Startracker (astro tracker)

I am a complete novice in this, but I'm going to attempt to create a so-called star tracker. I have found many examples of such, but lacks a little more information about what else I need to be able to make it.

Here is an example of what I want to create.

I've ordered these parts:
Due R3 Board SAM3X8E 32-bit ARM Cortex-M Controller Compatible For Arduino
LCD Keypad Shield, 2x16, 1602, for Arduino UNO, Mega2560, R3
A4988 Stepper Motor Driver + Heatsink
NEMA 17 stepper 40mm length stepper motor

What more do I need to connect them together?
And how do I connect these together?

(deleted)

How come?

(deleted)

Hi,
Welcome to the Forum

The site that you linked to uses Arduino UNO.

Tom... :slight_smile:

it's called a barn door and it is very easy to make.
it is very simple, suggest you get a good power supply for this.

I do not understand the need for the high-tech board, but if it can run a simple sketch, then you should be able to have fun.

you use wires to connect.
as for the display shield, did you get one with the buttons ?

for your next project, consider a double barn door.

spycatcher2k:
3.3V main board with a 5V shield - No guarantees of compatibility - you would of been better getting a mega2560. This is only my opinion.

Auch, didn't notice that.. Oh well, I learned something new :slight_smile:

TomGeorge:
Hi,
Welcome to the Forum

The site that you linked to uses Arduino UNO.

Tom... :slight_smile:

Yes, sorry. I copied the wrong title for the board. They sold two types of board, and I got the UNO not the Due. :slight_smile:

dave-in-nj:
it’s called a barn door and it is very easy to make.
it is very simple, suggest you get a good power supply for this.

I do not understand the need for the high-tech board, but if it can run a simple sketch, then you should be able to have fun.

you use wires to connect.
as for the display shield, did you get one with the buttons ?

https://www.adafruit.com/products/772?gclid=CjwKEAjwl4q-BRDtzJmSk-uGunkSJACmCOY-m9vFXGpl2EI1nHxuzouoz77ae3fGECcY29zn8TRdIBoCF7Xw_wcB

for your next project, consider a double barn door.

Double Arm Barn Door Drive - DaveTrott.com

Yes, I noticed the double barn door thing. But I’m not planing on taking +10 minutes exposure. Not yet anyway.

As preparation before the parts arrive, I’ve tried to set up a sketch on how to connect everything together. This is as far as I’ve come. With my extremely limited knowledge of electronics, I’ve probably done something wrong or missing something wires or something. :slight_smile:

I’m in on the right track here?

with only 2 AA batteries, you cannot power the UNO and the stepper will last a few minutes.

need more power cap’tn

584b875ad8e1927a1317f9e27fe658e405c4c157.jpg

dave-in-nj:
with only 2 AA batteries, you cannot power the UNO and the stepper will last a few minutes.

need more power cap’tn

584b875ad8e1927a1317f9e27fe658e405c4c157.jpg

Yes, I plan on using 8 AA batteries on the final build. Just didn’t figure out how to make the battery larger in the fritzing drawing.

How about the wiring? Will it work, you think?

An updated version.

Hi,
How do you plan to get the press buttons to work?
If you are trying to copy the analog method that is on the LCD/Pressbutton Shield then what you have will not work.
You have enough spare I/O to give each button its own digital input.

Tom... :slight_smile:

TomGeorge:
Hi,
How do you plan to get the press buttons to work?
If you are trying to copy the analog method that is on the LCD/Pressbutton Shield then what you have will not work.
You have enough spare I/O to give each button its own digital input.

Tom… :slight_smile:

I just followed a schematic of how to connect buttons to the board. Have no idea if it will work :slight_smile:

Here is a schematic view

And Parts list:
Arduino UNO R3
A4988 stepper motor drive
NEMA 17 bipolar motor
16 pin LCD screen
3 pushbutton (Start, reset and pause button)
3 resistors 2.2ohm (for the pushbuttons)
1 resistor 220ohm (for the screen)
1 potentiometer (for the screen)
1 Switch (on off power switch)
1 capacitor 47µF
1 battery (8x AA batteries)

3 separate buttons would be easier to code.

to make 3 buttons on one analogue pin

Vcc---------|1|-----///-------|2|-----///-------|3|-----///---ground

if you have 5 volts, and all 10k resistors.
you have
5 volts at #1
3.33 volts at #2
1.66 volts at #3

voltage dividers all ways use power, so are not preferred when batteries are involved.
using 10 k resistors to limit the current used.
any 3 matching resistors will have outputs. higher values will use less power.

22222222222222222222222222222222222222222222

need more power. I have a feeling you have not calculated how much power you will draw with a stepper.
think more like a car battery than AA cells.

this set-up will work, but is not efficient use of power on a few levels.
the Arduinos are not designed to be run on Batteries.
they can be made to run on batteries. but out of the box, they are designed for wall power.
you will need to power the LCD as well.
for a bench, it is not a lot of power
for batteries it is a hungry beast.

33333333333333333333333333333333333333333333

you do not show the Arudino getting power.
need a separate power source for that.

444444444444444444444444444444444444444444444

depending on your display board, you may or may not be able to pwm the lcd.
some were laid out wrong and the pwm could not work without modifying the board. cutting one trace and soldering in a resistor

As I mentioned in the first post, I have almost no idea what I'm doing. Everything I've done up to now is to see how others have done similar projects and tried to adapt it to my project.

I am trying my best :slight_smile:

Is there a way to reduce power consumption?
I need this to be able to run on 8 AA batteries.

frabraha:
As I mentioned in the first post, I have almost no idea what I'm doing. Everything I've done up to now is to see how others have done similar projects and tried to adapt it to my project.

I am trying my best :slight_smile:

Is there a way to reduce power consumption?
I need this to be able to run on 8 AA batteries.

the motor is the largest draw of power. you might be able to use a smaller gear motor and an encoder. steppers are power hungry.

loose the LCD or make it really dim. for night work you might be able to make it really dim.

as for the Arduino, you might considder getting a pro-mini.
need to loose the LED for power, loose the USB chip.

sleep mode is not too much of an option as you need to pulse the motor and driver the LCD
or sleep and pulse and sleep.

get a battery charger for the rechargable batteries. make sure they are of high capacity. cheap ones do not have the same rating as high output.

since you are only doing a few shots and each will be short, have a power kill switch and automatically kill the power after your use. press a button to start, let it time out and shut off. link the shutter to the on/off. allow the settling after start and shut it before you turn off the motor.

watch the scene from Jurassic park with the water showing the vibration. put a cup on your unit and see what effect the shutter does to vibrations. we used a black painted cardboard cover, held in place over the tele. opened the shutter, allowed the vibrations to subscide, removed the disk from in front of the lense, placed it back over the lens and then closed the shutter. the shutter movement on our SLR was horrendous !

All star tracker I've found have been made using the stepper motor, and is recommended for this use. I ordered a NEMA17 motor, and I'm getting a smaller version with a kit called 28BYJ-48.

I have also read that you shouldn't bring power directly into the UNO but through stepper motor drive. As I thought I had done.

I have a bunch of Eneloop AA batteries that have 2000 mAh capacity. Shouldn't that be enough?
The UNO draws just 50mAh from what I can figure out.

Here is an update on my build.

I’ll be very happy if someone could take a close look at it to se if I’ve done everything right.