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Hey thanks for reminding me about PID controllers. I took controls last semester, but I need to brush up a little bit on it. PID would be a closed feedback loop, where one measures the output with respect to a desirable output, and make changes to get desirable output correct? I did not know there was an Arduino PID library. I will look into it, but since you have implemented the library, how does it work? Thank you!!!
It seems that the battery must be fairly large and very heavy to produce the power you want for the duration you want. A rechargeable battery? You probably need a 12V motorcycle battery and a cart to carry it in.
The Temperature of the resistor May get to 60 degrees by Itself,
But when Sinking this heat to another Object, it is not likely to get anywhere near that temperature.
Maybe not even a 1 degree increase.
What are you attempting to heat with these resistors?
Just because the resistor can obtain 60 degrees, At What Ambient Temperature is this?
Are you putting INSULATION around the heater and the Object being Heated to prevent heat loss?
And What is the Mass of this object?
All these will greatly affect the Actual Heating temperature.
Good afternoon Mr Al, I hope all is well. Sorry for the late response, I was looking for some batteries to buy on ebay. I purchased 4 high drain batteries at a rating of 3.7V 2500 mAh each. I was thinking on configuring them two groups in parallel, with each group having two batteries in series. Giving us 7.4V and 5000mAh. For simplicity, I think I am going to experiment with having only 2 heating elements per group in our circuit. I am guessing the ambient temperature would be the human body, which would be exposed to the Winter weather (ranging from 0 C to -37 C here in Ottawa) . Heating elements will be protected from the weather by being placed inside the jacket beside the insulation material. And yes, I heating element of approximately 120 mm length 15 mm wide each needs 1.5A to heat up to 60 C. They are also flat like a piece of tape.
Now I am looking to buy the right type of MOSFET to run the experiment. I am guessing it would be an N-type MOSFET that does not get too hot and has small resistance. Would you know anything about MOSFETs?
I am attempting to heat the human body in Winter where temperatures can be as low as -37 C. I purchased 4 high drain batteries at a rating of 3.7V 2500 mAh each. I was thinking on configuring them two groups in parallel, with each group having two batteries in series. Giving us 7.4V and 5000mAh. Now I am looking to buy the right type of MOSFET to run the experiment of controlling the circuit through PWM . I am guessing it would be an N-type MOSFET that does not get too hot and has small resistance. Would you know anything about MOSFETs?
I am attempting to heat the human body in Winter where temperatures can be as low as -37 C. I purchased 4 high drain batteries at a rating of 3.7V 2500 mAh each. I was thinking on configuring them two groups in parallel, with each group having two batteries in series. Giving us 7.4V and 5000mAh. Now I am looking to buy the right type of MOSFET to run the experiment of controlling the circuit through PWM . I am guessing it would be an N-type MOSFET that does not get too hot and has small resistance. Would you know anything about MOSFETs?
You will NEVER heat a Whole Human Body with 36 watts.
You Might heat a Small Portion of the body, such as One Leg, if you can spread out this resistance to Cover the Entire Leg.
The Problem is Not Heating the body.
The Problem is STOPPING HEAT LOSS.
3.7V is the average voltage of a discharging Lithium rechargeable battery cell. It is ruined if it is discharged to below about 3.2V so you need a circuit to detect the voltage of each cell and disconnect the load when one cell drops below 3.2V.
Of course your battery needs a charger designed for a Lithium battery. Each cell is 4.2V when fully charged and when the charging current has dropped.
Another problem is no-name-brand Lithium 18650 battery cells from ebay. Some are fakes:
Good afternoon Mr Al, I hope all is well. Sorry for the late response, I was looking for some batteries to buy on ebay. I purchased 4 high drain batteries at a rating of 3.7V 2500 mAh each. I was thinking on configuring them two groups in parallel, with each group having two batteries in series. Giving us 7.4V and 5000mAh. For simplicity, I think I am going to experiment with having only 2 heating elements per group in our circuit. I am guessing the ambient temperature would be the human body, which would be exposed to the Winter weather (ranging from 0 C to -37 C here in Ottawa) . Heating elements will be protected from the weather by being placed inside the jacket beside the insulation material. And yes, I heating element of approximately 120 mm length 15 mm wide each needs 1.5A to heat up to 60 C. They are also flat like a piece of tape.
Now I am looking to buy the right type of MOSFET to run the experiment. I am guessing it would be an N-type MOSFET that does not get too hot and has small resistance. Would you know anything about MOSFETs?
Oh yes, very important you MUST get "logic level" MOSFETs, not the regular mosfets. Regular mosfets do not turn on with Arduino type logic output which is around +5v max. The logic level mosfets will have gate voltage turn on of around 2.5v or something like that.
I could post an example mosfet if you like.
The regular mosfets do not turn on all the way until maybe 10v, which is too high for most microcontroller logic.
The data sheet tells you this information.
You also want at least a couple amps, but the higher rating usually comes with low Rdson too.
3.7V is the average voltage of a discharging Lithium rechargeable battery cell. It is ruined if it is discharged to below about 3.2V so you need a circuit to detect the voltage of each cell and disconnect the load when one cell drops below 3.2V.
Of course your battery needs a charger designed for a Lithium battery. Each cell is 4.2V when fully charged and when the charging current has dropped.
Another problem is no-name-brand Lithium 18650 battery cells from ebay. Some are fakes:
One of the things that matters most in heating is the heat loss. If you have zero heat loss, you can heat the entire earth to a million degrees C with a candle flame. So one of the main goals is to reduce heat loss by using good insulation between the heater and the ambient air. Doing that means much less power requirement. Think, "space suit"
Agreed.
One thing I can think of that would be a good application for an electric warmer, a fork lift driver drives from a heated environment to outside in he cold on a regular basis, this can and has where I've worked in the past cause health issues.
A temp sensor on the clothing could warm the wearer in the cold and not in the warm, and not being a super thick clothing item will not be too warm in a heated building, or cumbersome to wear.
I think we are over examining things here, this is an project for this person to prove he understands basic product design and development.
Cmore have a look at this device, its a boost converter than can switch 3a and has a minimum supply of 3v, this chip has been digitally controlled on a few projects on the net. https://www.ti.com.cn/cn/lit/ds/symlink/lm2577.pdf
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I think we are over examining things here, this is an project for this person to prove he understands basic product design and development.
Cmore have a look at this device, its a boost converter than can switch 3a and has a minimum supply of 3v, this chip has been digitally controlled on a few projects on the net.
I hope my USB coffee warmer wasn't a discourager. I more believe in Dr, Peppers statement.
So,, when I go outside to shovel show: Ski goggles, An entire head/neck mask and a hat. High boots. Usually a Kevlar glove over a disposable vinyl one. A scarf.
Clothing that can be layered and my all means keep the water out. The weird stuff cam from a tact store. I'm out for no more than an hour or so at a time.
Keep dry, layer clothing, prevent heat loss (Head particularly). A layer is body - air - clothing - air - clothing - ambient Those air spaces insulate.
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Put that on Funny Images thread too AG ?
