Has anyone made bartels or Ek's box or similar - Page 6

bojan · #**101** 22-12-2009, 08:56 PM

Quote:

Originally Posted by mswhin63

If they are mechanical, it may require extra circuitry to get the pulses needed for EK box whereas the optical encoders provide the necessary pulses out from the encoder. I have never thought about the differences between mechanical or optical.

Not really..
Mechanical encoders have two sets of mechanical contacts -brushes - that open and close as shaft rotates, producing the series of pulses with help of pull up resistors on board (there are no pulses if shaft is not moving). .. just like optical encoders have two opto-interupter switches, and electrically the interface is exactly the same.

However, the are a special class of high resolution optical encoders that produce two sinusoidal output voltages (90° phase difference between them) as shaft rotates, and this type of output requires more involved electronics, Ek box does not handle them.

mswhin63 (Malcolm) · #**102** 22-12-2009, 09:14 PM

savvy cheers, looking at the cct I realise that now

Too many beers

bobson (Bob) · #**103** 22-12-2009, 09:18 PM

No worries guys, they are only $37 bucks. I'll let you know once they arrive

cheers

bobson (Bob) · #**104** 22-12-2009, 11:39 PM

I think they are optical encoders, not mechanical. I found some info about them:

Based on model # from Ebay, model: 91Q128-43-00110

http://www.electro-nc.com/products/900index.shtml

If you click on "Ordering" on above link it explains how to read a model #, based on this mine is definitely optical encoder

( I cant post link cos its done in frames

and it will always display the same URL)

Everything is there, specs, features, wiring diag.

mswhin63 (Malcolm) · #**105** 23-12-2009, 01:05 AM

Cool, see how it goes for accuracy, It is entorely possible to use low res encoders for general obs. Although if you can gear it like I have on my DOB you can acheive as much resolution as you need.

The gearing is quite easy to acheive on AZ but not as much as ALT.

bojan · #**106** 23-12-2009, 06:24 AM

That is good.. it is custom design it seems but now it is all clear re wiring.
Good luck with them :-)
I think I will get one pair too.. I am thinking of my EQ8 which I am modifying (with timing belts to avoid jitter in transfer gears).

bojan · #**107** 05-01-2010, 06:42 PM

Quote:

Originally Posted by bojan

I think I will get one pair too.. I am thinking of my EQ8 which I am modifying (with timing belts to avoid jitter in transfer gears).

The encoders are here..
Mechanically they seem Ok, apart from the fact that they have sleeve instead of ball bearings.. (which I hoped for, because according to order code, they are custom design).
The shaft is lubricated with very dense grease, it does not turn very easily so the friction coupling is out of question (because of slippage), but this will not be the the problem as I intend to couple them to the mount shafts by means of timing belts.

As stated eralier, the connection is as follows:
1) (black wire) GND
2) B
3) A
4) +5V

So be careful, it is not directly connectible to Ek's box (pins 3 and 4 must be swapped, then you can plug it in with GND pin on Ek's interface left free, because N/C marked pin is actually also connected to GND).

bobson (Bob) · #**108** 05-01-2010, 10:43 PM

Bojan,

Quote:

The encoders are here..

What? How come I didn't get mine yet? I ordered before you, I hope to get them soon

WA Wait a While state

cheers

bojan · #**109** 06-01-2010, 05:51 AM

Well, Perth is a bit further away (from US) :-) Or not..?

bobson (Bob) · #**110** 07-01-2010, 03:04 PM

Hi Bojan,

I got mine today

I found some hobby shop near by that sells all sort of small things like electrical and petrol remote controlled cars and many other things. They have all sort of pulleys and timing belts so I will go when I have time and see if anything is there that suits my setup.

cheers

mswhin63 (Malcolm) · #**111** 07-01-2010, 04:55 PM

I also went to a hobby shop but not very flexible. Managed to put some gears together but final make will go to smallparts.com.au site.

bojan · #**112** 07-01-2010, 06:29 PM

Old (and not so old) printers and scanners may be a supply for those things..
Timing belts used for moving printing head (30cm in dia) could be found in them.
Then, you only need a small pulley on encoder shaft.
The big wheel (or pulley) does not have to have all the teeth, only couple of them are enough (say, every 50th or 100th tooth is enough to keep sync and to prevent micro-slippage). Those teeth could be made by gluing them on the perimeter of the big pulley (appropriately dimensioned of course), using timing belt as template
In this way, it is easy to obtain 10:1 or more up-gearing (tested, the concept works

)

bobson (Bob) · #**113** 10-01-2010, 12:50 PM

Hello everyone!

Got a question to ask

I have some gears I am trying to use for my setup.
Now big wheel has 131 teeth
Small wheel has 35 teeth

I have another smaller wheel with 16 teeth, but would be hard to drill to fit encoder shaft.

Will this be enough resolution for the encoders I got? Just for visual observing that is of course.

cheers

mswhin63 (Malcolm) · #**114** 10-01-2010, 02:40 PM

Quote:

Originally Posted by bobson

Hello everyone!

Got a question to ask

I have some gears I am trying to use for my setup.
Now big wheel has 131 teeth
Small wheel has 35 teeth

I have another smaller wheel with 16 teeth, but would be hard to drill to fit encoder shaft.

Will this be enough resolution for the encoders I got? Just for visual observing that is of course.

cheers

131/35 *(128*4) Quadrature = 1916.342
131/16 x (128 *4) Quad again = 4196

Second will be better, but with gear running there will be backlash in the meshing of the gears and consequently errors will be encountered.
Timing gears with tensioning or direct/friction drive will be more effective.

Most encoders work effective on 5000 but for obs, may get away with either.

bobson (Bob) · #**115** 11-01-2010, 12:30 PM

Thanks Malcolm,

Yeah, I went to that hobby shop in Midland and asked the guy in the shop about what I need but no luck.

Did you get anything from smallparts.com?

cheers

bob

mswhin63 (Malcolm) · #**116** 11-01-2010, 01:29 PM

I am trying to work on a solution for myself using friction drive as timing pulleys are costly and complex, especially on the 12" which has very little clearance compared to a 10 or 8". Let you know.

Unfortunately I have a 10,000 step quad encoder for 1:1 gearing. So mine could be a bit complex electronically.

bobson (Bob) · #**117** 12-01-2010, 08:27 PM

What about this idea

I got some rubber belts that I bought from Dick Smith a while ago. I found some plastic wheels with like tyre rubber on it at Bannings. This tyre has grooves so belt can sit in it safely. Now, there are different sizes of this wheels. The one I like is 125mm in diameter.

Thats 392.5mm circumference.
Encoder shaft I thought to put peace of thin car vacuum hose over the shaft for better grip. Not sure of dimensions of the shaft yet with the hose over it. But thinking this should work and rubber belt should not slip. I can always put 2 idlers close to encoder shaft so the belt "hugs" shaft better and give better grip this way.

Now, what I need to know is how to calculate ratio between this 2 shafts. Is it as simple as taking this 392.5 and dividing it with thickness of the encoder shaft?

Lets assume encoder shaft is 6mm. Thats 18.84mm circumference. 392:18.84=20 (approx)

20 turns of encoder shaft while big wheel turns once?
20x512=10240

In other words how many times will encoder shaft turn when big wheel turns once?

thanks

bojan · #**118** 12-01-2010, 09:25 PM

Theoretically this is it (you just have to take ratio of diameters, BTW), however, there will be errors in measurement because of rubber wheels, they will squeeze and the ratio will depend on pressure..
I think it is better to measure how many ticks it takes for full rotation of the shaft (or 90°, I used bubble level for this.. this is how I found out the numbers, it is easy if you are using Bartel's software).
Try and find old printer with timing belt, this is the best

mswhin63 (Malcolm) · #**119** 12-01-2010, 09:27 PM

The encoder rating is 512 for a single turn in quad mode, ie: on your + and - are combined to give 512. This based on spec listed above. I was consider a friction drive around the bottom DOB base. that stays still while the encoder will spin. I myself purchace proper timing belts but did not have a good idler system, mostly experimenting to see if it works. Dur to the complexity of idler system the failure rate for such a system multiplies but the number of connecting parts, ie: belt, 2 x idler, 2 x gears. Friction against another object only give 2 points of failure. Fortunately my ALT encoder only has the single point of failure and exact 10,000 steps.

With DIY it really is a trail an error and that is why it is not taken u by the majority of people. Anyway, circumferance is one way but a simple way is just to divide the diameter/diameter depdnding which gear is driving the encoder.

The encoder shaft is not a good idea to drive on, I have ordered some drive wheels with Urethane tyre to provide friction. I am going to try 3 way to connect.

mswhin63 (Malcolm) · #**120** 12-01-2010, 09:31 PM

Quote:

Originally Posted by bojan

Theoretically this is it (you just have to take ratio of diameters, BTW), however, there will be errors in measurement because of rubber wheels, they will squeeze and the ratio will depend on pressure..
I think it is better to measure how many ticks it takes for full rotation of the shaft (or 90°, I used bubble level for this.. this is how I found out the numbers, it is easy if you are using Bartel's software).
Try and find old printer with timing belt, this is the best

I use ASCOM driver have a built in test results and I can accurately work out the resolution at any time. For friction I will be finding the hardest possible drive wheels to the stickiest compromise to come up with a satifactory solution. The DOB base is damn hard, only the wheels I have not yet checked.