I am developing a remote module (not wired to a computer) that has an Arduino Uno board, 5 volt hall effect sensor, xbee radio and data logger connected together. On this remote module,the data from the sensor will be recorded to my data logger every 15 or 30 minutes. The xbee radio though would need to be available the vast majority of the times.
For the xbee, I will configure the sleep mode the best I can to preserve battery. Ideally, I would like this to last a couple of years (as long as possible :D) without changing/charging the battery. For now, I am purchasing the hardware.
I wanted to ask what is the best battery I can purchase for this (i.e lithium, how many volts etc)? For this much time, I am thinking that I should use a few batteries and have something autotmatically switch or share power among batteries. Which switching regulator and battery would be good for this project? If need be, I can purchase a voltage regulator if it's needed.
The xbee radio though would need to be available the vast majority of the times.
For the xbee, I will configure the sleep mode the best I can to preserve battery.
If it's sleeping, it isn't listening.
Ideally, I would like this to last a couple of years (as long as possible smiley-grin) without changing/charging the battery.
I don't think this is realistic. Batteries have internal resistance, and will go dead with NOTHING connected, in less than 2 years.
Any considerations as to solar charging the battery during daylight?
First off, I wanted to say thanks for the replies. I look forward to one day becoming good like you guys/gals- and answer questions on this forum too :)
The module will be indoors and connecting to outside sunlight will not be possible. We may have 1.5 to 5 hours of indoor light. Would a solar panel in these conditions make a significant impact on battery life? If so, which solar models did you have in mind?
As a "newbie", if I had let's say 7 nine volt lithium batteries. As one was drained another was used. I just don't see why this couldn't last for around one year. 1 year could be sufficient too. Am I missing something here?
The module will be indoors
But, no power is available? Why does the device need to be battery powered?
I appreciate your time. Hopefully, we can find a way to accomplish this. We are not paying for the electric bill, and due to legal reasons the payers of the electric bill will not agree to using their power.
I used to work in the HVAC (heating and AC) industry and we used relays frequently. Relays will close (normally open) or open (normally closed) when power is applied to it. There are many different types of relays. I would imagine there are relays for 9 volts as well.
Attached to this post is a basic picture of what I am looking to do. In the picture I provided, when one 9 volt battery is low, the next will be used. Then, when the next is battery is low, the next one will be used and so on. This really could be used for any Arduino project- so this could help others.
The trick is, however, is finding a proper relay or switch that’s normally closed (open with proper power). It needs to close when the 9 volt battery is too low for the arduino. Do you know what range that would be? Do you have an idea what the part number would be for this relay/switch? I would be open to another design idea as well
How many mAH of capacity do you think you’ll need long term?
Say you were drawing 50mA all the time (guessing the XBee needs some current while listening).
.05A * 24 hrs/day * 365 day/yr * 2 years = 876AH
I think you’ll need a car battery with efficient 5V and 3.3V switching regulators to meet that.
Probably better to explain the timing of your device more exactly.
Does it only rad the Hall Effect sensor every 15 or 30 minutes, and which? When you say the XBee needs to be available most of the time, do you mean most of ALL or the time, or most of the times you log your data, every 15 or 30 mins?
The Arduino can keep track of timing whilst in low power mode and wake up at set intervals. If it is only going to log every 15/30 mins and need the XBee at that time, then the ATMega and XBee can sleep most of the time. You could use a RTC if required. :-
Check sensor and log data.
Transmit via XBee every d logs (2,4,8 etc)
Wake up 15 minutes later
In this case your device may only use significant power for a few cycles every 15 minutes, dramatically reducing your power requirements.
Thanks for the replies! Hopefully, we can come to a solution. I am not that experienced with this, I will try to answer your questions:
I don't have a definite schedule when we will want to read the data logger remotely. I could have the x-bee radio sleep for 1 or 2 seconds and awake every other second. We could walk by slowly to obtain the reading remotely as needed
The hall effect sensor uses 5 volts and the xbee uses 3 from the arduino. I haven't installed the shield from the real time clock. I don't think it will use much voltage as it will be used every 15 minutes and it has a battery. It's Ok if we miss an occasional reading.
So the Arduino Uno and the xbee could be for asleep 1 or 2 seconds and then awake every second. Then, every 15 minutes the hall effect sensor and clock willl record their readings on the data logger. Using the formula provided, maybe at least 700 AH total will be needed from the battery config.
I am unfamiliar with using a car battery in an application like this. The arduino documentation mentions that between 7 and 12 volts could be used to power it externally. So the 12 volts from a car battery may be OK, but does a car battery have too many amps (or other power metric) for the arduino? Does the Arduino just use the amps it needs and leaves the excessive amps or do we need a voltage regulator/capacitor decoupler? Could a car battery be used in the picture I provided- instead of the 9 volt battery?
I found a relay that may work for this purpose. It and the data sheet is available from the link provided below. Would the relay work for this purpose or perhaps a different one? The relay will throw with between 5 and 12 volts to switch. However, the Arduino needs from 7 to 12 volts. Is there another relay that you know of that throws at the same 7 to 12 needed by the Arduino? Do you think it's better to just use a car or lawn mower batter- why?
I haven't installed the shield from the real time clock. I don't think it will use much voltage as it will be used every 15 minutes and it has a battery. It's Ok if we miss an occasional reading.
The real time clock doesn't need to be externally powered, so this part is fine. The battery on that board will be good for many years of the clock keeping time (IIRC 10 years or so is typical), so you can have your Arduino get the current time and date from it as you need.
My thought is that more batteries is not a bad thing. I found a relay that may work for this purpose. It and the data sheet is available from the link provided below. Would the relay work for this purpose or perhaps a different one?
Any relay will of course consume its own power so there are losses inherent in this concept that you wouldn't have with a single, and larger, battery. Also the relay won't "sleep" like the rest of your system, and the one you linked to consumes 200mW so it's a big power drain relative to the rest of your project (perhaps an additional 4x your project's power needs based on Crossroads' maths above) which will significantly reduce your battery life. Also, a relay won't give you the fine voltage control over when to switch so you could leave usable power in your "spent" battery.
The module will be indoors and connecting to outside sunlight will not be possible. We may have 1.5 to 5 hours of indoor light. Would a solar panel in these conditions make a significant impact on battery life?
Could you get a panel outside wired into the battery? Alternatively could you get a solar panel to be located at a window that receives direct sunlight?
Due to limitations at the place of installation, outside solar is not possible. Which battery do you think would best?
Does a car (or lawnmower) battery have too many amps or other power metric for the Arduino? Does the Arduino just use the amps it needs and is a voltage regulator/capacitor decoupler needed?
"the Arduino just use the amps it needs" Exactly.
The board canbe powered from 12V, but then it will use its onboard Linear Regulator to knock 12V down to 5V, dissipating it purely as heat. Hence the suggestion to use a high efficiency switching regulator.
Thank you Crossroads and the others that replied. I appreciate you helping me getting started . From your last post, I can say a car (or lawn mower) battery can be connected directly to Arduino. It seems strange to connect such a powerful battery to this delicate instrument. Is that right?
Which switch regulator will work best for a 12 volt battery and should they be tied together like in the picture I attached? I think that should be all that I need to know for this.
A car battery must be maintained (charged regularly) or else its capacity will greatly diminish over time. There is a reason why the average car battery warranty is like only five years ($$$). While a car battery may have the capacity, this does not sound ideal for the battery's sake unless you can remove it periodically to charge it.
I want to implement what was posted here. What kind of connectors would I use to connect the car battery to the switching regular and from the switching regulator to the Arduino board? Lastly, which switching regulator will work well?
Get some connector terminals that mate with the posts on the battery you select.
The battery in my unused truck fired the truck up easily this summer. I don't really know the impact from long, slow steady drain.
If you go that route, the battery will feed the switching regulator, the switching regulator will feed the board.
What kind of connectors would I use to connect the car battery to the switching regular
Mostly depends on the battery terminals, some are threaded and some clamp-on; but since this isn't a typical application for a car battery, a little creativity is required (and possibly a fuse).
and from the switching regulator to the Arduino board?
smaller gauge hookup wire should be fine (18-24 awg).
I know about the connections now- thanks again. The last thing is the switching regulator.
seanz2003 provided a link to a voltage regulator. I think I would need one that allows me to switch between power sources when one is low. Is that the best one to use (cost is not too much of an impact) or perhaps an efficient efficient switching regulator with a relay? If so, which one. I know that some of you spent time on this question; I appreciate our time. That should be all.
Relays are relatively inefficient switches, a transistor or mosfet is much more efficient. You might check the schematic for the uno, specifically the "auto" power selection portion of the board.