# Hive Scale (GPRS Arduino) plus weather station



## Stephenpbird (May 22, 2011)

So my winter project was to build a hive scale. I wanted to be able to monitor honeydew flows remotely (the most sought after honey in my area) . There are many available commercially here in Germany but most are very expensive. Luckily I found someone who has built one and shared how he did it, on the internet. 

http://www.imker-stockwaage.de/

Mine is now up and running, sending data of an overwintered colony that's in two deeps. It sends data every hour (definable) to the website linked below

http://www.kippenheimimker.esy.es/stockwaage/graph.php

The scale runs on an arduino with a GPRS shield (mobile telephone), is able to weigh two colonies and sends the data as a text message to a phone and/or updates a website. It has a swarm and low battery alarm. The humidity and pressure sensors (they both have built in temperature sensors) provide the weather data. I am not too interested in rain and brood temperature so have not built in those sensors. I will in future build in a GPS tracker so I know the location of the scale just in case someone takes a liking to it. Obviously I wont make the exact location public.
So far the cost is under 300 euros for parts. I didn't follow the plans exactly and changed the sensors to more accurate ones, which cost me a lot of extra time.

How long did the project take? think in terms of days and not hours. I could not have completed this project alone, so have to thank Achim for sharing, his website and his help by email .


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## Tenbears (May 15, 2012)

Nice project. Glad you had success working it out.

I never understood the European fascination with Honeydew honey. 
Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. We all Know what the terminal opening to the gut is.


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## Steve in PA (Jan 26, 2015)

I'm working on something similar based on Pi right now myself.


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## yotebuster1200 (Jul 28, 2013)

Stephenpbird said:


> So my winter project was to build a hive scale. I wanted to be able to monitor honeydew flows remotely (the most sought after honey in my area) . There are many available commercially here in Germany but most are very expensive. Luckily I found someone who has built one and shared how he did it, on the internet.
> 
> http://www.imker-stockwaage.de/
> 
> ...


I have been wanting to build something like this for quite some time. I think I will have to tackle this project. Now I just need to translate the instruction PDF file.


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## Stephenpbird (May 22, 2011)

Tenbears said:


> Nice project. Glad you had success working it out.
> 
> I never understood the European fascination with Honeydew honey.
> Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. We all Know what the terminal opening to the gut is.


Yes that is very true, but then is it so different to eating normal bee barf? Insects produce the honey whether the nectar comes from plants or other insects its still honey. 
Not all Europeans will thank you for a jar of Honeydew honey, the English definitely wont. Mainly it was just popular in highly forested areas where there was very little other choice. Now it's developed into a delicacy, its the only honey people request and demands a 20% premium. It is also more challenging crop to target than a normal plant crop. But when everything falls into place you can get some unbelievable large flows. My interest in it ?" it sells itself and just walks out the door" There is never enough.:thumbsup:


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## Stephenpbird (May 22, 2011)

You can see the Lipo battery I used, a low C-rate Long Life LiPo Formular which isn't like a standard LiPo. It retains voltage for months on end and a waterproof case keeps everything dry. The wire goes to a 200kg load cell built into the hive floor.


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## Stephenpbird (May 22, 2011)

yotebuster1200 said:


> I have been wanting to build something like this for quite some time. I think I will have to tackle this project. Now I just need to translate the instruction PDF file.



Google does a good enough job for most things


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## Stephenpbird (May 22, 2011)

Steve in PA said:


> I'm working on something similar based on Pi right now myself.



I was keeping an eye on 
http://www.hivetool.org/w/index.php?title=HiveTool.org
they too use the Pi, looks like a great project as they have made things very simple, but doesn't suit my need of mobility. 
Eventually I hope to have 20 or so hives permanently mounted on a trailer all on scales.


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## EastSideBuzz (Apr 12, 2009)

Very interesting. I work for a company that does network management. We port our agent code down to a banana pi. I could do this with the pi then use my charting and graphing from my agent via wifi. Some of my bee yards have wifi. I need to know the parts you used. Where do I get the scale and what temp sensors did you use. It is the pluming I am missing and making the pi read them. Is there a English version out there of instructions you used.


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## Phoebee (Jan 29, 2014)

I'm about to pull the trigger on an Arduino-compatible purchase. I'd like a starter kit, ready to go and with good startup support. I have a Seeeduino knockoff in a box near me, which came with no other documentation than to suggest I read the Arduino website. Won't make that mistake again.

Any suggestions? There seem to be some Raspberry Pi starter kits that look promising and should be well documented.

I want most of my sensors to be I2C. I may do some straight analog, and a high-res A-D shield would be good. My apiary has a conduit to it for low voltage and I should be able to run this over an Ethernet shield.


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## Stephenpbird (May 22, 2011)

Phoebee said:


> I'm about to pull the trigger on an Arduino-compatible purchase. I'd like a starter kit, ready to go and with good startup support. I have a Seeeduino knockoff in a box near me, which came with no other documentation than to suggest I read the Arduino website. Won't make that mistake again.


 Adafruit is probably the best for starters, check out their website. The seeeduino is an Arduino knockoff it should work with the code.



Phoebee said:


> Any suggestions? There seem to be some Raspberry Pi starter kits that look promising and should be well documented.


Pi = $$$



Phoebee said:


> I want most of my sensors to be I2C. I may do some straight analog, and a high-res A-D shield would be good. My apiary has a conduit to it for low voltage and I should be able to run this over an Ethernet shield.


Ethernet and low voltage that screams Pi to me, again have a look at the hivetool website. I used a BMP280 pressure sensor breakout from adafruit and the SHT31 humidity breakout sensor also from adafruit both I2C (both have temp guages and are accurate to .2 of a degree). Their tutorials are all you need to get them up and running.

Hires ADC for load cells, there is nothing better cheaper or easier to use than the HX711. Loads of tutorials all over the web, just google hx711 arduino and you will get everything you need to know.


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## Stephenpbird (May 22, 2011)

EastSideBuzz said:


> Very interesting. I work for a company that does network management. We port our agent code down to a banana pi. I could do this with the pi then use my charting and graphing from my agent via wifi. Some of my bee yards have wifi. I need to know the parts you used. Where do I get the scale and what temp sensors did you use. It is the pluming I am missing and making the pi read them. Is there a English version out there of instructions you used.


the scale is built with a 200kg load cell from Bosche http://www.bosche.eu/en/products/load-cells/single-point-load-cell-h30a attached to an INA125p ADC which is read by the Arduino. See the other post for details of the sensors. Again if you want to use a Pi look at the hivetool website, they have done ALL the heavy lifting for you.
The instruction are only in German, but for those really interested Google translate does a surprisingly good job.


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## Stephenpbird (May 22, 2011)

Its worth saying if you follow the plans to make this scale you actually make a PCB based on a Arduino nano. Two ADCs to read the scales, to save power and to use a wide range of battery voltages there are a few extras circuits built in.


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## Phoebee (Jan 29, 2014)

Stephenpbird said:


> Its worth saying if you follow the plans to make this scale you actually make a PCB based on a Arduino nano. Two ADCs to read the scales, to save power and to use a wide range of battery voltages there are a few extras circuits built in.


A friend of mine built me a custom 24-bit ADC with an amplifier added for a microphone. The idea was to have a board that could do a hive scale plus Apidictor functions. The ADC is a MCP3911. But the INA125 sounds very familiar ... I think that was one we originally discussed. This was from an abandoned earlier attempt to build a hive scale two years ago. He hates Arduinos and wanted me to go with his system that programs in Forth. But I couldn't find enough info on it to have a clue how it works, and he lost interest. The board he built should talk to any of this family of single board computers.

I've worked with the MPC555 microcontrollers, as the brains of UAV sensor and control systems, so I know the basics of the hardware. But that company never let me get into the code, so this will be a chance to get down and dirty with writing software for the first time since the last millennium. I used to work with strain gages a lot, and I'm thinking I'm going to build my own custom load cells, especially designed for bottom boards. The ADC board we designed has a bridge excitation source built in. I'm pretty sure I can wire the two bridges in parallel and use one ADC channel. Done right it should automatically average the two and give total load.


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## Stephenpbird (May 22, 2011)

Phoebee, I looked at the Pi but in all honesty its just too powerful/over-specified for a Bioserver. The arduino however is near perfect, a few pins short maybe but there are various versions with higher specs/costs. I started out with a basic stamp long ago and only play around with electronics when I need it for a project. So I can say the Arduino is easy to learn to program because of the libraries that are available. 
What your talking about doing, well now that just way out of my league.


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## Phoebee (Jan 29, 2014)

Now that I'm looking at the Pi specs, the 2 and 3 variations are rather over-the-top. And power hungry. I'd like to run this setup off my solar power system. Some of the earlier Pi models draw less and are more than capable.

The Ethernet connection is tempting, though. I could add a shield to an Arduino but that adds a whole new level of bother. There is something in that family called a Trinket, but that one is too limited. It does run on very low power, though.

What I would really like is one of these built around a venerable MOSTEK 6502, with static ram memory. Clock speed is a couple of MHz, but power consumption would be maybe 2V at 5 mA. It would handle the job fine. I keep wishing this market would re-discover CMOS and get the power consumption back down where we used to be 40 years ago.


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## EastSideBuzz (Apr 12, 2009)

But with POE from the house I can power the Pi no problem. The pi can run many hives with one pi. It is all the german that I am having trouble with.


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## Stephenpbird (May 22, 2011)

One of the things that surprised me with this "Stockwaage" (colony scale) is that Achim provides it as a complete package right down to the instructions of how to create and set up the free web site. 
I bought a sim card which includes free data transmission up to 10 mb per month, which is enough to run the scale without data cost. So the only thing I pay for is if an alarm text is sent , either swarm or battery. Of course one can keep an eye on the battery as it's strength is part of the data collected which is sent to the website and displayed in the graph.


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## Phoebee (Jan 29, 2014)

Stephenpbird said:


> Its worth saying if you follow the plans to make this scale you actually make a PCB based on a Arduino nano. Two ADCs to read the scales, to save power and to use a wide range of battery voltages there are a few extras circuits built in.


I'd have to go back and check the specs on the ADC I used, but I think it may have its own processor, and may not even need an Arduino or Pi to run standalone. I know we were looking at one that could have controlled its own sample rate and even run the FFT analysis from the microphone. And the boards were going to be amazingly cheap, something like $12.


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## Phoebee (Jan 29, 2014)

I finally broke the code on the load cells the OP is using: http://www.phidgets.com/products.php?product_id=3135

These are $7 each in onesies, 6.55 if you buy ten at a time. If I did all three full sized hives, four per hive, that's actually pretty darned affordable.

What I was trying to do was buy cheap ($22) electronic bathroom scales and remove the feet from those for my load sensors. They are apparently 1 k strain gage half-bridges, and had a chance to have worked. However, they seem to have taken some shortcuts in their design that give worse temperature performance than strain gages can achieve, and I measured grossly unacceptable zero drift and scale factor drift over temperature. 

Since we are interested in year-round weight measurements, the temperature drift is important. The 2.5 g/C spec for the Phidgets load cells on scale factor gives 100 grams of error over a 40 C temperature change. The zero drift, 5 g/C, would be twice that. Multiply by four for the four load cells per hive, total drift might be a kg or so, a bit over 2 pounds from summer to winter. Not super precise but it should be good enough. Definitely better than the bathroom scales.

I still say it ought to be possible to parallel the load cells into one analog input. Impedance would be 250 ohms instead of 1k but that is fine. Averaging would be done by the analog circuit. 

It would be important never to rock the hive onto one foot, which would risk overloading these load cells. Rough handling or more than 110 pounds on a single foot might cause a permanent offset.

I would design mounting rails and feet for them rather than using them bare as shown on the website.

Bottom line, I think these are a pretty good choice, more affordable than any true load cell I've seen by about a factor of 8. I'm not sure you could hope for better at the price.


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## EastSideBuzz (Apr 12, 2009)

Phoebee said:


> I finally broke the code on the load cells the OP is using: http://www.phidgets.com/products.php?product_id=3135


Your picture has wires on it now it makes more sense. The German and the lack of wires had me baffled.

So then with the PhidgetBridge board it is USB to the Pi. This might work. So per hive it would be 120 bucks. Without temp sensors etc. 

Have you seen a bridge that takes more then 4 inputs. I only found 4 on the site. I would think 8 would do all the measurements per hive. And 90 seems a bit expensive. I might get one to try it out but, would love something cheaper.

I am going to order one set to keep weight on my honey warmer so I can hit it with a web browser to see if I got enough honey to fill the order.  I would like to do temp of honey and maybe temp of water in the cavity. Temp of room etc. This will be a great addition to my honey room. I just pulled the trigger and ordered one set.


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## Stephenpbird (May 22, 2011)

Phoebee said:


> I finally broke the code on the load cells the OP is using: http://www.phidgets.com/products.php?product_id=3135
> These are $7 each in onesies, 6.55 if you buy ten at a time. If I did all three full sized hives, four per hive, that's actually pretty darned affordable.


I got a quote from Chinesesensor china for those load cells "The total payment is USD80.00 unit for 20pcs including freight" so that price from phidgets is very good indeed.




Phoebee said:


> Since we are interested in year-round weight measurements, the temperature drift is important. The 2.5 g/C spec for the Phidgets load cells on scale factor gives 100 grams of error over a 40 C temperature change. The zero drift, 5 g/C, would be twice that. Multiply by four for the four load cells per hive, total drift might be a kg or so, a bit over 2 pounds from summer to winter. Not super precise but it should be good enough. Definitely better than the bathroom scales.


Your scale will only be as accurate as the known weight you use to calibrate it with, I think you should decide now how accurate a scale you would like and what would be the minimum accuracy you will accept and aim for somewhere between the two. 



Phoebee said:


> I still say it ought to be possible to parallel the load cells into one analog input. Impedance would be 250 ohms instead of 1k but that is fine. Averaging would be done by the analog circuit.


Hivetool do exactly that with the HX711, sparkfun (I think) even have a breakout board for doing that neatly. I am using the HX711 in v2 it is very good and cheep no programming neccessary, less than $5.



Phoebee said:


> It would be important never to rock the hive onto one foot, which would risk overloading these load cells. Rough handling or more than 110 pounds on a single foot might cause a permanent offset.


True, dropping a super full of honey on the scale could damage the load cell, you should build in protection, just a bolt is needed to limit the movement. The big no no is sideways movement.




Phoebee said:


> Bottom line, I think these are a pretty good choice, more affordable than any true load cell I've seen by about a factor of 8. I'm not sure you could hope for better at the price.


 I agree, tried and tested in hive scales too.


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## Stephenpbird (May 22, 2011)

EastSideBuzz said:


> Your picture has wires on it now it makes more sense. The German and the lack of wires had me baffled.












A and b are the two sensors BMP280 and SHT31, they are digital, they connect directly to the arduino at D. They use I2C so you can have a large amount of sensors on just two digital pins. No need for extra boards.

C is the wires from the load cell (scale) which is analog and needs to be converted to digital so the arduino can use the data, the INA125 chip does that, its under the blue GPRS sheild.

The X s are free connections to digital pins on the arduino, they can be used for things like brood temp or a rain gauge etc.


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## Phoebee (Jan 29, 2014)

Stephenpbird said:


> Your scale will only be as accurate as the known weight you use to calibrate it with, I think you should decide now how accurate a scale you would like and what would be the minimum accuracy you will accept and aim for somewhere between the two.


They remind you on their website that the scale must be calibrated against known weights, but even with calibration you need to know how well calibration holds over temperature. I used to do this for a living, repeating calibrations on instrumentation packages over a range of -40 to +70 C. The systems had temperature sensors so that we could compensate for it. For some sensors we repeated a full calibration every 10 C. It was a huge amount of work, and required a large and rather expensive environmental chamber.

Strain gages are available with their temperature coefficients matched to the underlying metal. For Micro-Measurements brand, the 03 compensation is matched to aluminum, reducing the temperature effects. If, in addition, one uses a full balanced bridge configuration (equal and opposite strains on identical pairs of gages), zero drift ought to be nearly completely eliminated. Strain gages usually have very little scale factor effect over temperature (i.e. the mV/V output for a change in applied weight from 0 to full scale) should not change noticeably. 

If you do have a bad zero drift over temperature, you might think you are seeing hive weight going up and down over a period of 24 hours. Similarly, if the sensitivity to weight change is not constant, and the hive has a lot of weight applied, the reading will track temperature. Is it bees coming and going, or a sensor problem? Hard to tell. And this could be important. You expect a drop in weight in the morning as foragers leave. You want to see weight up at the end of the day during a flow. So minimal temperature effects let you see the actual hive activity better. This may be more important than a precise calibration.


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## Stephenpbird (May 22, 2011)

Phoebee said:


> They remind you on your website that the scale must be calibrated against known weights, but even with calibration you need to know how well calibration holds over temperature.


Yes, but my point is how accurate is your known weight. How do you test it in the home environment etc. One really needs to have access to a very expensive accurate scale to measure your known weights so you can calibrate your own scale.

Its also worth pointing out that the load cell you choose should be tested on your system , mine is polled numerous times, the first few readings discarded and then an average weight recorded. It is amazing how much they fluctuate before settling down.

I knew nothing about load cells before I built this scale, I soon realized that my needs present a very harsh environment for a load cell, which include keeping the cell under constant load. That's why I decided to buy the best I could afford which is class C3 . Even so I would be surprised if its is accurate to within 1/2kg because of the reason stated above. But that's OK for now, Basically this is a tool to help me increase honeydew harvest and not some scientific apparatus. If my needs change I am sure I could fine tune this system as it stands.

I do agree with what you have said, one can only build up a picture of whats is happening when you take weight and environmental conditions into account. I think measuring light might be more important than rain for example. But then comes the question of what type of light white, UV or infrared. Obviously the light a bees eye sees and not a human eye.


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## Phoebee (Jan 29, 2014)

I don't concur that hive scales need to be especially accurate, only consistent. If you are off by a pound or two out of 150 pounds, that won't make much of a difference in your hive management decisions. Bathroom scale accuracy is OK.

What I'm using now is a 440-lb (200 kg) hanging game scale, with a resolution of 0.2 pounds. It does not have a NIST-traceable calibration, though.

I have worked in a lab where we had ten 1-pound class C calibration weights, and they were really sweet, consistent with each other to within 2/3 of a gram. We also had set of assorted steel and lead weights of 20 and 40 pounds, not so refined but very good (within 10 grams of correct when tested against the Class C weights). I'd love to have either set right now. Shopping around, I'm not finding any affordable weights, new or used. What is available would exceed the cost of my whole hive scale project. We also had a 220 pound steel weight. 

I suppose I could weigh my 100-year-old 160-pound anvil and use that as my standard, but it really is a beast to lift.

I've been shopping yard sales for a good set of barbells that I could use for a weight set, but have had no joy so far. Those are also uncalibrated and would need to be checked on a reliable scale.


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## Phoebee (Jan 29, 2014)

Regarding what should be measured ...

You mention a weather station and I concur. Temperature, wind, and humidity are all important, and recent precipitation will affect forage for a day or two afterwards. 

Temperature and humidity in the hive are worth recording, although temperature is tricky ... location of the sensor versus cluster location is tricky to manage. I've seen one study that used something like 192 thermocouples in overwintered hives, and was able to track cluster shape and position changing. If I stuck 6 16-channel boards into my UEI-DAQ system, I'd have about half of what is needed, and that system would cost about $6600 to put together.

If you want to add solar irradiance to your system, PM me and I'll send you some information. There is a website that gives instructions for building a simple photovoltaic pyranometer (a small photocell and a resistor), but that does not give true irradiance. I've been working with thermoelectric cooling modules, sold for around $3-5 from places like MPJA.com, that turn out to be excellent heat flow sensors. Paint one side black and put a heat sink on the other side, and you have a broadband pyranometer almost as good as the research grade instruments. I could give you one I've calibrated.

What the pyranometer will give you is a pretty good idea of cloud cover. Clear conditions give a very predictable and clean hump over the course of a day. Clouds give sharp drops in heat flow.

Near UV is a bit tricky, but there are some filters that would let you measure only the UV component with a PV sensor.

Bee traffic should be relatively easy to rig, but I have not tried building it yet. I think some of the links you gave cover it.


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## Phoebee (Jan 29, 2014)

Here is a typical day-long pyranometer plot from a research-grade thermopile pyranometer about 30 miles north of me. On a clear day, I can calibrate my pyranometers against it. Even without calibration, you can easily see when the sky is clear and when clouds blocked the sun partly or fully.


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## EastSideBuzz (Apr 12, 2009)

Found these sites. Seems alot of Adrino stuff out there.

https://hackaday.io/project/1741/logs
https://learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide
https://github.com/sparkfun/HX711-Load-Cell-Amplifier
https://www.youtube.com/watch?v=uEVRPUXjN8Q
https://www.youtube.com/watch?v=yL9RQgLKw_E
http://arduinotronics.blogspot.com/2015/06/arduino-hx711-digital-scale.html
https://hackaday.com/tag/hx711/

24 channel board http://store.hackaday.com/collections/spring-sale/products/jtagulator


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## Stephenpbird (May 22, 2011)

EastSideBuzz said:


> Found these sites. Seems alot of Adrino stuff out there.


Here are three of my favorites.

http://www.jeremyblum.com/
http://www.electroschematics.com/arduino/ 
https://www.adafruit.com/

Of course an automated filling machine for honey is doable...


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## Phoebee (Jan 29, 2014)

I was introduced to Adafruit on a project I'm just wrapping up for a client. They're carried by several large electronics suppliers, and seem to be a notch above some of the others.

Two sources I don't trust are Seeed Studio and Grove. A Differential Amplifier I ordered from Grove turned out to not be the part they had on their website. When I got the correct documentation for it, it failed to live up to the new spec (gain was way off). The Seeeduino computer, as mentioned above, was devoid of any documentation or meaningful support. They operate out of China. Granted, a lot of stuff comes ultimately from China, but I'd stick with suppliers with a presence closer to home, who offer support in a language you actually speak.


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## EastSideBuzz (Apr 12, 2009)

Stephenpbird said:


> Of course an automated filling machine for honey is doable...


Home Made Automated filling machine never. Just wanted to be able to say I have 100lbs of fireweed in the warmer. . Why because I can or want to.

I have an air driven box smasher that assembled my boxes for me. Why? because it was cool. Will it ever pay for itself nope. Will the money I spent on it ever justify the cost that I could have just bought the boxes already assembled and painted nope. but, it is fun to hit the lever and the box gets smashed together and squared up. Could I have afforded the one that nailed them together also nope.

Sometimes it is just a toy to have one the bucket list. And boy do I need to have less sugar before I start my rants.


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## Stephenpbird (May 22, 2011)

EastSideBuzz said:


> Home Made Automated filling machine never.


Come on it could be fun... I bet you can't resist clicking on the link to see how 

http://www.hw2sw.com/2011/10/21/liquid-filling-machine-part-1/ 


opcorn:


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## Phoebee (Jan 29, 2014)

Absolutely! I retired from working with other people's computers and electronics so I could work on my own!

My wife doesn't understand, but EastSideBuzz does.


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## Stephenpbird (May 22, 2011)

So the scale has not being functioning well, I left it running even though I had noticed something wasn't right. I hoped I could learn something from the data. Well it was waking up every minute or so sending data some of which was just nonsense. The Voltage reading was around 0, that coupled with the switching on and off was the key. The cause, fluff, when the humidity rose to over 90% it became conductive and shorted the mosfet. I found the fluff/fibers using a stereo microscope, removed them and the scale was back to normal.
So I applied a conformal coating and set up the scale outside again. Lets see how long it runs for this time.


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## Stephenpbird (May 22, 2011)

OK then, maybe a Arduino Queen rearing incubator...

https://www.gillaspyshoneybees.com/pages/incubator

opcorn:opcorn:


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## Stephenpbird (May 22, 2011)

since I had the scale in pieces I took a photo of the arduino based board


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## Phoebee (Jan 29, 2014)

Stephenpbird said:


> OK then, maybe a Arduino Queen rearing incubator...
> 
> https://www.gillaspyshoneybees.com/pages/incubator


No, no! The queen rearing incubator we built last year just needs a $10 digital thermostat.

The portable queen cell/brood frame incubator I'm currently building uses a nice 12V-powered PID temperature controller and DC SSR. The controller will double as an OAV vaporizer controller.


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## Phoebee (Jan 29, 2014)

Stephenpbird said:


> since I had the scale in pieces I took a photo of the arduino based board


0.1-inch pitch chips! A man after my own heart! I apologize for US English pitch components making life difficult for the rest of the world for so many years.


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## Phoebee (Jan 29, 2014)

With a little consulting money coming in, this is starting to get interesting to me again.

I'm still concerned about these 50 kg (110 pound) load cells. With the weight distributed across 4, they're good enough, but rocking the hive onto one leg is likely to damage that load cell. I'd feel better about 100 kg shear beams in a similar price range.

I did find a site called Chinesesensor.com that carries these CZL635 load cells and others, but I keep running into the 50 kg limit. It is interesting that they have a family of load cells designed a lot like the ones I was pulling out of cheap electronic bathroom scales. These are also 50 kg. The ones I tested have both scale factor and zero drift issues that caused me to abandon them. They also tend to rust.

http://www.chinesesensor.com/English/show.asp?id=150
http://www.chinesesensor.com/English/show.asp?id=148
http://www.chinesesensor.com/English/show.asp?id=147
http://www.chinesesensor.com/English/show.asp?id=145

I did find a place that has higher ranges, including some candidates in the 300 kg range, and this one that is $3.50 and has a number of rated loads, the top one being 100 kg.

http://hlhsensor.en.made-in-china.com/product/evPmhQcHXKVk/China-Aluminum-Load-Cell.html

I'm about to build a small heating/cooling temperature chamber based on Peltier cooling modules. I'll size it to make a test chamber for hive scales so I can evaluate the design. When not doing that, I can toss green drone frames it to make dronesicles (the real chest freezer is full of food).


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## Chris Muncy (Apr 2, 2015)

Those load cells look identical to the ones I got off of fleabay dirt cheap. I ordered 8. I also got a few amp boards and combiners from SparkFun. I'm thinking of printing a "U" shaped saddle with sheet metal at the top and bottom to protect the sensor. I also have a few Arduino Uno's with 2x16 LCD displays for local testing but I want to use some ESP 8266's that I already have for wi-fi connectivity.

One step at a time....


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