EEVblog

Who else but Dave can turn what was supposed to be a simple 2 minute AVR ISP hack video into a 30 minute episode on designing and measuring the performance of an LM317 voltage regulator circuit, with a bonus shootout between the Fluke 87V and the Gossen Metrahit XTRA multimeters?

[@folxsgalaxy993]

I very like that videos - showing how to design and read datasheet! Thank You!

[@TheCrazyInventor]

I liked it very much Dave. You've put a lot of work into it, as usual. Some nice and useful info for us students. :)

[@Dibblah1900]

Finally watched all the way through. Very enjoyable - Thanks!

[@igrewold2383]

Dude, u r da best as always. Please keep up the good work thanx

[@errold32]

Thanks for the performance characterization details. .....nice scope

[@michailvanis4532]

If you just want to give the board 5V, just solder a wire to TP1 (test point on the bottom of the board) and pin 2 of the 6-pin ICSP header. A little easier soldering on a test point than the actual USB pad.

[@EEVblog]

@keenantims Oops, bummer. Yes, I found 5.5V too. From memory I think (pin 27?) of the USB chip outputs 3.3V, but it doesn't have any current capability.

[@jimman1992]

Learned something new today! Thanks!

[@sciguy14]

great hack. I might have to try this; I too have found it annoying that I always need external power.

[@YeOldeSpellbooke]

Thanks Dave, i really learn much from you :)

[@dambuster6387]

My lm317t seems to change voltage over time +- .5 volts using 240 ohm and 5k set adjustment for 24 volts@ 100ma and 28 volt input. Can I expect some change in voltage over time?

[@jonathans1212]

Dave I have a question. I did this mod with a piece of wire to pin 2 since I only use 5v no switch when I plug it in to my arduino it powers it correctly and the green light comes on but the arduino IDE always has an error desoldered it and no problems???

[@EEVblog]

@fzsdude I had tons of LM317's, and I needed 3.3V, not 3V

[@tablatronix]

Is this why 13.8v power supplies are so common ? Dropout voltage , or just a load thing ?

[@86Ivar]

great video! How do you recommend regulating a 0,83v line? input will be 12v and load some milliamps.

[@roboxlabsofficial1899]

just wondering, how did you make that intro? It looks great!

[@EEVblog]

@electrodacus Tha twas my initial though, and I just dropped in an LM317 that I had available instead of waiting for a proper LDO. But with hindsight I should do it properly and use an LDO to maximise the available current from the USB.

[@kevinxbuffalo]

Very nice video as always. Thanks :)

[@First2ner]

great vid!!

[@EEVblog]

@Co265 Haven't found one yet. Anyone?

[@TerminalJack505]

Nice video, as always, Dave. I'm surprised the comments didn't turn into an AVR vs. PIC holy war. LOL.

[@38911bytefree]

Any improvemment usign a cap in the adj term ?. I saw as "recommended" in the 317 datasheet. I know it helps ripple rejection as well ... perhaps helps on lowering this noise appearing when you turn de input below 5V.

[@Co265]

Have you found schematics for this device? I have couple of fried ones in my drawer and I'm just curious is it worth to fix them. It looks like these devices don't have much of an input protection and they tend to blow up quite easily :).

[@h0ll0wm9n]

Dave notes there are "better" regs than 317. I assume he means for low-dropout use. However, if used WITHIN specs, many say 317 is better than LDO. I don't have enough experience to elaborate ... so please provide feedback. Thx!

[@EEVblog]

@38911bytefree It may very well help a bit in that respect. But I didn't bother trying in this case, I'd had enough shooting video this time around!

[@Dibblah1900]

500mA is only available (officially) after protocol negotiation with the providing hub. Most of the time, with cheap hubs, you can draw more - But it's certainly not guaranteed. 100mA is the official specification.

[@izzzzzz6]

Hi, is it easy to test for a blown LM317 and LM337 (the negative V version of the LM317) regulators? I think i have a blown LM337 but not sure if i'm testing it correctly. When using my transistor tester the LM317 shows two diodes uf=3.91V from pin 1 >to pin 3 and uf=1.46V from pin 3 >to pin 2 but the LM337 is showing no component or faulty part. When i check resistance with a multimeter the LM317 shows 975ohms with negative probe on pin 2 and positive on pin 3 and 535ohms with positive probe on pin 2 and negative probe on pin 3. no other readings. With the meter The LM337 is showing 1086ohms with negative probe on pin one and positive probe on pin3 then it shows 927ohms with negative probe on pin2 and positive probe on pin3 and 956ohms with negative probe on pin1 and positive probe on pin2. It shows 537ohms when i put the positive probe on pin2 and the negative probe of the multimeter on pin3 (no other readings). Any help would be appreciated. Thanks.

[@johncoops6897]

Put 0V and +12V into the input pins, a suitable resistor on the device for voltage, and measure the output voltage. No need for ANY of the other rubbish that you posted... it either works, or it doesn't.

[@fzsdude]

Why dont you choose a Voltage Regulator like the 78 Series? Im not an professional, so i´d like to know :) Wouldn´t it be enough to put in an 7803 regulator and have 3 Volts?

[@DLTX1007]

I use a LD1117-3.3 since it works out cheaper for me if i need a 3.3v source without any external resistors plus it's a LDO .

[@AgentDexter47]

DaveCAD - best drawing program

[@ZuNunchaku]

what about miso, mosi, sck volt out? it's still has 5 volt out right?, so basically we can't use this for ic that has max 3.3v ?

[@shapeshifter8986]

+Arief Adha As far as I understand it the voltage the sensor gets initiates the programming voltage on all isp connections. In this case 3,3 OR 5 Volt.

[@mrjn5786]

hey i have a question. If you adjust a voltage the more you change the voltage the more the current will change? example if i start in 1.5 volts with current of 200mAh then i set it in 5 vollts will it change it currents? will it change its current and if i have a 25Amp transformer. :) or 25000mAh transformer.

[@hannescamitz8575]

First: Are you drunk? Second: Current drawn depends on circuit it self, if it's a CC or a CV build. CC=Constant Current CV=Constant Voltage. LED driver are often CC, while your heater in your bedroom will gett hotter and draw a higher current if you go from 240VAC to 350VAC. Ohms law is your friend. ;) But then you got the power sources that you can change between 120 and 230 VAC they usually draws the double amount of current when used in a lower voltage environment. 5.2 A * 12 Vdc = 62,4W 2,6 A * 24 Vdc = 62,4W ;) BTW mAh are just for sales... I can bet my left foot on the fact if you would sell two powerbanks one that's rated 11'000mAh and one rate at 11Ah, the one rated higher would sell better...

[@agkwtechno]

Thank you!

[@williefleete]

davecad FTW. i have made my own adjustable regulator using a "jellybean" 741 opamp and diodes for a reference and a 10amp transistor series pass and it makes a nice beefy adjustable supply can pull about 4 amps at 8 volts and i made a mini adjustable constant current which does mA, enough for testing LEDs at EXACTLY 20mA etc

[@AB-yu2tj]

Wherr is that background cricket sound coming from? Very disturbing

[@EEVblog]

@mageepaddy Yeah, I don't now what possessed me to drill the hole in that spot. Doh!

[@EEVblog]

@WakkoXtreme Yeah, really loud bastard today!

[@neilaldenarmstrong9806]

Forgot to say this... you should have added a diode to keep a possibly powered microcontroller board from back-blasting the regulator......

[@thenerdyouknowabout]

Awesome t shirt

[@KeenanTims]

No 3v3 reg already on the board? Alright well that was a bad idea :P Just let the magic smoke out of the regulator on mine carelessly probing around. Seemed like it was actually boosting to 5.5V (from the ~4.85V my USB was providing), so I guess not - don't break yours! Now off to order a replacement and test my SMD rework skills...

[@ArumesYT]

28:18 I only hear output noise from a cricket.

[@aerofart]

PLEASE DO MORE COMPONENT DATASHEET TUTORIALS!!!!!

[@SimoWill75]

Nice mod. I'd have left out the on-off switch and just used a center-off toggle switch tho. Eg; 3.3v-off-5.0v

[@neilaldenarmstrong9806]

I use a tiny reed-relay with a 5V coil and integral flyback diode to automatically turn on Vtarg when RESET is pulled low (as happens when programming starts). Vtarg is only supplied during programming time, automatically.

[@AstralJaeger]

I would habe used a LM1117-3.3...

[@EEVblog]

@TerminalJack505 That has been known to happen hasn't it ;-)

[@ribb4200]

Three series 0.6v diodes = 1.7v drop. 5v-1.7v=3.3v

[@malangr]

Damn...! nice intro LOL

[@Tannz0rz]

@Shaunakde He said they were birds in his tree, lol.

[@PawnozTV]

damn crickets

[@DLTX1007]

@AgentDexter47 In the world

[@shapeshifter8986]

..or use a 3,3Volt zener diode..

[@neilaldenarmstrong9806]

Typical engineer - complex solution to a simple problem. Why not just use a 3.3V LDO regulator? And use a bit of double sided tape to attach it to the bottom of the PCB... and solder the input pin to the 5V test pad (or the output pin to the 6 pin ICSP pin #2) for added mechanical stability. Then solder a few chip caps for bypassing directly to the regulator and you're done. BTW, the "professor style" lecture on the LM-317 may impress some, but no one who would make this mod needed it. Sorry.