Barndoor tracker evolution

[Davey-T]

Been messing about with this for a while on and off and it's getting more involved with every incarnation.

Basically Arduino controlled stepper motor opening the tracker, wondering how to have LEDs indicting the state it's running at ie: sidereal or fast forward / backward with LEDs flashing at appropriate speeds.

Presumably just teed of motor windings would result in fast flickering lights ?

May evolve to have LCD display

May never get finished 😂

Dave

[vlaiv]

Should be easily done in code, no?

I'm guessing that your arduino code is looping and tracking time and at appropriate moments issuing step command. Therefore you really must have a flag that says - sidereal, fast forward / backward in order to control steps.

From there it is rather easy with one if and one counter.

If not sidereal then on step increase counter when counter hits some number (you can calculate number of steps that you want LED to be on off) - toggle state of LED.

One more piece of code - when changing speed if sidereal reset counter and set LED to on.

[happy-kat]

The Arduino code I'll use goes with switches for choosing forward at sidereal rate or backward to reset faster.

[Davey-T]

51 minutes ago, happy-kat said:

The Arduino code I'll use goes with switches for choosing forward at sidereal rate or backward to reset faster.

Similar here.

Dave

2 hours ago, vlaiv said:

Should be easily done in code, no?

I'm guessing that your arduino code is looping and tracking time and at appropriate moments issuing step command. Therefore you really must have a flag that says - sidereal, fast forward / backward in order to control steps.

From there it is rather easy with one if and one counter.

If not sidereal then on step increase counter when counter hits some number (you can calculate number of steps that you want LED to be on off) - toggle state of LED.

One more piece of code - when changing speed if sidereal reset counter and set LED to on.

Not really sorted the coding yet, trying to achieve better precision than your average Barndoor tracker.

Dave

[Mick J]

'May never get finished '

 

Know that one 

[vlaiv]

2 minutes ago, Davey-T said:

Not really sorted the coding yet, trying to achieve better precision than your average Barndoor tracker.

Dave

What sort of precision do you have now?

Tracking precision is really down to mechanical side of things. Precision machining and such.

Maybe you could try to do your own worm gear? I've seen you tube video of how it can be easily done with thread tap and drill. Let me see if I can find that for you.

https://www.youtube.com/watch?v=19jKlq8Ofd4

 

[vlaiv]

Another cool video:

https://www.youtube.com/watch?v=ZIOn6w7gwWU

I can't help follow thru those suggested videos on topic that interest me

 

[Davey-T]

19 minutes ago, vlaiv said:

Tracking precision is really down to mechanical side of things. Precision machining and such.

Here it is ATM, bearings at one end  and continuous 6 inch stainless ball bearing hinge at the other.

Depending on the camera focal length it may not need to track continuously, just go in small steps every second or so but can me messed about with in the code.

Dave

 

[Davey-T]

And the electrifying bit, only wired for single stepping ATM

Dave

[AlexK]

To the OP:
I would just add an ESP8266 or ESP32 module to feed your controller data (and controls) to BT or WiFi wirelessly and look it up on the smartphone (if you are nearby) or on the LAN/Internet from any other device remotely. That's orders of magnitude more convenient and also more economical than physical screens, indicators and levers. Actually you can build your entire controller on either chip and save on the integration effort too. It's even several times easier to implement and program than a typical Arduino (see my recent project for the UXD definition example and considerations).

No? Then, I believe, a whatever code (Morse comes to mind) you can remember yourself should work fine for you personally.

[AlexK]

5 hours ago, Davey-T said:

Here it is ATM, bearings at one end  and continuous 6 inch stainless ball bearing hinge at the other.

Depending on the camera focal length it may not need to track continuously, just go in small steps every second or so but can me messed about with in the code.

Dave

Looks seriously overbuilt, but why not if you can? I feel it could perform well even with some 8" reflector on the top board. Could you share that interesting long hinge source, please?

[Davey-T]

1 minute ago, AlexK said:

Looks seriously overbuilt, but why not if you can? I feel it could perform well even with some 8" reflector on the top board. Could you share that interesting long hinge source, please?

Only aiming for something like 5 min' subs with a 200mm camera lens, that would equal my SW Star Adventurer, just a project really to see what's possible.

Hinge is actually 2 x 3" stainless steel ball bearing fire door hinges available from most hardware stores or online.

Dave

[AlexK]

Thanks! "Fire door" is the key!

Let me elaborate on my "overbuilt" concern though (just my personal opinion, you are free to go as you see fit):

5 mins corresponds to less than 2 degrees of tracking. That's why I feel it overbuilt. Because simply having it weighted down on the rod you could simply push a steel plate up by the smoothened end of the rod that far, and thus go with the single hinge only. No need to elaborate on the driving rod's pivots that seriously. In fact, that might instead complicate the fine motion of a preloaded single hinge even on that small 2 deg arch into some erratic periodic driving error combining all hinges motion into a very complex dance on the CCD .

Also, I guess your plan is to drive it with some rate progression algorithm converting the linear motion into the sideral. It's actually easy to calculate if you need that or not at all for the given focal on the expected range and with the built lever length. I feel it should be fine even with the constant rate. So again, no need to improve on that. And still fine with some simple platform rewinding and precalculated speed curve approximation. But in a long run you will want to employ a single axis autoguider anyway (to use longer focal ranges, or compensate for the weather, or for the wear of the system). Thus again, mechanical imperfections of the single hinge will become nonessential, while the perfect approximation of its motion by a single pivoting axis will be the most crucial thing as you can autoguide in one axis only with the barn door motor.

[Davey-T]

1 hour ago, AlexK said:

Let me elaborate on my "overbuilt" concern though (just my personal opinion, you are free to go as you see fit):

As you say no need for it to be so elaborate just seeing what could be achieved by over engineering it.

Made one many years ago with floppy brass door hinges and wound by hand using an SLR with colour slide film then developing it.

The software will hopefully calculate the angle between the boards or more strictly half the angle based on how far apart the screw moves them to achieve sidereal rate, converted to radians somewhere along the way.

Obviously I could make one from just a steel gate hinge with a small stepper motor and couple of plastic gears, speed controlled with a potentiometer and achieve as good results but where's the fun in that 😂

Not planning on guiding it the main challenge may be polar aligning it.

Dave

Edited April 2, 2021 by Davey-T

[theropod]

When I had my barn door in a permanent setup I used drift alignment to get mine real close to polar alignment. I fiddled with a scope on a rail and tried dozens of times to visually put Polaris where it needed to be, but only using the drift alignment method gave me nice sharp stars.

[theropod]

Understand that my barn door is made so as to have east/west and up/down pivots, which are made by moving nuts on curved 1/2” allthread rod against a hard point for each. I’ve posted a pict of it here before. It’s ran from an Arduino Nano, Easy Driver, some gears from a dead VCR, curved allthread 1/4”x20 and a stepper motor salvaged from a inkjet printer. I’ve posted my “no delay” code before, and uses 6 lines of instructions. After SEVERAL step speed adjustments I ended up able to do 5 minute plus wide angle “meteor hunt” shots almost as well as my iOptron SkyTracker Pro. The little iOptron is just so much easier to use in almost every way, even with the bran door left out all the time(sans electronics). I still have the barn door ready to go, and during the Perseids I might have two wide field rigs running.