Thanks Lewis, explain very well with practical example. I am sure you will get surprise by seen the comment on this video after 5 years. You did great work.
I really appreciate the knowledge you shared gives me more insight on how to control the wild voltage output from my motorcycle bridge rectifier, still wondering how to reduce the heat dissipation. However, Thanks !
Excellent as usual my dear Lewis. I always enjoy watching your videos with excellent explaining, diagrams and experiments shown. Please keep your great videos. Merry Christmas to you and family.
Thank you!! Building a 500 MHz oscillator kit with SMDs. Instructions requires a constant current source of 40mA for protection in case of building errors then setup and alignment. Your video is well done. TNX K9QHO
Hi Lewis,I was wondering if you have any suggestions for constant current source circuits that can be implemented in negative High Voltage circuits for Vacuum Tubes. I am talking working over a range of -1KV to -2.5KV. Do you think I could implement zener diodes to drop the supply voltage heavily to be able to use one of these lower voltage circuits? Thanks in advance.
LM317 Adjustable Voltage current Boost Power Supply www.bristolwatch.com/ccs/LM317boost.htm LM317 High Power Constant Current Source Circuit www.bristolwatch.com/ccs/LM317b.htm LM317 Constant Current Source Circuits www.bristolwatch.com/ccs/LM317.htm
Can I use a LM317 circuit from 12v DC for electrolysis zinc plating small brackets/bolts etc. I need between 2.5 & 3 amps? Or do use a different circuit & components? Cheers very good videos.
Updated content: Arduino Measures Current from Constant Current Source ruclips.net/video/AtBdjvbhNhQ/видео.html www.bristolwatch.com/ele4/ccs_lm358.htm Constant Current Source Theory Testing ruclips.net/video/9ap49GaQPzY/видео.html www.bristolwatch.com/ele4/css.htm
Hi lewis... video is awesome .....please tell me how to control the output voltage.. suppose i have to run 6 v device with the above constant current source (LM 317) then i have to apply regulator to set to 6v at the output terminals or it automatically detects the required voltage?
Hi Lewis I made this circuit and the current changed when I changed the voltage. I didn't have an LED so I used a buzzer,I think its a pizoelectric buzzer. I'm new to this stuff but I'm trying to make a gadget that needs a constant current source.Any idea on why it didn't work. Although I used a DC power source,would this work with AC. Thanks
eamonn280958 A pizoelectric buzzer only works with a varying voltage and is not a current device. What is your input voltage and the voltage of the device?
Lewis Loflin Not sure what you mean by buzzer not a current device. I used a variable voltage power supply wound it from 0 to 15v and the amps changed accordingly. I did use a potentiometer where you had a resistor between the LM317 and the meter. I could put an LED instead of the buzzer. To clarify the buzzer or the LED will not be in the circuit when finnished its just to test that I am getting a constant current.
eamonn280958 A piezo buzzer does not draw a current. A voltage twist the crystal structure to produce a sound. This won't work with a piezo device. try a resistive load. See en.wikipedia.org/wiki/Piezoelectricity
There is something that people who fully understand this relationship get that those of us that don't struggle with. 'the missing link'. And they seem reluctant to grasp that others don't get it. So, for instance if I want 6 volts out at a max of 100mA, how do I do that?....and why? Perhaps we will eventually find someone willing to get a novice to edit their videos/tutorials before posting. Cheers
Gerry - if you want 6 Volts, you need a Constant VOLTAGE source. If you want 6 volts out a max of 160mA, you need a Constant Voltage Constant Current source. Most loads need constant voltage, because they cannot self-regulate so they will explode from over-voltage. And normal loads draw only what amps that they need, so there is absolutely no need for Current limiting. However LEDs are different - they are a diode and they have a fixed voltage drop (let's say 3V per chip). So if you feed an LED with 3V or you feed it with 6V or even 9V, it only ever drop 3V per chip. So, you don't need to control the voltage, since the chip does that automatically. The issue is that an LED is a current hog - it will draw whatever Amps you supply it with. Feed an LED with a Lithum battery, it will draw 1Amp or 2Amps or whatever... of course this causes it to get outrageously hot and it will die almost instantly. Hence, for LEDs you only need to limit the current. For battery charging you need to limit the current AND limit the voltage.
Hi after watching your video I found it very interesting and also looked at a LM334 but that varies with input voltage so I want to make a circuit that will provide 27 volts dc constant voltage with an output of 2ma so thought I could use two 317s one set for constant voltage and one set for constant current I don't need to adjust anything = 27v @ 2ma do you have any suggestions please Lewis Bob in the UK
It is VERY difficult for someone who is an expert in their field to come down to the level of a novice. This chap has not done a bad job but I would have liked to see the full circuit showing voltage and current regulation. I'm pretty sure you could just add the standard LM317 voltage regulation circuit straight onto the front end of the current regulation circuit. Also I prefer the LM338 as it can handle 5 Amps. You may not need 5 Amps but us peasants need everything going for us. A few diodes for protection ?
I need to handle Amps, not milliamps. Can I do that with this simple circuit, or do I need to learn about Switch mode Constant current supplies, or whatever it's called. I'm trying to design a circuit that can charge the LiPo in under an hour. Idk why, just do. Just in case the sunlight isn't there for my circuit.
Hi there! I'm very grateful for you sharing your knowledge, I'm learning a lot! I have a doubt about the lm317 and I'll be glad if you could help me! I've seen a lot of videos explaining lots of circuits of bench's power supply, but I still havent found one that put a lm317 as a regulated current source. I got an idea from another video, putting 2 LM317 in series, first one as a current regulator, second one as a voltage regulator. The only difference in the circuit, in comparison of yours, is that the guy put a variable resistor rather than fixed, like is shown in datasheet. The problem was that he changed all of the circuit along his vídeo, including the ICs. Well, I write something on the paper and I'm thinking in put a 1,2ohm resistor in series with a variable resistor ( any value in parallel with 120R). My doubt is how high the current will flow through the output resistors (to keep everything cold and not burned, rsrs) and if you could suggest a better solution for my application (bench power supply, using lm317 to control the current and voltage). Sorry for my grammar mistakes, greetings from Brazil!
saldin suljevic 9.2V is where 3V was across the LM317 from a 12V supply. The 5V charging a NiCD battery was an illustration - you need a separate voltage regulator set at 5.6-6.2V
Lewis Loflin Sorry I didn't understand... If Vin = 12V and R1 = 10 then Iout = 125mA, what is the value of Vout = ? and will Rload take as much voltage as it need so the current remain same? For example if Rload = 20, Vrload = 20 x 0.125 = 2.5V (Rload is not R1), in another case Rload = 40 so Vrload = 5V. Vrload = Vout ??? Vout vary with variations of Rload?? Thank you.
saldin suljevic This is not about voltage but current. The 9.3V was the drop across the three white LEDs in series. If I used two white LEDs in series it would still be the same current but 6.1V. Now if you have a load resistance that's too high say 2000 ohms well 2000 * 125mA will run the voltage almost to the power supply and there will be no current regulation.I don't know what you mean by Rload. You divide 1.25 by R1 (the 10 ohn I used here.) Again the current if FIXED the voltage depends on the load resistance - if the resistance is too high the current will not regulate.
First of all the voltage out depends on load resistance. By itself a LM317 will not carry 1.6A you will need a pass transistor which is not as stable as the LM317 by itself but should suffice. See ruclips.net/video/n94xqPMhmTo/видео.html
hmmm... u charge a 5v battery with a constant current source that can and will provide up to almost 12v ?!?!?!? that means it will raise the cell voltage and rais it even more so that your constant current can keep on rushing into the cell, no matter at what voltage your cell is. isnt it ?!
As per KilJD below...I also am lost. when just starting out these things are not obvious, and if I wasn't just starting out I wouldn't need this explanation. When you are charging a battery, how do you control the voltage so it doesn't overcharge or to ensure it gets enough to actually charge it? If charging a 5 v battery don't you need to go above that by 10% or so to force against internal resistance of the battery? Thanks
Finally a clear explanation of the LM317 as a current source regulator and how to set the current limit Thank you Lewis.
Thanks Lewis, explain very well with practical example. I am sure you will get surprise by seen the comment on this video after 5 years. You did great work.
I really appreciate the knowledge you shared gives me more insight on how to control the wild voltage output from my motorcycle bridge rectifier, still wondering how to reduce the heat dissipation. However, Thanks !
Excellent as usual my dear Lewis. I always enjoy watching your videos with excellent explaining, diagrams and experiments shown. Please keep your great videos. Merry Christmas to you and family.
Merry Christmas to you.
Thank you!! Building a 500 MHz oscillator kit with SMDs. Instructions requires a constant current source of 40mA for protection in case of building errors then setup and alignment. Your video is well done. TNX K9QHO
The 100 of 100 teaching and clear , good
Thank you.
Thank you for your insights. Quick and efficient!
Hi Lewis,I was wondering if you have any suggestions for constant current source circuits that can be implemented in negative High Voltage circuits for Vacuum Tubes. I am talking working over a range of -1KV to -2.5KV. Do you think I could implement zener diodes to drop the supply voltage heavily to be able to use one of these lower voltage circuits? Thanks in advance.
A very nice way of presentation.......
Great tutorial Lewis, Thank you very much... John ... :)
LM317 Adjustable Voltage current Boost Power Supply
www.bristolwatch.com/ccs/LM317boost.htm
LM317 High Power Constant Current Source Circuit
www.bristolwatch.com/ccs/LM317b.htm
LM317 Constant Current Source Circuits
www.bristolwatch.com/ccs/LM317.htm
Can I use a LM317 circuit from 12v DC for electrolysis zinc plating small brackets/bolts etc. I need between 2.5 & 3 amps? Or do use a different circuit & components? Cheers very good videos.
Updated content:
Arduino Measures Current from Constant Current Source
ruclips.net/video/AtBdjvbhNhQ/видео.html
www.bristolwatch.com/ele4/ccs_lm358.htm
Constant Current Source Theory Testing
ruclips.net/video/9ap49GaQPzY/видео.html
www.bristolwatch.com/ele4/css.htm
High powered LM317 current source: ruclips.net/video/n94xqPMhmTo/видео.html
Hi lewis... video is awesome .....please tell me how to control the output voltage.. suppose i have to run 6 v device with the above constant current source (LM 317) then i have to apply regulator to set to 6v at the output terminals or it automatically detects the required voltage?
Output voltage depends on load resistance. You can use a voltage regulator after the CCs.
3:37 Needs correction, you *can* pick values higher than 120 ohms.
New pages:
www.bristolwatch.com/ele/hysteresis.htm
www.bristolwatch.com/ele2/comparator.htm
www.bristolwatch.com/ele2/battery_charger.htm
www.bristolwatch.com/ele/vc.htm
Hi Lewis
I made this circuit and the current changed when I changed the voltage. I didn't have an LED so I used a buzzer,I think its a pizoelectric buzzer. I'm new to this stuff but I'm trying to make a gadget that needs a constant current source.Any idea on why it didn't work.
Although I used a DC power source,would this work with AC.
Thanks
eamonn280958 A pizoelectric buzzer only works with a varying voltage and is not a current device. What is your input voltage and the voltage of the device?
Lewis Loflin
Not sure what you mean by buzzer not a current device. I used a variable voltage power supply wound it from 0 to 15v and the amps changed accordingly. I did use a potentiometer where you had a resistor between the LM317 and the meter. I could put an LED instead of the buzzer. To clarify the buzzer or the LED will not be in the circuit when finnished its just to test that I am getting a constant current.
eamonn280958 A piezo buzzer does not draw a current. A voltage twist the crystal structure to produce a sound. This won't work with a piezo device. try a resistive load.
See en.wikipedia.org/wiki/Piezoelectricity
I'm lost. How is the voltage coming out controlled? I undertsand you can get a constant current but what voltage will you have on the output?
KillJD The current is fixed regardless of load below a fixed resistance. The load determines the voltage. See
www.bristolwatch.com/ccs/LM317.htm
There is something that people who fully understand this relationship get that those of us that don't struggle with. 'the missing link'. And they seem reluctant to grasp that others don't get it. So, for instance if I want 6 volts out at a max of 100mA, how do I do that?....and why?
Perhaps we will eventually find someone willing to get a novice to edit their videos/tutorials before posting.
Cheers
Gerry - if you want 6 Volts, you need a Constant VOLTAGE source. If you want 6 volts out a max of 160mA, you need a Constant Voltage Constant Current source. Most loads need constant voltage, because they cannot self-regulate so they will explode from over-voltage. And normal loads draw only what amps that they need, so there is absolutely no need for Current limiting. However LEDs are different - they are a diode and they have a fixed voltage drop (let's say 3V per chip). So if you feed an LED with 3V or you feed it with 6V or even 9V, it only ever drop 3V per chip. So, you don't need to control the voltage, since the chip does that automatically. The issue is that an LED is a current hog - it will draw whatever Amps you supply it with. Feed an LED with a Lithum battery, it will draw 1Amp or 2Amps or whatever... of course this causes it to get outrageously hot and it will die almost instantly. Hence, for LEDs you only need to limit the current. For battery charging you need to limit the current AND limit the voltage.
Thanks for the video. LM-317 will not work with a modulating input changing from high to low voltage, would it?
Veronica Fernandez Marmol I don't think so. What do you want to do?
Is the 1.25 from lout = 1.25 / R1 =125 mA is coming from the typical voltage reference from the datasheet?
Thanks,
JOHN CHAMBER That is the general formula. The 125 mA comes from the 10-ohm resistor I used.
Hi after watching your video I found it very interesting and also looked at a LM334 but that varies with input voltage so I want to make a circuit that will provide 27 volts dc constant voltage with an output of 2ma so thought I could use two 317s one set for constant voltage and one set for constant current I don't need to adjust anything = 27v @ 2ma do you have any suggestions please Lewis Bob in the UK
Recheck your circuit because it doesn't vary based on input. Voltage is based on load resistance.
You sir, you are awesome
Anirudh Vasudevan Thank you and so are you.
current coming is 125 mA, agreed, but what about the output voltage across the device, how do we control that
You use a separate voltage regulator after the current regulator before the load.
It is VERY difficult for someone who is an expert in their field to come down to the level of a novice. This chap has not done a bad job but I would have liked to see the full circuit showing voltage and current regulation. I'm pretty sure you could just add the standard LM317 voltage regulation circuit straight onto the front end of the current regulation circuit. Also I prefer the LM338 as it can handle 5 Amps. You may not need 5 Amps but us peasants need everything going for us. A few diodes for protection ?
can you use an LM350?
I need to handle Amps, not milliamps. Can I do that with this simple circuit, or do I need to learn about Switch mode Constant current supplies, or whatever it's called.
I'm trying to design a circuit that can charge the LiPo in under an hour. Idk why, just do. Just in case the sunlight isn't there for my circuit.
If you want amps use a pass transistor.
See ruclips.net/video/lnU5d-KBMLg/видео.html
nice video
Hi there! I'm very grateful for you sharing your knowledge, I'm learning a lot! I have a doubt about the lm317 and I'll be glad if you could help me! I've seen a lot of videos explaining lots of circuits of bench's power supply, but I still havent found one that put a lm317 as a regulated current source. I got an idea from another video, putting 2 LM317 in series, first one as a current regulator, second one as a voltage regulator. The only difference in the circuit, in comparison of yours, is that the guy put a variable resistor rather than fixed, like is shown in datasheet. The problem was that he changed all of the circuit along his vídeo, including the ICs. Well, I write something on the paper and I'm thinking in put a 1,2ohm resistor in series with a variable resistor ( any value in parallel with 120R). My doubt is how high the current will flow through the output resistors (to keep everything cold and not burned, rsrs) and if you could suggest a better solution for my application (bench power supply, using lm317 to control the current and voltage). Sorry for my grammar mistakes, greetings from Brazil!
+CTitocanto The current source use is right in the spec sheet.
I knew that... Maybe i didnt explain my doubt right. But ok, thanks.
Hi, How do I test my lm317 please? Many thanks John :)
+karen berry I used an ampmeter setting on my DVM and a few LEDs.
+Lewis Loflin Thanks very much for your quick reply Lewis :)
How did you get 9.2V and 5V on output? Thank you...
saldin suljevic 9.2V is where 3V was across the LM317 from a 12V supply. The 5V charging a NiCD battery was an illustration - you need a separate voltage regulator set at 5.6-6.2V
Lewis Loflin Sorry I didn't understand... If Vin = 12V and R1 = 10 then Iout = 125mA, what is the value of Vout = ? and will Rload take as much voltage as it need so the current remain same? For example if Rload = 20, Vrload = 20 x 0.125 = 2.5V (Rload is not R1), in another case Rload = 40 so Vrload = 5V. Vrload = Vout ??? Vout vary with variations of Rload?? Thank you.
saldin suljevic This is not about voltage but current. The 9.3V was the drop across the three white LEDs in series. If I used two white LEDs in series it would still be the same current but 6.1V. Now if you have a load resistance that's too high say 2000 ohms well 2000 * 125mA will run the voltage almost to the power supply and there will be no current regulation.I don't know what you mean by Rload. You divide 1.25 by R1 (the 10 ohn I used here.) Again the current if FIXED the voltage depends on the load resistance - if the resistance is too high the current will not regulate.
Lewis Loflin thank you, that was useful
hello this mahesh ( ac 11.5v & 1.6 amp ) how to make sir
This is a DC circuit not AC - change the voltage to DC.
send me proteus simulation of these circuit
where does the 1.25 value come from?
from the manufacture's spec sheet.
It's the internal voltage reference inside the chip.
correct.
how to make 11.5v & 1.6a
First of all the voltage out depends on load resistance. By itself a LM317 will not carry 1.6A you will need a pass transistor which is not as stable as the LM317 by itself but should suffice.
See ruclips.net/video/n94xqPMhmTo/видео.html
hmmm... u charge a 5v battery with a constant current source that can and will provide up to almost 12v ?!?!?!? that means it will raise the cell voltage and rais it even more so that your constant current can keep on rushing into the cell, no matter at what voltage your cell is. isnt it ?!
You still have to have a voltage regulator - the charge current is independent of voltage source and load current. That what was illustrated.
As per KilJD below...I also am lost. when just starting out these things are not obvious, and if I wasn't just starting out I wouldn't need this explanation. When you are charging a battery, how do you control the voltage so it doesn't overcharge or to ensure it gets enough to actually charge it? If charging a 5 v battery don't you need to go above that by 10% or so to force against internal resistance of the battery?
Thanks
Good video, bad editing. You repeat the same section at ~5 min and at the end.
Jim McPherson Yes I know - my apologies.