Sunday, January 13, 2019

T19 Build Guide - Part 8 - Logic Power Supply Module

Note that in the previous post, no logic power supply was placed on the Core board. Instead, we left it expecting external 5V as well as unregulated DC bus, because in this guide, an external power supply module is used. Obviously, you don't have to do it this way. The fiexibility should be apparent with this bit, as with everything else, but this harness-module affair is how I have set up my Model 101 "production" builds, for no specific reason.

Why was a 4 pin connector used in this guide, when 3 would have done? The answer is the prewired 4-pin female 0.1" connector that came on your OSM 17HS16-2004S1 stepper motor.

  • Soldering iron
  • Flush cutter/dikes/something that cuts wire
  • Wire stripper, or use knife.
  • Heat gun/Heat source for shrinking tubing
  • 4 pin 0.1" female connector pigtail cut off the 17HS16-2004S1 in Part 6
  • 2 x male 2mm bullet connector
  • 1/8" heatshrink
  • 5.0V output buck or buck/boost module. I recommend buck/boost. Buck-only converters can be a problem around high currents and noise. This should be rated for AT LEAST 18V input, ideally higher. The current required is low, <100mA for logic power only, so this is mostly constrained by voltage ratings.
    • The end-all module for this sort of stuff is the Pololu S18V20F5. This, however, is expensive.
    • Here, I use a cheap, Chinese module. Be mindful - these particular ones have XLSemi XL6007 ICs on them and seem OK so far. Some cheap generic buck/boosts can be dangerously junk and potentially blow your electronics up by putting out more than 5V under certain conditions.
    • I have some Pololu S10V4F5 to test out, which would be best used in a board-mounted installation. These are MUCH smaller and cheaper, similar to the S9V11F5. However, I have not proven this one yet.
  • Heatshrink or battery shrinkwrap to fit over module

Cut the wire pigtail to about 9" and Black and Red to about 4"

Recall pinout for this connector: 5V on one end, two grounds in the center, DC bus on the other end. We will use the BLUE side for DC bus and BLACK for 5V.

Wire the 2 shortened wires to the output of the module. Due to the reused connector, wire colors are wonky here: black to 5V output, red to ground! What?

Solder two more ~4" pieces of wire to the input side of the module.

Marry the ground from the input with the green (uncut ground wire from the output connector). Marry the input DC+ with the DC+ from the output connector. Twist these up and tin them.

Terminate input leads with 2mm bullets.

Shrinkwrap module. If not available, use 33 tape.


Next: Part 9 - DC Bus Harness

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