Now that you reminded me, it was FAR Electronics that I bought the PCB and programmed processor.. the rest of components I found in my drawers, they are pretty standard stuff
The Xtal oscillator might be slightly more difficult to source than the rest of the components, it's not something stocked by the likes of Jaycar, DSE or Altronics, but RS and Farnell have them.
I might have one or two(have a bag full of them ) salvaged ones floating around here if you hit trouble Bob.
I think Bojan has answered your question re the purpose of encoders with Bartels. I find goto works quite well with my system without them. I use Carte du Ciel or Astromist via bluetooth to transmit the coordinates. I just want the encoders for those occasions when kids knock the scope out of position.
If you want to contact my friend with the EK box set up, PM me. I am sure he would be happy to help.
I would like you to program the chip. I already downloaded the hex data for it and thought to make my own programmer. Back in kids days I used to make various things like two way radios and such.
What would you recommend to make the board from all those available:
Thanks Rod, I really appreciate your help. If I get stuck I'll ask for help thats for sure. The good thing is Simon is from Perth just like me
Now since you mentioned it, how much would it cost to make Bartels ? I do have two stepper motors from my Celestron GTL (5 wires I think).
Which one is cheaper option?
No worries, PM your address and I'll flash a chip and send it to you along with a Xtal Osc.
Your link didn't work, normal Veroboard (strip board) would be fine except the DB9 socket will not fit the hole pattern, might need to get a panel mount DB9 socket and run wires to the board.
You are right that Jaycar link doesn't work?? If you type "circuit board" into search on the left it will open whats available. What do you think about those press and peel, or PCB ETCHING KIT? I tried typing Veroboard and got what you recommend, very cheap indeed.
I've used Press-N-Peel, don't like it much. It does work, just not well.
If you choose to go with stripboard, there are freeware programs to help with design/layout. Stripboard Magic is one that comes to mind.
You can use the laser prints (on tracing paper, or transparency) from D Ek's webpage (http://digicircles.eksfiles.net/build.php) to produce very high quality PCB's.
The developer (KOH or NaOH) and etching solution (FeCl3) is still available at Dick Smith (but do not ask staff to tell you how to use these.. they know absolutely nothing about it :-()
As for PCB design, Easytrax from Protel is still available on web, and it is freeware.
Now since you mentioned it, how much would it cost to make Bartels ? I do have two stepper motors from my Celestron GTL (5 wires I think).
Which one is cheaper option?
cheers
bob
Hi Bob,
Great you have some local help. I never really costed out my Bartels system as I made it over a few years. I would guess the circuit board could be made for around $50 to $60. The steppers are definitely the tricky part to get right. A friend obtained two for me from old photocopiers and they are great. I had some earlier that just wouldn't tune. I used epoxy gears for the reduction system. They are probably the cheapest way to go. Mine probably cost around $100 to make in epoxy, plywood and nylon threaded rod. Then there are bearings and brackets (for the motors) - maybe another $40 in materials. So I guess that makes $200 plus the cost of the motors and your time. But Bojan is right: you need to be a compulsive tinkerer. I found it quite a learning curve but then I knew very little about electronics when I started it. You sound like you are in a better position.
I certainly think starting with David Ek is a good way to go. You will get a good result quickly and I think you can run these systems on equatorial platforms (depending on the planetarium you use) so you can add tracking later.
Yes, first I want to make EK box, I don't mind pushing it as long as I can find things easier, not that great in star hopping.
Now, about encoders, I got something from printer/scanner. I wonder if this can be used. There is a see through wheel with a lot of lines at the end of it and the optical reader for it with 4 wires.
Bob, this looks OK to me.
How many ticks you have on that wheel? And, more importantly, do you have two of them?
I took different approach to encoders, I dismatled couple of serial mice for parts. Basically, my solution is similar to some described on links you can find on Mel's webpage.
Regardless of friction coupling, I do not have much problems with slipping.
I made them like this because I wanted the tube to be easily mounted or removed from frame (now I am thinking of placing the timing belts from old printer around the drive wheels, this will not slip).
My optical wheels have 48 ticks, and taking into account the coupling ratio, I have around 7000 ticks per 360°, this is enough for what I am doing.
You will need better resolution, as you want to find objects with encoders.. whilst I am finding them by means of slewing from nearby objects I can find visually. Encoders are here only for my convenience when I have people around, so I do not have to reset the position too often when jumping to various objects from one side of the sky to another, and I still have good enough tracking for visual observing.
How many ticks you have on that wheel? And, more importantly, do you have two of them?
I assume one tick is clear window in this see through plastic wheel on the outer edge or one black line. Either way I don't think I would be able to count them as they are tiny and there are some many of them. I would have to magnify it to be able to count them There would be close to 500 if not more...
And no, I don't have two of them but considering the price of printer/scanner combo they are way cheaper than buying encoders.
bob
I assume one tick is clear window in this see through plastic wheel on the outer edge or one black line. Either way I don't think I would be able to count them as they are tiny and there are some many of them. I would have to magnify it to be able to count them There would be close to 500 if not more...
And no, I don't have two of them but considering the price of printer/scanner combo they are way cheaper than buying encoders.
bob
With Ek box, if you have 500 spaces on the wheel, you will have 2000 ticks per rev if this encoder is coupled directly on the shaft.
So you probably need gearbox 1:5 to increase this to 10000 per 360°, and you may need even more.
Or try to use timing belt and teethed pulleys for coupling.
You definitely need to know how many spaces you have on the wheel, otherwise you will not be able to set the resolution parameter right, so you need to count them somehow.
And do not forget, you will need two sensors per wheel, to be able to detect the direction of rotation.
I'm a bit out of practise, so it's a bit rough, some of the tracks will need touching up.
I'm unable to find my pcb drills, so you'll have to drill it too.
In light of this, I have made the board from phenolic, not fibreglass... glass blunts drills quicker than you can say Bob.
I'm not a fan of Daves artwork, the pads are too thin, so be carefull when drilling.
I have left the photoresist on to keep the copper from tarnishing, this can be removed with acetone.
) salvaged ones floating around here if you hit trouble Bob.
There would be close to 500 if not more...
