Designing a Li-Ion Battery Gauge with the LM3914 - EEVblog #204

[raphasanches]

Man, wonderful job! Congratulations! And, please, keep doing it!

[Kalkaekie]

Very interesting !! Enjoyed it.

[WhiterockFTP]

Is there a smaller chip for 4Peds

[FullWaveElectronics]

This is great!

[GiorgioCapocasa]

That's just beautiful :D

[daafies2]

what happens at 2V in dot mode?

[sismancocuk]

thanks a lot for the great video.

[axel1973w]

Is there an easy and practical way to "determine" unlabeled, unsoldered unknown diodes? Some way to find out their original parts name maybe if not printed on the casing?

[mrsestherhouse]

thanks for another great video Dave, i learned alot :)

[Super73VW]

Love the shirt Dave!!!

[dynetrax]

I like the way Dave pronounces 13 and 18. :D

[tejonBiker]

Very illustrative the uses of comparators, where can I buy the batteries? (I am from Mexico)

[NIKOSGEOR]

WE WANT MORE LIKE THIS.... SIMPLE OLD SCHOOL ELECTRONIC CIRCUITS!!!

[Erny1389]

Dave, what about current, which goes through 1k resistor divider network and comes through Rlo out and changes IADJ value?

[EEVblog]

@Erny1389 That's in parallel with the external resistor R1, so it is taken into account. There is no extra current that flows out of it, so no additional error term to worry about.

[megasmart1337]

nice man, can you do more basic stuff?

[maqsoodu23]

hello Dave, great tutorial. Love the attention payed to intricate detail! I would like to offer an idea to you:

Since your powering your chip with batteries, keep the configuration in bar mode and add a switch (tactile SPST) from your Vcc supply to the chip. In that way, you wont be drawing any current till you press the button.

So this how it would work:

1- Press button and hold

2- The circuit would display the voltage level available

3- Release the button and chip would disconnect

[brunotag]

I've got a question.

How did you power the circuit? With the "batteries" themselves or with a separate source?

[EEVblog]

@brunotag I mentioned that at the beginning, using a variable lab power supply.

[PoirierMike]

Like it, nice project. Learned a lot !

[ronaldlijs]

Hi Dave,

Great stuff!! This is how everyone can learn and learn and learn, 2500 views in 1 day!

As one of your supporters (AUD 8/month) I can't get enough of videos like this, they are very simple, but unveil pure knowledge, not in a formal/tutorial way, but as a natural approach to electronics . This is how the future of teaching looks like in my opinion :-)

Take care and keep them coming!

[odessa999]

Great video, good to see someone whos been in the game so long to get so excited about an old school project :) ... great stuff !!

[flubba86]

Thankyou for this video dave. Im an electronics technician and also like to design analogue and digital circuits as a hobby. Ive been following your video blog since the very first episode, and I particularly love videos like this.

I know a lot of people want introductory or basics videos, but you are very good at delivering technical content in easy to understand and easy to follow terms.

I look forward to more videos like this.

[mageepaddy]

More circuit stuff like this Dave please :)

[prayag123456789]

I can't seem to get daveCAD..... Can anyone help me ?

[timmylc]

more please :P

[shanearnfield]

Ah, I didn't realise it would become a challenge, but looking a bit further I have found a brand new LM3914N with a date-stamp of "8124". I also found a 74C926N with "8112". In 1981 I had not long obtained my Technicians Trade Certificate and remember I was fiddling with a number of LED projects... Oh it now seems so long ago!!

By the way, I love your video's. I look forward to seeing them and really enjoyed this one in particular.

Shane.

[EEVblog]

@shanearnfield We have a new leader! Can anyone beat 1981?

[tech33012]

Thumbs up for the FSM shirt!

[shanearnfield]

Gee Dave, I just checked my Component Bin and I have chips showing "8348", so I hope the electrons can still move after all these years! :-)

[EEVblog]

@shanearnfield Ok, who can beat Shane with an older chip?

[amtpdb1]

Thanks:

I enjoy watching and learning about electronics. I will have to Google- supply decoupling and what it does.

Thanks again.

[xng14]

31:38 DaveCAD released an update !

[EEVblog]

@xng14 Yes, this update has new (metric) Grid technology

[fingerboy18]

@EEVblog Does it have any snapping features? ;)

[amtpdb1]

Hi:

Where did you place the capacitor and why? How did you decide what type of cap and what value?

Thanks for the video.

[EEVblog]

@amtpdb1 Across the power rail. It is used for supply decoupling.

[CampKohler]

The RC people have lots of audio alarm batt voltage circuits. Searc LIPO monitor.

[ajm114]

Very cool tutorial! I would love to see more videos like this that explain alternatives, then just using a microcontroller on breadboard. ;)

[EEVblog]

@ajm114 Yeah, a micro just isn't the same is it?

[shogoonn]

When you subtract 8.4 V from 6.4 V, you'll get -2.0 V ;].

[EEVblog]

@shogoonn Momentary brain fart!

[ubuntututorials]

LM3914 would be awesome for a lipo monitor on model aircraft, but as far as I can tell, the chip isn't available in a small SMD package like SOIC. Which makes it quite big. Great video on this chip though Dave!

[Deckardsvr]

fantastic video, Dave, i love when you get into that kind of things, thanks again, i learned a lot today !

[LurkePus]

what is the difference betwene the LM3914 and LM3915 ?

[superdau]

@LurkePus (and the LM3916)

More or less just the scale. One's linear the other is logarithmic. Since most of human's sensory system is logarithmic (e. g. 10 lights look 2x as bright as 1, 100 lights look only 3x as bright as one aso., same with audio levels), it's nice for showing power levels.

[joshstube]

Great Vid Dave!

us junior engineers eat this design/ build stuff up!

I can't think of who I would rather talk me through a design!

a request:

How about making a separate play list on your channel for all of these design/build videos ??

[DanFrederiksen]

good video.

far be it for a mere christian like myself to correct someone as enlightened as a spaghetti monster servant like you but there can be significant differences in discharge curves from chemistry to chemistry. a sanyo 2.2Ah will for instance be over 95% discharged when it passes below 3.6V at low current.

depending on current and temperature, some batteries will even rise in voltage during discharge.

is it for any particular project or just educational?

[CampKohler]

How about using the bar graph, but blink it to conserve power?

[thefekete]

@CampKohler You could switch it with a 555 and have nostalgia overload!

[superdau]

@CampKohler

Problem is: the blinking circuit does not come for free. It needs power, too, adds things that can break, needs more space and may disturb the graph (see how it reacted to different meters?).

If you want to conserve power and can live with it, I'd just add a push button right into the supply line of the LEDs or the IC, so LEDs only light up when pressed.

[CampKohler]

@superdau Well, let's compromise. Use a push button when you need to read the level and then have a 6-beep/minute audible alarm to call the user's attention to the fact that the batt is almost discharged. Of course, there is always that age-old problem: 'WHERE THE HELL IS THAT BEEPING COMING FROM?"

[EEVblog]

@CampKohler Possibly, I like your thinking! If the ultra-lowest power level was required though, I'd probably use a slow running low power micro.

[TheAdambee7]

Excellent. building a small PIC based solar and battery operated synthesizer. perfect add on. nice one.

[kevinxbuffalo]

great video Dave, many thanks :) I am gunna go try it out myself now!

[lartti83]

great video!

[bswain9999]

I guess at the very low V, the LM3914 was behaving as a resistor to ground but there had to be just enough V to overcome the forward voltage of the LEDs. As the V rose the chip turned on and the LEDs went out. What was the min V for the chip on the datasheet?

Generally excellent, really enjoyed.

[EEVblog]

@bswain9999 Yeah, something like, sounds feasible. Perhaps the IC process design experts can shed some light on the exact mechanism?

[mechadrake]

Thanks for video, i learned a few things. Such videos always welcome :)

[fettfettmerafett]

Somehow the plastic display cover is still on the metrahit!

Remove that silly thing and take it on a canyon trip!

[EEVblog]

@fettfettmerafett No way, I love my Metrahit!

[TheEPROM9]

Good to see no use of microcontrolers. I can't program very well so they are useless to me but everyone else in the world loves them as they reduce the fun part, the hardware.

[Kankki1]

Oh, that nostalgiar ;)

[Chuechco93]

Is there a similar IC which can handle up to 30V or so?

[sonicfunplex]

Great video Dave! I remember playing with the LM3914 back when I was in high school.

[azrimola]

Finally! Back at the lab.

[efhc12]

Neat, nice and smart. Greetings from Mexico Dave.

[ciprianwiner]

Thanks for the info, I really love this kind of video, please make a blog about optocouplers and comparators. Regards Cip

[williefleete]

i got a few of these hanging around, a dip package and the PLCC type ones, i might see if the dip one works at some stage. might do a response vid

[threedozer]

Really liked this.

[soclt]

Engineer is happy whith LM3914, which is produced for DECADES! :D

[Kethlar]

2 Questions.... What about a Bar Bar Graph... like an Audio Bar type graph? Will this work with one of thoes? Q2: different Color LEDs? Meaning Out of 10 The first 6 are green, then 3 yellow, then 1 red at the end of the bar/dot when dead. Does this Chip allow different colors as the output? or do I actually have to use resistors to use different colors?(Also with the Bar Bar Graph as well)

[superdau]

@Kethlar

A1: Yes, it can be used. But use the logarithmic (that's how our ears work) version (LM3915) for audio.

A2: Since the LED outputs are current regulated and not voltage regulated, any color LEDs can be mixed. They will all be driven with the same current though. If the brightness is too different at the same current, you have to use other LEDs. A resistor in series wouldn't change anything, since the IC will up the output voltage so the current stays the same.

[EEVblog]

@Kethlar @superdau already answered, yes, any type of LED will work. Although high voltage drop Blue LEDs for example may not work at the lower ends of the voltage rails the chip is capable of working at.

[4833504F]

great video, hope it saves the dignity of some arduinos ^^

[GLaDOSProductions]

yay!