Low Power: How much current? [Solved]

NeverDie

Lets put this all in perspective. a CR2025 coin cell is 165mAh.

If we are sleeping forever @ 6uA that means the circuit will last for: 27,500 hours or 1,145 days. The question I guess we need to figure out is what is "good enough" for coin cell applications?

My goal is to figure out a way to sink the total circuit to around 1uA. That should be possible if Arduino is 100nA and NRF is 800-900nA.

So why does the NRF draw so much current when connected to Arduino? I know its been touched on already but is there a cleaner way in software without adding mosfets or extra hardware to have the NRF in sleep mode but not drawing any current from Arduino?

Even if you wanted to turn the NRF completely off using just software, I don't see that it's even possible. It may require a hardware switch to pull its plug.

Here's some brainstorming:

According to the datasheet, NRF Powr Down state is defined as "All register values available are maintained and the SPI is kept active, enabling change of configuration and the uploading/downloading of data registers."

You need something to keep the NRF's memory alive in the registers, unless you prefer to pay the price of a full startup cycle (which is an option).

In theory you could lower the NRF's supply voltage to 1.9V, because that is the minimum specified in the NRF datasheet. Current might be similar, but I'm guessing that with lower voltage it would be using less energy in total?

If so, then notionally maybe you could dial down the NRF's voltage by putting a cap across across ground and its Vcc, and then sending it just enough PWM to make the capacitor voltage hover at 1.9V? Perhaps there's a more elegant way to do it, but lowering its voltage seems like the only avenue not yet explored that might yet payoff, short of just turning it off. Unfortunately, capacitors tend to be lossy, so it might be a net loss.

Or, if using Scalz's boost converters, maybe you could lower all voltages to the minimum 1.9V by simply not boosting them higher than that? You'd need an adjustable boost converter for that, assuming you run at a nominal 3.3V when the arduino isn't sleeping. Adjustable boost converters do exist, so I see no problem with that approach. The Atmeg328p can function even down to 1.8V, although you may need to operate it at 4Mhz if doing so (says the arduino spec sheet). If awake, would the arduino datalines still need to operate at 3.3V, or could they work just fine at 1.8-1.9v also? Important question: does awful boost conversion efficiency at such low voltages more than ruin the potential NRF energy savings from this approach, as outlined above?

If you could turn off the NRF's SPI, and later turn it on again, without losing the registry values, that might be worth exploring also. I don't know if that's feasible though. However, the arduino's SPI is turned off, so there's nothing for the NRF's SPI to talk to anyway during the Arduino's power-down sleep, so if you could turn off the NRF's SPI too (again, it may be impossible), it would make sense to do so. Correct?

Out of the above spitballing, the prospect of adjusting voltage to 1.91v through the boost converter to me sounds the most promising. A lot would hinge on the efficiency curves of the boost converter though. If the numbers don't support that, then maybe running the NRF's supply voltage separately at 1.91v would work?

Maybe there's a pony in there somewhere. :smile:

scalz

dc booster sequence is not my idea! It is first Charles. But these type of sequence are well explained in app notes of supervisors and dc boosters.

In my case, I turn off nrf by mosfet . so all registers are lost I think. So I power and reinit it on wake up. and no problem of transmission, I didn't see any fails.

for dc booster, maybe you don't understand the concept of Charles ulpnode. This is a fixed 3v dc booster with true enable. you charge a capacitor on vcc. Turn off dc booster and go to sleep. Let the capa discharge. When capa vcc is < 2V. a supervisor chip irq toggle the enable pin of dc bosster and d3 int on arduino. You have a hardware watchdog which consumes very small current. On wake up maintain enable on booster. . of course, with the capa discharge 3v to 1.8v, you will have less power consumption. but the useful thing is the hw watdchdog generated by capa. choose right capa and adapt your cycles..

NeverDie

@brolly759 Is your design finished or still evolving? Are you planning to say how you did it in exacting detail, or just in general terms? At the moment I see your results (above), but at the moment I'm not sure exactly what you did, other than it involved starting with a Pro Mini, removing the Power LED, removing the power regulator, and invoking a sleep cycle. Is the following the best summation to date? http://forum.arduino.cc/index.php?topic=341958.0 If so, please let me know, and I'll give it a more careful read. On the other hand, if something else is a better summation, please let me know what that is, and I'll add it instead to the round-up.

Yesterday I placed an order with Great Wall Electronics for 10 Arduino Pro Mini's. That may take anywhere from two to four weeks to arrive. Meanwhile, I should receive the three red Pro Mini's from Amazon (above) tomorrow. With those I plan to start with the same three steps as before and then see how the measurement numbers look. If promising, I guess I'll next proceed based on what I find in the links you and scalz provided:
http://forum.arduino.cc/index.php?topic=341958.0
http://www.gammon.com.au/power
hallard.me
jeenode
lowpowerlab

and see where that gets me. At the moment, those are the only guides I have that are reasonably detailed. If in addition anything else should be on that list, please let me know.

brolly759

@NeverDie I will rewrite everything up again. The numbers I posted about was me just unplugging wires and seeing what my current draw was.... haha the link is where my dual post is located where I am talking to Gammon about this problem :)

@everyone So Gammon said this about our problem:

"I am guessing you are parasitically powering the NRF. Before sleeping make sure you set the connections to it to high-impedance. For example, SPI.end() followed by making sure the SPI (and other two) pins are inputs (or maybe outputs and LOW). For example, a snippet from my code with that gadget:"

 bool ok = radio.write (&reading, sizeof reading);
  radio.startListening ();
  radio.powerDown ();
  SPI.end ();
  // set pins to OUTPUT and LOW  
  for (byte i = 9; i <= 13; i++)
    {
    pinMode (i, OUTPUT);    
    digitalWrite (i, LOW); 
    }  // end of for loop
  ADCSRA = 0;  // disable ADC
  power_all_disable();

I am looking in the library to see if we do SPI.end() before sleep but cant find anything...

brolly759

So an update, you can find all the sleep functions in the MySensor.cpp file.

scalz

yes. Gammon is right. I needed to do pinmode output=0 when I tested. I didn't do the spi.end but I think is good thing to do.
@Neverdie: I hope and am sure you will get it!
in the mean time I am redesigning my board with some feedbacks you gave me. thx.
it will be 0805/atmel solderable version, no mini pro. and will be 5cmx2.3. same specs as I did on my other board. so far so good but now 4layer. only for rfm for the moment. can't do magie. but two boards on a 5cmx5cm. not expensive at elecrow... I hope I will get it finished for this week...

brolly759

YESSSSSSSSSSSSSSS!!!!! I got sleep down to 1.5ua - 1.6uA with NO hardware changes!!!!! WOOOT sorry, kinda excited here lol

scalz

great I'm happy for you.

brolly759

Okay, so originally I was getting 2.7-2.9uA with Arduino/NRF. Stock MySensors library and Arduino 1.0.6 IDE. ( I am using the BinarySwitchSleep Sketch from MySensors lib)

To get even lower power.... If you open up mysensors.cpp the sleep function is there. For the BinarySwitchSleep sketch you are looking for this sleep function as there are a few:

You want to add this:

SPI.end();	
	for (byte i = 9; i <= 13; i++)
    {
    pinMode (i, OUTPUT);    
    digitalWrite (i, LOW); 
    }  // end of for loop

to this:

bool MySensor::sleep(uint8_t interrupt, uint8_t mode, unsigned long ms) {
	// Let serial prints finish (debug, log etc)
	bool pinTriggeredWakeup = true;
	Serial.flush();
	RF24::powerDown();
	attachInterrupt(interrupt, wakeUp, mode);
	if (ms>0) {
		pinIntTrigger = 0;
		sleep(ms);
		if (0 == pinIntTrigger) {
			pinTriggeredWakeup = false;
		}
	} else {
		Serial.flush();		
		LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
	}
	detachInterrupt(interrupt);
	return pinTriggeredWakeup;
}

and it will look like this:

bool MySensor::sleep(uint8_t interrupt, uint8_t mode, unsigned long ms) {
	// Let serial prints finish (debug, log etc)
	bool pinTriggeredWakeup = true;
	Serial.flush();
	RF24::powerDown();
	attachInterrupt(interrupt, wakeUp, mode);
	
	SPI.end();
	
	for (byte i = 9; i <= 13; i++)
    {
    pinMode (i, OUTPUT);    
    digitalWrite (i, LOW); 
    }  // end of for loop

	if (ms>0) {
		pinIntTrigger = 0;
		sleep(ms);
		if (0 == pinIntTrigger) {
			pinTriggeredWakeup = false;
		}
	} else {
		Serial.flush();		
		LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
	}
	detachInterrupt(interrupt);
	return pinTriggeredWakeup;
}

Because you are shutting off and turning all pins low, you will need to add this to the beginning of your program loop to reinitialize the NRF:

void loop() 
{  
  sensor_node.begin();

If you add just the SPI.end(); your current will be 2uA.
If you add both SPI.end(); and LOW pin loop, your current will be 1.5uA

brolly759

Some more facts here:

If you ONLY do the for/loop to shut off PIN9-13 in the sleep function and do NOT shut off SPI... you do NOT need to reinitialize the radio on wake-up.

The current draw for For/Loop LOW w/o shutting off SPI is 2.1uA-2.2uA.

This is a good and bad. If you have a sensor that is going to be switched on and off a lot, the re initialization time is noticeable on a fluke meter. You can see it staying high much longer. So, if someone knows how long it takes to initialize, then we can determine if shutting off SPI is worth it. ~600nA savings vs high reconnect time.

NeverDie

@brolly759 said:

So, if someone knows how long it takes to initialize, then we can determine if shutting off SPI is worth it. ~600nA savings vs high reconnect time.

I have an o-scope, so once I get everything set up, I can try measuring that time duration for you if you like.

Really the comparison should be an energy comparison, which might be roughly::

((~600nA)(# microseconds powered-down)) vs ((arduino's current draw while powered up)(# microseconds extra setup time if NRF was turned off))

brolly759

I have an O-scope just dont know how to use it completely lol. Leaving work now. Stayed extra 2 hours to play with power settings lol

@NeverDie did you still need me to write up what I did or you followed it pretty much?

NeverDie

@brolly759 said:

I have an O-scope just dont know how to use it completely lol. Leaving work now. Stayed extra 2 hours to play with power settings lol

@NeverDie did you still need me to write up what I did or you followed it pretty much?

I'd prefer to have a nice consolidated write-up for two reasons:

So I can be sure I'm following it right. If I do it differently, then any measurements I might get won't do you much good, if any. And,
So others, including noobs, can follow along to both understand it as well as replicate it for themselves, because then you leverage the true power of open source. It's well proven: the mores eyes on something, the better it gets, and the more everyone benefits from the experience. For that to work, the clearer the "something" is, the better. The more details the better too.

OK, finished editing. :smile:

brolly759

I keep watching you edit your post, its freakin me out! lol

scalz

@Neverdie @brolly759 : I will follow your progress with interest and help if I can. For the moment, I have a lot of work before playing with my uCurrent. And for respect for Charles work, I am waiting his release. But when I will receive my boards (at then end of the month), if lib is not released yet, I will clean my code. And don't forget, I am using boosters and mosfets, so it is different. but roads are crossing of course. with booster what I like is, I will have 3.3v vcc during the whole battery life too.
Too late for me! 2am, lol. time to powerdown. See you soon:smiley:

brolly759

Running Arduino+NRF24l01 w/ interrupt consuming 1.5uA in sleep

I am using this Arduino Nano Pro 8mhz 3.3v :link text
I am using this NRF chip: link text

Here is my test environment:

Arduino Nano with desoldered jumper for bypassing voltage regulation (If you dont have bypass jumper on the knock off Nano, look at this post: link text )
NRF connected via pinout on MySensors guide
3V direct supply from 2 AA Batteries
uCurrent Gold testing voltage current
Fluke 179 reading in mV
Using the BinarySwitchSensor sketch in the MySensors library

If I upload the sketch as is with the recommended setup guide, Pin 2 or 3 is an interrupt pin and that goes to GND and acts as a switch. Pin 2/3 is HIGH and uses the internal pull up resistor. We will refer to the 2 different states of the switch as follows:

"oState" (Open, when Pin 2/3 does NOT touch GND)
"cState" (Closed, when Pin 2/3 touches GND)

When running everything I get these sleep numbers:
oState: 23-24uA
cState: 117uA

I downgraded my Arduino IDE from 1.6.5 to 1.0.6 and here are my new numbers:
oState: 2.5-2.7uA
cState: 98-100uA

Everything is looking good but my cState is still too high for any battery applications that I am trying to get.

Removed digitalWrite on pin 2/3. Connected 10M resistor from pin 2 to VCC. GND is switch to pin 2.
oState: 2.5-2.7uA
cState: 3.1-3.2uA

Reference measurements:

At this point I ran the "DallasTemperatureSensor" to test current using the WDT, I did NOT connect Temp sensor
Sleep current with WDT enabled @ 30 seconds: 7.6-7.8uA

Using "BinarySwitchSensor", remove NRF completely and only have Arduino:
Sleep current: 110-120nA OR .4-.5uA (had issues reading this but I believe it is the nA)

Connecting VCC/GND only to NRF to read standalone current:
NRF only: 800-900nA Shutdown current

Useless numbers while running the BinarySwitchSleepSensor sketch:
Sleep current: 2.7-2.9uA with NRF/Arduino fully connected
Sleep current with nRF GND disconnected: 1.7uA
Sleep current with nRF VCC and GND disconnected: 294nA
Sleep current with nRF VCC/GND/Pin9 disconnected: 281nA
Sleep current with nRF VCC/GND/P9/P10 disconnected: 196nA
Sleep current with nRF VCC/GND/P9/P10/P11/P12/P13 disconnected: 110-112nA
Sleep mode with ONLY Arduino: 110-112nA
NRF plugged into VCC/GND only: 800-900nA

At this point we are getting 2.7-2.9uA with Arduino/NRF. Stock MySensors library and Arduino 1.0.6 IDE. ( I am using the BinarySwitchSleep Sketch from MySensors lib)

To get even lower power....

Open up mysensors.cpp with NotePad++ application
Look for this code:

bool MySensor::sleep(uint8_t interrupt, uint8_t mode, unsigned long ms) {
    // Let serial prints finish (debug, log etc)
    bool pinTriggeredWakeup = true;
    Serial.flush();
    RF24::powerDown();
    attachInterrupt(interrupt, wakeUp, mode);
    if (ms>0) {
        pinIntTrigger = 0;
        sleep(ms);
        if (0 == pinIntTrigger) {
            pinTriggeredWakeup = false;
        }
    } else {
        Serial.flush();     
        LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
    }
    detachInterrupt(interrupt);
    return pinTriggeredWakeup;
}

We are going to add this code:

SPI.end();  
    for (byte i = 9; i <= 13; i++)
    {
    pinMode (i, OUTPUT);    
    digitalWrite (i, LOW); 
    }  // end of for loop

The final code should look like this:

bool MySensor::sleep(uint8_t interrupt, uint8_t mode, unsigned long ms) {
    // Let serial prints finish (debug, log etc)
    bool pinTriggeredWakeup = true;
    Serial.flush();
    RF24::powerDown();
    attachInterrupt(interrupt, wakeUp, mode);
    
    SPI.end();
    
    for (byte i = 9; i <= 13; i++)
    {
    pinMode (i, OUTPUT);    
    digitalWrite (i, LOW); 
    }  // end of for loop

    if (ms>0) {
        pinIntTrigger = 0;
        sleep(ms);
        if (0 == pinIntTrigger) {
            pinTriggeredWakeup = false;
        }
    } else {
        Serial.flush();     
        LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
    }
    detachInterrupt(interrupt);
    return pinTriggeredWakeup;
}

IMPORTANT: Because you are ending SPI, you will need to call the sensor at the beginning of your loop to reinitialize the NRF

void loop() 
{  
  sensor_node.begin();

Adding both SPI.end(); and for(); loop:
Sleep current: 1.5uA

If you add just the SPI.end();
Sleep current: 2uA

If you just add the for(); loop:
Sleep current: 1.9uA - 2.2uA

If you are using ONLY the "for(); loop", you do NOT need to reinitialize the radio when you come out of sleep. I have noticed a much longer up time when having to reinitialize.

OTHER MEASUREMENTS using the DallasTemperatureSensor with WDT at 30 seconds, no sensor connected:

Edited Sleep with for(); loop:
Sleep current: 6.4-6.5uA

Edited Sleep with for(); loop AND SPI.end();:
Sleep current: (Could not get SPI.end(); to work on sleep(w/WDT))

Quick comment: There are a few sleep options in the MySensors.cpp Depending on which one you are calling will depend on which one you need to edit. Here are some examples of the sleep functions in the .cpp file:

void MySensor::sleep(unsigned long ms)

bool MySensor::sleep(uint8_t interrupt, uint8_t mode, unsigned long ms)

int8_t MySensor::sleep(uint8_t interrupt1, uint8_t mode1, uint8_t interrupt2, uint8_t mode2, unsigned long ms)

NeverDie

@brolly759 said:

When running everything I get these sleep numbers:
oState: 23-24uA
cState: 117uA

I downgraded my Arduino IDE from 1.6.5 to 1.0.6 and here are my new numbers:
oState: 2.5-2.7uA
cState: 98-100uA

Nice write-up!

Is it known why there's a difference in the measurements depending on whether you're using IDE 1.6.5 or IDE 1.0.6? Which IDE version should I use?

brolly759

Someone else complained about the exact same issue here:
http://forum.mysensors.org/topic/1345/sensebender-micro/250

Sparkman

@brolly759 That's a different issue altogether. It's related to measuring battery voltage...

Cheers
Al

brolly759

@Sparkman said:

@brolly759 That's a different issue altogether. It's related to measuring battery voltage...

Cheers
Al

tlund posted 2 months ago reply quote 0
@tbowmo

My NRF's are the same $1 nrf's listed in the mysensors store, so probably fake. But I have still measured them to draw ~900nA in powerDown.

But I think I have found the culprint now. It seems the extra 20uA is caused by Arduino 1.6.5 (it may be that my installation is faulty).

My test setup:

pro mini
nrf
a simple sketch that does gw.sleep(60s)
1st test: sketch compiled & uploaded via Arduino 1.0.5-r2: 6uA
2nd test: sketch compiled & uploaded via Arduino 1.6.5: 24uA

Low Power: How much current? [Solved]

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