Electrical Engineering

6:00 PM

@rawbrawb: Yes, if using TLC5940 the transistors would have to be PNPs. Do you want to write that up as an answer? — angelatlarge 21 hours ago

Anindo Ghosh

@angelatlarge Not going to answer that question, but you did check out the TPIC6A595, yes? It's the monster-in-law of the measly 595 you mention

angelatlarge

@AnindoGhosh Is that because your coffee came out of your nose all over the KB?

jippie

good morning

did anyone release the magic blue smoke?

angelatlarge

@AnindoGhosh I think I saw that in one of your answers somewhere, but the shift registers have more serious speed problems. I was just trying to answer this comment.

Anindo Ghosh

@angelatlarge Wow, that was a delayed repartee! No, that's because my keyboard is an incredible 8 years old, I still have not found a suitable replacement so I struggle on. Logitech MX5000. I love the hefty mouse and the solid feeling keyboard.

angelatlarge

6:02 PM

@jippie Yes @user1832583's AVRISP

Anindo Ghosh

@angelatlarge Yes. No. Check out the speed of that baby.

coding_corgi

@angelatlarge Yeah, all that work for nothing...

angelatlarge

@AnindoGhosh huh?

Anindo Ghosh

@angelatlarge The TPIC is pretty fast. Not relevant for your purposes, just telling you so you keep that in mind for any time you need a fast, high current shifter.

angelatlarge

@AnindoGhosh Using shift registers, instead of PWM, I would have to update the shift registers every three nanoseconds for 256 linear intensity levels

@AnindoGhosh Yes, yes, and yes. But not for my POV, unfortunately.

Anindo Ghosh

6:04 PM

@angelatlarge The single biggest reason to opt for an LED driver over a transistor / MOSFET drive stage is the sheer component count reduction due to not needing current limiting. LED drivers typically take care of that end.

jippie

@angelatlarge Watched too much "Home improvement" => "more power"?

►

angelatlarge

@AnindoGhosh: the OP on the @W5VO's question (with your peace offering) 13. You saw that, right?

Anindo Ghosh

@angelatlarge Yes, I don't make peace offerings to people old enough to be able to deal with life.

@angela what is the mA per channel you needed?

coding_corgi

@jippie user1832583 = coding_corgi, hi, i have a question, if I follow this tutorial: youtube.com/watch?v=_ZL-YNOH_jA, can I run this command: sudo avrdude -p t85 -c arduino -U flash:w:src.hex

?

Anindo Ghosh

@angelatlarge Have you looked at the AS1116? "The AS1116 is a compact LED driver for 64 single LEDs", it is SPI programmable.

jippie

6:13 PM

@coding_corgi you have to add an extra parameter -P /dev/ttyUSB0 or something similar

angelatlarge

@AnindoGhosh It's like at least 15mA. 20mA would be nicer

@AnindoGhosh Charlieplexed?

Anindo Ghosh

@angelatlarge Another thing: This is unsolicited advice, but between 10 mA and 20 mA, you won't see much difference unless you are comparing one against the other. Typical 20mA LEDs are pretty bright beyond 8mA.

coding_corgi

@jippie ok

@jippie or would it be /dev/ttyACM0 ?

jippie

@coding_corgi I would skip the FUSES part until you feel more confident.

@coding_corgi that is possible, yes.

likely even :)

The Photon

@angelatlarge I was gonna upvote his first question, but he would have had to change his name to coder106.

coding_corgi

6:15 PM

@jippie yeah, I will use avrdude not a make file

angelatlarge

@ThePhoton :)

The Photon

(Unfortunately somebody came along and upvoted him so his name no longer matches his rep)

Anindo Ghosh

@angelatlarge No, the AS1116 is not a charlieplex, it's a straight 8x8 mux-drive, IIRC. I don't have the patience to open up the datasheet at the moment.

angelatlarge

@ThePhoton It was @AnindoGhosh

@AnindoGhosh Yeah, multiplex at 30mph is not good.

@AnindoGhosh Actually, depends on the scan speed I suppose

jippie

@coding_corgi makefiles are really cool, but indeed first get the hang of how things work without the makefile

angelatlarge

6:17 PM

@AnindoGhosh Yeah, beyond 8mA is what I need. 8mA was pretty dim.

Anindo Ghosh

@angelatlarge Don't knock it till you try it. It's used in big stadium size digital TV screens a lot.

angelatlarge

@AnindoGhosh But the stadium size digital TVs are not moving.

Anindo Ghosh

@angelatlarge Well, most everything I suggest would do 15 mA or so.

angelatlarge

@AnindoGhosh Why is that?

Anindo Ghosh

@angelatlarge Think this through. A stadium TV needs to show fast action without smearing or stutter. So they have pretty demanding timing needs.

coding_corgi

6:18 PM

@jippie STAY with me ATtiny85!!!

Anindo Ghosh

@angelatlarge Because I've never used a part that does less than 15 mA per channel :-D

coding_corgi

@jippie My poor ATtiny85 is burning up!!!

@jippie Ok, he's ok

@jippie I got an error: avrdude: stk500_getsync(): not in sync: resp=0xe0, what should I do?

Anindo Ghosh

@angelatlarge Also, check which of the AS111x parts have their own pattern memory. If you plan right, you might be able to use that to some benefit

angelatlarge

@AnindoGhosh 0.8 Khz... that's only 800Hz, meaning that each cycle takes longer than it does to draw a horizontal pixel. Not workable

coding_corgi

Maybe my ATtiny85 isn't wired up right...

angelatlarge

6:21 PM

@AnindoGhosh Sorry, can you explain that? You are saying "don't drive the LEDs at > 15mA" because you never "used a part that does <15mA"? I am confused

@coding_corgi It might also be toast due to the results of the smoke liberation procedure you ran.

Anindo Ghosh

@angelatlarge Remind me, did you once mention already trying out the Atmel LED thingie with the MOSFET drive + current control? MSL something? I think I suggested it to someone who wanted a fancy 200 mA per channel.

coding_corgi

@angelatlarge Ok, i''l try my other guy...

angelatlarge

@AnindoGhosh No. I never mentioned that.

@AnindoGhosh linkie?

Another AC vs DC distribution question.

Anindo Ghosh

@angelatlarge No, context mismatch. You said you wanted more than 8 mA, so I responded that sure, in any case my suggested parts would all be able to cope with that, they would cope with at least 15 mA each

angelatlarge

@CamilStaps Free beer for you!

@AnindoGhosh Yes, ok.

Anindo Ghosh

6:24 PM

@angelatlarge atmel.com/Images/F1_MSL2162_DB.pdf

angelatlarge

@AnindoGhosh Thank you, kind sir!

Anindo Ghosh

@angelatlarge I only mention that part for one-off runs, or really huge current draw requirements - it's expensive in bulk, Atmel does not discount well for volume.

angelatlarge

@AnindoGhosh They have samples :)

Anindo Ghosh

@angelatlarge Fast 20MHz SPI Bus Supports up to Eight MSL2162s per SPI Bus Chip Select.

angelatlarge

@AnindoGhosh They PWM at 8Khz, which still might not be enough. I am PWMing the TLCs at 20Mhz :)

@AnindoGhosh I am driving them off the AVR clock signal.

Anindo Ghosh

6:28 PM

@angelatlarge Yeah, they are decent about sampling, unlike Fairchild. I've wanted a few FAN5646 samples for ages, but no dice. "We don't ship to India, sorry" - and I can't buy them because the local distributor does not carry that series.

@angelatlarge Would you consider the possibility that there is a design flaw there? The idea is not to PWM off a remote clock, just use the internal oscillator wherever possible.

@angelatlarge Remote delivery of a PWM clock to a part that can internally do PWM is perhaps avoidable.

@angelatlarge The only clock link you should be using is the SPI clock

angelatlarge

@AnindoGhosh At 8Khz, each pwm clock is 0.125ms. That means that at 256 greyscale levels, each full PWM cycle takes 32 ms. Too long.

@AnindoGhosh Incorrect. TLC5940s need a greyscale PWM clock.

Anindo Ghosh

@angelatlarge You really really need to revisit your design, I propose. People have done massive PoV projects before, without coming up with the challenges you perceive.

angelatlarge

@AnindoGhosh Of course. But TLC5940 needs a greyscale clock

@AnindoGhosh Sure, lets talk about that. Are we done with the clocking of the TLC5940?

Anindo Ghosh

@angelatlarge No, I said "wherever possible". The MLC boasts internal clocking

angelatlarge

@AnindoGhosh I was just responding to "The only clock link you should be using is the SPI clock". If that's a comment on the design, that's possible. If that's a comment on how to implement a TLC5940-based circuit, that seems wrong.

@AnindoGhosh I think mine is more massive.

@AnindoGhosh And by massive I mean more lights given the movement speed.

@AnindoGhosh I think that car link you posted comes close, actually.

Anindo Ghosh

6:35 PM

@angelatlarge Actually, even a TLC, I've always used a separate 4-pin XOSC for gr-clk, so I don't know about pulling MCU clock to it. Maybe that's a separate problem / solution?

angelatlarge

@AnindoGhosh If you do that you need a separate counter to trigger the BLANK pulse, right?

user61389

@angelatlarge whoo, where?

angelatlarge

@CamilStaps I was jokingly referring to the power distribution question.

@AnindoGhosh So if I need more processor clocks, I was thinking of externalizing the clock/BLANK part of the design, yes.

user61389

@angelatlarge sorry, which one?

angelatlarge

3

Q: If we could start our electrical grid from scratch with today's technology, which would be the most efficient choice? AC or DC?

Lately, I’ve been reading about the many advantages of HVDC transmission systems for long distance transmission, undersea links, and others. The historical reason of why AC was picked over DC was mostly due to the invention of the transformer, which allowed easy manipulation of AC voltage enablin...

That stuff always gets upvoted.

user61389

6:37 PM

@angelatlarge well it's interesting, I can't disagree :)

angelatlarge

@CamilStaps Yes, this one is more actually much more articulate. I'll upvote it too.

@AnindoGhosh If I write up a document describing why I think what I am doing is difficult, and how it compares to other POV projects, will you read it?

user61389

@angelatlarge I'm generous today, let's upvote it too :)

jippie

@coding_corgi sorry, I'm walking in and out tonight. How did you manage to fry the other programmer?

angelatlarge

@jippie He meant the other ATtiny

jippie

@angelatlarge I know

@angelatlarge but I want to know how he fried the programmer

angelatlarge

6:40 PM

@jippie This was in response to my comment that when he had a small fire, he might have fried the ATtiny as well.

@jippie Oh... we haven't fully figured it out. He hooked up external power.

jippie

@angelatlarge I understand that

angelatlarge

@jippie Ok, sorry.

jippie

@angelatlarge hmm ... it is good practice to learn from mistakes ..

angelatlarge

@jippie I don't know why I am saying "he". Could be a lady

@jippie Agreed. The OP didn't seem super interested in pursuing that topic, so I didn't. But if you do, I'd like to hear about it.

@jippie Not that I ever plan on buying an AVRISP...

jippie

@angelatlarge I hear they get zapped easily ;o)

angelatlarge

6:42 PM

@jippie Really? I would have thought that Atmel parts were quality parts.

jippie

it is a lot easier to smile about that if it isn't my own programmer

angelatlarge

@jippie Yeah, fer sure

@jippie What do you use?

jippie

But I definitely know the feeling

angelatlarge

@jippie (besides Ardweenos)

jippie

Maybe I'll program an ATtiny45 as programmer. Not entirely sure about the memory footprint.

angelatlarge

6:44 PM

@jippie Do you have a non-bare-chip programmer?

jippie

?

not sure what you mean

coding_corgi

@angelatlarge It's a he, i'm sure, :)

angelatlarge

@jippie Do you have an ISP programmer that isn't an Arduino or a bare chip? Like an USBtinyISP, or USBASP, or AVR Dragon?

@coding_corgi What would YOU know about that?! :)

jippie

@angelatlarge no, why should I? The Arduino does all I want and if I don't like it I change the software.

coding_corgi

@angelatlarge Yes, do you have any recommendations? (P.S. the funeral for my poor (stupid) little AVRISP MKII programmer is tomorrow)

Anindo Ghosh

6:48 PM

@angelatlarge Yes, I will.

jippie

OK, debugWire is on my wishlist and that is definitely non-Arduino

@coding_corgi what happened?

Anindo Ghosh

@angelatlarge Not a separate counter, no. Why not just use code and a regular GPIO to do the BLANK blipping?

Hmm, that's essentially a counter, but far simpler to use an external counter for that than the MCU one.

coding_corgi

@jippie Ok, long story short: the red led was on meaning no target power source, so I hooked up my battery pack to my attiny (don't worry, it was only 5v) and my computer shut down, I smelled smoke from my programmer, I opened it up, and I saw a chip that was blown up in there, got, really mad, 37 USD down the drain, etc. ...

icarus74

Hello Folks

coding_corgi

@icarus74 Yo!

@jippie what is the pin for portb on the ATtiny85?

icarus74

6:55 PM

Is the community holidaying or partying too hard ... :-) ??!!

Pretty surprising... no one took a stab at my question -

2

Q: Wireless water level sensor, in sump. Installation best-practices for longivity

My wireless water-level sensor is working fine, and when deployed in the sump-well, it is giving me periodic readings quite well. At this stage, I have the circuit still on a breadboard, and now plan to put it on a veroboard, and finally install this thing in the sump-well for long-term reading p...

rf design antenna waterproof heat-protection

Anindo Ghosh

@icarus74 hiya

angelatlarge

@AnindoGhosh Well, I need all of clock cycles, so I use timer PWM for BLANK tripping, and I output the clock signal on a pin to drive the greyscale clock: it doesn't take any CPU clocks to drive the TLC5940 this way.

icarus74

hi @Anindo

angelatlarge

@AnindoGhosh And it is 20Mhz fast, which is nice for my purposes.

Anindo Ghosh

@angelatlarge does that not unduly limit the dot clock?

coding_corgi

6:56 PM

@icaurs, whoa! where did you get a water sensor?

jippie

@coding_corgi check the datasheet

Anindo Ghosh

@coding_corgi ultrasonic sensor to sense water surface by reflection

angelatlarge

@AnindoGhosh Wait, I think there is disconnect somewhere. I thought you suggested using the main MCU for the TLC5940 grescale clock, and then I seem to read the opposite. Where did I get confused?

jippie

@coding_corgi type 'datasheet attiny85' in google, then find the link that points to the atmel.com website and find the datasheet from one of the tabs there.

coding_corgi

@jippie I know, it just says: clk, sck gnd, etc...

icarus74

6:57 PM

@coding_corgi it's a 'water level sensor' using Ultrasonic range sensing... original idea, thanks to @AnindoGhosh

jippie

@coding_corgi share the url to the datasheet here

Anindo Ghosh

@coding_corgi See his earlier question and my detailed techniques with cardboard binoculars :-)

angelatlarge

@AnindoGhosh Cool. Will do that after I finish the damn Android thing.

Anindo Ghosh

@angelatlarge I said I've always used an external 4-pin xosc

angelatlarge

@AnindoGhosh Yes, so I said that at some point I might switch to that.

Anindo Ghosh

6:59 PM

@angelatlarge yup

angelatlarge

@AnindoGhosh But you'd need a counter so that you can blank after 4096 or 256 cycles.

coding_corgi

@jippie is portb = pb0? That's mosi...

angelatlarge

@AnindoGhosh Or would you use the main MCU for the blanking, and xosc for the greyscale?

@AnindoGhosh Because the two need to be coordinated.

Anindo Ghosh

@angelatlarge 256 is easy, 8 bit counter or even an attiny, and you can share that output across all the TLCs

jippie

@coding_corgi 2nd page: pin configurations

coding_corgi

7:00 PM

@jippie yeah we're looking at the same datasheet

jippie

@coding_corgi some pins share multiple functions.

Anindo Ghosh

@angelatlarge Like I tried to say earlier, that too is an option.

coding_corgi

@jippie oh, ok...

angelatlarge

@AnindoGhosh Yes, of course. But the way I am doing it currently doesn't take any MCU cycles from my main MCU, and has the same highest clock speed as the ATiny counter + xocs, so I don't see much difference. Or am I missing something?

coding_corgi

so if I had the same code you gave me it would be okay to put the led pin on pb3

jippie

7:02 PM

@coding_corgi best to do while experimenting is to avoid PB0, PB1 and PB2. Leave them configured as input in DDRB. Also you want series resistors (say 220 ohm) between the ATtiny and the Arduino pins. Again to prevent the pins for overcurrent.

Anindo Ghosh

@angelatlarge Hmm, I think I see what the disconnect is: You're using a fast MCU to talk to the TLC. I've always used slower ones, so in order to get a good dot clock speed, I used separate XOSC + counter for the grey clock, independent of the MCU

angelatlarge

@AnindoGhosh But then you'll need your MCU to count. Since 20Mhz is the limit regardless (no AVR runs faster, except XMegas), then why not just output your 20mhz main MCU clock on a pin (it is free: you just set a fuse), and you got your clock.

@AnindoGhosh Ah! Ok, awesome, cleared up.

jippie

@coding_corgi that I used PB3 is not a coincidence ;o)

coding_corgi

@jippie would 330 ohms be okay?

@jippie resitors for every port?

angelatlarge

OK, back to android for a while.

Anindo Ghosh

7:03 PM

@coding_corgi Or get a resistor array so all ports are covered with less individual part count.

rawbrawb

@ThePhoton good comment on the power-line question.

angelatlarge

Don't forget everyone: plz-remambar-send-teh-codez-nao-nao-nao

coding_corgi

@angelatlarge that's a funny tag!

jippie

@coding_corgi maximum current for an AVR on most pins is 40mA. At 5V and 40mA, the resistor must be at least 5/.04 = 125 ohm. I'm not sure about an upper limit, but I guess everything under 1k should work just fine. So, yes: 330 ohm works just fine. Use it for MISO, MOSI, CLK and !RESET

coding_corgi

so 4 pins?

wait, arent there two CLK pins?

angelatlarge

7:06 PM

@ThePhoton: No extended discussion? then I quit!

The Photon

@angelatlarge That's what chat is for.

jippie

@coding_corgi CLK = clock, sometimes indicated as SCK

coding_corgi

@jippie so 6 pins?

jippie

@coding_corgi MOSI = Master Out Slave In (serial data from Arduino to ATtiny)

@coding_corgi MISO = Master In Slave Out (serial data from ATtiny to Arduino)

coding_corgi

SCK, RESET, MOSI, MISO, CLK0, CLK1, is that right?

jippie

7:08 PM

@coding_corgi !RESET ... reset

@coding_corgi Vcc and GND, that is all

@coding_corgi ah I see where your confusion comes from

coding_corgi

@jippie, so no resistors for vcc and gnd?

jippie

Use pin 7 labeled SCK for programming, do not use CLKO and CLKI for programming.

@coding_corgi no resistors on VCC and GND

coding_corgi

so no resistors on vcc, gnd, clk0 and clk1

jippie

correct. dont connect clko and clki to the programmer

back in a little

coding_corgi

@jippie so reset, sck, miso, miso, for resistors, right?

angelatlarge

7:47 PM

@ThePhoton I know :) I was just make an unsuccessful joke.

jippie

@coding_corgi for series resistors, yes

coding_corgi

@angelatlarge Did you get your arduino project working

angelatlarge

@coding_corgi What Arduino project? I don't have an Arduino project.

coding_corgi

@angelatlarge The thing you were trying to get to work

angelatlarge

@coding_corgi The LED thing? No. still-waiting-fur-teh-codez

coding_corgi

7:52 PM

@angelatlarge Stop making tags like that!

@angelatlarge What is the default programmer for the Arduino IDE, I started to play around with those settings, and now it won't find my Arduino when I upload the Arduino ISP

jippie

Tools => Programmer => Arduino as ISP

Tools => Serial port => ttyACM0

Tools => Board => pick your exact board.

@coding_corgi .

coding_corgi

@jippie so is the 'Arduino as ISP' the default setting?

jippie

I never changed that

coding_corgi

@jippie ok...

jippie

and it is set to that setting for me

coding_corgi

7:59 PM

let me upload the ArduinoISP

...

@jippie got this error: avrdude: stk500_getsync(): not in sync: resp=0xe0

what should i do

i've seen it before... But know I am all confused with the ATtiny thing!

jippie

carefully draw a circuit diagram from what you have and upload it here so we can check.

but it is time for bed for me

coding_corgi

@jippie why a circut diagram?

jippie

because you are doing something wrong.

and we can't tell if you don't show us exactly what you are doing

/me is out

coding_corgi

@jippie is a fritzing file okay?

angelatlarge

@coding_corgi It doesn't actually make a tag, just formats text as a tag. It is harmless.

coding_corgi

8:08 PM

@angelatlarge okay, is a text file okay?

rawbrawb

@angelatlarge I was looking at the LTC5940 datasheet to look at the o/p structures. That beast will drive 120 mA as long as you don't over heat the package. So if you choose the rails carefully and don't drop too much voltage over the outputs, you should be able to drive at least 100 mA. Given all the same color LED. Why do you think you need more current?

coding_corgi

@angelatlarge Oh stupid me! I though you were talking about the fritzing file! Yet those 'fake' tags are funny

angelatlarge

@rawbrawb 120mA total, right? For 16 channels isn't that just 7.5mA/channel?

@rawbrawb What am I missing?

rawbrawb

@angelatlarge it's 120 mA PER channel!

you just can't scrub too much voltage across the current sink.

angelatlarge

@rawbrawb What?!

@rawbrawb r u shoor?

(pulling up datasheet again.... stratch head)

rawbrawb

8:22 PM

@angelatlarge eqn 6 page 14 - r = 640 (like used to test) -> 61 mA

angelatlarge

@rawbrawb OK, so the I\$_{OLC}\$ line is 120mA/channel...

rawbrawb

thermal calculation eqn shows X16!

angelatlarge

@rawbrawb What about the Ioutput in absolute maximum ratings as 130mA? On page 2

@rawbrawb That doesn't look per/channel-ish.

rawbrawb

the thing to realize isthat this is a current sink, so most of the heat is in the LED drop. But the circuit sink needs a little bit of head room. the head room is less for lower currents. But at 120 mA you have ~1 V. IF you run a LED with Vf of say 2V off of a 6 V ril then your current mirror will need to drop 4V at 120 mA. hurts ville!

@angelatlarge that is per pin.

angelatlarge

@rawbrawb Just so that I can learn something from this, how would I know that?

rawbrawb

8:26 PM

@angelatlarge look at the total amount of evidence. Power calc. explicit pin calc. and if it it isn't mentioned that it is per pin, it certainly never says that that it's a total!

also if set up right it shouldn't HAVE to burn a lot of current.

angelatlarge

@rawbrawb I see.. I figured that the 120mA calculation on page 14 was for the (weird) case where you are running a single LED at 120mA.

@rawbrawb But that would mean that if all channels are at 120mA * 16 channels, this thing would be sinking more than 1A through its single ground pin. That also seems like a lot. 2A actually.

rawbrawb

@angelatlarge are you using lots of different colors?

angelatlarge

@rawbrawb RGB

rawbrawb

@angelatlarge to keep the power down you may have to have different rails for teh LED's

angelatlarge

@rawbrawb So you really think that this thing can actually sink 2A through its GND pin?

rawbrawb

8:30 PM

@angelatlarge that does seem like a lot,

jippie

@coding_corgi circuitlab.com

angelatlarge

@rawbrawb In order to keep the voltage the TLC5940 on its outputs as close Vheadroom?

@rawbrawb so it doesn't have to dissipate a lot of "voltage"?

rawbrawb

@angelatlarge yep, key curve is figure 5. you want to be just above that knee.

jippie

@coding_corgi pick custom part for attiny and custom part for arduino. Label the pins properly so we can actually read the circuit

/me is oout

angelatlarge

@rawbrawb Right. A long as we are right on the 120mA/channel :)

@jippie Goodnight

rawbrawb

8:32 PM

@angelatlarge yep, below the knee it's not working very well as a current sink, above that it has to drop the volatge some how = heat.

angelatlarge

@rawbrawb The spakfun board agrees with you: 120mA/channel

rawbrawb

@angelatlarge but you don't care so much about that you only need 20 mA

@angelatlarge actually it's not me, it's the datasheet . ;)

Anindo Ghosh

@angelatlarge It's something like 60 mA per channel with all simultaneously on, at room temperature with headroom at the minimum which I had shared with you the other day.

angelatlarge

@rawbrawb I'd be 100% on board if that scary-looking absolute maximum rating said "per channel" too.

Anindo Ghosh

Sorry, I was AFK.

angelatlarge

8:34 PM

@rawbrawb Looks like @AnindoGhosh also agrees with you.

rawbrawb

@AnindoGhosh I just did a qucik back of the envelop calc and came up with 100 mA so that makes perfect sense.

Anindo Ghosh

@angelatlarge The AbsMax is per channel, yes, but you cannot actually run it at that. Realistic running is about half that, because calculation is done for 50% on.

angelatlarge

I guess the premise of my question is wrong, so let's all go and downvote @angelatlarge's question now!

rawbrawb

@angelatlarge but the voltage rateing are per pin, aren't they? ;)

angelatlarge

@rawbrawb I don't know anything any more.

rawbrawb

8:35 PM

@angelatlarge LOL

Anindo Ghosh

@angelatlarge Do you still have that headroom calculation (figure 5 or something) that I had done for you?

rawbrawb

@angelatlarge welcome to my club.

angelatlarge

@AnindoGhosh yes.

@AnindoGhosh It is figure 5 of the datasheet

Anindo Ghosh

@angelatlarge and another thing, are you not forgetting that I had suggested a separate TLC for each color, rather than R G B of each LED in one TLC?

@angelatlarge Yes but from that figure I think I had given you some actual numbers for minimum headroom. You'll want to use those.

angelatlarge

@AnindoGhosh I think the figure shows the headroom graph, does it not? You gave me a ballpark figure from memory, but you had more precise figures in the answer you linked to.

Anindo Ghosh

8:38 PM

@angelatlarge That way, any TLC running a red channel has the LED supply voltage at V.fwd.red + headroom, green channel is calculated for green, etc, if you want absolutely the coolest running.

@angelatlarge Yes, I am referring to my precise figures, which were in some comment to some answer I had written and which I can't be bothered to find at 2:08 am, sorry :-(

angelatlarge

@AnindoGhosh Yes. If it is 120mA/channel I am not so worried. I don't plan on using this as a searchlight. I just want more than 7.5mA/channel, that's all.

@AnindoGhosh Yeah, I got that.

Anindo Ghosh

@angelatlarge I know I have routinely used them at 15 mA per channel, which is my default for LED longevity. For power longevity I go with 8 to 9 mA instead, or even 1 mA for indicator functions.

rawbrawb

@angelatlarge why do you want to separate out the G's and G's and B's strcitly speaking from a circuit stand point it shouldn't matter. Just as long as they each have their own rails.

angelatlarge

@AnindoGhosh Can you tell me the relationship between current and longevity in LEDs? It is new to me.

rawbrawb

@AnindoGhosh rather the Q above is for you.

Anindo Ghosh

8:41 PM

@rawbrawb I suggested the separating out, as that way the whole mental picture for the circuit becomes simpler (at least for me): each TLC is dedicated for use with one color, both programming wise, and rail wise.

rawbrawb

@AnindoGhosh and current flow is cleaner for noise reasons. Just was wondering if there was something sneaky you had thought of.

angelatlarge

@rawbrawb No, I am not opposed to that. I guess the question is : where to throw away the excess voltage, in the Vreg or in the LED driver. It might be easier to organize my power around natural units of 6 drivers and their LEDs, so that would be the only opposition.

Anindo Ghosh

@angelatlarge Oh, there's no hard relationship - I recall reading somewhere that while LEDs are typically rated at the nominal current, and are typically in the 10k to 100k hours range, when you drive at 75% of nominal, you get a significant increase in longevity. Below that, no great benefit.

@rawbrawb what Q is above what?

angelatlarge

@AnindoGhosh I see. OK, thanks.

rawbrawb

@AnindoGhosh @angelatlarge these are typically driven by the Aarhenius eqn and it's dependance upon Temperature. exponential. bet below a "activation energy" and it will last aad last and last.

@AnindoGhosh I had angela's tag in the question about mixing rails.

Anindo Ghosh

8:45 PM

@rawbrawb Now that is the scientific explanation for the "IIRC" data I gave @angelatlarge :-)

OK if there's nothing pressing, I need to go now.

rawbrawb

@angelatlarge I suppose I should explain, ... since these are current sinks, it doesn't matter what the rails are, and you need not separate them out as long as the given LED is driven by the right rail.

@AnindoGhosh well I need to know that shit man. have a good night!

angelatlarge

@rawbrawb Yes, I understand that.

@AnindoGhosh Thanks and goodnight

Anindo Ghosh

GN all :-)

rawbrawb

@angelatlarge after all that convincing and only Anindo gets a thanks?

angelatlarge

@rawbrawb He is the one that's leaving :)

rawbrawb

8:48 PM

@angelatlarge thats fine, als long as I can avoid answering one of your questions .... ;)

angelatlarge

@rawbrawb So you'd put a Vreg in front of each rail getting the Vrail as close to Vled_forward + Vheadroom, right?

rawbrawb

@angelatlarge yep, but keep in mind that the LED Vf will vary.

coding_corgi

Geek fight (rap battle)! www.youtube.com/watch?v=njos57IJf-0‎

angelatlarge

@rawbrawb Hopefully just between each channel type

@rawbrawb And not between LEDs like in the recent post :)

rawbrawb

@angelatlarge certainly between each color, they get the color by using different materials which have different bandgap's. I am talking about WITHIN a given color.

angelatlarge

8:51 PM

@rawbrawb I guess one problem I see is that most Vregs need some headroom too, and I might not get enough voltage from two LiPo cells for that.

@rawbrawb So you would test each LED???

rawbrawb

@angelatlarge there are some sweet LDO's now a days.

angelatlarge

@rawbrawb True.

rawbrawb

@angelatlarge I don't have a sense of the variability, Anindo would.

@angelatlarge I gotta go, ciao

angelatlarge

@rawbrawb Ok, thanks very much! That was helpful.

@rawbrawb ...and depressing.

@rawbrawb Very helpful, actually. Thanks!

angelatlarge

9:08 PM

@user1832583 Your question will not survive very long, I predict.

@user1832583 IF you seriousely rephrase it it might have a better chance.

coding_corgi

@angelatlarge Nooo!!!!! I must find a perfect replacement for deceased programmmer!

@angelatlarge Like? ...

@angelatlarge please remember my new username is 'coding_corgi'

angelatlarge

@user1832583 I am seeing only "user18...", and that's what autocompletes for me. @coding_corgi I'd have to type out every time.

@coding_corgi On your question, it is a shopping question, and there isn't one correct answer.

coding_corgi

@angelatlarge Yea! Shopping!

angelatlarge

@coding_corgi Oh, and when I click reply on your messages I get "user1832583".

coding_corgi

@angelatlarge Yes, yet I asked for a recommendation...

angelatlarge

9:17 PM

@coding_corgi Shopping questions are off-topic.

coding_corgi

@angelatlarge So should I ask shopping.google.com?

:)

angelatlarge

@coding_corgi From the FAQ: "and it is not about … a shopping or buying recommendation"

@coding_corgi I don't know.

coding_corgi

@angelatlarge I think I might delete my question...

I don't want to lose my ability to downvote now!

angelatlarge

@coding_corgi But I don't think it will survive very long here. If you really like it, you'd be better asking "What are some of the features and benefits of various programmers" or something like that.

@coding_corgi As in "why might I want this over that and the other thing"

@coding_corgi And then limit the programmers to cheap, out-of-the-box, etc.

@coding_corgi That would have a better chance.

@coding_corgi And would cause me to research the features of various programmers and put it in a table, which would be useful.

@coding_corgi But probably not today.

coding_corgi

@angelatlarge I edited it a little so there would'nt be that much of a shopping sense

@angelatlarge Should I just ask people here in the chat instead?

angelatlarge

9:21 PM

@coding_corgi It says "best" in the title and in the body. That makes it look like shopping.

coding_corgi

@angelatlarge Err... ill change that..

angelatlarge

@coding_corgi The larger point is that there is no best: it all depends on how your various criteria are ranked: Do you want cheapest? Do you want most reliable? Do you want most versatile?

@coding_corgi I think that'd be good. OK, I'll go work some more.

coding_corgi

@angelatlarge is 'most recommeded AVR programmer' ok?

Anindo Ghosh

@angelatlarge reload your chat browser-window to get @coding_corgi instead of User_whatsit

@angelatlarge also, I have found some neat switch regs that work down to very low headroom. Will look up tomorrow

coding_corgi

@angelatlarge do use the arduino to program your avr chips?

angelatlarge

9:27 PM

@coding_corgi I wouldn't advise it

@coding_corgi No. I use USBtinyISP

coding_corgi

@angelatlarge those are neat!

@angelatlarge Do use linux?

coding_corgi

10:14 PM

Found a replacement for my deceased programmer!

pololu.com/catalog/product/1300

Seems like a nice 'lil programmer, going to search for some tutorials on it, do not want to waste my time again with that AVRISP MKII situation all over again

Nope, turns out that programmer wasn't really too linux friendly...

coding_corgi

10:32 PM

Now I think I have found a nice friendly programmer: sparkfun.com/products/9825

rawbrawb

11:21 PM

@angelatlarge why depressing? or was that humor?

coding_corgi

Yo yo yo!

hhh

Sorry stupid question: anyone using here Windows 8 and can recall the button to the normal Desktop?

(I am trying to use some CAD softwares only in Windows but cannot even find the traditional desktop, annoying...)

coding_corgi

11:41 PM

@hhh What? Please explain your question, isn't there a button on the bottom right side of the toolbar that if you mouse over or click that will take you back to the desktop

or if you went full screen press F11 to exit full screen

hhh

More complicated thing: I am using Parallels under OS X and the desktop is somewhere but I cannot find it, very irritating.

(W8 virtualized)

coding_corgi

@hhh Oh so you're using virtual box?

hhh

Virtualizaton under Parallels (not Sun's Virtualbox), much easier to use normally....

coding_corgi

@hhh Where did you get the iso for winders 8?

hhh

It was the student site: I get it free as a student. If you are a university student, you get it free (at least in my case besides other m* softwares)

coding_corgi

11:46 PM

@hhh oh, anyways

so your running win8 in a virtual machine on mac osx an you cant get back to the desktop?

hhh

@coding_corgi actually, I solved the problem by restarting -- so now I got there. No idea what the problem was.

It was something to do with it that I am using my computer with multiple screens so I could not find the screen having the desktop...

coding_corgi

@hhh what do you have triple head to go, multiple vga ports, siig's usb 2.0 to vga?

hhh

laptop on a display like a workstation but using many different displays over day etc so display settings somehow got bad without any restarting

coding_corgi

@hhh oh

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