Topics

Converting Black HEQ5

Jason
 

I tried searching board to see if anyone has tried this but it would appear not.  I have an older HEQ5, the black one, that is tracking only.  It has the 2 gear drive with gearbox steppers (that have a lot of back lash in them, I mean a lot.)  I don't want to cough up the $500+ to covert it over to synscan. Plus I think this would be a real fun project.  I need some help figuring this out.  Reading through the stuff here is like drinking from an aqueduct to me.  So for me I have 2 options, I think:

1. Go full blown conversion with new steppers and belt drive to take advantage of the slew rates for goto.
or
2. See if it is possible to build a set up to connect to the hand controller to allow some sort of plate solving and guiding.  (I looked at the shoestring approach but why not get better integration with     onstep...maybe, I'm not to sure if one works better then the other.)

I know you cant slide nema 17 steppers into the stock location, but it looks like nema 14 steppers would work.  Would lower holding torque be an issue with the 14 or is that just a ratio issue?

Dave Schwartz
 

There are lots of examples of converting EQ-5 mounts in the showcase (https://onstep.groups.io/g/main/wiki/Showcase%3A-What-Users-Built-With-OnStep).

On 2020-03-28 12:10 p.m., Jason wrote:
I tried searching board to see if anyone has tried this but it would appear not.  I have an older HEQ5, the black one, that is tracking only.  It has the 2 gear drive with gearbox steppers (that have a lot of back lash in them, I mean a lot.)  I don't want to cough up the $500+ to covert it over to synscan. Plus I think this would be a real fun project.  I need some help figuring this out.  Reading through the stuff here is like drinking from an aqueduct to me.  So for me I have 2 options, I think:

1. Go full blown conversion with new steppers and belt drive to take advantage of the slew rates for goto.
or
2. See if it is possible to build a set up to connect to the hand controller to allow some sort of plate solving and guiding.  (I looked at the shoestring approach but why not get better integration with     onstep...maybe, I'm not to sure if one works better then the other.)

I know you cant slide nema 17 steppers into the stock location, but it looks like nema 14 steppers would work.  Would lower holding torque be an issue with the 14 or is that just a ratio issue?

Howard Dutton
 

On Sat, Mar 28, 2020 at 09:10 AM, Jason wrote:
I know you cant slide nema 17 steppers into the stock location, but it looks like nema 14 steppers would work.  Would lower holding torque be an issue with the 14 or is that just a ratio issue?
I'm not aware of anyone who's converted one of these, perhaps a MiniPCB will fit in the motor bay though.

As for the NEMA14 working I'm just not sure, depends on the overall reduction and you still have to couple the output shafts to the worms... I looked at a this guide and it looks somewhat complicated.

Jason
 

The minipcb looks like I can cram it into the drive bay and move the ports to the stock location on the mount for a clean look.  But I would most likely do an external setup with jumpers from the motors to outside the mount for testing purposes and to get it up and running as fast as possible. Is there a better set up then the minipcb since external mounting is a option?  I'm trying to get through the technical part of this but there is a dizzying array of options for the uninitiated. 
I'm not familiar with the stepper drivers and what they can support, the stock motor specs are as follows:

RA Motor
:  SYNTA DW1323008
Model:  42BYJ07
Step Angle:  3.75º /  7.5º
Voltage:  12VDC (6 pin connector) wires are red, brown, yellow, blue, black, white.
Ratio:  1:131.876

DEC Motor:  SYNTA DW1323009
Model:  42BYJ08
Step Angle:  3.75º /  7.5º
Voltage:  12VDC (4 pin connector) wires are red, brown, yellow, blue.
Ratio:  1:131.876

Would this even work? 
Also I put the numbers into the configuration calculator.  I'm not sure I have the right numbers in the right place.  GR1 I used the ratio from the gearbox on the stepper and GR2 is the ratio for the worm, I then reduced the steps by half as they are 3.75 degree steppers.  Should I reduce the steps more to come in line with 7 degree steps?



Also here are the ratios for the mount.  In case someone else needs them.

Worm  1/144
Worm gear to motor gearbox gear  54/72
Motor gearbox  1/131.876


Khalid Baheyeldin
 

On Sat, Mar 28, 2020 at 05:12 PM, Jason wrote:
I'm not familiar with the stepper drivers and what they can support, the stock motor specs are as follows:

RA Motor
:  SYNTA DW1323008
Model:  42BYJ07
Step Angle:  3.75º /  7.5º
Voltage:  12VDC (6 pin connector) wires are red, brown, yellow, blue, black, white.
Ratio:  1:131.876

DEC Motor:  SYNTA DW1323009
Model:  42BYJ08
Step Angle:  3.75º /  7.5º
Voltage:  12VDC (4 pin connector) wires are red, brown, yellow, blue.
Ratio:  1:131.876

Would this even work? 
Also I put the numbers into the configuration calculator.  I'm not sure I have the right numbers in the right place.  GR1 I used the ratio from the gearbox on the stepper and GR2 is the ratio for the worm, I then reduced the steps by half as they are 3.75 degree steppers.  Should I reduce the steps more to come in line with 7 degree steps?

Also here are the ratios for the mount.  In case someone else needs them.

Worm  1/144
Worm gear to motor gearbox gear  54/72
Motor gearbox  1/131.876

If it was me, I would use the motors that are in the mount, if they have 4 wires each (i.e. it is a bipolar stepper). This removes the hardest part in the conversion, which is mounting the motors and pulleys.

So I would start by experimenting with that, and see how it goes. If it does not work, then the controller will still work, you just need to change the motors and pulleys.

You should not use 200 in the spreadsheet for Stepper-Steps. That is only for 1.8 degree per step.

The motor specs you listed are a bit ambiguous.
Is the step angle 3.75 degrees or 7.5 degrees?

Your Stepper-Steps is either 48 (7.5 degrees) or 96 (3.75 degrees).
So that goes in the spreadsheet.

The other factor is the motor gearbox ratio has to be multiplied by the intermediate ratio.

So: 131.876 X 1.33333 = 175.83466667 goes to GR1.

So the lines in the spreadsheet will be:

48 steps per rotation, 8 microsteps, 175.83466667 GR1, 144:1 GR2

If you use 1/8 microsteps that gives you 27,008.2048 steps per degree, and 0.13"/step resolution.

You can also use 1/16.

Change the 48 to 96 if the motor ends up being a 3.75 degree one.

Jason
 

Sorry for being a novice but......

I to was confused by the two different step angles.  Could this be dependent on how the motor is wired up?  Like unipolar vs bipolar?

How do you determine what the micro step should be? 

Given the number output in the calculator I can go with a Teensy 3.2 driver because the fast slew rate is 18.5 us/step.  Is the fastest slew rate related to the stepper shaft speed calculated?  I believe there is no way these steppers will hit 4300 rpm or any for that matter.  Is there a way to calculate max slew rate for the motor or is it a test to find kind of deal?

Howard Dutton
 

On Sat, Mar 28, 2020 at 03:57 PM, Jason wrote:
I to was confused by the two different step angles.  Could this be dependent on how the motor is wired up?  Like unipolar vs bipolar?
No, I was thinking you probably have 48 step motors there and they list the half-stepping steps per rotation (prior to the gear reduction.)  Weird but only explanation I can think of.

How do you determine what the micro step should be? 
Khaild's recommendation of 8x is about right from what I can see, read the spreadsheet recommendations.

Realize you will very likely not be able to do fast gotos with the stock motors they will crawl... might be as slow as 0.2°/s or if you're lucky perhaps 0.6°/s.

Khalid Baheyeldin
 

On Sat, Mar 28, 2020 at 06:57 PM, Jason wrote:
I to was confused by the two different step angles.  Could this be dependent on how the motor is wired up?  Like unipolar vs bipolar?
No. The step angle of a motor is fixed and cannot be changed.

How do you determine what the micro step should be? 
You are free to use any microstepping that is supported by the driver that you will use, within a reasonable range.
Usually 1/4 to 1/32 work for most drivers.
You have to make sure that steps per degree is between 12,800 and 61,200.
Less and it is too coarse for astrophotography. More and you exceed OnStep's hard limits.

Given the number output in the calculator I can go with a Teensy 3.2 driver because the fast slew rate is 18.5 us/step. 
The STM32 can do 20 us/step, and that can go down to 16 us/step if you use a different microstepping for slewing (like I do, not in the spreadsheet).

Measure the space that you have, and see if a MiniPCB2 will fit. If it will, then go with that.
If not, then you have choice per other considerations (lower cost, ...)

Is the fastest slew rate related to the stepper shaft speed calculated?  I believe there is no way these steppers will hit 4300 rpm or any for that matter.  Is there a way to calculate max slew rate for the motor or is it a test to find kind of deal?
Yeah, that RPM is crazy fast, and can never work.
What was the slewing speed with the stock board and firmware?

You change the desired slewing speed to reduce the RPM.

Khalid Baheyeldin
 

On Sat, Mar 28, 2020 at 07:11 PM, Howard Dutton wrote:
Realize you will very likely not be able to do fast gotos with the stock motors they will crawl... might be as slow as 0.2°/s or if you're lucky perhaps 0.6°/s.
That is because of the very high gear reduction (175:1).
If the stock motors don't work for some reason, at least you know that, and can use pulleys for a more reasonable reduction.

The goal is 12,800 to ~ 38,400 steps per degree.
More and you have fast RPM (motors stall), or slew slewing speed.
Less and it is too coarse for imaging.

Dave Schwartz
 

I think I can provide a bit of experience on reusing the existing guide upgrade motors... When I started with OnStep on my guide-motor-upgraded EQ-5 mount, it had 48-step motors (with some built-in reduction ratio I don't remember now), 1:1 transfer gears and 144-tooth worms. Yes, I got OnStep to work with it (using the unipolar motors in half-coil mode) but the gotos were incredibly slow... glacial you could say. That might not be too bad for imaging where you go to only a few objects per night but at a star party your friends will be laughing behind your back. The guide motor upgrades were intended to do 'push-to', then engage the clutches and guide... not to slew across the sky.


On March 28, 2020 7:11:01 PM EDT, Howard Dutton <hjd1964@...> wrote:
On Sat, Mar 28, 2020 at 03:57 PM, Jason wrote:
I to was confused by the two different step angles.  Could this be dependent on how the motor is wired up?  Like unipolar vs bipolar?
No, I was thinking you probably have 48 step motors there and they list the half-stepping steps per rotation (prior to the gear reduction.)  Weird but only explanation I can think of.

How do you determine what the micro step should be? 
Khaild's recommendation of 8x is about right from what I can see, read the spreadsheet recommendations.

Realize you will very likely not be able to do fast gotos with the stock motors they will crawl... might be as slow as 0.2°/s or if you're lucky perhaps 0.6°/s.

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

George Cushing
 

Vixen used two reductions on the PF42-48 Nippon Pulse motors 300:1 and 120:1. With 300:1 you run out of motor speed pretty quickly. .



For the MiniPCB2s I've built to drive the PF42-48s. I set µsteps to 8 for 46080 µsteps/° of RA axis rotation. Surprisingly, I've found A4988s to work the best with these motors.

Jason
 

Mr. Schwartz, I'm not worried about goto at this time so push to and then guiding will work just fine for me.  I'm assuming the speed should be fast enough to plate solve once I get as close as I can to the target.  I can test all this later so no worries there for now.

I have sent Mr. Cushing an email regarding some stm32 kits.  Hopefully they are still available.

How do you order the pcb for the minipcb builds?  I seen instructions some were but have had so many tabs open that I have forgotten were it was at and cant seem to find it anymore.  I'm going to put together a couple of different flavors of onstep to try.  I got 2 more smaller mounts I can slap some nema 17 motors on.

Dave Schwartz
 

For the miniPCB, go to the group Wiki and to the miniPCB page. In the is a link to where Howard built the schematic and PCB on jlcpcb.com. Follow that link and you will be able to have the PCBs made and there is also a bill of materials too.


On March 29, 2020 8:12:36 PM EDT, Jason <jasontaylor1311@...> wrote:
Mr. Schwartz, I'm not worried about goto at this time so push to and then guiding will work just fine for me.  I'm assuming the speed should be fast enough to plate solve once I get as close as I can to the target.  I can test all this later so no worries there for now.

I have sent Mr. Cushing an email regarding some stm32 kits.  Hopefully they are still available.

How do you order the pcb for the minipcb builds?  I seen instructions some were but have had so many tabs open that I have forgotten were it was at and cant seem to find it anymore.  I'm going to put together a couple of different flavors of onstep to try.  I got 2 more smaller mounts I can slap some nema 17 motors on.

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Howard Dutton
 
Edited

Here's the link.  Note this is a MiniPCB version 1 and more suitable for building into a mount than the version 2 board.
https://onstep.groups.io/g/main/wiki/2E-MiniPCB

Go through to EasyEDA and look at the PCB (open it in the editor - runs in your web browser), get dimensions, etc. and some idea if it'll fit.
https://easyeda.com/hdutton/OnStepMiniPCB_BT_v1_24-cb1f4ebb3e044cec91131b18f35d7f36

Jason
 

Another question...of course.  I already have some A4988 stepper drivers and was looking at the TMC2130 v3 from bigtree.  They are on Amazon but they have some extra pins.



I would imagine that I would just cut the pins on top and de-solder the 2 extra on the bottom and it should be good to go right?

Also does it matter if I use 5% resistors or 1%?  And does the wattage matter?

Khalid Baheyeldin
 

On Tue, Mar 31, 2020 at 11:44 PM, Jason wrote:
Another question...of course.  I already have some A4988 stepper drivers
If your spreadsheet provides a steps per degree of 12,800 per more with 1/16 microsteps or larger (1/8, 1/4), then start with the A4988 that you already have. Once you get things working you can then decide if a jump to a different driver is needed or not

Howard Dutton
 

On Tue, Mar 31, 2020 at 08:44 PM, Jason wrote:
Also does it matter if I use 5% resistors or 1%?  And does the wattage matter?
Read the Wiki:

https://onstep.groups.io/g/main/wiki/2E-MiniPCB

"Some components, such as resistors, are generic so feel free to pick a 1/8 watt or 0.1 watt metal film or carbon resistor of approximately the same value I used, give or take even 50% of the value is ok in all cases.  LED's will be brighter or dimmer depending on their associated resistor value so feel free to experiment (within the limits of the LED) before soldering those in if you like.  You could even buy a resistor kit for future projects and have all common values on-hand they don't cost much.  I built with 1/4 watt resistors since that's what I have on-hand and they are a tight fit (a bit larger) but it worked out fine."

Howard Dutton
 

On Tue, Mar 31, 2020 at 08:44 PM, Jason wrote:
I would imagine that I would just cut the pins on top and de-solder the 2 extra on the bottom and it should be good to go right?
Yes those two extra pins on the side are not used, if they don't touch anything leave them as is if you like... or cut them off on both sides.. or de-solder/remove them carefully (!)

Khalid Baheyeldin
 

Jason,

Another thing to do before you start, or order anything, is check this new EQ5 conversion by Sebastian. See the videos attached there.

Here he describes all the parts he started with, and here is Omega Centauri through his rig.

This is proof that an EQ5 can do a decent job in astrophotography.

He used a different board (MKS Gen-L) which will not fit inside the mount, but in a box on the accessory tray.
I would still start with the motors that you have (eliminates a lot of work that way) and A4988, then move to something else if the need arises.

Jason
 

I ordered parts to build with the minipcb but do to shipping on some will not be able to complete on till the end of next month.  So I a blue pill kit.  It's put together but I don't know how to set the jumpers for the A4988 or if it even needs the jumpers.  All the instructions are for jumper positions for drv8825, lv8729, or the tmc series of drivers.  Do the A4988 even need the jumpers?