Low Power/Temp Heat Gun

Hi Louis @inst-tech, @huckohio, @frogandtoad,

re: I found this Watts to heat calculator https://www.omnicalculator.com/physics/watts-to-heat

Thanks for that ... it will be doing the same calculation as I alluded to ... which is a rough guide when you are directly heating a known mass of a given material in a short period of time, so that the heat loss to environment is small.

As you say, I don't think it is applicable to @huckohio 's question, which is why I didn't detail how to calculate it fully. Obviously, a quick calculator is easier to do!

Best wishes, Dave

@davee @frogandtoad

Dave, I am upgrading a system I put into my wife's rabbit shed last year to control fans in the summer and heat lamps/water bowl heater in the winter (pictures of existing system added to thread).  I do not need precision temp measurements, just close enough.  I am testing the new design and was looking for a method to apply heat to the temperature sensor to simulate summer temps (70-80 degrees) to make sure the fans turn on and off at the desired set points.  I need relatively low temps, so the easiest approach was to heat up my finger and touch the sensor.  My heat gun applies too much temp to fast and my original questions was if there was a better approach than rubbing my finger across my jeans.  I am not a fan of tea, so I went with the hair dryer.  I found a child's hair dryer on Amazon that was only 1000W with two fan speeds.  I think slowly applying the heat from the gun will work.

Thanks for the reply!

@frogandtoad I will look for Bill's video.  Thanks.

@huckohio  Great looking project..it looks like you may have have some industrial or comercial electrical experience by the way your wiring hookup looks.. I was an industrial instrumentation/electrical tech for over 45 years, plus 4 years as an electronics tech in the Navy..( Electronic warfare systems (EWS, D.A.S.H, Asroc)

Good luck with your on-going project..

regards,

LouisR

@inst-tech Thank you, but I have no industrial or commercial electrical experience.  I did use wax cord to bundle wires when I was in the Air Force (comm maintenance), but mostly I try and keep the project wiring neat for testing/troubleshooting.

Posted by: @huckohio

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@inst-tech Thank you, but I have no industrial or commercial electrical experience.  I did use wax cord to bundle wires when I was in the Air Force (comm maintenance), but mostly I try and keep the project wiring neat for testing/troubleshooting.

Indeed, neat wiring hookups makes it much easier to troubleshoot, and makes for a good looking project.

regards,

LouisR

@davee

Posted by: @davee

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Hi @frogandtoad,

Re: Perhaps someone like @davee can provide the formula to convert voltage/watts to heat?

Sadly, no such 'general formula' exists.

If you apply a source of heat to an object, then in 'real' circumstances, some of the heat energy will be absorbed by the object, causing its temperature to increase, and some of the heat energy will be dissipated into the environment.

For a specific amount particular material, it is possible to look up the number of Joules needed to raise its temperature by 1 °Celsius ... and hence use that proportionality for a particular situation ...

   e.g. 1 g of liquid water at about 20°Celsius requires 4.186 Joules to heat it by 1 °Celsius

        Noting that a 1 Watt power flow is equal to 1 Joule per second...

The value of 4.186 J/g°C is only an 'average' measured figure for water at a 'standard temperature' ... another material will have a different value.

And, this assumes no heat is lost to the surroundings ... which is an impossibility, although insulation, etc. may minimise the heat loss. Clearly it depends on the physical situation which is usually complex to determine and it is not a simple formula.

Furthermore, if the water changes state as a result of the heating e.g. ice <-> liquid or liquid <-> vapour, then a large amount of energy is involved in those transitions.

[snip]

Thank's Dave,

I didn't think it was easy, but I had seen some kind of formula in one of my old electronic books, a long time ago, so thought you might have a good handle on it, much more so than me 🙂

I see that @inst-tech (thanks), has come across a formula to which I also searched for, and found one pretty identical here. 

Thank's for your explanation.

Posted by: @frogandtoad

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@davee

Posted by: @davee

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Hi @frogandtoad,

Re: Perhaps someone like @davee can provide the formula to convert voltage/watts to heat?

Sadly, no such 'general formula' exists.

If you apply a source of heat to an object, then in 'real' circumstances, some of the heat energy will be absorbed by the object, causing its temperature to increase, and some of the heat energy will be dissipated into the environment.

For a specific amount particular material, it is possible to look up the number of Joules needed to raise its temperature by 1 °Celsius ... and hence use that proportionality for a particular situation ...

   e.g. 1 g of liquid water at about 20°Celsius requires 4.186 Joules to heat it by 1 °Celsius

        Noting that a 1 Watt power flow is equal to 1 Joule per second...

The value of 4.186 J/g°C is only an 'average' measured figure for water at a 'standard temperature' ... another material will have a different value.

And, this assumes no heat is lost to the surroundings ... which is an impossibility, although insulation, etc. may minimise the heat loss. Clearly it depends on the physical situation which is usually complex to determine and it is not a simple formula.

Furthermore, if the water changes state as a result of the heating e.g. ice <-> liquid or liquid <-> vapour, then a large amount of energy is involved in those transitions.

[snip]

Thank's Dave,

I didn't think it was easy, but I had seen some kind of formula in one of my old electronic books, a long time ago, so thought you might have a good handle on it, much more so than me 🙂

I see that @inst-tech (thanks), has come across a formula to which I also searched for, and found one pretty identical here. 

Thank's for your explanation.

 

@davee, @frogandtoad,

Indeed, most of these formulas require more specific information then what most of us are prepared to give...lol

But, understanding that in most cases, close is close enough as we are not trying to build a space ship..

I think the low temperature heat gun will probably suffice for what @huckohio is trying to accomplish.

regards,

LouisR

Hi @inst-tech,

   Of course, it is always difficult to know what level to pitch an answer .... sometimes the person is looking for a pragmatic fix to a problem .. other times they are trying to understand some of the details.

I confess, I wouldn't have suggested the use of a heat gun to check out whether a system will respond at a particular temperature ... but please bear in mind, the only heat gun I have is usually used for stripping paint, so if I used it a little too vigourously on a sensor with a twisted wire pair connection, it would probably melt the wire insulation and short the wires!

But I can see 'wafting' it in the general direction could be used a simple test.

Best wishes all,

Dave

Posted by: @davee

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Hi @inst-tech,

   Of course, it is always difficult to know what level to pitch an answer .... sometimes the person is looking for a pragmatic fix to a problem .. other times they are trying to understand some of the details.

I confess, I wouldn't have suggested the use of a heat gun to check out whether a system will respond at a particular temperature ... but please bear in mind, the only heat gun I have is usually used for stripping paint, so if I used it a little too vigourously on a sensor with a twisted wire pair connection, it would probably melt the wire insulation and short the wires!

But I can see 'wafting' it in the general direction could be used a simple test.

Best wishes all,

Dave

Hi @davee,

Yep..I can understand how that could be a problem in your case...lol

BTW: there's nothing wrong with giving your detailed explanations to a query from an OP..we are not mind readers after all, or at least I'm not..haha  enjoy reading your well though out comments..

The heat gun I use is an old 2 speed hair dryer that I use for heat shrinking..it's a Clairol "Son of a Gun" model, 1250 watts, 2 heat setting, low, and high, independent air switch off, low, med, and high settings.. works great!

I like the fact that I can turn the air off if I need to, or turn it to the low setting..this works good for heat shrinking so I don't over heat the components.

One thing that I did learn working as an industrial tech for 49 years is most of the time, a simple solution will suffice..My engineer colleagues often designed in complex systems that only caused us headaches when trying to troubleshoot and fix the problems they created.. So I just stick with the K.I.S.S. system... LOL

regards,

LouisR

Hi @inst-tech,

   Whilst I confess to probably being closer to the 'engineer colleagues' group in a past life, part of the issue is recognising what is required for the particular situation.

I also like KISS ... my grey cell can't handle anything beyond 'simple'!

Sadly, the 'simple' answer is not always the 'simplest' to spot.

-----

Consider the situation of designing and manufacturing a mass production electronic widget (not for a safety critical application).

The first few widgets built to a new design are likely to be subjected to a barrage of tests to ensure that the design meets all the required specifications, usually to within specified tolerances, maybe applying extended time tests to ensure it does fail prematurely, and so on...

By contrast, the majority of subsequent widgets built will be intended for delivery to customers, and may only receive 'cursory' testing to ensure they have been constructed correctly, assuming (with justification) that design and production controls were sufficient to guarantee a very high percentage of units passing the cursory tests would also meet the full expectations.

So when we make a unit for our project, are we aiming at the pre-production situation or the volume production situation?

Probably neither, but I think it is useful to briefly consider the extremes before deciding on a reasonable compromise.

Best wishes, Dave

Posted by: @davee

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Hi @inst-tech,

   Of course, it is always difficult to know what level to pitch an answer .... sometimes the person is looking for a pragmatic fix to a problem .. other times they are trying to understand some of the details.

I confess, I wouldn't have suggested the use of a heat gun to check out whether a system will respond at a particular temperature ... but please bear in mind, the only heat gun I have is usually used for stripping paint, so if I used it a little too vigourously on a sensor with a twisted wire pair connection, it would probably melt the wire insulation and short the wires!

But I can see 'wafting' it in the general direction could be used a simple test.

Best wishes all,

Dave

@inst-tech, @davee

What I like about the forum is the variety of answers, from the simple to complex.  While I appreciated the complexity of the engineering solution, the hair dryer suggestion was the perfect suggestion given the simple testing I was trying to achieve.  I was able to find a hair dryer for children that was only 1000W that also had a "cool" button to reduce the temp.  I was able to wave the hair dryer above the sensor to reach the required temp range.  Besides, the engineering level answer may not be what I needed, but it doesn't mean it won't help others.  Thanks again. 

@huckohio 3rd response https://forum.dronebotworkshop.com/postid/35448/

Posted by: @davee

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Hi @inst-tech,

   Whilst I confess to probably being closer to the 'engineer colleagues' group in a past life, part of the issue is recognising what is required for the particular situation.

I also like KISS ... my grey cell can't handle anything beyond 'simple'!

Sadly, the 'simple' answer is not always the 'simplest' to spot.

-----

Consider the situation of designing and manufacturing a mass production electronic widget (not for a safety critical application).

The first few widgets built to a new design are likely to be subjected to a barrage of tests to ensure that the design meets all the required specifications, usually to within specified tolerances, maybe applying extended time tests to ensure it does fail prematurely, and so on...

By contrast, the majority of subsequent widgets built will be intended for delivery to customers, and may only receive 'cursory' testing to ensure they have been constructed correctly, assuming (with justification) that design and production controls were sufficient to guarantee a very high percentage of units passing the cursory tests would also meet the full expectations.

So when we make a unit for our project, are we aiming at the pre-production situation or the volume production situation?

Probably neither, but I think it is useful to briefly consider the extremes before deciding on a reasonable compromise.

Best wishes, Dave

@davee. Indeed..I agree with your assessment completely..For the most part, we are usually just trying to make the projects work in some satisfactory way, but then , In my case, the "creeping elegance" swoops in and the project takes on a life of it's own...lol

As far as the "simple answer" goes, Using the tried and true methods of back to the basics, and the old "black box theory" of input and outputs analysis has served me well in sorting out complex problems..but your right, the easy, or simple solutions are not always easy to see. Many years ago, back in the mid 70's I think, I came up with a touch lamp that used the capacitance of a JFET , a 555 timer, and a J-K FF. It took me weeks to finally get it right, lol.. but in the end it worked fine..You didn't even have touch it as it was sensitive enough to just wave your hand with in 2 or 3 inches, and it turn on or off depending on what state is was in. The 555 was  a one-shot, set at one second RC time delay for each trigger pulse to the J-K FF that worked as a latch. If you held your hand near long enough, it would pulse the output at one sec intervals..The transistor driver was driving a 12 v mini low power bulb, housed in an old train signal lantern, and powered with a wall wart 12 vdc power pack. I hung it in the corner of the living room and it was a source of amusement and wonder for all my friend, family, and guess to came to visit..I called it the "magic lamp", for in those day, as you can probably remember, that would of been a novelty as electronics were still in the low to intermediate stage ( less than 600 gate)..and to my knowledge, there was nothing on the consumer market like it..Should have patented it... but it was just for fun...lol

Regards,

LouisR

Posted by: @huckohio

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Posted by: @davee

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Hi @inst-tech,

   Of course, it is always difficult to know what level to pitch an answer .... sometimes the person is looking for a pragmatic fix to a problem .. other times they are trying to understand some of the details.

I confess, I wouldn't have suggested the use of a heat gun to check out whether a system will respond at a particular temperature ... but please bear in mind, the only heat gun I have is usually used for stripping paint, so if I used it a little too vigourously on a sensor with a twisted wire pair connection, it would probably melt the wire insulation and short the wires!

But I can see 'wafting' it in the general direction could be used a simple test.

Best wishes all,

Dave

@inst-tech, @davee

What I like about the forum is the variety of answers, from the simple to complex.  While I appreciated the complexity of the engineering solution, the hair dryer suggestion was the perfect suggestion given the simple testing I was trying to achieve.  I was able to find a hair dryer for children that was only 1000W that also had a "cool" button to reduce the temp.  I was able to wave the hair dryer above the sensor to reach the required temp range.  Besides, the engineering level answer may not be what I needed, but it doesn't mean it won't help others.  Thanks again. 

I like the hair dryer option too, but how about a simple light bulb next to the sensor, controlled via a simple POT? 😀 - At least you don't have to hold it 😉

Cheers