Hi All,
I am using Moteino R4 with a temperature sensor(lm35), I am testing it with two kinds of batteries, lipo 3.7V 1000mah and
standard duracell 9V battery.
Now the lipos on some of the sensors are working as expected, whilst others not so great, bearing in mind all the them have same firmware.
On the other hand, results of 9V battery are more consistent(so far). Now, my question is, to get more life out 9V batteries, do I need to unsolder the on board voltage regulator ?
Thanks,
No, you would not want to do that. Supplying 9V to any of the chips will fry them.
What's the battery life you're looking to get?
Lipos should last you a lot longer if they are good quality. Also more important than anything is to sleep your nodes properly and reduce any sensory consumption to nothing while sleeping if possible.
Quote from: malik on September 30, 2015, 07:58:04 AM
Hi All,
I am using Moteino R4 with a temperature sensor(lm35), I am testing it with two kinds of batteries, lipo 3.7V 1000mah and
standard duracell 9V battery.
Now the lipos on some of the sensors are working as expected, whilst others not so great, bearing in mind all the them have same firmware.
On the other hand, results of 9V battery are more consistent(so far). Now, my question is, to get more life out 9V batteries, do I need to unsolder the on board voltage regulator ?
Thanks,
The LM35 requires a minimum of 4V to operate properly - this is too high for the LiPo battery to operate reliably. Assuming that you are tying the LM35 VCC pin to VIN, I'd recommend using 3 AAA or AA Lithium batteries to get the longest life from this arrangement. Supplying a voltage above nominally 4.5V would work, but then you're just throwing away the extra voltage (power).
Tom
@ Felix, i am looking to get 6-9 Months, am sending temperature every 4 mins. Whilst Vcc of the LM35 is connected to 3.3.
@Tom One thing which puzzles me, is some Lipos batteries are working fine for weeks, other lasting few days. Where as setup and firmware is same.
malik,
Please note that the LiPos will charge up to 4.2 volts, which is slightly above the LM35 low threshold as Tom indicated. So a fully charged LiPo might as well run fine for a few weeks, then when it drops below 4V the LM35 starts to act flaky.
A LiPo is considered discharged when it drops below 3.3V.
For the purpose of using a LiPo with Moteino, you should consider it discharged when it's around 3.55 V because of the regulator dropout voltage which requires an input voltage to be around 0.2V above the output voltage.
Quote from: malik on September 30, 2015, 12:10:43 PM
@ Felix, i am looking to get 6-9 Months, am sending temperature every 4 mins. Whilst Vcc of the LM35 is connected to 3.3.
@Tom One thing which puzzles me, is some Lipos batteries are working fine for weeks, other lasting few days. Where as setup and firmware is same.
If the LM35 VCC is truly connected to the 3.3V pin, then I have no explanation as why it works with 9V and not with some LiPos unless, as Felix points out, a discharged LiPo will not be able to supply 3.3V after the regulator. The LM35 minimum recommended VCC is 4.0V (although I did see a chart, attached below, showing minimum supply voltage vs temperature with values significantly lower than 4.0V - so your guess is probably better than mine at this point).
Tom
Here's are some projects that use 9 Volt batteries:
https://lowpowerlab.com/forum/moteino/moteino-r4-9v-battery/msg9213/#msg9213
https://lowpowerlab.com/2013/03/01/mailboxnotifier-moteino-based-mail-event-notifier/
https://lowpowerlab.com/2013/11/17/motionmote-moteino-motion-sensor/
Would a 9V power source damage a Moteino? If so what are the alternatives to provide power (I'm looking at several months operation on a single battery using advanced sleep)?