I am trying to make a concrete crack detection system (thanks to all the feedback from arduino experts in this forum). I am not quiet familiar with battery and power consumption. I would appreciate if somebody could guide me in selecting appropriate battery.
In total I have sixteen arduinos. Each arduino has following:
SHT75 RH-sensors (Datasheet) in three digital pins.
Five potentiometers* in ANALOG pins. All the potentiometer reading is set to max value (ie. 1023) till the circuit breaks down when the reading will be 0.
[These analog pins reading are what i’m using as concrete crack detection system. One pin of power supply (for instance, 5V pin) is connected to 5 feet 30 AWG Kanthal wire. This 5 feet long wire is epoxied to the surface of concrete. When this wire cracks due to crack in concrete, the analog reading will change from 1024 to 0. All I need is the time at which the value changes.]
I’m using Adafruit data logging shield with Sandisk SD card to store the data. Sensors will record RH, and analog reading every 15 minutes. These values will be stored in SD card, in addition to date and time as a .txt file.
In future, my plan is to add a Xigbee module to send the data wirelessly from these arduinos to a master Raspberry Pi.
The system will be deployed in a site without power source, so a battery should be able to support it. I would appreciate if anyone could guide me in selecting battery. From what I have learnt online so far is, I have to figure out how much mA current is drawn by my arduino. Based on the mA I measure, I need to buy a battery with certain mAh.
Hours that my arduino will last = (mAh of battery / mA of my arduino system)
- How do I compute the mA consumed by my Arduino? I read that I should make a multimeter a part of system and measure it. With my arduino and shield, how do I measure that?
- My another doubt is in selection of potentiometer such that my power consumption is reduced. So, each potentiometer is connected to analog pins from A0 to A4 (and to gnu and 5V). Which potentiometer is good to reduce current consumption of the system? 10K, 50K, 100K, 500K as all I need to know is the time when the analog reading drops from 1023 to 0? Some noise can be alright (even change of value as much as 100 or 200 is alright.
- Do i need to only focus on mAh of battery? What other parameter do I need to consider? Or is it as simple as getting a bunch of 9v batteries with very high mAh?
- For the batteries, to last about 1 or 2 months (or even more — longer the better), can I connect a bunch of batteries (for instance - 9V batteries) in parallel and connect to arduino ?
- Is there any feature in arduino (such as shutting down the system or putting it in sleep mode) to reduce the power consumption?
- What type of battery will be suitable for long term deployment? Also, if solar system is used, how would I determine the power of panel.
Please let me know if I’m not clear in explaining my situation. I would really appreciate if someone can help me. This is a wonderful forum and I am being really inspired to use arduino in my project after getting the feedback about the project. I hope to get good suggestions again.
Thank you very much.
PS: Does anyone know any receptacles that can be used with SHT75? I did not find a suitable receptacle for it. I want to solder and use shrink tube on the spliced part before embedding the RH gage inside concrete.