I have an ultimate goal - to warm up bottle of milk to 37C (+-1C) in 5-15 minutes, either indicate that it's ready or keep it to SP until I turn it off. I've bought and eventually returned few bottle warmers from Amazon. They are simply not able to do what I want. Most of them doesn't have current temperature display and just warming up leaving measurements to user. The others have display, but overshooting a lot. So it looks like the task is not so trivial, since there is no commercial product capable of doing this.
My post here is to determine how feasible it is to implement such device based on heater basin from one of commercial products(have Avent SCF355 which I haven't returned yet). My researches in finding any existing project close to that device are failed.
The input variables are basin initial temperature, bottle type(glass, plastic), initial water temperature in bottle, room temperature, if I didn't miss anything.
Having all that variables, is it possible to achieve mentioned above, using DS18B20 and some PID library?
Yes, your project is entirely feasible. You said it already there are commercial products which do what you describe but you are not happy with their accuracy.
You will be able to be more accurate then those products in my opionion using that sensor and library.
It still would depend on the volume of the bottle fluid, surface area, the heat transfer, the initial temp of the bottle fluid, and probably several other factors. When you place a time limit on the transfer, it introduces other factors.
There may not be a product out there because there isn't any easy and consistent way to do it.
This is essentially impossible, you would need a submerged sensor into the milk, and your not gonna be able to do that and keep it sanitary.
As there is different bottle types there is different milk and formula types, and ready to feed and powder formula are different as well, making math or inferred temps really hard.
If you made a special bottle with a sensor built in that is washable could make this possible.
Off the wall, who-knows-if-it'll-work idea; use an infrared thermometer which has an output signal and aim it at the side of the bottle. Of course, you'd have to do some tests to get numbers to compensate for glass/plastic, room temp., etc.
Maybe include a magnetic stirrer so the temperature doesn't stratify.
If you want the opinion of a professional scientist with a 3-year-old: Use. Your. Microwave!
There is literally no better way to warm up a fluid. It's what an induction stove is to metal pot. I know that people claim that it is harmful. We read that too when our son was born, and in the state of postnatal stupidity, we followed the advice. 5-15min is an ETERNITY, 3 o'clock at night, when your 4 month old is hungry and crying. You can have it in 20 seconds. It is easy.
Regarding concerns:
Remember the 80s and early 90s, when people claimed microwaved food gave you cancer? You know how that is nonsense? Somehow the milk part stuck, but there is probably nothing more esoteric and irrational than the baby market.
Yes, there is a study. I read the paper and it is the most terrible methodological bullcrap I have ever read. It is pure nonsense that should never have passed review.
"Microwaves heat unevenly." That's true to a point. But we are talking about a fluid. It is trivial to turn the bottle around a few times (don't shake to much, it gets air in there) and everything will be absolutely evenly mixed. On the other hand, the overall energy going in is pretty exact. Get your time for a given amount once and the resulting temperature will be reasonably the same each time. Caveat: Do not try to calculate other amounts, test them. And be careful with other microwaves, they may be different. In any case, it is trivial to test. Have a microwave with a digital timer. Or put a clock next to it.
Anything else can easily become dangerous. As I said, 5-15min is an eternity. When I investigated on this, I read about postnatal hospital wards that kept their milk ready at 36-37 degree. They basically kept a perfectly tempered bacteria breeding ground in their kitchen to feed it to sick newborns. It's crazy.
If you insist on building something yourself that is reasonably fast, you will need something that stirs and probes the temperature. And you need a heat source that can be switched of fast, since it needs to be overheated to transfer energy fast enough. The other option is to increase contact surface, like sending your milk through a thin pipe, but that has massive hygiene issues.
I would probably go for a for a magnet stirrer, a infrared thermometer pointed to the surface and induction heating of the container.
Delta_G:
The problem with those things is that they can't actually measure the temperature of the milk. They at best just measure the temp of the outside of the bottle and depending on the type of bottle it may be slightly different on the outside to get the milk inside right. If you really want to beat them, then get a temp sensor that can be submerged in the milk itself.
Now it getting more clear for me that the temperature from basin is not immediately transferred to the milk. Submerged sensor is not an option unfortunately.
tinman13kup:
It still would depend on the volume of the bottle fluid, surface area, the heat transfer, the initial temp of the bottle fluid, and probably several other factors. When you place a time limit on the transfer, it introduces other factors.
There may not be a product out there because there isn't any easy and consistent way to do it.
cfherrman:
This is essentially impossible, you would need a submerged sensor into the milk, and your not gonna be able to do that and keep it sanitary.
As there is different bottle types there is different milk and formula types, and ready to feed and powder formula are different as well, making math or inferred temps really hard.
If you made a special bottle with a sensor built in that is washable could make this possible.
Well, I'm not going to make some universal product for all kinds of things, but only crafted to my needs.
dougp:
Off the wall, who-knows-if-it'll-work idea; use an infrared thermometer which has an output signal and aim it at the side of the bottle. Of course, you'd have to do some tests to get numbers to compensate for glass/plastic, room temp., etc.
Maybe include a magnetic stirrer so the temperature doesn't stratify.
.02
Pricey solution I wonder if there is anything laser based around 50€, which can sense through the plastic bottle.
Alternatively, having a digital kettle which will maintain 37C would work for me. Currently I have Russell Hobbs digital kettle, but it is not very accurate and set temperature is discrete by 5C (35, 40, etc), also the overshoot is too high.
Question - how accurate result I can achieve by modding this kettle and putting my own sensor and board? What would be the best overshoot if I just start from 18-20C to set point 37C, can I achieve it? Would like to evaluate if it's worth to start the hacking it.
pashkatarakashka:
But how exactly microwave is able to give me 37C ? Mine only has power and timing control, not temperature.
It's all about consistency. If the milk is always the same temp from the refrigerator, and you always use the same volume, and microwave at the same power level and time, you will achieve consistent heating results.
That means a little trial and error to establish the time required to heat to the desired temp and then use that number. For him, it was 15sec.
tinman13kup:
It's all about consistency. If the milk is always the same temp from the refrigerator, and you always use the same volume, and microwave at the same power level and time, you will achieve consistent heating results.
That means a little trial and error to establish the time required to heat to the desired temp and then use that number. For him, it was 15sec.
So it's like doing mental PID Not so practical in the middle of night.
pashkatarakashka:
So it's like doing mental PID Not so practical in the middle of night.
No, it is not. There is no closed loop involved. 160ml for 45s consistently gives milk at the temp our 3 year old likes it in the evening.
It takes about 5min to find the right time for your usual amount in your microwave. After that, it is fill, set time turn around, turn back, stir, done.
With my first two kids I microwaved a coffee cup of water and heated the bottle that way, my current 5 mo old I'm using a Dr browns bottle heater that heats up water to steam and the steam heats up the bottle. With some testing I believe you could infer bottle temp by measuring the steam temp and duration at the top. I don't think this would be a easy task.
I wonder if there is anything laser based around 50€, which can sense through the plastic bottle.