Telescope Reviews: Orion Sirius EQ-G (Skywatcher HEQ5) made wireless

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Orion Sirius EQ-G (Skywatcher HEQ5) made wireless
#2231534 - 03/02/08 03:42 PM

One thing that keeps bothering me is the lot of wires connected to expensive astronomy equipment. Since I got my Orion Sirius EQ-G (Skywatcher HEQ5) I was looking for wireless solutions.

Today I'm very close to a solution. It consists of:

Shoestring Astronomy EQDIR interface
LM Technologies LM058 Bluetooth to Serial interface
A way to retrieve power from the mount in order to deliver 5VDC to pin 9 of the LM058

At the moment I'm finalizing the PCB layout (thanks to everybody who provided help on this!). The parts will be laid out as follows:

View from the top:

Note that the small capacitor will be replaced with a ceramic 100nF capacitor (instead of the electrolytic 10µF one).

View from the bottom:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231542 - 03/02/08 03:47 PM Attachment (220 downloads)

In order to retrieve the required 5VDC from the mount I need to retrieve it from where the EQDIR connects to the mount. Fortunately the mount provides 12VDC, hence I use a 7805 series voltage regulator to transform the 12VDC into 5VDC.

To keep the footprint of this circuit as small as possible I decided to go for 2 small PCBs instead of one larger PCB.

Here's the circuit of the 1st part, between the mount and the EQDIR:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231544 - 03/02/08 03:49 PM Attachment (191 downloads)

Here's the PCB overview of the 1st PCB (called PCB A). As you can see I use a standard Ethernet-type connector, which allows me to use a standard (short) Ethernet patch cable between the mount and PCB A:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231552 - 03/02/08 03:52 PM Attachment (169 downloads)

As you can see I use the bottom of the PCB for all the connections and the soldering. For this reason the text in blue is mirrored. Here's the etching mask for PCB A:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231557 - 03/02/08 03:55 PM Attachment (166 downloads)

I will use a simple 2-wire connection with a click contact for connecting both PCBs (for supplying the 5VDC to the LM058 on pin 9).

Here's the schematics of the 2nd board, implementing a simple direct connection (hence requiring an additional low profile gender changer) with 5VDC power on the LM058's connector:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231558 - 03/02/08 03:56 PM Attachment (180 downloads)

This 2nd board (PCB B) looks like this:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231560 - 03/02/08 03:57 PM Attachment (164 downloads)

And here's PCB B's etching mask:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2231642 - 03/02/08 04:47 PM Attachment (161 downloads)

I put the correct size PCB etching mask and drilling pattern in a 600dpi drawing with the Gimp, and created a 600dpi PDF that I attached to this post.

I believe this time I shouldn't have problems with too narrow clearances; my initial attempts used too small clearance.

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2233969 - 03/03/08 06:09 PM Attachment (155 downloads)

And here's an updated etching mask. I shrunk the pad diameter for the D-Sub and Ethernet connectors in version 7.

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2235742 - 03/04/08 02:35 PM Attachment (138 downloads)

Version 8 is identical to version 7, I only added 2 vias to better position the drilling holes for the Ethernet 8P8C modular connector (a.k.a. "RJ45").

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2258160 - 03/14/08 08:50 PM Attachment (142 downloads)

OK, since I can't find a 9-pin D-sub gender changer that does NOT preserve the orientation of the connectors I will most likely have to work without gender changer. As a result I will have to use a couple wire bridges on my PCB that connects the EQDIR and the bluetooth module.

An example:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel [Re: Olivier Biot]
#2258172 - 03/14/08 08:56 PM Attachment (160 downloads)

On the previous figure, the red lines represent wiring I will add (no 2nd PCB layer). All I will have to do is join the vias I created.

Here's the corresponding etching mask:

Edited by Olivier Biot (03/14/08 08:59 PM)

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jcjr
professor emeritus

Reged: 01/06/08

Loc: TN, USA

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel [Re: Olivier Biot]
#2258358 - 03/14/08 10:41 PM

It is looking great, Olivier. Jumpers are a lifesaver (grin).

Here is a really trivial issue, which would affect the circuit not one bit--

To my eye, a completed board looks 'tidier' if it is possible for all discrete components and jumpers have the same orientation, either all horizontal or all vertical.

Of course it is better to have a proper-working circuit than a tidy look.

Anyway, the top-left jumper is the only one that runs horizontal. It would be easy to move the left-end pad of that jumper, up and to the right, so that all the jumpers 'point the same way' on the circuit board.

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel [Re: jcjr]
#2258792 - 03/15/08 08:21 AM Attachment (141 downloads)

Thank you for your feedback

In the meantime I tried another iteration where I wanted to get rid of the jumpers altogether. I used 16 mil width for all lanes except for 5VDC and GND (32 mil).

Here's the overview of the new board:

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel [Re: Olivier Biot]
#2258816 - 03/15/08 08:48 AM Attachment (163 downloads)

I attached the CAM output as a PDF to this post: parts layout, etching mask, drilling template. As you can see I got rid of the large GND area which is not really required.

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jcjr
professor emeritus

Reged: 01/06/08

Loc: TN, USA

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2259318 - 03/15/08 01:54 PM

Looks real good. Appears to be better use of the board space than the previous large ground plane.

Ground planes can have advantages for minimizing EMI interference and parasitic oscillations, etc. Which may not be concerns on your connector board.

Another trivial advantage, is that if you have large un-etched areas of the board, necessary ground-plane or not, then it consumes less etching chemicals and might etch a little quicker.

In a perfect world all the copper would etch off at a constant rate. But I've etched boards with thin traces, where all the traces and pads would etch pretty quickly, but there would still be assorted shiny spots in the blank board space. In order to get the shiny spots completely clear, would have to leave the board in the etchant longer than necessary for the traces, risking under-cutting the thin traces just to get a 'pretty board' with no orange-peel specks of stray copper in large blank regions.

Maybe such a thing will never happen to you. Just relating experiences.

Just sayin, it can sometimes be useful to leave blank areas full of copper, even if you don't need the ground plane shielding effect.

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: jcjr]
#2259335 - 03/15/08 02:03 PM

Thanks

So far I never etched a PCB on my own. A fellow ATMer is offering assistance in doing so. We will try a different process than the traditional film and UV: instead we will try the laser printer toner transfer process. There's a readily available product "Press 'n Peel" that does this, but it appears that you should be able to do the same with regular T-shirt transfer paper. You transfer the printer toner from the paper to the copper with a hot iron.

Cheers!

Olivier

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jcjr
professor emeritus

Reged: 01/06/08

Loc: TN, USA

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: Olivier Biot]
#2259384 - 03/15/08 02:34 PM

Hi Olivier

I agree, the direct-application of laser printer toner sounds like an excellent easy method, and what I would try to do if making boards today. Also, since it has been some years since I made boards, am hoping that if I give bad advice, someone will correct it.

With an ultraviolet-light contact-printing method, for one thing the photo-sensitive boards are more expensive. For another, you can have a transparency which looks very dense to the eye, but it so happens that the UV light just shoots right thru the masks, resulting in a developed blank piece of copper with no resist stripes. You can almost always get dense-enough transparency stripes with a manually-made tape-on-mylar method, or with darkroom photographic copying, but other transparency methods can be difficult to get dense-enough masking.

Scrub the board really well, is the main thing to assure good etching.

For very simple quick boards, especially if you don't care about a perfect visual appearance, you can scrub the board well, and free-hand draw stripes with a sharpie marks-on-anything lacquer pen. Try to avoid fingerprints on the copper.

You can overlay the board with your paper printout or hand layout, and then use a center-punch or *BLEEP*-punch to put a small dimple on the copper where every pad will be. Then freehand-draw stripes and pads between the dimples.

(edit-- the *BLEEP* punch is apparently an obscene word. It is the punch with a sharper-tip than a center punch (grin))

A fresh sharpie works best, and for whatever reason, one pen might work better than another pen of the same model number.

Toward the end, I would just send artwork to a circuit board company, because the company in Hunstville made much prettier tinned-drilled boards than I could ever manufacture.

The other annoyance, which is probably my lack of skill-- I would use a small drill press with tiny drill bits for the holes. Maybe a skilled person could make one of those tiny bits last a long time, but I seemed to break maybe one bit per board. If a bit lasted for two boards it was a miracle. And the bits were not dirt-cheap. So its a good idea to have several replacement bits in the toolbox.

Edited by jcjr (03/15/08 02:40 PM)

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Don W
demi-god

Reged: 05/19/03

Loc: Wisconsin, USA

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: jcjr]
#2259391 - 03/15/08 02:39 PM

My my you've been a busy boy, Olivier.

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Olivier Biot
Amused

Reged: 04/25/05

Loc: 51°N (Belgium)

Re: Orion Sirius EQ-G (Skywatcher HEQ5) made wirel new

new

[Re: jcjr]
#2259417 - 03/15/08 02:54 PM

Quote:

Scrub the board really well, is the main thing to assure good etching.

Will normal household cleaning products do this job? I was considering 2 products right now: a power cleaner or a special product for removing tarnish from copper.

Quote:

Toward the end, I would just send artwork to a circuit board company, because the company in Hunstville made much prettier tinned-drilled boards than I could ever manufacture.

I'm all OK with working with a circuit board manufacturer if more than one needs to be made. But that solution would be a bit costly for this small fun project

Quote:

The other annoyance, which is probably my lack of skill-- I would use a small drill press with tiny drill bits for the holes. Maybe a skilled person could make one of those tiny bits last a long time, but I seemed to break maybe one bit per board. If a bit lasted for two boards it was a miracle. And the bits were not dirt-cheap. So its a good idea to have several replacement bits in the toolbox.

Good point! I have no miniature drill press at the moment so I'll have to inquire about how this is usually done.

Cheers

Olivier

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