About 25 years ago I assembled a circuit exactly similar to your first schematic. The output current varies by more than 10% depending on the temperature of the transistor. This phenomenon disrupts the performance of the device I built. The solution is to arrange the transistor as _'sziklai'_ for the LM317. I used 6.8 ohms as _Rbe_ (LM317 draws a current of around 100mA). The collector is connected to pin 2 and the input end of _Rsh._ Pin 1 is connected to the _Rsh_ output side as the final output. The constant current output will be 1.25/Rsh. The variation in output current is less than 1% due to the influence of transistor temperature, so the device I built can work well. Minimum drop out voltage was about 4V. Thank you
Mr. Loflin, as usual I am so pleased to watch you explain so well circuits in general, including this updated one. Please keep on producing more videos as you are a wonderful teacher for so many practical electronic stuff for all hobbyist, and enthusiasts like me. Of course I have subscribed a long time ago now, and created special links of interests pointing at your videos.
Newbie here. How can this be adjusted to be current limiting device. I want to test broken motherboards with voltage injection (usually 1 up to 5 volts) but need to protect the motherboard from too much current (100ma to 1000ma range). How would this be achieved ? Can you make video about this?
Pl make a video on foldedback current and its calculation of resistors ( linear regulated power supply with short circuit protection as fold back current limit). Thanks
Great video. In regards to the PNP power transistor used, if I require a higher input voltage of say 200VDC and output current of 8 - 10 amps, could I swap out the single PNP power transistor for a Darlington Transistor? Also the LM317 would be changed to LR8NS
About 25 years ago I assembled a circuit exactly similar to your first schematic. The output current varies by more than 10% depending on the temperature of the transistor. This phenomenon disrupts the performance of the device I built.
The solution is to arrange the transistor as _'sziklai'_ for the LM317. I used 6.8 ohms as _Rbe_ (LM317 draws a current of around 100mA). The collector is connected to pin 2 and the input end of _Rsh._ Pin 1 is connected to the _Rsh_ output side as the final output. The constant current output will be 1.25/Rsh. The variation in output current is less than 1% due to the influence of transistor temperature, so the device I built can work well. Minimum drop out voltage was about 4V.
Thank you
This is an update to an earlier video on the LM317-transistor combo at th-cam.com/video/n94xqPMhmTo/w-d-xo.html
Mr. Loflin, as usual I am so pleased to watch you explain so well circuits in general, including this updated one. Please keep on producing more videos as you are a wonderful teacher for so many practical electronic stuff for all hobbyist, and enthusiasts like me. Of course I have subscribed a long time ago now, and created special links of interests pointing at your videos.
Newbie here. How can this be adjusted to be current limiting device. I want to test broken motherboards with voltage injection (usually 1 up to 5 volts) but need to protect the motherboard from too much current (100ma to 1000ma range). How would this be achieved ? Can you make video about this?
Good info.
why did you use pnp transistor for Q1 ? which better to use NPN or PNP ?
This uses a PNP. The TL431 circuit uses an NPN.
Pl make a video on foldedback current and its calculation of resistors ( linear regulated power supply with short circuit protection as fold back current limit).
Thanks
Great video. In regards to the PNP power transistor used, if I require a higher input voltage of say 200VDC and output current of 8 - 10 amps, could I swap out the single PNP power transistor for a Darlington Transistor? Also the LM317 would be changed to LR8NS
No, unless all polarities are reversed. As for that kind of power I'd recommend not playing around with that.kind of power.
Thanks for sharing your knowledge
Lead Acid battery and Lithium ion battery are the same charging strategy or different?
Yes. Just observe the proper voltage level.
Just wondering why you deleted my comments about the cadex battery site?
What comment? I never saw it.
dear sir please explain about the capacitor on the point 3 of lm 317?????
I added that for noise. This circuit can also be pulse-width modulated.
@@LewisLoflin thanks for the reply but it always hold a voltage up there ....
can you make an ac current source using this and pwm ?
No. You have to use phase control. I have a video on that let me look it up and i'll post it.
@@LewisLoflin Thank you