Timeline for LM317 voltage regulator varying voltage output depending on the load
Current License: CC BY-SA 4.0
19 events
| when toggle format | what | by | license | comment | |
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| Mar 15, 2023 at 8:24 | comment | added | EmeraldMonk | @PStechPaul, thats sounds like a good solution in the future, when i need to do a redesign of the PCB, which is almost certain that i have to. | |
| S Mar 11, 2023 at 14:10 | history | suggested | Peter Mortensen | CC BY-SA 4.0 | Copy edited (e.g. ref. <https://en.wikipedia.org/wiki/Hall_effect_sensor>, <https://en.wiktionary.org/wiki/load#Verb>, and <https://english.stackexchange.com/questions/15953>). Applied some formatting. More specific title. |
| Mar 11, 2023 at 8:09 | review | Suggested edits | |||
| S Mar 11, 2023 at 14:10 | |||||
| Mar 10, 2023 at 23:42 | comment | added | PStechPaul | You can add a series resistor from the 24V supply to the LM317, to drop as much as 8V under heaviest load (100 mA?) to remove 800 mW from the device, leaving 16V for the input. Just make sure to have an adequate bypass capacitor on the input. | |
| Mar 10, 2023 at 17:37 | history | became hot network question | |||
| Mar 10, 2023 at 14:37 | comment | added | glen_geek | If 30mV variation is unacceptable, LM317 long-term-stability spec of 1% might be a red-flag, especially if those comparator threshold voltages are critical. But do stay with a linear regulator (versus a switcher). | |
| Mar 10, 2023 at 13:51 | answer | added | Simon Fitch | timeline score: 7 | |
| Mar 10, 2023 at 13:37 | comment | added | Lundin | Back in the days you'd use one of these regulators like LM317 from 24V to somewhere around 15V and another like 7805 to take it from 15V to 5V, only to spread the heat between several parts. In modern design you'd rather use a buck regulator to go from 24V to 5V and then maybe from there a linear regulator from 5V to 3.3V, in case you need to power RF electronics or similar sensitive parts. | |
| Mar 10, 2023 at 13:13 | comment | added | EmeraldMonk | Yes, exactly what I was thinking. Ive swapped out the resistors to the values I edited in the above post, just haven't updated them in the Altium schematic. Do you think if I supply the 5V voltage regulator also with the 13V from the LM317, might help to stabilize the output a little more? | |
| Mar 10, 2023 at 13:03 | comment | added | Lundin | Yeah so you kind of sit in a nasty place where drawing too little load will cause LM317 to go loco with the resistance values originally picked, whereas drawing too much load will cause it to melt. But as shown in the answers swapping the voltage divider resistors to something with lower resistance will solve the first problem. | |
| Mar 10, 2023 at 12:49 | comment | added | EmeraldMonk | Yes, I am not. The LM317 is used currently only to provide the 13V to the voltage dividers that acts as reference levels to a comparator which is in not in the schematic above and the Input to the Hallsensor which together is 50mA(high estimate) as the complete circuit draws 50-80mA from the power supply(Depending on the load used at the Hall sensor input). | |
| Mar 10, 2023 at 12:42 | comment | added | Lundin | A SO-8 version is even worse at dealing with the heat. Don't expect to drive more than 100mA or so from it. | |
| Mar 10, 2023 at 12:05 | comment | added | EmeraldMonk | You are right about the heat it produces. The switching regulator might of been a good replacement, but im using SO-8 package IC from. | |
| Mar 10, 2023 at 11:56 | comment | added | Lundin | Additionally, LM317 might melt through the floor if you go from 24V to 12V. It's essentially a radiator with the side effect of also producing an output voltage. There's very few reasons to use it for such voltage gaps. There's TO 220 drop-in replacement switch regulators that can replace it, for example. | |
| Mar 10, 2023 at 11:53 | comment | added | Lundin | LM317 works poorly with too high voltage divider resistance. The behavior will be just as described: voltage will vary depending on load. | |
| Mar 10, 2023 at 11:03 | answer | added | fgrieu | timeline score: 6 | |
| Mar 10, 2023 at 9:56 | history | edited | EmeraldMonk | CC BY-SA 4.0 | added 123 characters in body |
| Mar 10, 2023 at 9:52 | answer | added | Justme | timeline score: 7 | |
| Mar 10, 2023 at 9:34 | history | asked | EmeraldMonk | CC BY-SA 4.0 |