High Powered Silicone Heater

Hello Ladies and Gentleman,
I have looked into Mosfets, transistors and Relays so far but couldn’t find a suitable one for my needs. Mosfets don’t have enough power, relays(and Mosfets ) can’t support the heater either.

I want to keep the temperature of this plate under control using this heater::

I will probably be needing even bigger heater in the future. Can someone suggest me what to use to power it up? I need a really tight temperature range so I really don’t want to use mechanical relays.
Thanks you.

Hi,
What specs are you looking for.
Supply is 12V, 150W is 150/12= 12.5A

A mosfet will do the trick, it needs to be for safety, and usually are rated at over Vds 50V and Id 20A.

Tom… :slight_smile:
Others will probably give you more accurate info.

A 100A MOSFET is more what you want - the current rating is the current the device
can handle with infinite heatsink at absolute maximum power dissipation - totally
irrelevant.

You choose a MOSFET by the on-resistance, Vds(on), such that the power dissipation
is within the bounds of your heatsinking arrangement and the max Vds(on) is much
smaller than Vgs(on).

For a 12V 12.5A load I’d choose a device with <= 0.005 ohms on resistance, limiting
dissipation to under a watt - a medium/small heatsink will handle that nicely. Because of the
high power I’d choose a MOSFET driver chip so that PWM will be efficient and allow use of
a standard MOSFET (logic level MOSFETs are less abundant). The MIC442x family are
available in DIP and SOIC8 and will drive almost any size of MOSFET without the slightest
struggle (good decoupling is absolutely mandatory). There are many many other low-side
driver chips (literally 100’s of product lines).

These days its not too hard to find 20V and 30V MOSFETs down to 0.001 ohms on-resistance,
so a heatsink is not actually necessary.

Dissipation = I^2 x R = 12.5^2 * 0.005 = 0.78W
Vds(on) = I x R = 12.5 * 0.005 = 62 mV

Mosfets don’t have enough power

I suspect you haven’t found a real electronics stockist’s site! Try this one as an example:
http://uk.farnell.com/international-rectifier/auirf1324s-7p/mosfet-n-ch-24v-240a-d2pak-7p/dp/1864802

MarkT:
A 100A MOSFET is more what you want - the current rating is the current the device
can handle with infinite heatsink at absolute maximum power dissipation - totally
irrelevant.

You choose a MOSFET by the on-resistance, Vds(on), such that the power dissipation
is within the bounds of your heatsinking arrangement and the max Vds(on) is much
smaller than Vgs(on).

For a 12V 12.5A load I’d choose a device with <= 0.005 ohms on resistance, limiting
dissipation to under a watt - a medium/small heatsink will handle that nicely. Because of the
high power I’d choose a MOSFET driver chip so that PWM will be efficient and allow use of
a standard MOSFET (logic level MOSFETs are less abundant). The MIC442x family are
available in DIP and SOIC8 and will drive almost any size of MOSFET without the slightest
struggle (good decoupling is absolutely mandatory). There are many many other low-side
driver chips (literally 100’s of product lines).

These days its not too hard to find 20V and 30V MOSFETs down to 0.001 ohms on-resistance,
so a heatsink is not actually necessary.

Dissipation = I^2 x R = 12.5^2 * 0.005 = 0.78W
Vds(on) = I x R = 12.5 * 0.005 = 62 mV
I suspect you haven’t found a real electronics stockist’s site! Try this one as an example:
http://uk.farnell.com/international-rectifier/auirf1324s-7p/mosfet-n-ch-24v-240a-d2pak-7p/dp/1864802

I kinda understand what you are trying to say but not really. Can you please explain what each of those things mean like you explain to a 5 year old? I am a biochemistry student so I will use this for keeping my cells at 37C while I do some other tests on the cells. Anyways I still believe I don’t understand how to choose a Mosfet. Also a link for a US website would be really appreciated. Thanks a lot

MarkT:
A 100A MOSFET is more what you want - the current rating is the current the device
can handle with infinite heatsink at absolute maximum power dissipation - totally
irrelevant.

You choose a MOSFET by the on-resistance, Vds(on), such that the power dissipation
is within the bounds of your heatsinking arrangement and the max Vds(on) is much
smaller than Vgs(on).

For a 12V 12.5A load I’d choose a device with <= 0.005 ohms on resistance, limiting
dissipation to under a watt - a medium/small heatsink will handle that nicely. Because of the
high power I’d choose a MOSFET driver chip so that PWM will be efficient and allow use of
a standard MOSFET (logic level MOSFETs are less abundant). The MIC442x family are
available in DIP and SOIC8 and will drive almost any size of MOSFET without the slightest
struggle (good decoupling is absolutely mandatory). There are many many other low-side
driver chips (literally 100’s of product lines).

These days its not too hard to find 20V and 30V MOSFETs down to 0.001 ohms on-resistance,
so a heatsink is not actually necessary.

Dissipation = I^2 x R = 12.5^2 * 0.005 = 0.78W
Vds(on) = I x R = 12.5 * 0.005 = 62 mV
I suspect you haven’t found a real electronics stockist’s site! Try this one as an example:
http://uk.farnell.com/international-rectifier/auirf1324s-7p/mosfet-n-ch-24v-240a-d2pak-7p/dp/1864802

Also the heater is 24v not 12 v :slight_smile:

Why are you asking on the Arduino forum? 37c is not an unusual temperature. There must be a hundred cheap thermostats which will do this.

MorganS: Why are you asking on the Arduino forum? 37c is not an unusual temperature. There must be a hundred cheap thermostats which will do this.

Because I want to build it myself using temp sensors and heater??????? Isn't this DIY and hacking community?

Might be easier to use a 120 volt A/C pad, then you could use a SSR to control it, like this:

http://www.aliexpress.com/popular/sharp-s202s02.html

I use one on my "cat house" heater, works very well.

Farnell == Element 14. There are probably > 10,000 MOSFETs there or at Digikey or Mouser - they have parametric search tools on their websites. They will all have open-frame 12V power supplies too...