Not sure yet, ultimately would like the data to self publish to a database in the cloud somewhere
Pellet stove meter: prototype needed
- Thread starter smwilliamson
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if'n yer gonna measure the pellets it has to be in mass, in which they are theoretically sold, not volume. Though it is often measured in lbs/cu ft...it does vary some based on the production runs. If you're looking for something accurate, not just general, you should weigh the stuff. Anyone with a "50 lb hopper" who's had to push the pellets around just to get 1 whole bag in knows what I mean 
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All you need to measure and store is the sum of the ON times of the auger motor, say a total time in minutes for each month. Then, for each stove make and model, one would have to determine the pounds-per-minute feed rate of the auger, and multiply that by the monthly minutes to get the monthly pounds of pellets used, which times approx 8000 BTU/Pound, would give you the BTU value of the biomass fuel consumed per month.
Since auger motors typically driven ON, and OFF by the control board (other than a stove that uses a variable speed DC auger motor that is run continously, but I don't think any stoves have this type of design), and therefore the auger motor current is a step waveform, that could be easily monitored with an inductive clamp-on probe on the auger motor feed wire, or, if the stove meter is sophisticated and sensitve enough, could be sensed completely external to the stove, on the 110VAC line-cord. The Stove Monitor would just be a box that plugs in between the stove line cord and the wall socket, and with an WiFi internet conenction could automatically report the stove pellet consumption on a monthly basis.
Since auger motors typically driven ON, and OFF by the control board (other than a stove that uses a variable speed DC auger motor that is run continously, but I don't think any stoves have this type of design), and therefore the auger motor current is a step waveform, that could be easily monitored with an inductive clamp-on probe on the auger motor feed wire, or, if the stove meter is sophisticated and sensitve enough, could be sensed completely external to the stove, on the 110VAC line-cord. The Stove Monitor would just be a box that plugs in between the stove line cord and the wall socket, and with an WiFi internet conenction could automatically report the stove pellet consumption on a monthly basis.
What if the the auger was binding or if the motor where weak or say and auger bushing meltdown or N auger jam? You still get signal but little less or no rotation?
skibladerj
Member
I could probably put something together but my time extremely limited currently with a 60+hr, 6 day work week and a 2 month old.... I'll try to play with some things this sunday. couple of questions;
What would the end product budget be?
what type of accuracy do you need?
How long would you need to store data before uploading it?
What would the end product budget be?
what type of accuracy do you need?
How long would you need to store data before uploading it?
I guess we kinda need a working prototype before we can really answer those questions. Ultimately data should be bumped every 24 hrs to a cloud based webserver
If we can get a working prototype that Maryland will accept, I'll start a kickstarter campaign to crowd source funds for future development. I have connections at State and Federal levels...
skibladerj
Member
Every stove is different, kinda. Most are 1 rpm, some are two, three, four or six. There is one out there that is 8. Some Are even 2.4 or 1.65. Really depends on the model and manufacturer.
If your not gonna use on time x rotations.
Your gonna have to count physical rotations so a micro switch / photo cell / pin wheel / magnet switch somewhere on the coupler / auger shaft. Magnet switch would probably the most dependable counter.
On time would be the easiest for the majority of stoves me thinks, but wouldn't be as accurate.
I guess another problem is all stove's have different feed rates based on auger size / chute size / burnpot and even pellet size would affect it right?
Your gonna have to count physical rotations so a micro switch / photo cell / pin wheel / magnet switch somewhere on the coupler / auger shaft. Magnet switch would probably the most dependable counter.
On time would be the easiest for the majority of stoves me thinks, but wouldn't be as accurate.
I guess another problem is all stove's have different feed rates based on auger size / chute size / burnpot and even pellet size would affect it right?
Yeah, but each stove is rated for min/max BTU which is calculated by the amount of pellets that can be delivered by X amount of turns. The actual BTU through the stove may not be known 100% but anything close will do. If we could get a firebox temp then we could figure actual efficiency...I'm sure stove makers wouldn't like that very much. IT would be fun to set up one of these to monitor every component of the stove, so that a tech like me could just plug in to find the problem...(ah dreamland)
Pellet stove auger motors are synchronous motors, and they rotate at the rated RPM until their maximum load torque limit is reached, beyond that they just stop rotating. The auger motor either rotates at the correct rated speed, or it does not run at all. It is therfore no more accurate to measure the actual auger RPM, you just have to know the ON time, which can be sensed from the 110VAC input current of the stove, as I posted earlier. You want a stove monitor system which just plugs into the stoves line-cord (to sense the auger motor current), rather than an RPM sensor that has to be installed inside a stove, with every model of stove needing a specific mounting configuration.
skibladerj
Member
... we are digressing. Scott where would you want to mount the temp sensors so I can start to source some components? P.S more than likely the first gen will need to be hardwired to a laptop or download to a laptop manually for cost reasons.
skibladerj
Member
Okay after looking into matters further I think what "Pelleting in NJ" said might carry some validity as almost every augar motor i looked at was rated for 1-2RPM's. Which if true would make monitoring a duty cycle pretty easy.
How desirable would having internal firebox be on top of the air temp and exhaust temp be?
How desirable would having internal firebox be on top of the air temp and exhaust temp be?
Your also going to pick up the igniter current, I woud think any stove running a t-stat on/off mode would not allow any accuracy with this method.
I would suggest a CT on the motor leads directly.
Yes, you will see the ignitor current when the stove starts, but the microcontroller can easliy be programmed to ignore a line-cord current step that lasts for more than 30 seconds, and therfore easily filter out the long ignitor current versus the much shorter (1 to 10 seconds) current step of the auger motor ON time.
Again, the ultimate Stove Monitor design would not require that the stove be opened-up to install RPM sensors, temperature sensors, current sensors.... You want a Stove Monitor that is just a small box that plugs into the stove line-cord and the wall outlet. I don't think stove owners want internal mods to their stove that would void the warrentee, and you, as installers should prefer an easy, plug-in, minimal labor installation.
They way I see it, before you just throw some sensors on a stove you need to FIRST decide what the BTU consumption algorithm is. Different algorithms need different sensors. In my opinion, there are two ways to do it :
1) Input BTU of Fuel : Measure the amount of pellets fed into the burn-pot : easily done with probably good enough accuracy by monitoring and summing the auger ON times, in conjunction with the particular feed rate characteristics of each stove model, and the known BTU per pound of pellets. That feed rate can be easily measure, one-time, for any particular model : With the stove not burning, run the auger for 60 seconds and measure the pounds (or ounces) of pellets in the burn-pot. Concerning variabilty of the auger speed, I don't think you want to design the Stove Monitor for use on stoves with mechanical probles (like binding auger bearings.......).
2) Output BTU : Measure the BTU output of the stove by determining the CFM of the output air (stove into room), and determining the temperature rise of the output air, with two temp sensors. You probaly also need a humidity sensor as this (I think) has some effect on the calculation of the output BTUs. The CFM of the output air could be indirectly measured from the RPM of the room blower, but you will need to know the CFM versus RPM characteristic of each stove model (which is not easy to measure). The microprocessor would then calculate the output BTU from the RPM, air temp in, air temp out, and input air humidity. I really don't think this method is as practical or easy to implement as the one above.
Again, the ultimate Stove Monitor design would not require that the stove be opened-up to install RPM sensors, temperature sensors, current sensors.... You want a Stove Monitor that is just a small box that plugs into the stove line-cord and the wall outlet. I don't think stove owners want internal mods to their stove that would void the warrentee, and you, as installers should prefer an easy, plug-in, minimal labor installation.
They way I see it, before you just throw some sensors on a stove you need to FIRST decide what the BTU consumption algorithm is. Different algorithms need different sensors. In my opinion, there are two ways to do it :
1) Input BTU of Fuel : Measure the amount of pellets fed into the burn-pot : easily done with probably good enough accuracy by monitoring and summing the auger ON times, in conjunction with the particular feed rate characteristics of each stove model, and the known BTU per pound of pellets. That feed rate can be easily measure, one-time, for any particular model : With the stove not burning, run the auger for 60 seconds and measure the pounds (or ounces) of pellets in the burn-pot. Concerning variabilty of the auger speed, I don't think you want to design the Stove Monitor for use on stoves with mechanical probles (like binding auger bearings.......).
2) Output BTU : Measure the BTU output of the stove by determining the CFM of the output air (stove into room), and determining the temperature rise of the output air, with two temp sensors. You probaly also need a humidity sensor as this (I think) has some effect on the calculation of the output BTUs. The CFM of the output air could be indirectly measured from the RPM of the room blower, but you will need to know the CFM versus RPM characteristic of each stove model (which is not easy to measure). The microprocessor would then calculate the output BTU from the RPM, air temp in, air temp out, and input air humidity. I really don't think this method is as practical or easy to implement as the one above.
You may be on to something here. If all of the electrical monitoring could be done with the power cable i think the only other sensor that would be needed would be one hole drilled in the exhaust to monitor the stack temps. Wow that would be really simple and awesome at same time,
Sure, you would see a drop from 6amps or so down to 3amps, thus knowing proof of fire was achieved.
we dont really need to measure fuel as the manufactrurer has already rated the appliance for min and max
What do you want to "do" with the exhaust temp? That would only relate to the BTUs of the stove if you also measure the exhaust gas volume.
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