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Good slides and great lecture. Thank you Warren.

Iron

Have used ADCs in sensor designs (human vital signs).

Iron

Have used RTC and comms interrupts as wake-up triggers.

Iron

have used ammeter to measure current, but as stated, accuracy can suffer.

Iron

I am a software engineer, my primary focus is embedded software development. I have spent the last 23 years working in the medical device industry.

Iron

Downloading slide deck...

Iron

Hello from Beaverton, Oregon.

Iron

hello all from edmonton, Alberta.

still getting caught up.

Iron

now, i am in the last page of the lecture of sir warren, once again, thanks to sir warren for a GREAT and EXCELLENT presentation...much appreciated all...

now, preparing for the day 4 lecture of sir warren to finish them all in today's off day of mine...

thanks to DIGIKEY and DESIGN NEWS....bye all...

i think i need to go through with the electronics engineering course to apply them all as well as to go through with the electronics company...but, i have learned those lecture, great...

now, i am on slide 17 of the lecture...

i am now on slide 15 of the presentation...GREAT LECTURE sir warren, much appreciated!

i am now on slide 9...

i am now on slide 4 of the lecture...

i am now about to download the lecture slides for reference and for future reference as well...thanks again...

good afternoon once again sir warren, here i am again to continue your lecture...

thank you for a continuing interesting class

Iron

Good presentation!  First two classes laid the foundation for this class.  Good mix of marketing and technical (and pedagogical) approaches.

There was a question from Class 3 slide 19 on Serial Ports in Low Power Designs. One of the bullets is -

- Transmission/Reception

    - Data length

    - Phase, MSB, Polarity

These are just common characteristcis  of serial ports and don't have any appreciable effect on power dissipation.

The key low power point of this slide is really the table that shows the Total Charge needed to transfer data by UART, I2C and SPI. Typically the faster you can send data the lower the overall power (total charge) will be. Backwards from what you might expect!

Iron

Great to have access to the recorded sessions!

Iron

Better late than never...

Iron

Taking the offline class...

Iron

thanks for another useful lecture

use a/D for sensor readings

Your audio bar doesn't play the video when you click the play button.

Iron

I use ADC for taking sensor values like LDR, Gas Sensor, Temp. Sensor etc

Iron

I generally use timer interrupt.

Iron

Hi everyone, good morning!

 

Iron

Thanks Warren; catching up

Iron

Really great lecture. Very helpful tips. I tend to use A/Ds for checking supply voltages in my designs.

Iron

Use A toD converters for sensors

Iron

Using A/D coverters for reading various sensors.

Iron

catching up -- missed yesterday

Iron

Maybe (true)  P=I x E

so you may substitute a E over R for an I or some such,

but... P ? does not equal E or V * C * dV/dT

 

I or current still looks good as coulombs while voltage

has none. No power, no coulombs or volume of electrons.

I,m done, gotta get tomorrows notes studied up. OK

Iron

Yes.  As I said   P = V * I     and since I = C dV/dt  then P = V *  ( C dv / dt )   =  V^2 * f * C

Iron

P does not equal V, or E times C dV/dT

it is I = C times dV/dT as on slide 9 sir

Iron

Actually, as BruceMcLaren points out, we are not talking about Ohm's Law here, where the voltage is applied to a fixed impedance (R or Z).  We are talking about I=CdV/dt, the charging of capacitances.  So P = VI   and   P = V * C * dV / dt   where the dV would equal V, since the internal logic swing for the MCU will be rail to rail.   and  1/dt  is the frequency.  So now you have  P = V * C * V * f  or  P = V^2 * f * C

Iron

Also, it would have to be the reciprocal of F times C to be true would it not?

Iron

RE: JayPaxman

correct on the E squared over R

No go on slide 8   V squared times F times C

Rod. R.

Iron

rruther2: Keep in mind the formula on slide 8 (P=V^2*f*C) is particular to dynamic power, the power CMOS gates consume by charging and discharging internal capacitances. It brings out the effects of transistor scaling very effectively. 

Sorry rruther2

P = V^2 / R    and   P = I^2 x R     Same, since V = IR

Iron

If it,s power that we are conserving,

current is the major factor not voltage.

later

Iron

My point,

Voltage potentiates energy, it does not imply power as current does.

I almost got a part time job lecturing High School and first year

AC/DC physics, one of my first college coursrs in the early 70s.

                                                       Rodney B. Rutherford

 

Iron

Yo Warren and DN crew

slide 8, I disagree,

My formula     P aprox = I squared R     or Z or 1 over 2 pi F times C

NOT Voltage!!!

as current implies power, a source, a load and a complete circuit

or power is a function current, power is an exponential function of current.

 

Iron

@JayPaxman- Good details. Thanx!

Iron

Thanks for the presentation.  More tomorrow.

Iron

Sure -- hopefully your cap leakage is small (if not, get a better cap).  A 100nA leakage on a 1 uF will drop 0.1 volt in 1 second.     Of course if the load you are going to be measuring is much larger you will need a larger cap or the voltage will drop too much to keep the MCU functioning.

Iron

Thanks Warren. Really great examples and I especially liked your comments of things to watch out for.

Iron

Good chat, Thank you Warren for lecture to! See you tomorrow

Yes, sometimes higher value external pull ups can save power.  Also some I2C chips require pretty low value pull ups like 2.2K. 

Iron

Any other questions I can answer?

Thanx to everyone for attending todays class. Hope to 'see' you all tomorrow.

Iron

Anatolly1086- It is important to check the internal value. I have seen some recent MCUs with much better pull-up characteristics. I think I saw this on a recent PIC MCU, but I'm not positive.

Iron

@WarrenM I believe that a typical internal pullup value is from 1k to 4.7k that is very weak pullup considering temperature variations and some other factors in design to avoid leaks.

@JayPaxman- Good point on the meter leakage. Would it be better to apply the meter after some time instead of keeping it connected?

Iron

Keeping your meter on the cap is going to take 100 nA per volt just to your meter (assuming a 10M input)

Iron

@nschneck- I have seen these but have not used one. It seems like a great approach as long as it can be accuate enough for your MCU. If you need to measure very low currents (nA range) I would make sure the current measuring device is accurate enough.

Iron

@WarrenM  I think I asked this earlier, but have you used external current monitoring ICs that communicate via SPI or I2C to the MCU and measure current on a common voltage bus? We are considering using one in a design.

Iron

@Anatolly1086- Most Low Power MCUs have very low power pull-ups available internally. I prefer these unless I need a specific value then I guess you need an external resistor.

Iron

Q: For floating I/O pins what does a preference for internal or external pull ups?

@DonH- Good point on the capacitor leakage rate. One tehcnique is to let the cap just sit, unconnected to anything except your meter. This will measure all the leakage and you can adjust you MCU current measurement to account for the leakage. measure the volatge

Iron

Thanks a bushel Lauren & Warren

Iron

@BruceMaclauren- Good idea on using the shunt resistor in the ground path. That does take some planning but is probably well worth the effort.

Iron

@Warren     OK.  After thinking about it you could determine the capacitor value by timing the charge rate with a precision voltage and resistor.

Iron

excellent, now all I have to do is watch it again

thanks all yall...

Iron

@GarySxt- I don't have a specific recommendation, but this technique was given in the MicroChip app note I include in the reference section. It might call out specifics on what Cap to use.

Iron

Thanks Waren et.tal.

Iron

Great presentation, Thanks alot

Iron

Thanks Warren... from cape town

 

Iron

Thank you Warren and Lauren

Iron

Why is the sound up and mine starts later?

No window yet, for a minute or two late to ...

 

Iron

ADC for external sensor info

Iron

Thanks for the presentation - it was very informative for me.

Iron

Thanks Warren and Lauren.

Iron

Thank You Warren and Lauren!

Iron

Thanks for the lecture!

Iron

Very good presentation Warren, best yet in this series. Thks Lauren.

Iron

I use ADCs for audio signal digitizing and storing

Iron

Have used ADC but usually try to to level sensing such as comparitor.

Iron

Yes, ADC to monitor signals

Iron

voltage variations control by ADC

Virtually always use ADCs; battery voltage, temp, humidity, MEMS accels, light.

Iron

multilex slow rate multibit data into one ADC input using r2r DAC

Typically use ADCs for accelerometer and temperature sensors

ADC for measuring analog input like temperature, pressure ETC

Iron

Use ADC for voltage measurement

Iron

Use A/D for sensing, battery monitoring, with a pot for user control, etc.

Iron

Yes, Thermistor measurements

 

Iron

uses for ADC for sampling thermistors, current shunts & potentiometers.

Iron

A2D: monitoring, diagnostic, measurements

Iron

Yes, we use ADCs for measurements from analog sensors

Iron

Yes, control monitoring

Iron

low power WDT and external high/low inputs

Iron

interupt from sensors such as photo or thermal.

Also timers or squarewave inputs.

Iron

WDT, light, temperature, vibration, ext input, RSSI comparator logic output, others.

Iron

Wakeup sources typically timer or external interrupt

External interrupts touch control, ADC

WDT, CAN interrupt, (pushbutton) I/O interrupt

Iron

Interrupt source is change of state (high to low or low to high)

Iron

My low power designs so far have used wake up on the watch dog timer and interrupt from external pin change.

Iron

Interrupt from sensor such as an accelerometer

 

Iron

Mostly sensors. Accelerometer, gyroscope, magnetometer, temp sensors, etc

Iron

Have used low-power timer for periodic wakeup.  Also wake-on-change input.

Iron

Most commonly use wake on interrupt from ADC

Iron

Interrupts for ADC, timers

Iron

WDT or external interrupts

Iron

Typically timer interrupt (WDT or RTC update Timer)

Iron

Typical interrupt is a timer.

Iron

For ADC, you need to add settling time for the sampling capacitor.  Depending on your circuit, this could be as long as the sampling time.

Iron

best to have test poinis built into circuit card design for current measurement...I hate shunt resistors.

Iron

Could also increase the resistance values.

Iron

I've used an ammeter and a GPIO to track when the controller is in sleep.

I've used amnmeter, of course. Also used shunt resistor with a scope measuring across it to get an idea of dynamic current. Better results when the shunt resitor can be in the ground path, but that isn't always reasonable. 

I have used resistor/scope. I like the capacitor idea but question accuracy. You would need a precise high value capacitor with very low leakage. Warren: Can you recommend a specific cap?

Iron

We've also used the battery gas gauge to estimate current usage...

Iron

http://www.adafruit.com/products/882

This helps reduce the voltage drop and power used by a typical ammeter.

Iron

Measuring current with a shunt does not work well since the voltages are so low.  The capacitor is good, but you need to measure the internal leakage discharge rate of the capacitor to ensure that is not significant.

For µA,  I use a meter.

Iron

Technical Supervisor, machine controls & interfacing

Iron

Just ammeter current measurment

Iron

have not measured P.

Iron

Yes, used these plus data acquisition to measure device current over longer times.

Iron

Shunt resistor is very handy technique

has anyone used I2C or SPI current measurement ICs?

 

Iron

used shunt resistor for measuring current

 

Iron

We've just used an ammeter to measure current on our project so far - in the range of several hundred microamps.  But your capacitor idea is pretty clever and we might try it...

Iron

I used ammeter technique

Iron

Capacitor technique is good when the uC has spikey currents.

Iron

academic embedded design

Iron

Problem with audio?  Click play and then pause immediately for a few seconds.  Click play again.  You'll be a few seconds behind but it won't stop on you.

 

Iron

i wish the audio would start automatically. i have to click to play. then click againg to play the webinar

Iron

Mechanical Engineer, recently converted to Hardware Engineer, 4 years

Iron

Primary discpline: Software, embedded firmware and hw. 30+ years

Same problems as yesterday. Only about a second of audio and then it dies.

 

Iron

Here we go, audio is up!!

Iron

Hi All from rainy Boston!

Iron

Great info, Great Webinars so far

Iron

Good Afternoon from Snowy Bedford, MA

Iron

Good morning from Santa Cruz California!

 

Iron

Links all seem to work today. They might require you to cut and paste into browser however. Next course I will make sure to include clickable links.

Iron

Good Morning from San Jose, CA

Iron

good morning from SLC UT, it has warmed upto 21F

Iron

Please join our Digi-Key Continuing Education Center LinkedIn Group at http://linkd.in/yoNGeY

Platinum

Still no snow in Chicago

Iron

Hello from the still wet and cool south.  So beginning in the morning about 2am.

Iron

Hello and good morning from Oregon

Howdy from sunny North Texas!

The streaming audio player will appear on this web page when the show starts at 2pm eastern today. Note however that some companies block live audio streams. If when the show starts you don't hear any audio, try refreshing your browser.

Platinum

32 degF in Minneapolis today!

Iron

Back in again from Chicago!

Iron

Helloo!

By the way, yesterday and today I've had trouble logging in.  I click on the link and it gives me an error message.  Today it only took one page reload before it came up, but yesterday it was 3 or 4.

Iron

Good morning from the great white north

Iron

Be sure to click 'Today's Slide Deck' under Special Educational Materials above right to download the PowerPoint for today's session.

Platinum

Good morning from Scottsdale

Iron

Good Morning from rainy northeast Tennessee

Iron

Good morning everyone

Iron

Checking out the slide deck for today ... stuff on the energy cost of power management looks good.

Good Morning from Mobile, AL



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