Transistor

Liz0905: what do you mean?

meaning a 10W heating element is ideally what you should be using.

a 50W - and five of them at that seems to be (to the experts) waay overkill.

i'm a newbie as well, so would also be thinking along your thoughts of "why can't it be used at all" - but i guess there are all sorts of considerations of "under-powering" an element meant to be used for higher outputs.

especially with transistors, where (from what i understand) they are best used in full-on (saturated) or off conditions - the in-between is where a lot of energy is wasted (as heat).

BabyGeezer: meaning a 10W heating element is ideally what you should be using.

a 50W - and five of them at that seems to be (to the experts) waay overkill.

i'm a newbie as well, so would also be thinking along your thoughts of "why can't it be used at all" - but i guess there are all sorts of considerations of "under-powering" an element meant to be used for higher outputs.

especially with transistors, where (from what i understand) they are best used in full-on (saturated) or off conditions - the in-between is where a lot of energy is wasted (as heat).

Ok thank you, but I can use the PMW pin to provide low voltage and thus supply enough current but on the other hand I will limit it to not reach the maximum power as well as the maximum temperatures, Correct me if I'm wrong

i think what all the seniors are saying is that the act of "under-powering" itself is the no-no. (due to inefficient heat dissipation running the device at half-speed)

Liz0905: ...I realized that in order to operate it I needed a transistor to provide a sufficiently high current.

you don't "need" the transistor to provide a sufficiently high current - you need it because the Arduino cannot handle it directly.

you should really look up how transistors work - i'm not quite sure if this applies to MOSFETs but to those "power transistors" (like the TIP120) - they can handle a range of current, as you are thinking - BUT the trade-off is that the power that does NOT get utilised, is wasted through heat - and if you are running the device at, say, even 20% (of it's maximum rating) - that means - you are dissipating 80% as ... ironically - heat !!

-cmiiw-

BabyGeezer: i think what all the seniors are saying is that the act of "under-powering" itself is the no-no. (due to inefficient heat dissipation running the device at half-speed) you don't "need" the transistor to provide a sufficiently high current - you need it because the Arduino cannot handle it directly.

you should really look up how transistors work - i'm not quite sure if this applies to MOSFETs but to those "power transistors" (like the TIP120) - they can handle a range of current, as you are thinking - BUT the trade-off is that the power that does NOT get utilised, is wasted through heat - and if you are running the device at, say, even 20% (of it's maximum rating) - that means - you are dissipating 80% as ... ironically - heat !!

-cmiiw-

OK I got it. Sorry for the ignorance. This is the first time I've been dealing with electronics and with Arduino, so I'm trying to understand. If so, if I find the same heating element but with a 10W power supply and use a transistor, should this solve my problem?

The short answer is yes a Mosfet will be able to switch the heater current on and off.

Terminology: Transistor could be a BJT (bipolar junction type) or it could be a MosFet (Metal oxide field effect). Both are considered transistors. However in this forum folks use the term "transistor" for a BJT and the term MosFet as... well a MosFet.

So a Mosfet is a type of transistor. When used to switch heaters on and off it could be helpful to think of it as a type of relay:

Relay: when the coil is energized (has voltage on it) the contacts are closed allowing the load to be ON.

Mosfet: When the Gate is energized 5V the drain allows current to flow from the drain to the source.

Hope this helps.

Liz0905: OK I got it. Sorry for the ignorance. This is the first time I've been dealing with electronics and with Arduino, so I'm trying to understand.

when one is learning, you shouldn't have to apologize for ignorance - the whole point about learning something is because we are ignorant to the facts surrounding the topic !

the folks here are very understanding and patient enough if you can respond to whatever further clarifications they request.

Liz0905: If so, if I find the same heating element but with a 10W power supply and use a transistor, should this solve my problem?

that's probably the other way around - you (ideally) want the 10W heating element.

just to clarify from your earlier post; this --> https://www.sparkfun.com/products/10213 does not "provide" the current - it controls it - the current comes from the power supply unit. (battery, wall-wart, etc.)

Liz0905: what do you mean?

250W is crazily high and will burn you. 1W will do nothing. So 10W is about right as a starting point for designing a warmer like this. Perhaps it should be 20W, perhaps not, you need to experiment. Remember a lot of soldering irons use 40W or less...

BabyGeezer: when one is learning, you shouldn't have to apologize for ignorance - the whole point about learning something is because we are ignorant to the facts surrounding the topic !

the folks here are very understanding and patient enough if you can respond to whatever further clarifications they request.

that's probably the other way around - you (ideally) want the 10W heating element.

just to clarify from your earlier post; this --> https://www.sparkfun.com/products/10213 does not "provide" the current - it controls it - the current comes from the power supply unit. (battery, wall-wart, etc.)

Thank you very much!

MarkT: 250W is crazily high and will burn you. 1W will do nothing. So 10W is about right as a starting point for designing a warmer like this. Perhaps it should be 20W, perhaps not, you need to experiment. Remember a lot of soldering irons use 40W or less...

Ok, thank you. so for my purpose I can use five heaters with a power of 10W. If I want to power an Arduino with an external battery, Will the next battery be enough for me

https://www.aliexpress.com/item/UNITEK-USB-9V-rechargeable-lithium-ion-battery-1200mAh-6F22-li-ion-cell-for-wireless-microphone-Guitar/32822609362.html

And would I need a transistor for each element? Suppose I use all the heaters simultaneously. Should I connect the heaters in a circuit? So that they are independent of each other

What are the gloves to be used for - I suspect that the insulation is as important as the heat source.

Will the next battery be enough for me

https://www.aliexpress.com/item/UNITEK-USB-9V-rechargeable-lithium-ion-battery-1200mAh-6F22-li-ion-cell-for-wireless-microphone-Guitar/32822609362.html

No.

so for my purpose I can use five heaters with a power of 10W.

That is 50W, this requires a current of about 5.5A. That looks way too much for that battery, even if it was not then at 1.2Ah it would last at the most 13 minuets and probably not more than 8 or 9 minuets in practice.

I would have thought 50W in a glove is way too much. What is the purpose of this glove? It makes a big difference. My 50W soldering iron is quite big, you can solder with a 25W iron or even a 15W one.

ChrisTenone: What are the gloves to be used for - I suspect that the insulation is as important as the heat source.

I want to measure the temperature of a finger and warm it if the temperature falls below a certain threshold

Grumpy_Mike: No. That is 50W, this requires a current of about 5.5A. That looks way too much for that battery, even if it was not then at 1.2Ah it would last at the most 13 minuets and probably not more than 8 or 9 minuets in practice.

I would have thought 50W in a glove is way too much. What is the purpose of this glove? It makes a big difference. My 50W soldering iron is quite big, you can solder with a 25W iron or even a 15W one.

ok i got it. what about those:

https://www.ebay.com/itm/PTC-heating-element-60-1-2-5W-12V-consistant-temperature-ceramic-Thermostatic-/152897933551

Hi,

The

https://www.ebay.com/itm/PTC-heating-element-60-1-2-5W-12V-consistant-temperature-ceramic-Thermostatic-/152897933551

is designed to always be at 60 °C, much too hot for skin.

I did some work with PTC heaters a few years back and they are great for constant temperature, however I've not seen any where the transition (control) temperature is low enough to be useful for contact with humans.

I've not been following closely but have you looked at flat silicone heaters?

JohnRob: Hi,

The is designed to always be at 60 °C, much too hot for skin.

I did some work with PTC heaters a few years back and they are great for constant temperature, however I've not seen any where the transition (control) temperature is low enough to be useful for contact with humans.

I've not been following closely but have you looked at flat silicone heaters?

Because I'm really new to the whole thing, I did not even know which way to look

HI,

This is not the place you would normally purchase a flat heater but it gives you an idea.

Silocone heaters

They could also be flat Kapton heaters.

For a practical understanding of watts and heat look for one of these "GE 4-Watt Nightlight Incandescent Light Bulb". You can hold it in your hand and get a "feel" of what 4 watts will be like.

I guess that these heated gloves might be for a motorcycle.

In which case there is no power supply problem.

Commercial products are freely available - why not investigate these?

Allan

allanhurst: I guess that these heated gloves might be for a motorcycle.

In which case there is no power supply problem.

Commercial products are freely available - why not investigate these?

Allan

The project is part of my studies and one of the goals is to create something that does not exist something that is exactly the same

create something that does not exist something that is exactly the same

??

They do exist, and have been developed over many years.

Do you have a much better approach?

A

allanhurst: ??

They do exist, and have been developed over many years.

Do you have a much better approach?

A

Of course they exist and I studied them, the goal is to use components that are not used in warming gloves available in the market