If these instructions don’t match what you received in your kit, please see the Safety Cutoff Rev. C instructions. The MakerBot Safety Cutoff Kit is a small kit designed to cut power to the heater in case of a catastrophic failure. Contents of the Kit- 1 x Green Printed Circuit Board (PCB) with white printing on top (“Rev D” indicated)
- 2 x 1K Ω resistor, 1/6W (small, brown-black-red-gold bands) [R1] [R5]
- 1 x 10K Ω resistor, 1/6W (small, brown-black-orange-gold bands) [R2]
- 1 x 6.8K Ω resistor, 1/6W (small, blue-gray-red-gold bands) [R3]
- 1 x 120 Ω resistor, 2W (large, brown-red-brown-gold bands) [R4]
- 1 x black relay with 8 pins
- 3 x green, 2 pin terminal blocks
- 1 x red LED
- 1 x green LED
- 1 x black, SL type 4 pin connector
- 1 x MakerBot Endstop Cable
- 1 x Large Diode
Assembly InstructionsRemove the tape from the ends of the components. Orient the board with the white printing on top and two large corner holes toward you. You should see a a pair of circles in the top middle of the board, one labeled FAULT and the other labeled NORMAL. Place the red LED in the FAULT position and the green LED in the NORMAL position, with the longer lead in the hole toward the edge of the board and the shorter lead in the hole on the flat side of the circle. Confirm that the flat side of the LED matches up with the flat side of the circle printed on the PCB. Bend the leads out at 45o angles to hold in place. Place the large 120 Ω resistor (brown-red-brown-gold bands) in the square on the lower left hand side of the board labeled [R4]. Bend the leads out to hold in place, with a bit of space between the resistor and the board. Likewise find the two squares marked [R1] and [R5] on either side of the pair of LEDs. Insert a 1K Ω resistor (brown-black-red-gold bands) into each square. Bend the leads out to hold in place. Find the square marked [R2] between the pair of LEDs and insert the 10K Ω resistor (brown-black-orange-gold bands). Bend the leads out to hold in place. Find the square marked [R3] to the left of the [R1] square and insert 6.8K Ω resistor (blue-gray-red-gold bands). Bend the leads out to hold in place. Solder the resistors and LED in place. Clip the tails from the soldered components. Place the three green terminal blocks, FET 12V IN, HTR 12V OUT, and TEMP CUTOFF in position. Make sure that the openings are facing out! Then flip the board over so it rests on the three terminal blocks and solder them all in place. Then it should rest on the terminal blocks so you can solder nicely while it’s upside-down…
Place the black SL type connector in the positon labeled ALERT. Make sure the connector lock faces inward as in the diagram and solder in place. And then flip over again and solder…once again it should stay in place while upside-down. After those terminals are in place, next add the relay and solder that as well.
And now for the tricky part. The Rev. D version of this kit includes a large diode — this is the big thing that looks like a transistor or voltage regulator. We need to not only solder this through a couple of holes, but we also need to attach its heat sink to a large heat sink pad. It’s just a bit difficult because we’re actually soldering a heat sink — which by definition can soak up a lot of heat. This means that we’ll be keeping our soldering irons in contact with the parts for much longer than we’re used to. Don’t worry — we’ll walk you through it. First, we’ll tin the pad. Hold your iron with one side in good contact with the pad; after a few seconds try to add some solder. At first, a few jagged blobs might stick to the pad. That’s not good enough; we need to flow all the solder on the pad. Continue holding the iron on the pad until the entire pad flows. When it gets to the melting temperature, the solder will suddenly get shinier and flatten out, spreading all over the pad. When it does that, it’s well-tinned; it should look like the picture below (or even smoother.) Next, we’ll put the diode in place, and then bend the leads so it makes contact with the pad.
Next, I’d recommend bending the diode leads opposite each other to hold it in place better. And now the trickiest part: actually soldering the heat sink down to the pad. Basically, all you have to do is hold the tip of your soldering iron through the hole in the diode’s heat sink. Slowly feed in some solder as it’s heating to make sure there’s enough flux. Eventually, all the solder will flow nicely; you’ll see it get shiny again, and suck down into the gap between the heat sink and pad. When this happens, add enough solder to also cover the top side of the heat sink. Last, use another tool to hold the diode in place as the solder cools. Angled snippers are good for this task. Make sure you’re already holding the diode down as you remove the soldering iron so the contact is good as the solder cools and solidifies. When you’re done, the solder smoothly cover the hole over so it’s not even visible. Now, flip the board over and solder the leads down. Use something from the workshop to prop up the diode if you need to. And now you’re all done with soldering. Phew! Install it in place on your bot!Now that your board is soldered together, it’s time to mount it in place. One good place is the right side of the Z-stage. There aren’t any holes, so we’ll have to drill them. Hold the board in place and use a pencil to make the position of the holes. Then drill (carefully) with an electric drill. You’ll use a 3mm bolt, so a 1/8″ bit will work well. Vacuum up the sawdust before you continue! Now just bolt it in place with some 1/8″ spacers and M3x16mm bolts and nuts. To be continued…Now that your safety cutoff board is in place, continue on to the body and electronics installation pages for instructions about how to connect the wiring up to the bot.
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