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Snowbot V1.0

A holiday project to build a little Snowbot with an adjustable speed larson scanner for an eye.

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I published this design as a 2015 holiday project for the users of my website. It's a little PCB Snowbot, with a six LED larson scanner for an eye, and arms you can snap off and solder in place.

The pictures are of the final prototype. The final version is shown in the 3D render, featuring some fancier silkscreen layer on the PCB.

The Snowbot has three major subsystems: Power and Timer and Display.

Power Subsystem

The power subsystem uses a 3.7V LiPO battery boosted to 5V with an SC4503 boost converter to power the fully analog circuit. It requires a set of passive components in order to generate the higher voltage.

Timer Subsystem

The timer subsystem is comprised of a 555 IC that generates a clock signal. The speed of the clock is adjusted by twisting the potentiometer (the nose of the snowbot). The clock signal ticks through the outputs of a CD4017 decade counter, lighting each LED in sequence, then moving back through them again.

Display Subsystem

The display subsystem involves taking the output of the CD4017, and directing it to six red LEDs in the form of a larson scanner. In addition to lighting the LED, the current also charges a 22uF capacitor through a diode. When the output moves to the next LED, the cap discharges through a 2.2K resistor (part of a resistor network), fading the LED out gracefully.

snowbot_2015_rev1_kicad_project.zip

Full KiCad project archive

x-zip-compressed - 79.37 kB - 02/09/2016 at 05:13

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snowbot_2015_rev1_gerbers.zip

Snowbot gerber files

x-zip-compressed - 140.77 kB - 02/09/2016 at 05:12

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snowbot_2015_rev1_quantities.csv

BOM sorted by quantity

ms-excel - 1.31 kB - 02/09/2016 at 05:12

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snowbot_2015_rev1_full_bom.csv

BOM by individual line item

ms-excel - 8.20 kB - 02/09/2016 at 05:12

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snowbot_2015_rev1_paste_stencil.zip

Stencil Files for Hot Air Soldering / Reflow

x-zip-compressed - 2.66 kB - 02/09/2016 at 05:11

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  • 1 × 555 Timer TLC555CDR
  • 1 × Power Reg Protection Diode VS-10BQ015-M3/5BT
  • 1 × 555 Timing Adjust Pot 3310P-125-103L
  • 1 × 8 x 2K2 Resistor Network 742C163222JP
  • 1 × 10pF Switched Mode Reg Feedback Cap C0805C100KBRACTU

View all 20 components

  • 1
    Step 1

    The original build instructions can be found here: https://rheingoldheavy.com/snowbot-assembly-guide/

  • 2
    Step 2

    When you receive the PCB, it should look something like this (assuming you used OSHPark). The arms will still be attached to the body of Snowbot by the little 3-drill mousebites at the bicep and forearm areas of the arm. It’s up to you if you want to detach them and solder them in place, it’s purely cosmetic.

    Please note that I have added polarity markings to the PCB that don’t appear in the image above. The following render shows the corrected silk screen that is associated with the gerber files and OSHPark project.


  • 3
    Step 3

    Mounting The Arms

    I don’t recommend soldering the arms into the slots until all the rest of the board is done, because they make laying the board down on your work surface impossible. If you do want to snap the arms off, it’s best to give them a snip with your side cutters or diagonal cutters. There should be enough room to get the tip in to make the snip. I just worried each arm off by gently pressing back and forth until they stressed enough to break easily. You’ll want to sand or file the edge down smooth, but you’re sanding / filing fiberglass (the FR4 insulating material of the PCB sandwich), so make sure you don’t breath any of the dust.

    The arms are mounted into the slots using something called Sheadel Joints (named after all around awesome OSHPark guy @tekdemo). The idea is to slide the arms into their slots and then solder them in place by flooding the area where the surface pad and the through hole drill intersect. No need to be fancy about it, just feed the solder in until it starts to bead up. Super easy, and super strong.

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Discussions

oshpark wrote 01/18/2017 at 19:36 point

Awesome project!

  Are you sure? yes | no

Dan Hienzsch wrote 01/18/2017 at 23:23 point

You're just saying that because of the Sheadel joints :)

  Are you sure? yes | no

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