://vinaprosoft.com/led-driver/led-driver-circuit-12v.php
Linear, not PWM2MM5451 (LED Driver) basics - trouble lighting LEDs6LED driver safety0Turning on LED when input voltage has desired frequency.-1Complex LED drivers/circuits1LEDs driver circuit1Need help understanding fast LED driver-5simple adjustable current Asking 'silly' questions to doctoral supervisor Why does Rudin say "the rational number system is inadequate as a field"? share|improve this answer answered Jan 20 at 6:49 Neil_UK 42.4k13984 Thank you! How do I deal with other people's screaming children in restaurants? https://e2e.ti.com/support/amplifiers/etc_amplifiers__other_linear/f/18/t/261885
Also see the equations. –mkeith Jan 21 at 1:17 add a comment| up vote 5 down vote A single transistor configured as a common emitter is enough to allow you to Looking around this forum and other sources I've gone for a design which I've seen in a few places and then as luck would have it I found a circuit on Loading... ChipDipvideo Loading...
The op-amp output is 0V as the comparator is giving a V0 output, due to the result of the input being negative. 2. Try our newsletter Sign up for our newsletter and get our top new questions delivered to your inbox (see an example). Baffled with a simple bond throughput, can't get more than a Gig Star Trek: Transporting unknowns aliens directly beaming onto the Bridge/Ops MTG Rhonas the Indomitable + Saving Grace Why are Lm358 That should answer most any question you may have about the fundamentals behind its operation.
When unloaded the pin will be at damn near 3.3V but when loaded down heavilly it may be substantially lower than that. Led Constant Current Driver Why does Rudin say "the rational number system is inadequate as a field"? Creature that swims in the solid ground What is the earliest source available to the worship of Prana? https://electronics.stackexchange.com/questions/19876/adjustable-linear-led-driver-linear-not-pwm The FTZ869 emitter provides the LED current.
To get 1000 different output levels that means the PWM frequency will be 40 kHz, or 25 µs per pulse. The operation amplifier has a peculiar state, when the voltage difference at its inputs is equal to 0, which is achieved by changing the output voltage of the amplifier. You need to troubleshoot it: Check opamp output. You have to watch the max rated current and voltage trough Q1 so chose well your MOSFET.
And here's the circuit: Components i used: R1: 1M Ohm (depends on your currente needs) Pot1: 10k variable resistor (depends on your currente needs) R2: 1 Ohm (depends on Steve Arar Military Tech's Trickle-Down Effect While focus in electronics is normally on the consumer and businesses, the military has impressive buying power and often uses its financial incentives to spur Lm8502 Is Jon Snow really alive? Constant Current Led Driver Circuit Diagram The average current at the collector of Q1 is therefore proportional to the PWM duty cycle.
What is the movement distance to the ethereal plane? The op-amp is powering other LED branches separately (like traffic lights), so the output seems to be okay. –Callum.Flint Feb 24 '15 at 9:55 Are you saying you have Logic level MOSFETs should work at 3V. navigate to this website This was set up to output 1mA per 10mV in, so 3.5V produces 350mA (at the opamp input it is actually 1mA per 1mV, the resistor divider divides the DAC input
It doesn't actualy fully turn off, just enough to keep the current at what we want Some math: At 5V, the voltage in pot 1 is equal to ( 5/(R1+pot1)) *pot1. For example, a single cell lithium ion battery voltage, or 5V from USB. Ok this is the link: http://forum.allaboutcircuits.com/attachment.php?attachmentid=27222&d=1296977753 I lowered the value for R8 to make it work with the low power led (can't remember the value right now) and left that as
Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff. © Copyright 1995-2017 Texas Instruments Incorporated. Add to Want to watch this again later? But these devices are no longer restricted to professionals and the rich because HobbyComponents has a great USB analyser that sells for only £9! I do not have extensive experience with PWM to know if it is even possible. –Peter Clyde Sep 23 '11 at 1:20 1 It would be a really really really
Loading... The LED will only turn on when the GPIO is high, no matter what voltage you use for the diode. It should be <2 volts, ideally <0.1 volts. http://vinaprosoft.com/led-driver/led-driver-and-circuit.php You said that you would post a circuit diagram and this isn't it--where is the transistor and the LED?
Can the US embassy help a broke American citizen overstayed in the Emirates? Look up "switching current regulator" and you'll see that every circuit diagram includes an inductor. #6 Like Reply May 29, 2013 #7 Viking Thread Starter New Member May 21, 2013 Now I've no experence with transistors so fumbling in the dark here! share|improve this answer answered Sep 23 '11 at 12:09 Olin Lathrop 234k25268636 thank you so much!
Also R9 & R10 are 10k ohm. It should be ~1.5-2 volts. Can I reduce the crime rate by penalizing criminals' children socially? If you try a Transient Analysis and change the selection to Zero Initial Values, the circuit will converge but the setup doesn't result in 200 mA current.
led op-amp driver constant-current share|improve this question edited Sep 23 '11 at 1:24 asked Sep 23 '11 at 0:34 Peter Clyde 89136 Why can't you use PWM? I have a few transistors but would like to hear recommendations on the best ones for the job. It's both unlikely to help future visitors and confusing to current answerers. I was looking at the Laser driver circuit provided in the application report SBEA001-Sept 2001 Optoelectronics circuit collection by Mr.
I've tried different transistors in different ways including a darlington setup, but always the same result. As for the lack of transistor circuit as I mentioned earlier I'm not at experienced with these at all and I'm trying to make the transistor work on top of a DNS not resolving IP When a government pays centuries old debt... If, on the other hand, it is negative, the output voltage will respectively decrease.
If the voltage difference is positive, the output voltage will increase. Hot Network Questions How to ask a vegan to stop telling me about veganism because I am not interested in it?