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Build Log: Automated Barn Door Star Tracker

My friend Jim Choate told me about his ideas around building an Arduino based barn door star tracker. I decided I could use one of these for some astro-photography out at The Cabin. After checking my parts bins, I found almost all the parts needed to build one. I set out with the goal of building a tracker with the least out of pocket costs.

 

I am reusing some MDF 3/4 inch board for the base and top. I drilled and tapped a piece of acrylic for the tripod mount on the bottom. This worked surprisingly well. I had to purchase a hinge at Home Depot. This is the largest source of “slop” in my implementation. The hinge is hard to mount such that the bottom and top “door” align when closed. I’m using the other hinge to anchor the stepper motor. I purchased a $13 lead screw off Amazon and a 5mm to 8mm shaft adapter. The camera mount is a ball head adapter for a tripod.

I have not wired this up yet. I’ve ordered a replacement shaft adapter. The one initially purchased has a spiral anti-backlash cut. It flexes dangerously when rotating the lead screw by hand. I predict it will break.

 

tracker1

 

 

 

 

 

 

 

tracker2

 

 

 

 

 

 

 

 

tracker mount

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Venus Equilateral

As a kid I grew up reading this book in my dad’s collection: The Complete Venus Equilateral by George O. Smith. I didn’t know it at the time, but that book (really a collection of related short stories) was long out of print. Quite a few years ago, my mom found me a battered copy at a used book store in Fremont.

Parts of the stories are a bit dated, such as all the vacuum tubes. Surprisingly, a large portion of the hard science is still valid (orbital mechanics, physics, etc). These stories were written between 1943 and 1947.

venus equilateral

 

 

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Upper Klamath National Wildlife Refuge

 

upper klamath lake wildlife refuge

I was looking through my photo collection and found this photo of the Wildlife Refuge. We’ve visited there a few times. It’s a great flat stroll for the kids. This photo needed serious cropping and some help with ON1 Photo 10 (which I get to work on).

 

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Op-amp Arduino Shield

Recently I needed an op-amp front end for taking some measurements using a bpw34. I put together a circuit on a  bread board, took the measurements, then put all the parts back. I decided to build a shield that can be configured for two or three different op-amp configurations, then feed the signal into A0. The core circuit uses a LM358D with a soic footprint. All other parts are thru hole. There is some prototype space, and two additional soic-8 footprints.

The LM358 has two op-amps in it. They are chained together, One could bypass the first or second stage by soldering a jumper.The second stage has a voltage divider that brings the input voltage to Vcc/2. The second stage also provides some feedback (if you solder in R6 and C4). This and a few other changes provide about six permutations of highly useful op-amp circuits.

 

opamp arduino shield

My first draft has a few minor errors, but is usable.  The next step is to write a comprehensive manual that lays out multiple use cases.

 

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Seek Outside 8 Person Tipi

It’s almost camping season here in Oregon. After a few years absence as our youngest child got older, it’s time to start taking the kids outside again. I’m ashamed to say it’s been several years since the whole family went camping in a tent. Yeah, we go to the Cabin, and stay in yurts. That is just not the same as sleeping on the ground, in a tent, not in a campground.

It was time to upgrade the tent; to fit the whole family and the upcoming dog. I settled on an 8 person tipi from Seek Outside. I did some research; read the reviews, forum postings. Sat on the fence because of price for about a year. I was planing for a smaller tipi, but a rare sale come along to get the larger one.

image5

 

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W7ZOI bi-directional RF amplifier PCB

It’s been a busy month. Sent two PCB designs out to Seeed in China for fabrication. The first one is a reproduction of W7ZOI’s IF amplifier circuit. This circuit is termination insensitive, and bi-directional. One could use two of these amplifiers, on each side of a crystal filter to reuse the it for transmit and receive. W7ZOI designed this as a contribution to the BITX transceiver aficionados. This is my own PCB design. I added SMA connectors and prototype space.

 

img_0908.jpg

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Smd inventory 9/3

10k 1206 partial reel

22nf 0805 partial reel

68pf 0805 partial reel

50k 0805 partial reel

100pf 0805 partial reel

22uF 16V partial reel

47uF 6.3V partial reel

680pF 1206 2500pc

82pf np0 0805 partial reel

100nf 0805 partial reel

100pf np0 0805 partial reel

470pf 08085 ~3900 pcs on reel

33nf 0805 partial reel

1nf 0805 partial reel

56pf 0603 partial reel

82pf 0805 partial reel

1uF 0603 ~100 unknown voltage

1uF 0603 ~100 25V (Mouser)

1k 0805 partial reel

22uh 1206 2000pc

red/blue LED Dialight p/n 597-7701-507 705pc

MMSD914T1G 3000pcs SOD123

47pf NP0 0805 360pcs

4.7k 0603 ~5000 pcs on reel

10k ~100

4.7k ~100

100R ~100

Machrone WB-C3-403025 ~500 on reel

78L05 ~100

Red LED 0805 ~20
Green LED 0805 ~20

Blue LED 0805 ~20

Whitre LED 0805 ~20

AP115AY33G-13 LDO 15V ~10

CD4066BM96E4 ~10

74hC4053D ~4 two channel mux

74HC4040PW ~2 twelve stage binary counter

MCP23008-E ~2 in/out I2C interface

AAT3681AIJS4 ~4 usb port/ac adapter

BCX56 ~20 NPN transistor 80V/1A ft 180mhz

2SC3337 ~30 NPN transistor 15V/100ma ft 4.4ghz

BAS16 3000pcs (new reel) TO-236AB

MMBZ5231BLT1 5.1V zener diode SOT-23 ~ 3000

MMBTH32_Q ~300

BAV99W ~50 SOT323

mmbt3904~100 PNP transistor

mmbt3906 ~100 PNP transistor

2N7002K ~100

MC34063A ~10 step-up/step-down switching regulator

C5706 ~20 PNP transistor ft 360mhz

L9110S ~30 Dual channel motor driver

200uf 100V electrolytic ~500

330nf 0603 ~ 4000 reel

BAV70 sot-23 ~ 1000

ZMM5228B 3.9v zener ~1000

3pf C0G 50V 0603 ~4000 reel

BAS19 SOT-23 ~1000

CDLL1A0 schottky diode ~ 700 DO-213AB

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3S lipo batteries for KX3

There was some recent discussion of using 3S (three cells in series) lipo batteries with the KX3 on either the NASOTA Yahoo group or the QRP-L list (I can’t remember). The gist is that the KX3 will keep running with a lower input voltage. A fully charged 3S battery will provide 12.6V. To get ten watts output, you need 12-14V, but closer to the 14V.  Less than 12V,  the KX3 drops to 5W power output.

I was browsing the HobbyKing website for 3S batteries and discovered they offer pickup at a few discrete locations. One of these locations is in Tualatin, OR. This is close enough to warrant save the $7 on shipping.

 

 

 

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Frozen pipes and burn piles, spring after a frozen winter

I finally got away from work and took one of the kids down to the Cabin. Winter started in earnest about Thanksgiving and only now really started to thaw. There are a few patches of snow left.

february snow

The temps hit 0F at least three times this winter. One of the few pieces of PVC that exist in the water system froze and cracked.

cracked pvc valve

 

For late February, the ground is also thawed out too. Very wet, but not frozen. It’s not feasible to burn brush and rotted wood in the summer and fall. Pretty much exclusively in the winter. I managed to take of about a third of a burn pile.

burn pile

Also upgraded the firmware on the Midnite Classic 200. I waited right up until the deadline to do the upgrade. A few new pieces of data are available via the cloud portal, such as the Wiz Bang Jr’s amp rating.

midnite data

On the way back to the valley, stopped by Odell Lake and took a few photos.

odell lake