FET Bed Heater Board

[Donziboy2]

Shrank it again and added a zener incase your VCC is higher then your VGS Max. I also added a small solder jumper so you can just jumper the Z1 if you dont need it.

I think if I make it much smaller I may compromise its ability to cool. I may add holes on each side of the Dpak Fet so that a heatsink can be screwed down, or lay the TO220 out so that it can be screwed down with a heatsink onto the board.

HeadBed PCB6.jpg

[Donziboy2]

Moved Q1 around to allow it to be bent down and secured to the PCB.

HeadBed PCB7.jpg

Added changes to first page.

Feels like im talking to myself sometimes...

[printbus]

Feels like im talking to myself sometimes...

Well, what you're basically doing is designing and building your own solid state relay. Most people would likely just purchase a commercially available SSR like discussed in other threads and go that route.

I don't have a link to provide as evidence, but this also isn't the first time someone has designed a MOSFET replacement for the mechanical relay board.

EDIT: Here's a post that introduces one attempt at a MOSFET replacement board: http://3dprintboard.com/showthread.p...ll=1#post38740

[Donziboy2]

Well, what you're basically doing is designing and building your own solid state relay. Most people would likely just purchase a commercially available SSR like discussed in other threads and go that route.

I don't have a link to provide as evidence, but this also isn't the first time someone has designed a MOSFET replacement for the mechanical relay board.

EDIT: Here's a post that introduces one attempt at a MOSFET replacement board: http://3dprintboard.com/showthread.p...ll=1#post38740

I have noticed that TechMasterJoe vanished a while back. I was looking at his post on ATX boards but he has not been on the forums in a while and all the images where not visible.

[printbus]

On the relay board, I recall maybe a couple of other threads where, in addition to providing a MOSFET switch, the person was adding other useful stuff onto their custom board. For example, adding an ABL servo or a Raspberry Pi Octoprint controller can leave you starved for 5V, so people were adding 5V regulators on their boards. I remember suggesting that providing 12V distribution and a few lightweight MOSFETs for things like fans or lights would be a good idea.

[Donziboy2]

On the relay board, I recall maybe a couple of other threads where, in addition to providing a MOSFET switch, the person was adding other useful stuff onto their custom board. For example, adding an ABL servo or a Raspberry Pi Octoprint controller can leave you starved for 5V, so people were adding 5V regulators on their boards. I remember suggesting that providing 12V distribution and a few lightweight MOSFETs for things like fans or lights would be a good idea.

Im actually thinking of following in TechMasterJoe footsteps and using an ATX power supply. For me atm its hard to guess what will and will not be useful, I just got the check today that will be going toward my 10" Pegasus, I have spent the last week or so just looking at things I plan to change from the start. The Mosfet Driver seems to be the easiest to tackle and I can see it being used for other things, I just ordered 3 boards and parts today. p.s. I can see some Chinese guy making and selling them for $3 in a few weeks time lol.

I will say the ATX power supply's nowadays can give more then 1A in standby on the 5V line, this can power all the small stuff until the controller decides it needs more power and turns the supply on. I also looked at reworking the Ramps 1.4, but thats a long battle for later.

[Donziboy2]

Got 2 boards assembled, boy its hard to tell just how small those resistor pads are until your trying to solder them. The worst ones are those attached to large planes, good thing I have a good soldering iron. Used the iron at work to do the large stuff, industrial irons are awesome lol.

[Dustin B]

Can only comment on the size of the mechanical relay. When I got a 12" piece of glass cut I had to get them to trim a notch in it to go around the relay. It sticks into the plane a full sized built plate needs by about an 1/16 to an 1/8th of an inch. I've since removed the relay and just jumpered the connection and will be using the SSR recommended in other threads for now.

[Donziboy2]

Did some testing at work, the D2Pak case gets to around 85C running at 0.7ohm load at 95% Duty Cycle (500Hz, 12V, 17Apk, 16.5A RMS).
I took the TO220 board and added a large heatsink , it had no problems at the same levels as the D2Pak and seemed fairly stable at around 70C case temp.

I need to increase the size of the PCB to add space for a larger HS/larger copper pad for the D2PAK.
I found reducing the switching frequency also lowered temperatures fairly nicely, about a 10-12C drop going from 500 to 250Hz.

edit..
Got another 10C drop going from 250 to 100Hz
At lower frequency's the two packages have close to the same case temperature, both are sitting happy around 50-55C.

[Donziboy2]

Slowly getting things setup. V2 of the board will be larger but I want to see how V1 holds up under load first.
V2 will be the same size as the stock relay on the right.