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Peter Stoneham
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191 followers
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A number of you will have seen this quote in one of my Rigidbot upgrade parcels. As you will see it is penned by one of our active members so I thought I would share it with the wider community. I am sorry to say I have been rather inactive of late so a big thanks to +William Eades (AKA Frostbyte at his local Maker Space in Tallahassee) for your ongoing regular contributions to this community and to the advancement of 3D printing! Great Quote!
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There is a dearth of decent 30mm 24V extruder fans on the market so I got myself some nice 30x30x10mm 12V SUNON MagLev fans and added a resistor. They run super quiet as the MagLev technology has virtually no friction as the shaft is floating in air.

Here is the formula for working out the Resistor Value working back from the fan Wattage which in my case is 0.44W and the amount of voltage you want to drop across the resistor which is 12V.

P = V x I
0.44W = 12 x I
I = 0.44/12 = 0.0366Amps

R = V/I
R = 12/0.0366 = 327 Ohms

Standard resistor value is 330 Ohms (0.5W)

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I have just bought five MKS Trinamic TMC2100 based stepper drivers. I had been using the DRV8825 drivers with my Sainsmart 2 in 1 but haven't been overly impressed with their performance compared to the Rigidboard A4988s. By performance I mean the ability to drive my Y-axis without losing steps. My Y-axis is not your regular setup as I have added counter weights but the Rigidboard steppers drove it without a slip and had fantastic holding torque. One of the main issues with the commonly available DRV8825 boards is trying to dissipate heat because the driver chip is on the wrong side of the board. So when I saw these MKS boards I was impressed that they put the chip on the bottom where it should be. I also bought some larger heatsinks which should also help keep things cool. I plan to run these in SpreadCycle Chopper mode rather than StealthChop - not as silent but way more torque. I will post again once I have them installed.

Link to Tom's Review of the Trinamic TMC2100 driver chip; https://www.youtube.com/watch?v=g6Bxoqr8QlY

Trinamic TMC2100 datasheet; http://www.trinamic.com/_articles/products/integrated-circuits/tmc2100/_datasheet/TMC2100_datasheet.pdf
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9/4/16
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Update on Sainsmart 2 in 1 heated bed MOSFET fail. See previous post here; https://plus.google.com/100637857751025322015/posts/fcNCVF5Qu7B

The MOSFET failed and short circuited ON! The solder melted on the base pad (cathode) and on the two anode pads. I used this failure mode to remove the Fairchild MOSFET which revealed a solder mask that covered a large proportion of the pad - you can see a diagram in the photos showing what the recommended D2PAC pad should look like (snipped from the Fairchild spec. sheet) - so I decided to scrape the mask off according to this design recommendation. This revealed that the intense heat had melted and delaminated the copper in the centre of the base pad. I saved what I could of the copper and re-soldered the new Infineon MOSFET in place.

The newly installed MOSFET only gets slightly warm (maybe 30 - 40°) on full power. The main difference between the two MOSFETs is the drain to source resistance in the on-state. Thanks must go to my clever electronics friend +Damon Partington who helped with the MOSFET selection albeit he recommended I choose a lower Gate Threshold Voltage as the MOSFET is logic driven directly by the micro.

Here are the spec. sheets for the replacement and original MOSFETs respectively;

Infineon N-channel MOSFET 40V, 120A, 1.9 mΩ http://www.infineon.com/dgdl/auirfs8405.pdf?fileId=5546d462533600a4015355b7069d14de

Fairchild N-Channel MOSFET 60 V, 62 A, 13.5 mΩ
https://www.fairchildsemi.com/datasheets/FD/FDB13AN06A0.pdf
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2016-08-09
8 Photos - View album

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Here is a short video update on progress with my experimental Single Stepper Tilting Dual Extruder. It has its failings but I am optimistic that I can iron out most of the issues in the next iteration. So it's back to the drawing board to make prototype 2.

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OK I am up and printing with my Sainsmart 2 in 1 controller thanks to some of the pillars of our community +Ed Williams +Ernesto Martinez and +Tony Gomes. My only concern now is that the MOSFET for the heated bed gets very hot - hot enough to smell hot and burn a finger. I have added a heatsink (see picture) to help the situation but it is still to hot to leave your finger on it for more than a couple of seconds. Should I limit the current using #define MAX_BED_POWER 255 (255=full current) or is this normal?
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I am switching from my trusty Rigidboard to the Sainsmart 2in1 with a RepRap discount full graphic smart controller and I am having some teething issues. On the Main screen the LCD says it has detected the SD card but in the next screen it says, "No SD card" and I can't see any gcode files. I have uncommented #define SDSUPPORT and have reformatted card as Fat32. Any ideas?
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2016-07-19
5 Photos - View album

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Fan Cowl for my prototype tilting extruder. Totally Volcanic Baby!
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2016-07-06
4 Photos - View album

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Single Stepper Tilting Dual Extruder TAKE 4

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+Ed Williams flexible router guide challenge!

+Clint O'Connor 
+Neil Ferreri 
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