Transistor

[MarkT]

10W is a starting point.

[Liz0905]

Then you should not do the project.

Are you serious?! there is no option to use it?!

[Liz0905]

10W is a starting point.

what do you mean?

[ChrisTenone]

Here's the kind of heater you want for gloves: https://www.sparkfun.com/products/11288

[Liz0905]

Here's the kind of heater you want for gloves: https://www.sparkfun.com/products/11288

i have to use a separate heater for each finger

[BabyGeezer]

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).

[Liz0905]

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

[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)

...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-

[Liz0905]

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?

[JohnRob]

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.

[BabyGeezer]

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.

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.)

[MarkT]

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...

[Liz0905]

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!

[Liz0905]

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

[ChrisTenone]

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