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Startracker design questions
09-10-2017, 09:57 PM
Post: #1
Startracker design questions
It would appear that the greater the distance between the hinge and the drive rod the faster the drive rod will need to turn, and the longer it will need to be? Is that correct?

Do you think there is any increase in tracking accuracy by making this distance (between the hinge and the drive rod) longer? (Ie the drive rod has to turn faster, and travel farther, meaning more steps of the motor for a certain time period.)

Also, there is an inherent error in "barn door" designs known as the "tangent error". Does the arduino code compensate for this? If not, do you think accuracy would be increased by using a curved drive rod? Or using a "corrective cam" as I've seen on some designs?
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09-12-2017, 04:12 PM
Post: #2
RE: Startracker design questions
(09-10-2017 09:57 PM)Jamey Wrote:  It would appear that the greater the distance between the hinge and the drive rod the faster the drive rod will need to turn, and the longer it will need to be? Is that correct?
Yes. Correct
(09-10-2017 09:57 PM)Jamey Wrote:  Do you think there is any increase in tracking accuracy by making this distance (between the hinge and the drive rod) longer? (Ie the drive rod has to turn faster, and travel farther, meaning more steps of the motor for a certain time period.)
Yes, it will increase the accuracy but the system will get too large to hold the camera + tripod in balance (from my experience). Right now meets the compromise between size and accuracy, but the larger, the better... Sleepy

(09-10-2017 09:57 PM)Jamey Wrote:  Also, there is an inherent error in "barn door" designs known as the "tangent error". Does the arduino code compensate for this? If not, do you think accuracy would be increased by using a curved drive rod? Or using a "corrective cam" as I've seen on some designs?

Using a modern camera, you will need only 200 seconds (TOP) of exposition (ISO200-300). For that time, the tangent error is negligible. This error becomes a problem when the angle is over 15ยบ (if I recall it properly, I made the calculations time ago)

The tangent error can be corrected via CODE but will narrow down the options of creating the STARTRACKER using another physical elements... Will just work for certain dimensions and rods metrics.
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09-16-2017, 10:35 AM
Post: #3
RE: Startracker design questions
Thank you for your quick reply! One last question - I may have to order the drive rod from Amazon - how long, at minimum, does the drive rod need to be?
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09-17-2017, 11:35 AM
Post: #4
RE: Startracker design questions
You are welcome ;-) 12 cms at least
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03-30-2018, 01:11 AM
Post: #5
RE: Startracker design questions
To add on to the Tangent issue, would an option of making the "groove" that the screw goes into have a curve built in, such as seen below? (just a quick sketch, so not proportional to what the curve would actually have to be in order for it to keep the barn door mount opening at the correct speed)

[Image: ixhwaJ.jpg]
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04-02-2018, 05:46 PM
Post: #6
RE: Startracker design questions
(03-30-2018 01:11 AM)jaburkhardt Wrote:  To add on to the Tangent issue, would an option of making the "groove" that the screw goes into have a curve built in, such as seen below? (just a quick sketch, so not proportional to what the curve would actually have to be in order for it to keep the barn door mount opening at the correct speed)

[Image: ixhwaJ.jpg]
Well, yes. That is an option. To solve tangent problem mechanically. For that you will only need a DC motor rotating at constant (and controlled) rpm
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04-02-2018, 05:58 PM
Post: #7
RE: Startracker design questions
(04-02-2018 05:46 PM)JJrobots JP Wrote:  
(03-30-2018 01:11 AM)jaburkhardt Wrote:  To add on to the Tangent issue, would an option of making the "groove" that the screw goes into have a curve built in, such as seen below? (just a quick sketch, so not proportional to what the curve would actually have to be in order for it to keep the barn door mount opening at the correct speed)

[Image: ixhwaJ.jpg]
Well, yes. That is an option. To solve tangent problem mechanically. For that you will only need a DC motor rotating at constant (and controlled) rpm

Okay, sounds good. To add on...are you guys going to sell the motor control board that works the arduino pro and driver that the code refers to? I bought the arduino Leonardo and brain shield by mistake, and it obviously does not work with the coding you provided. Just want to wrap this project up and get the camera rolling. Thanks
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04-09-2018, 02:06 PM
Post: #8
RE: Startracker design questions
(04-02-2018 05:58 PM)jaburkhardt Wrote:  
(04-02-2018 05:46 PM)JJrobots JP Wrote:  
(03-30-2018 01:11 AM)jaburkhardt Wrote:  To add on to the Tangent issue, would an option of making the "groove" that the screw goes into have a curve built in, such as seen below? (just a quick sketch, so not proportional to what the curve would actually have to be in order for it to keep the barn door mount opening at the correct speed)

[Image: ixhwaJ.jpg]
Well, yes. That is an option. To solve tangent problem mechanically. For that you will only need a DC motor rotating at constant (and controlled) rpm

Okay, sounds good. To add on...are you guys going to sell the motor control board that works the arduino pro and driver that the code refers to? I bought the arduino Leonardo and brain shield by mistake, and it obviously does not work with the coding you provided. Just want to wrap this project up and get the camera rolling. Thanks
The Brain shield is capable of handling the startracker but its code will need some adjustment. I will email Jose asking for a new code. I might take a little bit but it is doable.
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04-09-2018, 03:45 PM
Post: #9
RE: Startracker design questions
(04-09-2018 02:06 PM)JJrobots JP Wrote:  
(04-02-2018 05:58 PM)jaburkhardt Wrote:  
(04-02-2018 05:46 PM)JJrobots JP Wrote:  
(03-30-2018 01:11 AM)jaburkhardt Wrote:  To add on to the Tangent issue, would an option of making the "groove" that the screw goes into have a curve built in, such as seen below? (just a quick sketch, so not proportional to what the curve would actually have to be in order for it to keep the barn door mount opening at the correct speed)

[Image: ixhwaJ.jpg]
Well, yes. That is an option. To solve tangent problem mechanically. For that you will only need a DC motor rotating at constant (and controlled) rpm

Okay, sounds good. To add on...are you guys going to sell the motor control board that works the arduino pro and driver that the code refers to? I bought the arduino Leonardo and brain shield by mistake, and it obviously does not work with the coding you provided. Just want to wrap this project up and get the camera rolling. Thanks
The Brain shield is capable of handling the startracker but its code will need some adjustment. I will email Jose asking for a new code. I might take a little bit but it is doable.

Thanks for the response. Hope to hear from you soon
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