Powering with LiPo a mini pro without regulator



  • I intend to build a battery-powered gas sensor. Components would be Arduino Mini Pro 3.3V, nrf24L01+, a MQ-2 sensor, a step-up regulator to power the 5V sensor and a 3.7V 2000mAh LiPo ( I have a few of them from another proyect). I haven't bought any of the others components yet, so I'm totally open to changes.

    I read here that in order to save some battery, the 3.3v regulator and the led lines can be cut.

    I have a few doubts though. Would the arduino or the radio be damaged if there's no regulator due to the 3.7V input?
    If so, would you leave the regulator and keep this battery or cut the line and use a 3.3V button cell / 2x1.5V AAA?



  • Did you consider not recharging the battery over 3.3v? The nrf's 3.3v is a must. You can't go over 3.378v. (tested by me, before the poor little guy fried)


  • Hero Member

    I'm not sure using a battery would be possible, datasheet says "less than 800mW", some other site "Operating current 40mA".

    I've done this test with MQ135 and it lasted... 2 minutes.;.



  • It lasted 2 minutes because you read the sensor way to often. For an extended battery life you need to put the arduino to sleep for as much as possible and read the sensors value very rarely.


  • Hardware Contributor

    @Vladut-Grecu said:

    Did you consider not recharging the battery over 3.3v? The nrf's 3.3v is a must. You can't go over 3.378v. (tested by me, before the poor little guy fried)

    Any ideas then why the spec says 1.9-3.6V ?



  • The original nrf may support 3.6 but the chinese models that i have die faster :'/


  • Hardware Contributor

    @Vladut-Grecu
    Good point.



  • What I don`t get is why you want to cut the 3.3v regulator when you only get a 220 micro Amps consumption reduction and the resistors that you use to measure the actual voltage over the Analog pin use way more..

    Use the internal arduino voltage measure. You will see 3.3v even if you get over 3.3v but what you actually need know is when the voltage drops under 3.3v so you know when you have to start recharging your li-po.


  • Hardware Contributor

    @Vladut-Grecu
    "the resistors that you use to measure the actual voltage over the Analog pin use way more" ??

    The recommended voltage divider for 2AAs is 1M+470k and e.g. for 4AAs I use 1M+5M with success.. ~1uA is not that much.



  • The rezistors + the code that needs to be run? The extra cycles for you to read the Analog pin? I go with the idea that if there is allready a measuring in the arduino anyway why do i need to reinvent the wheel? The voltage divider thingy is ok if you want to measure voltages that go over the vcc value


  • Hardware Contributor

    @Vladut-Grecu
    The internal method is the obvious choice when battery voltage is Vcc. Whether you need regulator, step-up/down etc or not, is determined by things like sensors and battery range etc.

    I doubt there are extra cycles compared to the internal method. Besides, I'd say the power loss from extra cycles would be neglectable

    Regarding the use of voltage divider above and under Vcc, I refer to my answer here.



  • @m26872 said:

    the power loss from extra cycles would be neglectable

    You are right. But 220uA are neglectable aswell. (For me at least)


  • Hardware Contributor

    @Vladut-Grecu said:

    But 220uA are neglectable aswell. (For me at least)

    Sorry, but the 220uA is drawn continously. Since most of my (and many others) battery applications have long sleep durations, the sleep mode power consumption is the first priority. Second is probably limiting the radio usage (meaning you can do things with just the arduino).


  • Hero Member

    @Vladut-Grecu not really, but keep in mind that some sensors need to reach the needed temperature to be read, so you may need to heat for 10 minutes before reading and thus you will drain your battery. Also, even with a slepp, you may need an on/off on powering the gas sensor for it is continuously powered.



  • Sorry, I've been swamped the last couple of days.

    @Vladut-Grecu said:

    Did you consider not recharging the battery over 3.3v? The nrf's 3.3v is a must. You can't go over 3.378v. (tested by me, before the poor little guy fried)

    LiPo batteries should not go below 3V if I'm not mistaken, so charging it to 3.3V would make me recharge it more often. The sensor is for my folks because they still have butane gas for hot water, so I'd like it to last as long as possible. If, like you say, the chinese clon can't operate at more than 3.378V, I'll stick to 2 x AA batteries.

    As the main power drain occurs when the sensor reads and the radio sends, I thought of measuring the battery just after that happens, which in this case it'd be like a minute or so. Therefore the extra cycles to read the analog input should be negligible.

    About the step up converter, the store has a couple listed. This one http://goo.gl/1gwmm2 has a usb input and the other one http://www.ebay.com/itm/291352631612?rmvSB=true doesn't. The second one is better to use ion this case, isn't it?

    @epierre said in Powering with LiPo a mini pro without regulator:

    @Vladut-Grecu not really, but keep in mind that some sensors need to reach the needed temperature to be read, so you may need to heat for 10 minutes before reading and thus you will drain your battery. Also, even with a slepp, you may need an on/off on powering the gas sensor for it is continuously powered.

    So you say the sensor would be continuously powered even though we do a gw.sleep?? The heater has a power consumption of 900mW.



  • Neither. Those will boost it till 5v. You need something like this.



  • @Vladut-Grecu said:

    Neither. Those will boost it till 5v. You need something like this.

    But that one wouldn't be enough to feed the 5V that the MQ-2 gas sensor requires, would it?


  • Contest Winner

    @m26872 said:

    Sorry, but the 220uA is drawn continously. Since most of my (and many others) battery applications have long sleep durations, the sleep mode power consumption is the first priority. Second is probably limiting the radio usage (meaning you can do things with just the arduino).

    My take on low power measurement.
    I have not gotten around to actually build it yet but I hope to do some measurements in my "lab" this spring.



  • Oh.. for the gas sensor they are ok. Last one (green) seems a little bit more polished. The presence of the usb port is not important, you can solder it off. The usb is the output. Check the picture again. It's your choice.



  • @Vladut-Grecu said:

    Oh.. for the gas sensor they are ok. Last one (green) seems a little bit more polished. The presence of the usb port is not important, you can solder it off. The usb is the output. Check the picture again. It's your choice.

    Yes, you're right, it's the output. I didn't take a close look to the image. The green one seems more polished as you say. I'll try with those.

    @Anticimex said:

    @m26872 said:

    Sorry, but the 220uA is drawn continously. Since most of my (and many others) battery applications have long sleep durations, the sleep mode power consumption is the first priority. Second is probably limiting the radio usage (meaning you can do things with just the arduino).

    My take on low power measurement.
    I have not gotten around to actually build it yet but I hope to do some measurements in my "lab" this spring.

    That's a very interesting project. In the thread some of you say that if VBatt = Vcc (no regulator like I'd like to have) then using the divider to measure the charge is non-sense and it's way better to use the internal functionality, Am I wrong?


  • Contest Winner

    @Viper_Scull
    I have not looked into how internal measurement is done. So I don't know what constraints that type of measurement has. But for external measurement using a voltage divider allows the measurement point to be biased with respect to the ADC reference voltage and my proposal limits the standby current draw of the voltage divider.
    But if no regulator is done internal measuring is provable better, how that now can be achieved. I am guessing by using vcc as reference to the ADC.


  • Hardware Contributor

    Here's one link about the "internal method".


  • Contest Winner

    Right. Thanks. That was something along the line with what I expected. I think it is an adequate option as long as you run the Arduino directly off the battery (without regulation). But with regulation it won't work.


  • Hardware Contributor

    @Viper_Scull said:

    "...way better to use the internal functionality, Am I wrong?"

    Yes, "way better" given that it is a real low-power application. Saving 1uA and 2 resistors isn't always that important.


  • Contest Winner

    @m26872
    This is mostly a matter of opinion. There are several options available. Personally, I will design so that I have three options to choose from depending on the sensor type (and long term measurement data)


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