Sizing and placement of diodes, and general wiring, 5xc

Controllers Smoothie
1

My son and I have built the physical parts of our 3d printer, and are trying to install the smoothieboard 5x.

Our power supply is a Dell server supply, 12v 57A, we will be using xyz, 2 bowden extruders and a dual tip chimera hotend, 6 endstops, 4 to 6 25mm-40mm fans, a makerfarm 12x12 20A heat bed w heat bed relay…

A. I want to use P2_4, P2_6 small mosfets for the fans to enable software control , and will wire a direct, always on wire/switch for the Chimera hotend heatsink fan. …(I have the 1A diodes to install behind the mosfets as indicated i the fan section instructions)

B. I want to use 2 big mosfets, P2_5 and P2_7 to power the dual hotends on the e3D Chimera.

C. For the 12x12 20A heatbed we will be using a makerfarm heat bed relay (See makerfarm website) I’d like to connect the relay to P1_22 small mosfet. Will this work? Do I need to adjust the Hz output of P1_22 , to the relay board as described in:
(…SSRs have a low maximum frequency they can be switched at. You need to specify that frequency or Smoothie will drive it way too fast. In this example, the maximum frequency is 20Hz….)? I will also be adding an inline 25A fuse from the power supply to the heater bed as protection if there is a short.

D. We are stuck at the wiring layout where the instruction manual suggests directly running pos+ power to each of the mosfets. They also show that a diode needs to be the pos+ line (to left part of the image near the 12-24v inputs) . In all my reading I have found no real indication of the proper type or size for the diode they suggest be placed inline, at the VBB (a notation about the fan section shows 2 small 1a ones to install behind fan mosfets, but that is all).

Does there need to be ONE BIG MAIN diode installed near P1_22 as shown on the smoothieboard schematic, which protects the entire pos+ power line to all the mosfets? If so how do we size it? I may be overthinking this but reading about potential setup problems in the forum, it seemed that mosfets can easily burn out if not properly protected with diodes. I really don’t know anything about diodes and reading on the web has not helped me understand much better. Is a MAIN diode needed?? Is something like a # 1N2128A … 50v 60A Power silicone rectifier diode the right kind? do I need to worry about any voltage drop and try to adjust the output of the power supply?

E. Is there any sort of pictorial for dummies that would show real world wiring solutions?

http://www.makerfarm.com/index.php/catalog/product/gallery/id/297/image/652/

http://www.makerfarm.com/index.php/catalog/product/gallery/id/254/image/579/

http://chibidibidiwah.wdfiles.com/local--files/3d-printer-guide/smoothieboard-mosfets.png

http://media.digikey.com/Photos/GeneSiC%20Semiconductor/1N2130AR.JPG

thank you for your help

Imported from wikidot

2

Hey.

A. Make sure you add adequate diodes to the mosfets or the fans will burn them.

B. That sounds good

C. Yes, using a small mosfet will work, but you absolutely need a diode on there. The one in the picture you linked is extremely overpowered, just use a normal/smaller diode to protect the mosfet, see http://smoothieware.org/3d-printer-guide#toc18

C2. A mechanical relay is extremely noisy, you don’t want to use PWM, even at low frequencies, you want to use bang-bang
Simply uncomment these two lines : https://github.com/Smoothieware/Smoothieware/blob/edge/ConfigSamples/Smoothieboard/config#L174

D. An example of a good diode is indicated at http://smoothieware.org/3d-printer-guide#toc18 ( 1N4004 ). Only loads like fans, motors, selenoids and relays need to be protected by a diode, hotends do not need to be.

What do you mean by " directly running pos+ power to each of the mosfets. " ? You run + and - to the mosfet input, and then connect your hotend/fan/relay to the output.

E. There are so many different possible setups, there can’t really be one example. smoothieware.org/3d-printer-guide should have all the info you need.