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ci700


Khalid Baheyeldin
 

On Sat, Dec 28, 2019 at 05:33 AM, Tong wrote:
Here is the low-cost TMC5160 for $12. The seller promised me to mail the test product to me on Monday
Note that this is not in the StepStick form factor.
Therefore, it cannot plug directly in any of the current OnStep boards.

You may still get it to work on a separate custom Perfboard, but you have to run wires from your OnStep board to that.


--Oz--
 

I think the normal TMC5160 is $15 I think, so saving $6 for two by making two adapters is a question of time. Let us know how it works out.

The new driver (forgot the number) is $20 each.


--Oz--
 

As I mentioned, I am going to try servo motors first (as i have them already mounted, so here is my next question:

I will be using the https://github.com/misan/dcservo 
FW with arduino and was going to use A4950 motor driver

It looks to me to be compatible with the L298 servo driver, what do you guys think?
Chopper mode is just current limiting mode and should not be a factor in servo motor mode.


--Oz--
 

I got the stm32 kit C, and I have say a few words:
Quick shipment to California, excellent packing, assembled nice and quick. I am impressed with everything, great job guys. 

Now to the more difficult programming for me. 


--Oz--
 

As i am first trying servo motors and the misan/dcsero on the arduino pro mini with Gemini servo motors with 250 line encoders with 25:1 gearbox and 180t main gear.

Q1: What driver do i choose in the OnStep configuration? (there is no mode adjustment using the misan/dcservo)
(DRV8825, A4988, LV8729, RAPS128, ST820, S109, TMC2208)

Q2: I am hoping to get 5 degrees per sec slew rate, but could live with 3 (just may put up with 2).
Here is some numbers from the excel (I am using the stm32 processor)
maxR   Slew   rpm     Khz
1          6.25    4687   31
2          3.13    2343   15.6
3          2.08    1562   10.4
5         1.25     9.37    6.3

The motors are fine at these rates (but the pro-mini may not be, I am guessing the stm32 is fine at these speeds)
Here is the notes in the excel file, am I already doomed?  :)
General MaxRate recommendations:
Mega2560 >= 32,  Teensy3.2 >= 16
Teensy3.5 >= 12,  Teensy3.6 >= 8


Khalid Baheyeldin
 

On Fri, Jan 10, 2020 at 07:50 PM, --Oz-- wrote:
Q1: What driver do i choose in the OnStep configuration? (there is no mode adjustment using the misan/dcservo)
(DRV8825, A4988, LV8729, RAPS128, ST820, S109, TMC2208)
None of the above.

In your case, you will use one of the GENERIC or SERVO external drivers.

Look through the Models.h file, lines 27 to 34, and choose the one that best matches the dcservo stuff.

Q2: I am hoping to get 5 degrees per sec slew rate, but could live with 3 (just may put up with 2).
Having 3 deg/sec is very adequate, specially when you will be doing mainly conventional astrophotography.
That is, you only slew between objects a few times per session.
Even 2.5 deg/sec is adequate.

Here is some numbers from the excel (I am using the stm32 processor)
maxR   Slew   rpm     Khz
1          6.25    4687   31
2          3.13    2343   15.6
3          2.08    1562   10.4
5         1.25     9.37    6.3

The motors are fine at these rates (but the pro-mini may not be, I am guessing the stm32 is fine at these speeds)
Here is the notes in the excel file, am I already doomed?  :)
General MaxRate recommendations:
Mega2560 >= 32,  Teensy3.2 >= 16
Teensy3.5 >= 12,  Teensy3.6 >=

The figures for MaxRate is uSec/step (not kHz), and based on the desired maximum slew rate that you enter, the spreadsheet will calculate a slowest and fastest rate for you. For the STM32, it can do 20 uSec/step. If the slowest/fastest are within that range, then you are good

Good question about the Pro Mini. Don't know the answer. I guess you will know when you try things out.


Howard Dutton
 

Should look like this I think... the encoders are 250 line so 1000 count right?  I put the base slew rate at 2.0 deg/s and max is 4.0 deg/s on an STM32 (without using pulse mode which probably isn't advisable in this case.)


Khalid Baheyeldin
 

About your spreadsheet values.

First you are using an old spreadsheet. Download the new one (version 1.16).

Second, you have too much (virtual) gear reduction there.
The StepsPerDegreeAxisX are usually below 61,200 with a tested maximum of 102,400.
You are at 160,000.

The new spreadsheet version will request that you enter the desired slew rate, and it will calculate the slowest/fastest uSec/step rate.


tnut55
 

Um...where is the v1.16 spreadsheet?  The Wiki, Uploading the Firmware, still points to the v1.12 download.


Khalid Baheyeldin
 

The correct link is on the Construction page. It is to version 1.17.

I fixed the other one so they are the same now.


tnut55
 

Thanks.

The link on the STM32 BP page also directed to v1.12.



On Saturday, January 11, 2020, 7:47:55 PM CST, Khalid Baheyeldin <kbahey@...> wrote:


The correct link is on the Construction page. It is to version 1.17.

I fixed the other one so they are the same now.


Khalid Baheyeldin
 

Fixed that one too.

But having 3 places to update will cause them to go out of sync eventually (as they did here).

Howard, can you make the latest spreadsheet be without any extension, as it used to be, then the older ones have a version?

So, ... assets/downloads/spreadsheet.xls is always the latest version. That way the three pages link to the latest one.
Then as you update it for the next version, you rename assets/downloads/spreadsheet.xls to assets/downloads/spreadsheet118.xls?