A RAMPS board is one of the most common boards used to control RepRap and other hobbyist 3D printers. RAMPS is essentially an Arduino shield that is capable of controlling stepper motor drivers, taking temperature readings, powering heating elements, and other tasks necessary for 3D printing.
Unfortunately, some of the boards on the market are of sub-par quality - the components and connectors used are not rated for the amount of current they're required to pass. For instance - a 12V heated bed can draw of 8A by itself. On some of the cheaper Chinese boards, the power MOSFETs aren't rated for nearly this current, and will get dangerously hot, which can pose a fire hazard. Similarly, the power connector the brings power to the board might not be rated for the upwards of 10A the board draws as a whole.
This Instructable covers the replacement of the MOSFET that powers the heated bed (labeled "2" in the picture) with one capable of handling the high current drawn, as well as replacing the power connector with 16 gauge wires soldered directly to the board (labeled "1" in the picture).
Components you will need:
- RAMPS Board
- 16 gauge stranded wire
- 4 pairs of (at least) 15A rated Anderson Power Poles (the ones shown are rated for up to 30A)
IRLB3034PBF Power MOSFET
(optional) Appropriately sized heat sink for MOSFET
Tool you will need:
- Solder Pump/Desoldering Braid
- Soldering Iron/Solder
Step 1: Removing the Power Connector
First, unclip the male end of the power connector, and set it aside.
Next, slowly work the female end of the clip (the one that's soldered to the board) up, to the point where you can slip your wire cutters underneath. Carefully cut the four leads, allowing the plastic bit to detach.
Now, you should only have the 4 leads which are soldered into the board.
Step 2: Desoldering the Power Leads
Using your wirecutters, carefully trim the leads down to size.
Using your soldering iron, heat up the solder around the remaining nubs, allowing you to work them free from their holes. Once they have been removed, it's time to remove the excess solder and clean up the holes.
With your soldering iron on one side of the board and your solder pump on the other, heat up the remaining solder until it is completely liquid. Pressing the solder pump flush against the board, use it to suck up the solder. What should remain is a perfectly clean hole, allowing you to put in new wires.
Repeat this process until all four holes are cleared, and then move onto the next step.
Step 3: Prepping Your Power Wires
Cut four short lengths of wire, two red and two black. Strip the ends so there's a workable amount of wire.
Step 4: Soldering the New Wires In
Now, carefully insert the wires back into the board as shown, making sure to match the original polarity (which should be indicated on the board). As you do this, make sure all of the strands go cleanly through the hole, and that none split off which could later cause a short circuit.
Using the soldering iron, solder the wires into place, making sure the insulation on the other side it firmly butted up against the board. Once all four wires are securely soldered, use your wire cutters to trim the excess wire off.
Now is a good time to make sure the wires are not shorting to each other before proceeding. This step is critical, as a short circuit in a high-current circuit poses a significant fire hazard.
Step 5: Replacing the MOSFET
Locate the MOSFET that powers the heated bed, as seen in the pictures. Make note of the orientation - installing the new MOSFET backwards could potentially fry your board.
Using your wire cutters, carefully cut the 3 leads connecting the MOSFET to the board. Following the same procedure as before, desolder the remaining leads and clear out the holes.
Matching the orientation of the original, carefully insert the new MOSFET into place. Solder into place, and trim the excess length of the leads as before.
Step 6: Installing the Connectors
Now we install the power poles that allow us to connect the RAMPS board to the 12V power supply.
First, strip the free ends of the four power wires as before.
Crimp on the connectors that came with your power poles, making sure that you have a secure fit. Slide the contacts into their housings according to the instructions that came with your chosen connectors. Double check to ensure they're completely seated and secure.
Step 7: Optional: Adding a Heatsink to the MOSFET
If you chose to use a heatsink with your MOSFET, now is the time to add it.
Sandwiching an electrically insulating slip between the MOSFET's body and the heatsink, attach the heatsink and secure properly. Make sure the metal body of the heatsink isn't touching any other components that may potentially cause a short circuit.
Now, your upgraded RAMPS board is ready to hook up and run a test print.
Good luck, and happy printing!