Measuring the weight of a beehive

[Clemens]

Hi Lars, there is a recommendation for an ADS1231 as ADC: 24bit and 128x PGA sounds good to improve accuracy a lot:
http://forum.arduino.cc/index.php?topic=198139.0

[GoForSmoke]

I've seen a 12 bit ADC home game controller unit that's already got instructions to use short shielded wires and needs care to not get garbage readings. What care must be taken past 16 bits? They aren't snap-together Lego blocks.

[Trottel100]

Hi,
how Long stays the battery?
more than one month?

Best regards

[vasco-vls]

Hello,

I am working on the same project! I started in July 2013 and at first, I used 4 load cells from cheap digital scale. I connect them together to form Wheatstone bridge, excitation voltage and amplification was done by INA125, analog-digital conversion with internal ADC in ATMega328P. For wireless communication, I used ZigBee at 2.4 GHz. My results were:

• Do not use cheap 3-wire load cells. They drift with temperature and time. They lost precision. Creep is problem.


• Do not use 2.4GHz if you need to communicate over 100 m. This frequency if full of Wifi/Bluetooth/noise. Everything from grass to trees will reflect your signal.


• INA125 is good, but expensive.


• 10bit ADC in ATMega is good, but not sufficient.

In my second version of electronics, I used 868MHz (yes, I'm from Europe) mesh modules from RadioCrafts (they call it TinyMesh). Maximum transmit power is 9dBm. I am testing them last few months and it looks very promising. I am able to communicate for distances over 150 m. Frequencies 868 or 433 MHz are much better in those projects.

The electronics is powered from 2AA batteries via step-up converter. With this, I'm getting quite stable 3 V. Also, I removed RTC and external crystal and for waking up MCU from power-down I'm using watchdog in interrupt mode. Thus, MCU will wake-up every 8s.

Instead of 4 small load cells, I used one 4-wire load cell (LEGO-lars used similar). This is my last problem with this project. The reading from ADC is not stable and it drifts with time. I put 2 kg on my 20kg load cell and after 2 weeks, the readings from ADC were lower then first day. Do you have similar experience with load cell?

Now, last month I am working on 3rd version of electronics. The digital part remains the same, but I completely redesigned analog part. I removed INA125 and used precision opamp MCP6V07. They have very low temperature drift and low noise. Instead of internal ADC inside of ATMega, I pick MCP3551 -- 22bit sigma-delta, low-speed 13sps. This new version of electronics will contain 2 opamp and 2 ADC, so I'll be able to measure 2 beehives with one electronics.

--------

I am not fan of load cells. I would like to use multi-turn potentiometer. Unfortunately, I'm not mechanical engineer and don't know how to change weight into movement. It would be necessary to use some kind of lever and spring and gears to change small changes in spring into several turn of potentiometer shaft. Not sure if this is doable.

This is my second version of electronics.

[Trottel100]

Hi how Long will stay your battery?

From where did you come from (Europe)?

[vasco-vls]

Question about battery life is quite difficult to answer. My first version of electronics used ZigBee and step-up converter to 5 V. I was able to run it with 2AA alkaline batteries for 16-20 days, measuring and sending data every 15 minutes.

My second electronics uses different radio and different step-up converter to 3 V. I didn't test this version for longer time than 6 days, but during this time I used fully charged new NiMH batteries and their voltage drop was 100 mV per 6 days, measuring every 5 minutes. So maybe 48-50 days with NiMH batteries? With alkaline batteries, those numbers would be different.

I'm from Czech Republic.

[Trottel100]

Hi Thank you.

I have build a scale with arduino and 3g shield.
I us a Pb Akkumulator with 7,2Ah. In first time only 3 Weeks, the consumption of the systhem was 60 mA at 12V.
Now the Systhem Needs 5 mA at sleeptime.
I haven´t testet it yet but i think that 2 or 3 month are posible.

Best regards

[vasco-vls]

I don't  have experience with 3G shield for Arduino, but I think GSM modules can draw about 500 to 1000 mA during data transmission. Maybe you can save several measurements in memory and send them later at once. This can safe some power.

If your 3G shield has no sleep mode, try to use power MOSFET to turn it off. This can save a lot of power. ATMega328P in power-down mode draws max. 8 uA (@3V, watchdog enabled). INA125 (or other analog circuitry) can be disabled for most of the time. I think it should be possible to reduce power consumption at sleep mode below 0.5 mA.

Also, try not to use linear voltage regulator (ie. 7805), they are inefficient. Use step-down DC/DC converter (I suppose your accumulator gives 12V) to make 5 or 3 V. Their efficiency is 80 % and more. But remember, you have to choose step-down converter with at least 2A output current, because of your GSM module.

[Trottel100]

Hi,

yes, i have bought stepdown power suply, this will i test in next time, i turn the 3g modem off and i have disabled the led´s, so it does only Need less than o,1ma.
I stop although the INA 125p.
I think next week i will do the first test.

Now i know that i am on the right way.

I must only work on save data, at time i send every 1 hour one datapackage.

By
.

[NZbeek]

Hello everyone, I am a commercial beekeeper from New Zealand. I am an amateur with electronics but would like to work on a project that is practical and that I can use. I can make the physical scales, but I do not know how to make the electronics or write the program. I know how to put electronic components together and can upload a program to an Arduino, can you help with the rest?

Trottel100 your project sounds most like what I would like - a scale that works remotely, I would like to use an Arduino with a GSM shield, this can make one weight recording at the end of each day and send once per day, even once every 2 days is fine. Our hives are a bit heavier, up to 200kg gross. I would like to be able to connect auxiliary hive scale to the master scale to get an average, ideally wireless but wired is not an issue. I would like a long term power source, solar or a 12v sealed acid battery or something along those lines.

If the forum can help suggesting parts, and if there is someone who could provide me the bare bones of the code and walk me through changes, or if there is code that exists I would really appreciate it. I am excited to try and learn something new.

Thanks!

[GoForSmoke]

Just a thought.

If you put the hive at one end of a lever on a pivot and the scale at the other then you could by making the lever arms uneven, use a scale rated for much less weight than the hive.

A very precise lever could be very short but practical I think may be 1/2 meter or longer to get 10:1. That way the tolerances of making the lever and positioning points can be cabinetry instead of space rocket.

[Trottel100]

Hello,
the scale runs, in this year i build up a Homepage, where i would schow how to build the scale.

But i think the time i Need to build the Homepage would be the end of this year.

www.imker-stockwaage.de is the Homepage.

Best regards

Achim

[NZbeek]

Thanks Achim, I know you may not have time, but do you think you could send me a list of the components you are using and perhaps the code? It might at least give me a starting point. It is winter in New Zealand but I would love to have a couple of prototypes ready for November to test on our hives this summer.

[NZbeek]

This may not be the right place to ask - but what is the best board I could use to achieve 1 input (weight reading from the hive from Shear Beam Load Cell), data send via GSM shield and ability to be solar charged? I have looked at the Arduino mini on the understanding that they use much less power however they do not seem to be compatible with standard shields and may not support GSM? All power savings I have seen appear to be for barebones custom boards/breadboards, I am not technical enough to solder a custom board and would rather buy a ready-made but basic board that will support the aforementioned functions.

Are there Arduino clones that support the same form factor for shields, but are configured for low power consumption? If so, what are they?

Thanks in advance

[GoForSmoke]

You program the chip for power consumption by lowering the voltage and speed and/or using sleep mode and/or turning off parts you don't use. AVR chips with P at the end of the name are branded "pico-power" because of power saving options.

GSM and other addons usually require libraries and some RAM. Stack enough up and you will not be looking at the cheapest chips regardless of the board. Chip size is not directly how much power uses either, they sleep about the same and the running power isn't greatly different at the same clock speed.

But since you are looking for ready made software it would be best to get that and the hardware to match.
Other questions, save for if you will have to choose your own and start a development project that can take months.