<p>I have looked over the 20 or so most expensive MOSFETs in that shop, and none are suitable.</p>

<p>It might be easier to go with a DC Solid State Relay rather than a bare MOSFET.</p>

<p>If you do want to go with a bare MOSFET instead, a TO-220 package MOSFET can dissipate around 1W without a heatsink, and around 3-4W with one. For 25A of current, that means the resistance of the MOSFET can be at most 1.6mΩ (without heatsink) or 5.6mΩ (with heatsink).</p>

<p>The <a href="http://www.infineon.com/dgdl/irlb3034pbf.pdf?fileId=5546d462533600a40153566027b22585" rel="nofollow">IRLB3034</a> might be suitable. It is readily available on ebay (for under $1 shipped). 195A, 40V and an Rds(on) of only 1.4mΩ. A caveat is that this resistance is specified at a gate voltage of 10V, whereas it is slightly higher at lower gate voltages (1.6mΩ-2.0mΩ at 4.5V). This is on the upper edge of what is acceptable without a heatsink, but should still work (junction to ambient resistance is 62C/W, so in the worst case of 2.0mΩ the temperature would get to 77C above ambient - the MOSFET is rated for operation up to 175C). With a heatsink it will definitely work well.</p>

<p>Note that the gate charge is much higher (10x) than that of the MOSFET used on RAMPs so you should use a low switching frequency.</p>

CC BY-SA 3.0
2016-09-15T17:54:56.153Z
Thanks man, I'll try and get the IRLB3034, I was considering an SSR, though I've heard the DC ones tend to wear out over time at high frequencies, not sure if it's true, but I figured sticking to a MOSFET would keep things simpler.
Snickers
CC BY-SA 3.0
2016-09-15T18:08:22.493Z
Will probably run wires to it off the board to mount the MOSFET to the aluminum case, and keep the frequency low.
Snickers
CC BY-SA 3.0
2016-09-22T10:41:06.647Z
Just got the IRLB3034 and it's awesome, doesn't heat up at all, I do have a small heatsync on it, but yeah. Great advice, thanks!
Snickers
CC BY-SA 3.0
2016-09-22T11:33:33.563Z
Awesome, good to hear! I wrote this entire post just going by datasheets, so I don't have any practical experience with this MOSFET. Glad it works for you.
Tom van der Zanden
CC BY-SA 3.0
2016-09-29T13:42:35.200Z
I wouldn't have expected you to buy and test a bunch yourself, but yeah works like a charm :), your reading docs skills came in handy.
For anyone else in South Africa that might be trying to get that component, I found it here
http://za.rs-online.com/web/p/products/6887204/
Snickers
CC BY-SA 3.0
2016-09-15T17:12:52.423Z
2016-09-15T18:18:44.073Z
2016-09-15T18:18:44.073Z
Tom van der Zanden
<p>I'm building a 3D printer from scratch (My first one, so yeah, tall order), so I'm buying all the parts separately, now one of the things I bought was a <strong>300x300 12v 25A Silicon heaterbed</strong> (Yeah, I know, should have gone for a higher voltage, but that's the only one I could get at the time)</p>

<p>I have a <strong>RAMPS 1.4</strong> board in all it's crappy MOSFET glory, so I tried giving my math skills a shot in trying to find a decent MOSFET that won't explode, though I'm still having issues deciding. And due to where I live, getting anything very specific is not the easiest thing to do.</p>

<p><strong>So can anyone recommend a MOSFET that I can use to switch 25A</strong> and mention if it will need a heatsink?</p>

<p>I live in <strong>South Africa</strong>, So one place that I can get them from is from <a href="http://shop.rabtron.co.za/catalog/mosfet-transistors-c-35_88_265.html?sort=5d&amp;page=1" rel="nofollow">RABTRON Electronincs</a></p>

<p>There are a couple other places, but I'd prefer to get them here if I can.</p>

<heated-bed>
12v 25A 300x300 Heater bed Mosfet
Snickers
# 12v 25A 300x300 Heater bed Mosfet

(Asked by: username_0 on 2016-09-15)

I'm building a 3D printer from scratch (My first one, so yeah, tall order), so I'm buying all the parts separately, now one of the things I bought was a **300x300 12v 25A Silicon heaterbed** (Yeah, I know, should have gone for a higher voltage, but that's the only one I could get at the time)

I have a **RAMPS 1.4** board in all it's crappy MOSFET glory, so I tried giving my math skills a shot in trying to find a decent MOSFET that won't explode, though I'm still having issues deciding. And due to where I live, getting anything very specific is not the easiest thing to do.

**So can anyone recommend a MOSFET that I can use to switch 25A** and mention if it will need a heatsink?

I live in **South Africa**, So one place that I can get them from is from [RABTRON Electronincs](http://shop.rabtron.co.za/catalog/mosfet-transistors-c-35_88_265.html?sort=5d&page=1)

There are a couple other places, but I'd prefer to get them here if I can.

**Tags:** heated-bed


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## 1 answers

### Answer by username_1 on 2016-09-15. Score: 2 | Accepted answer

I have looked over the 20 or so most expensive MOSFETs in that shop, and none are suitable.

It might be easier to go with a DC Solid State Relay rather than a bare MOSFET.

If you do want to go with a bare MOSFET instead, a TO-220 package MOSFET can dissipate around 1W without a heatsink, and around 3-4W with one. For 25A of current, that means the resistance of the MOSFET can be at most 1.6mΩ (without heatsink) or 5.6mΩ (with heatsink).

The [IRLB3034](http://www.infineon.com/dgdl/irlb3034pbf.pdf?fileId=5546d462533600a40153566027b22585) might be suitable. It is readily available on ebay (for under $1 shipped). 195A, 40V and an Rds(on) of only 1.4mΩ. A caveat is that this resistance is specified at a gate voltage of 10V, whereas it is slightly higher at lower gate voltages (1.6mΩ-2.0mΩ at 4.5V). This is on the upper edge of what is acceptable without a heatsink, but should still work (junction to ambient resistance is 62C/W, so in the worst case of 2.0mΩ the temperature would get to 77C above ambient - the MOSFET is rated for operation up to 175C). With a heatsink it will definitely work well.

Note that the gate charge is much higher (10x) than that of the MOSFET used on RAMPs so you should use a low switching frequency.

> **Comments:**
> **username_0**: Thanks man, I'll try and get the IRLB3034, I was considering an SSR, though I've heard the DC ones tend to wear out over time at high frequencies, not sure if it's true, but I figured sticking to a MOSFET would keep things simpler.  
> **username_0**: Will probably run wires to it off the board to mount the MOSFET to the aluminum case, and keep the frequency low.  
> **username_0**: Just got the IRLB3034 and it's awesome, doesn't heat up at all, I do have a small heatsync on it, but yeah. Great advice, thanks!  
> **username_1**: Awesome, good to hear! I wrote this entire post just going by datasheets, so I don't have any practical experience with this MOSFET. Glad it works for you.  
> **username_0**: I wouldn't have expected you to buy and test a bunch yourself, but yeah works like a charm :), your reading docs skills came in handy. For anyone else in South Africa that might be trying to get that component, I found it here http://za.rs-online.com/web/p/products/6887204/  

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