I've seen these circuits til I'm blue in the face. However, placing a fixed resistor in parallel with a variable resistor to limit current is really cool. I learned something new. Great video, sir!
I generally use a LM317L with a 220ohm resistor between A and C and a LED for the load as an easy "no think" way of indicating "output/testpoint high" on the breadboard. It works from 3.3V and up. It can easily be put on a 2 pin header and protected by a piece of heatshrink for reuse.
I am using the LM317 to regulate voltage to my model train smoke heater to maintain nice smoke plumes during various speeds as fan puffs increase cooling air flow. Thanks for sharing. D
OK. I couldn't sleep either so I was up until after 3am. So I really can't think well now but I will think on it. Thanks for showing another side to the LM317!
Great video I'm a. Disabled electrician but in the early 80s I worked on video games pinball record machines etc. I'm going to get back into the hobby because of other hobbies I'm going to use at least one if not two server smps what's the best way to add an adjustable voltage and adjustable constant current to the output with volt and amp meter? I'd like your opinion on this..lol I can't sleep either hope you feel better my mom dad brother and best friend had cops thanks for taking time to share the videos
Adding the cap in parallel stores unused potential and dissipates it back in to the circuit when it falls below a threshold, choosing the right value cap like a .01uF with the right time constant will fill in the noise gap nicely
hi, i don't have a breadboard but i have lose wires. is it possible to connect the potentiometer, LM317 and resistor and power source directly with each other without breadboard?
What is the part name for the potentiometer that you used ? I have seen a 4.7k pot and a 10k Pot - but does not look like the one in the video ! Nice video and thanks for sharing.
Ok, very nice. I did not realize it would be this simple. I built an ATX power supply with voltage selector and volt meter. One terminal is constant 12V. Another terminal can be switched to the 3 diff. outputs. I should take the 12V off that terminal, guess why? Anyhow. I want to charge various rechargeable batteries with it and need a currant regulator. battries can range from 1.5 to 12V. I just wonder if this circuit will cover all the mA ranges I will encounter? This looks promising thanks; thumbs up.
Well if it's a cap it'd have it's own charge wouldn't it? Up to Xvolts it was rated, usually higher then the input voltage? Also, if I were to connect a LM317 circuit to a SMPSu (watch out KINDA like other crazy question lol) Could I theoretically draw just up to whatever voltage and amps I was setting the variable voltage to an what the LM/ my circuit demanded? or would connecting that just right to the output bare the full 5v 25amps against the LM and or whatever circuitry I had inline with it since LM317 max is only 1.5 amps..(being hooked up to/running a VERY expensive LD) Or would I be good to power that off that? Or would the weird SMPSU try to limit its draw all together to only 5 volts(which is fine), (12v 18amp is a option to but I'll get alot more heat from volts stepping down.. just worried/confused about the amp thing an the behaviors..) an to 400ma again like usual? Or would me placing the demand unlock the amps the same way I saw when I hooked my DC motor up? ..Is this the same question? I'm done. I'll just wait for your reply an hopefully that helps me get it lol cause it's all obviously related..
Using the last two videos, I looks like it would be possible to build a regulated voltage supply that is current limited by putting the two circuits together in a series circuit. Is this correct? I guess I now have to get some LM317's to play with!!! I need more room!!!!
hi paul, i learn a lot from your videos, thank you! how much amps did you set the load here? what should i do to increase the swing to a max current of about 3 to 5 amps? how would i configure this with a power transistor to achieve higher current limiting?
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.
Got similar problem. But I never got more than 100mA so even a tiny LED reduce the voltage a lot. I wonder if it depends on what model (x) of LM317x it is.
dan blankenship thanks Dan. I'm not nitpicking just clearing up the exact location as complete beginners may copy the circuit without question and wonder why they're getting different results!
This circuit is meant to regulate current, but a mosfet is a voltage controlled device. You can use this circuit to regulate the base current of a bjt But if you do that the transistor will saturate during constant current operation and dissapate a lot of heat which is not ideal
Just for the fun of it, put a led and a resistor as your load. Set the current at 15ma for instance. Afterwards, vary your input voltage a bit, up and/or down, just to show how the regulator will do its best to keep the current constant. You might consider putting a voltmeter across the led, showing the impact. By the way, I noticed two little "hoopsies" in your clip. First one was around 04:10 when you said "7 ohms swing" instead of "7 milliamps swing". The second one was aound the 05:03 mark when you drawn the resistor on your schematic. I think you put it on the wrong side because as shown, it is shorted across the A & B terminals. I understand that our minds aren't always as sharp as we would like them to be in the middle of the night. Been there, done that too ! For the effect of the cap on the input I'm not sure. I was under the impression it was mainly for filtering/stability purposes but now we can see it has a another side effect. As per my understanding of the LM317, I'd be lead to believe that the capacitor could potentially be adding a small variation of the current on the ADJ pin which in turns is amplified by the internal Darlington transistor, thus slightly increasing the output voltage leading to a wider current range. It's almost like lottery, we simply hope to have the proper combination.
Hello if anyone have time please help me. How Can i use for example 10k adjustable potentiometer to act as 200R ? A mean i drive LED from 18650 battery with cca 270R using resistor... But i need IT to be regulable but resistors in size i need i see only like 10K and so.... So in final i will have 200R smallest and 400R highest resistance using 10K regulable resistor...
Hello. I am a total novice. I have soldered, stick welded, and wired houses, so, I do have a healthy respect for electricity, just f.y.i. but not too much knowledge. I have a purely selfish request, but maybe it will be of benefit to many just by way of reminder. And , also, it feels good to help others. I want to make a simple 1000 watt (or maybe 1500 watt) adjustable voltage regulator. I think I want to make 2-3. I want to control heating elements without use of inconsistent mechanical thermostat; and I also plan on making a peltier freezer/fridge ( or maybe just ice maker). I have limited funds. I have soldering iron and elec solder. Any help is greatly appreciated.
i have a feeling like the lm317 is entirely redundant here, if you have a constant voltage, you can just use a pot to vary the resistance and with that the current that flows
