Measuring the weight of a beehive

Time for an update on my project :) lately I have been focusing on the wireless interface and power consumption of the sensor nodes. The ina333 op-amp workes great in my low voltage setup. I have a prototype up and running on a breadboard(see the schematic)

To optimize the battery life, I am running a barebone AtMega328P on the internal 1Mhz clock, the bod level is set to 1.8v and is software-disabled while the processor is sleeping. Also i am using a pnp-transistor to shut off the current to the loadcell and op-amp, so they only consume current a few milliseconds while sampling. I am also using the Collector voltage of the transistor as my analog reference, so the voltagedrop of the transistor won't affect my measurements. Since The Internal ocilator is'nt accurate enough, I connected a 32.768 khz crystal to the chip's clock-pins. This crystal feeds Timer2 and creates an accurate interupt every second. This way the the AtMega also works as an RTC, and I save the cost and powerconsuption of an external RTC. All in all including the radio tranciver my crappy multimeter shows a current consumption of 2-5µA :astonished: when everything except the 32khz crystal and timer2 is sleeping.

The wireless comunication was a real twist. I want the sensor nodes to sleep as much as possible, and there will be a lot of sensornodes trying to communicate with one "master-module". The solution I foud, is to let the master-module decide when the sensor-node can start transmitting. So when a sensor-node is waking up from sleep, the master-module will already had started listening to that exactly node. Then when the sensor-node has sent it's data to the master-module, the master will respond by sending how long time to next datatransfer. The whole prosses of waking up the prosessor, wait for the op-amp to stabilize, take ten samples and calculate the average, sending the data, reciving the time to next datatransfer, and go back to sleep only takes about 100ms with an average current consumption of 6mA :astonished: If i take one measurment each hour, I would get an average current consumption of 5.25 µA 8) Anyone who know how long this thing will run on a cuple of AA? ;)

the next tasks on my todo list: 1. Use the internal bandgap reference of the AtMega chip to measure the battery voltage, and make a low battery warning. 2. upload the measurements to Cosm.com using a gprs-module. (I just smoked my gprs-shield so this can take some time :)) 3. put everything in a watertight box and do a real longtime outdoor test of the loadcell.

ps. It looks like this thread is turning into a worklog. Mabye a moderator can move this thread into a more suitable category.

I'm not sure that this will be good for beehives but if you have a mass that can move freely and an accurate accelerometer, especially at low G's, then if you apply a known force... F=MA.

gardner: For this type of application, I have imagined two approaches: ... (2) build a pneumatic balloon system under the load, like a hot water bottle. Inflate it and seal it up, then just measure the pressure in the balloon. If its hard to keep the balloon inflated all the time, then let the weight rest at the bottom and make a contact closure. When reading is needed, pump air into the balloon until the contact closure opens, take pressure readings for a while, then kill the pump and let the weight settle back against its stop.

That has given me an even simpler idea of how you could solve the problem. Fill the 'balloon' with (coloured?) oil and use a manometer type system (a U tube) to measure the pressure (= weight). Detecting how far up a tube the fluid level is would be far simpler than using stress gauges, which will have to be regularly zeroed. The narrower the tube, the more accurate it will be. You could use ultrasound to measure the distance of the fluid from the top of the tube. You may need a floating passive reflector for this. That way, no pump is needed and readings can be taken at any time. You will still need a 'dummy' hive to take into account ambient temperature (and, therefore, volume) variations. You'll also need to calibrate the tube (once) by adding known weights onto the 'balloon'.

I'm not sure a "balloon" type system would work quite as expected. When weight is added to the hive the balloon will flatten out and result in a non-linear pressure reading at your manometer?

Using the example of a car tire, pressure measured in PSI, the footprint (in square inches) of the tire multiplied by the inflation pressure equals the weight supported by the tire (an "ideal" tire, ignoring sidewall stiffness, etc.). When weight is added the footprint can increase and the pressure can stay near or at the original pressure.

I might be totally off my rocker.

I'd suggest using magnets and coils to raise the hive instead of a balloon but the fields might have a long term effect on the bees.

Thank you for your ideas but I have decided to use loadcells for my project. It looks like my prototype using a loadcell meets my requirements in both accuracy, power consumption, cost and simpleness. :slight_smile:

That's great! The world does need more bees.

Chagrin: I'm not sure a "balloon" type system would work quite as expected. When weight is added to the hive the balloon will flatten out and result in a non-linear pressure reading at your manometer?

Using the example of a car tire, pressure measured in PSI, the footprint (in square inches) of the tire multiplied by the inflation pressure equals the weight supported by the tire (an "ideal" tire, ignoring sidewall stiffness, etc.). When weight is added the footprint can increase and the pressure can stay near or at the original pressure.

I might be totally off my rocker.

Not off your rocker, but have you thought about a flat square 'balloon', the same size as the base of the hive? Remembering that he's starting with 100+ Kgs on it, the few grams more or less wouldn't make any difference at all to the footprint.

But after sleeping on the idea, I realised that a manometer system would need an equal weight of oil to balance the hive. 200 litres of hydraulic oil doesn't come cheap!

Henry_Best:

Chagrin: I'm not sure a "balloon" type system would work quite as expected. When weight is added to the hive the balloon will flatten out and result in a non-linear pressure reading at your manometer?

Using the example of a car tire, pressure measured in PSI, the footprint (in square inches) of the tire multiplied by the inflation pressure equals the weight supported by the tire (an "ideal" tire, ignoring sidewall stiffness, etc.). When weight is added the footprint can increase and the pressure can stay near or at the original pressure.

I might be totally off my rocker.

Not off your rocker, but have you thought about a flat square 'balloon', the same size as the base of the hive? Remembering that he's starting with 100+ Kgs on it, the few grams more or less wouldn't make any difference at all to the footprint.

But after sleeping on the idea, I realised that a manometer system would need an equal weight of oil to balance the hive. 200 litres of hydraulic oil doesn't come cheap!

Or you could measure the height of the flattened balloon... I would use an inner tube to rest something on and maybe fill with dry CO2 or nitrogen.

But I think that his load cells are better than springs of any type.

I understand that putting mechanical strain on any conductor changes its resistance, even copper.

LEGO-lars: 2. upload the measurements to Cosm.com using a gprs-module. (I just smoked my gprs-shield so this can take some time :))

Thanks for this update! May be this combined board is usable: http://imall.iteadstudio.com/im120411004.html It is an Arduino, GSM, XBee, SD-Card on one board. It is cheap, but I do not know how power saving can be done.

Perhaps the new Arduino GSM shield is more power saving and battery compatible but there are some inconsistent information atm: http://arduino.cc/forum/index.php/topic,148708.msg1156939.html#msg1156939

When <400 mA peak current is correct this would be an interesting board. But you have to pay nearly 100 Eur for the board only!

Lars, what resolution do you have with your scale? We had some ideas and came to the solution not to use an amp but instead an external ADC with a higher resolution than the 10bit Arduino, do you use an other board (e.g. the DUE has a 12 bits resolution)?, see http://hackerbee.com/2013/03/18/100-hive-losses-this-year/ or did we forget something? and a resolution of max load / 1024 is with the INA333 possible? I think it amplifies only the signal or does it do any digitalization?

Hi Clemens :) Thanks for the link. A lot useful information on that page. You are right in that the arduino 10 bits of resolution is a bit low. However, there is a way to increse the resolution of the ADC called oversampling. http://www.atmel.com/images/doc8003.pdf In short, 16 10-bits sampeles are equal to one 12-bit sample. In my scale, I have no problem to get a stable resolution of 0.1kg.

http://dl.dropboxusercontent.com/u/128833299/bees.htm

Uses 50kg Load Sensor PPSEN-10245 for weight monitoring.

Photo Interrupter GP1A57HRJ00F to count the bees going in and out of the hive.

What has happen to this project? Is there any farther progress?

Hi toadstul. I have been quite busy with some other projects lately (and got a bit bored :blush:), so nothing has been done on this project in the last 6 months. However, before I took a break I was doing great progress. I've got the PCB for the wireless scales manufactured. I've got the the power consumption low enough for the scale to work several seasons before battery change is necessary. I have made the base station with the GPRS-module, a wether station, and a solar panel. I've also got the whole setup working on my workbench, and uploaded data to Cosm.com.

What remains is to make the actual scale that fits under the beehive. I also have some problems with the wireless trancievers (probably due to a designflaw on the PCB :blush:). Then I have to make everything watertight. On the computer side, I would like to download the data into a spread-sheet, and use some algorithms to calculate which beehive needs attention.

I plan to start up again this winter when I will have some more spare time.

I could probobly post some pictures and explanation of the current setup if there is any interest.

LEGO-lars

Measuring bee-hives? :fearful:

NOPE. Nope nope nope. nope.... nope...

shudder nope!

Is there any particular reason you bother yourself with power consumption as you can put a car battery with a solar panel charger to rid yourself of power consumption problems.? It's not like you'll leave your bees to themselves for two seasons? :)

Or am I missing something?

The two main reasons for the fiddling with the power consumption, is cost and flexibility. If this system turns out to work, I would like measure all our 200+ hives (my father works full time as a beekeeper). Therefor the cost of each weightscale is critical. Powering the each scale with 2 AAA batteries would be a lot cheaper then using a car battery and solar panel, even if I could power several scales from the same battery.

The second reason is flexibility. When the scale is completely wireless, everything can be hided under the hive with no wires lying everywhere to be tripped over. The hives are also moved a couple of times during the season (to get more honey), so rigging the system up and down have to be easy and fast.

A last benefit with my wireless modular system is that it is easy to add or remove modules from the network. The plan is to let the base station in every bee-farm auto detect the wireless scales without intervention from the user.

Lego-lars

Too bad you can't just use one of these:

http://www.flickr.com/photos/jtr27/8399594421/

(Or can you?)

Hi LEGO-lars Sorry about the delay of my answer(i was changing isp) What method did you follow to lower the power consumption? What chip did you use to amplify the signal from the loadcell? You say ''I plan to start up again this winter when I will have some more spare time. I notes that you are from Norway, I think you already have winter up there :P !! So please start again your project asap. Pictures and explanation...? of course there is interest !

On my side I have buy already tow arduino uno, tow loadcell 160kg, tow ina125, tow DS3231 rtc, tow DHT22/AM2302 Digital Temperature And Humidity Sensor, and i am waiting an Arduino GSM Shield (antenna connector). I plan to connect all these together and get daily reports of weight to my mobile. That will help me to know when the nectar flow stars or ends.