Has anyone made bartels or Ek's box or similar - Page 4

bobson (Bob) · #61 22-10-2009, 09:45 PM

Quote:

Originally Posted by mswhin63

am considering a 10,000 step system and mount it centrally

Is this from Gary from Wildcard Innovations or you have some other source?
I am still shopping for encoders too, can't decide which way to go

bob

mswhin63 (Malcolm) · #62 22-10-2009, 10:03 PM

I haven't decided yet, as I deal in the electronics industry I am able to source some stuff a little differently. I am also weighing up optical or magnetic encoders.

Magnetic encoders are usually sheilded but may require a different interface. I am now interested in the overflow problem if it is a problem or not, so i may run a series of overload tests before I purchace them.

bobson (Bob) · #63 23-10-2009, 08:10 PM

Hey guys,

Could you please have a look at this encoder and tell me if it would be good for my project (EK box push system):

http://www.usdigital.com/products/en...rotary/kit/e3/

Thanks

bob

bojan · #64 23-10-2009, 09:31 PM

Hi Bob,
I had a look at data sheet and it seems OK to me.
It is incremental encoder (with index output -you will not use this - and two channels, just what you need).
Good luck

bobson (Bob) · #65 23-10-2009, 09:38 PM

Hi Bojan,

Thanks for that mate.
I was a bit confused with number of pulses.
So they are 10 000 or not?

Thanks again

bob

bojan · #66 23-10-2009, 10:15 PM

Depend on what you order.
Have a look at data sheet (from the same webpage, a bit lower: http://www.usdigital.com/assets/gene...atasheet_4.pdf)

2500 CPR will give you (with Ek box or equivalent) resolution of 10000 ticks per rev (because it uses both channels for counting, and also it counts rising and falling edges of individual pulses- that is why the res is 4X).

bobson (Bob) · #67 23-10-2009, 10:30 PM

Well, thats a bit a problem, I can not find anything to tell me that from Ebay where I found it

http://cgi.ebay.com/NEW-US-DIGITAL-R...item5ad451fb03

Edit:

Model number: E3-1000-375-IH

I just figured it out this particular one has only 1000 CPR (second # in model), thats only 4000, not enough I am afraid

bob

bojan · #68 23-10-2009, 10:50 PM

Yes, I was just about to write exactly the same thing.. but this is if you mount them directly on shafts
If you use timing belt reduction (it has no backlash), you can have more.. as much as you like actually.
4:1 is not huge reduction, but it will give you 16000 ticks...

bobson (Bob) · #69 23-10-2009, 11:00 PM

Yeah, I know but that complicate things a bit. Just to clear something for me, when you say 4:1 you mean encoder shaft=4 and Alt or Az shaft=1, or other way round?

I am getting confused a bit and thats why direct drive would be preferred method

bob

mswhin63 (Malcolm) · #70 24-10-2009, 02:18 AM

I am still considering to option of gearing the encoder, I feel that any minor tolerance that a dob would experience would be amplified using a direct drive, without testing it is difficult to know.

I am not ready to look into the encoders yet until i get the other items, but I like the price on those encoders. I would pay that little bit more from the manufacturers website. The Ebay looks like older stock as there is a couple of digits missing in the part number.

bojan · #71 24-10-2009, 06:17 AM

Quote:

Originally Posted by bobson

Yeah, I know but that complicate things a bit. Just to clear something for me, when you say 4:1 you mean encoder shaft=4 and Alt or Az shaft=1, or other way round?

I am getting confused a bit and thats why direct drive would be preferred method

bob

4 on telescope shaft, 1 on encoder. This way you have up-reduction 4:1.
Well, it does complicate a bit, but have alook at what I have done... I have 120mm wheel on scope, and 6mm diameter shaft on encoder (with 48 ppr). This is 20:1 ratio.. (however offset by small number of slots in optical wheel, but I still have ~7000 tics per rot and it is enough for me)
I simply drop the scope in and that's it.
You can use the section of timing belt, to prevent slippage.

bobson (Bob) · #72 24-10-2009, 12:10 PM

Forget about it, they don't deliver to Australia? How about that?

Quote:

Sorry we don't ship there.

Best Regards,

SVCompucycle - Sales Support Team

Please visit our eBay Store for many new attractive items at bargaining
prices:

http://Stores.eBay.com/SVCOMPUCYCLE

Looks like Gary from Argo Navis is the only option.

bob

mswhin63 (Malcolm) · #73 24-10-2009, 12:28 PM

Try the manufacturer directly, may need a few to go as they use Fed Ex to delivery http://usdigital.com/

I have a lot of money recently on camping gear for dark nights but am on money control ATM so I am being a bit careful at this stage otherwise I could share.

I do have another shipper using VPOST which could reduce the over cost of delivery. Just not ready yet need clean out my workshop as well.

mswhin63 (Malcolm) · #74 24-10-2009, 12:31 PM

BTW I was also looking at this http://www.dmm-tech.com/14BitsAbsoluteEncoder.html but the interface seems to be incorrect.

bobson (Bob) · #75 24-10-2009, 02:54 PM

Hi Malcolm,

The price for the one from Ebay is $29 USD, the same one from USDigital is over $75. USDigital does ship to Australia but this guy from Ebay doesn't for some reason.

I am not sure about that magnetic encoder, Bojan said something against them if I remember correctly, I might be wrong though.

Gary from Wildcard sells 10000 for around $98 AU dollars plus delivery.

When you convert $75 USD plus shipping to AU, makes sense to buy it from Gary since you know what you are getting and Gary's support is second to none according to many ISS members.

cheers

bob

mswhin63 (Malcolm) · #76 24-10-2009, 03:30 PM

Quote:

Originally Posted by bobson

Hi Malcolm,
Gary from Wildcard sells 10000 for around $98 AU dollars plus delivery.

You are right, I was considering the cost of Argo Navis as being so high never thought the encoders would be relatively low. So yes I would consider Wildcard to purchace the encoders.

On another note, ASCOM drivers functionality would be good to try and create Stepper motor driving for DOB's. Bartels is a bit old technology but noticed that it seems to be a relatively simple Stepper motor driver curcuit. I haven't really looked at it closely but there are plenty of Microstepping stepper motor driver around so it would be interesting to create ASCOM Drivers to drive newer steper motors. I will consider that option when i am ready to motorise my DOB.

chrisp9au (Chris) · #77 24-10-2009, 05:17 PM

I've been quietly watching this thread for a while, now I have a couple of questions!

I have the David Ek box together with US Digital S2 2048 encoders.
This was all checked and massaged into working order by Bojan earlier this year, thanks again Bojan!

I have this connected to a heavy IBM laptop which is about to be replaced with a Palm Lifedrive, probably running Astromist.

Question 1.
My understanding is that the David Ek circuit, using S2 encoders, delivers 8192 steps, which equates to 2.6' per step.
Is it really necessary to introduce gear reduction mechanisms to deliver greater accuracy?
I would have thought, for visual observing, 2.6 arc minutes was accurate enough?

Question 2.
And this is really a question for those using Palm devices.
Where can one buy a reasonably priced serial cable to connect the David Ek box to my Palm Lifedrive?
Is it that simple? Do I need a null modem adapter?

I've thought about using the Bluetooth facility, but the cost and the complexity are too daunting!

Cheers

Chris

mswhin63 (Malcolm) · #78 24-10-2009, 05:44 PM

Quote:

Originally Posted by chrisp9au

Question 1.
My understanding is that the David Ek circuit, using S2 encoders, delivers 8192 steps, which equates to 2.6' per step.
Is it really necessary to introduce gear reduction mechanisms to deliver greater accuracy?
I would have thought, for visual observing, 2.6 arc minutes was accurate enough?

Eventually I would like to configure a Stepper drive that could allow better observation for CCD. Valid point though it maybe a waste of time going for 10,000 steps for a DOB if eventually i decide to go into EQ mount.

Quote:

Originally Posted by chrisp9au

Question 2.
And this is really a question for those using Palm devices.
Where can one buy a reasonably priced serial cable to connect the David Ek box to my Palm Lifedrive?
Is it that simple? Do I need a null modem adapter?

I don't know too much about PALM but try this http://serialio.com/products/cables/PalmMulti_RS232.php if it works I don't know but I am interested in working it with my Pocket PC.

MrB (Simon) · #79 24-10-2009, 05:52 PM

Cheers for the question regarding the Palm Chris... it lead me to discovering a very interesting Palm program for Canon DSLR exposure control... PalmDSLR

The one I was writing for a PIC is now on the backburner!

bojan · #80 24-10-2009, 07:14 PM

Quote:

Originally Posted by mswhin63

Bartels is a bit old technology but noticed that it seems to be a relatively simple Stepper motor driver curcuit. I haven't really looked at it closely but there are plenty of Microstepping stepper motor driver around so it would be interesting to create ASCOM Drivers to drive newer steper motors. I will consider that option when i am ready to motorise my DOB.

Bartel's software is actually micro-stepping motors, up to 40 micro-steps.

It is not the question of "old" technology here (stepping and/or micro-stepping), because this part will not change significantly in the foreseeable future.
Please note, you have source code provided as well (C).. So, for someone who knows how to do it, it would not be a problem to rewrite the code for micro-stepping motor drivers.. even to put the whole thing into microcontroller...