Constant Current Regulator Circuit - Quick, Dirty, and CHEAP!
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- เผยแพร่เมื่อ 27 ก.ย. 2024
- Someone was just asking me about my old videos on constant current regulators and thought I'd expand on those with a much cheaper and simpler circuit. I think this is perfect for most LED applications if this is what you're looking to do. Of course, you can always regulate down the voltage to a known level, then drive LEDs with a current limiting resistor... but then, all LED current goes through the voltage regulator... and the larger that regulator has to be, the more expensive things get... lots more things to consider as well, but just throwing this out there for consideration!
Here's that link to the simulation: tinyurl.com/y5w...
Those videos I made previously:
Using TLV431
• How to Drive LEDs - Ea...
and heavy loads:
• Heavy-Current Dummy-Lo...
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Yo, this was exactly what I was looking for for a project I'll be returning to now that school is over. Great video
Yep definitely one of those discrete "back pocket" circuits to keep in mind.
I really like this kind of "basics" video. I haven't worked with transistors for decades, and the refresher is great.
I love that kind of videos. Keep them coming. 👍
Thank you, Kevin. I think this is just what I needed to drive the LED's in my project.
Cascading BJTs in parallel could be problematic. They may run into thermal runaway, where one transistor will allow more current to pass and become hotter as the current increases. MOSFETs do not run into thermal runaway, which makes them a better candidate for parallel connections.
Thanks.
lol, ran into that once, but this circuit doesn't have that problem because each transistor has its own resistor to ground, so it self regulates if one transistor starts to run away... that voltage increases on that one resistor, thus forcing the "driver" transistor off. You just gave me an idea to show how thermal runaway works. Might cool to see it happen with straight parallel connections vs this.
I see these circuits explained on youtube with BJT's. Why not use a mosfet? Lower forward voltage means less heat loss.
Woah that Falstad Simulator is so cool this will help me plan out my LED circuits ahead of time before electrocuting myself hahaha
Nice and useful Tutorial. But what happened with the TLV431?
Love have you just get started. So many videos have 2-3 minutes of wasted intro time. Ain't nobody got time for that. 😁
yea, thanks!
Thank you so much for the instructive video on constant current regulator circuits !
Very clear explanation, thanks.
Could a mosfet be used to drive a larger load without running into the higher base current problem?
A very clever circuit but be careful where you use it. That 0.7v reference is subject to variation between units and changes with temperature at about 2.1mv per degree centigrade.
yea, that's why it's "dirty" :)
Awesome! I’m going to put one of these together tomorrow!
Why not put a 100R resistor in the base circuit for the single transistor design?
For larger currents, rather than go parallel I guess I could change the driver transistor for a TIP120 is similar right?
Great Video,
A question about the TrigBoard. Is it possible to differentiate the difference between a wakeup by the timer or an external switch. I have the following Szenario: Door is open and the board sends me a notification. The door than stays open for a long time and the timer wakes up the module every hour. Can I differentiate if the board was wake up by the timer or the door opening? The thing is It is not possible to read out the pin for the door because that one is always open. I would be happy to get a response because I am trying to wrap my head around fixing that issue.
Yes, you can. Check Kevin's wiki about trigboard...you'll find ya answer to this question.
@@fredericguiet2077 Thanks for the answer. Could you tell me in what paragraph I can find that because I wasn't able to find it there.
So the 2 transistors keep turning each other on/off really quick as there is a signal from the microcontroller right ?
"Besides the constant 0.7 v that draws the constant current depending on the value of R ofc "
What would it look like if I replaced the Led with a dc aquarium pump motor. I know it'll have to be beefy but would it work?
Could we use it for costant discharging lithium batteries, for example? Using higher power transistor and a discharge current of about 1 amp would be possible ? Thanks
can the 3.3v from the micro processor be swapped for just a regular power signal and if so could if be a different voltage, like could it be changed to a higher voltage and maybe change the 1k resistor to a higher value im thinking a 14v supply and a 10w 9v led , finally could it use the same supply as the led and would it need a diode to stop back feed , cool video, thanks for the upload .
Yep, that would work. Try it out in the simulation for yourself
This we one of the circuits we added to thr variable power supply we built in high school electronics nano on 1968
is this possible on 2n3906?
Awesome well explained video!
Can be made similar circuit but with PNP transistors?
Does this work on DC or is it AC?
Hi Kevin, I believe you are using DC source? On the simulation there is AC 40Hz. Can we even use AC PSU?
The purpose of the AC source is to show that the current doesn't change depending on the input voltage. The kicker here is that the AC source has an offset making all voltages applied positive. So, no this would not work with a zero-biased AC source.
What is the difference between the cascade and normal ??
Elegant project/Design
Thanks for sharing :-)
How If i want to build 14v 3A constant current from 12v..?
Very informative video
ingenious!
*Damn, very nice!* 👍
Don't need the base resistor and you don't need the blue transistor. Set the emitter resistor to be Vh (from uc)-0.6V/desired current. 2 less components.. And does the same thing.
I agree, I’m a total noob with this stuff, but if I am interpreting this correctly, and you are just driving the red transistor between fully on and fully off very quickly to achieve a dimming effect, I see no need for any of the blue part of the circuit. And if this is correct you have just applied a very fast switch to an LED and a current limiting resistor. In which case, from my understanding FETs are more generally used for this function.
Fantastic this great
❤👍
REGULATORS... MOUNT UP!
ffs.. linear led driver ICs with max current setting and pwm dimming are as cheap as 15-20 cents each.. ex Diodes inc AL5802 or Nexperia NCR405U (random cheap led drivers on Digikey)
Yoiu can add a few of these whenever you order other components for a project... like you'd order transistors.
its not about the actual driving of leds, it is about understanding the fundamentals of electronics and how things work. obviously you wouldn't use this circuit for production
This is what u need to get a computer running I think.
Hi, very interessing video. By the way, a more crude CCS can be obtained removing your blue NPN, and the 1k base resistor. The current will rely on the output voltage of the µC typically 3.3V. The current will be equal to I = (Vio - Vbe)/R
Hi, good video, you need to show the advantage of the circuit with different loads.
That is, more than one LED in SERIES. As long as the circuit volt drop can accommodate them.
yea, I like that idea!
Modifying the voltage is as good as modifying the load, tricked me at first!!
Thanks Kevin.
I was planning to use some PT4115 to drive a few large LEED arrays, but this simplifies things considerably (and reduces the cost too!)
Brilliant
Even simpler...
Use two small signal diodes with a resistor to v+ to generate a steady low voltage. Dive the base of an NPN transistor through a resistor from your constant voltage source. Use the gain of your transistor to select your transistor driving resistor. Use your minimum operating voltage (minus the ~1.4 voltage drop). This circuit lets you operate a 2 volt LED from a 3v lithium cell with constant brightness across the full charge. The circuit above doesn't go as low because you lose ~0.7 volts driving 1 transistor.
Hello, very nice video ! i did the same, i used 1.5 Ohm to have an output of max 1A, but when i plug a load to my 12v lamp bulb, the voltage drops to 4v, is it normal ? many thanks.
I have used many times the PNP version of this constant current source. It works great.