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Inexpensive BT serial adapter for Sky Safari

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#1 derelicte

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Posted 25 September 2013 - 11:54 AM

I found an inexpensive Bluetooth to RS-232 adapter that works with my Nexstar mount and Sky Safari:

Posted Image

http://www.ebay.com/...ion-Master-S...

It cost less than $16 shipped and included the battery! I've used this with my Nexus 7 and it works perfectly. The board includes a built in battery charger that charges the battery over usb.

All you need to do is slide the switch to "Slave", pair it with your device and plug it into your mount. The default baud rate is 9600 but I haven't found a way to change it.

The transmit and receive pins are flipped on the DB-9 connector, so you'll need a null modem adapter to connect it to most mount serial cables.

The data sheet for the BT module is here:

http://www.electronc...Spefication.pdf

and the schematics for the board are here:

http://www.electrodr...O_schematic.pdf

I have no affiliation with this seller other than having bought one from them.

I searched for other posts about modules like these but found none. I have a hard time paying $50 - $100 for the same thing in a plastic case. I originally was going to design one myself, but after searching on ebay for a few minutes it became clear I couldn't have made one for less than double this.

Enjoy!


#2 frolinmod

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Posted 25 September 2013 - 02:49 PM

Can that be powered via PIN 9 on the DB9?

#3 derelicte

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Posted 25 September 2013 - 02:56 PM

No. Although that pin is a no connect so you could run a wire but the max voltage for the regulator is 6.5 V.

#4 darethehair

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Posted 03 October 2013 - 03:02 PM

Cool find! Thanks for pointing it out!

So, then, of all the bluetooth options mentioned on Southern Stars website, this is (by far) the least expensive, right?

http://www.southerns...pe_control.html

I hadn't considered the need for a power supply for this stuff, but I guess it has to be powered by *something* (USB would supply 5V, if there was such a thing).

#5 derelicte

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Posted 06 October 2013 - 07:28 AM

I haven't found anything cheaper. If you do please share!

#6 darethehair

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Posted 06 October 2013 - 07:30 AM

Can you point out and/or recommend any of the 'null modem adapters' on eBay that do the transmit/receive pin swapping that you indicate is required? The ones that I see only appear to be 'gender changers' (?).

Thanks!

#7 derelicte

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Posted 06 October 2013 - 08:42 AM

This should work:

http://item.mobilewe...itemId=12118...

I'm replying from my phone so hopefully that worked. I used a null modem adapter from radio shack but I'm not sure they still sell them.

#8 darethehair

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Posted 06 October 2013 - 08:51 AM

This should work:

http://item.mobilewe...itemId=12118...

I'm replying from my phone so hopefully that worked. I used a null modem adapter from radio shack but I'm not sure they still sell them.


Yes, thanks for the link! Great price :) Terrible shipping charge :(

#9 derelicte

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Posted 06 October 2013 - 09:01 AM

Yeah. You can look around for a better price. I only searched for 30 seconds.

#10 derelicte

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Posted 07 October 2013 - 07:44 AM

Here is a cheaper one:

http://www.ebay.com/...3?pt=LH_Defa...



#11 frolinmod

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Posted 07 October 2013 - 09:05 AM

And here are even less expensive ones as well as a far greater variety of types:

http://www.monoprice...word=null modem

Be sure to scroll all the way down the page.

#12 darethehair

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Posted 07 October 2013 - 12:49 PM

Here is a cheaper one:

http://www.ebay.com/...3?pt=LH_Defa...


Better price, but does this one swap the transmit/receive pins? I used to know this stuff better, when serial was king and there was no such thing as USB :) Perhaps, by definition, *all* null-modem adapters swap the transmit/receive pins?

Null Modem Cables and Null Modem Adaptors

If you connect two DTE devices (or two DCE devices) using a straight RS232 cable, then the transmit line on each device will be connected to the transmit line on the other device and the receive lines will likewise be connected to each other. A Null Modem cable or Null Modem adapter simply crosses the receive and transmit lines so that transmit on one end is connected to receive on the other end and vice versa. In addition to transmit and receive, DTR & DSR, as well as RTS & CTS are also crossed in a Null modem connection.

Null modem adapter are available at most computer and office supply stores for under $5.



What is RS232 and Serial Communications? | TALtech

#13 derelicte

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Posted 07 October 2013 - 01:55 PM

And here are even less expensive ones as well as a far greater variety of types:

http://www.monoprice...word=null modem

Be sure to scroll all the way down the page.


yeah, but what happens when you add shipping to those?

the one I posted on ebay from monoprice includes free shipping.

#14 derelicte

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Posted 07 October 2013 - 01:58 PM

Here is a cheaper one:

http://www.ebay.com/...3?pt=LH_Defa...


Better price, but does this one swap the transmit/receive pins? I used to know this stuff better, when serial was king and there was no such thing as USB :) Perhaps, by definition, *all* null-modem adapters swap the transmit/receive pins?


did you read the description in the auction?

RS-232, DB 9 pin male to female null modem. Null modems are used to connect two computers or other devices together to achieve file transfer. Null modem connectors are different from straight through connectors because the receive and transmit conductors are crossed. This is a miniature null modem with a male connector on one side and a female on the other.



#15 derelicte

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Posted 07 October 2013 - 02:17 PM

And here are even less expensive ones as well as a far greater variety of types:

http://www.monoprice...word=null modem

Be sure to scroll all the way down the page.


yeah, but what happens when you add shipping to those?

the one I posted on ebay from monoprice includes free shipping.


I calculated shipping for one and it came out a little more expensive than their ebay price. I've bought a lot of cables and other stuff from monoprice before, but the shipping was always at least $6.95. It looks like they have a much cheaper shipping price for tiny little items.

#16 BluesNebula

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Posted 02 November 2013 - 06:08 PM

I found an inexpensive Bluetooth to RS-232 adapter that works with my Nexstar mount and Sky Safari:

Posted Image

http://www.ebay.com/...ion-Master-S...

It cost less than $16 shipped and included the battery! I've used this with my Nexus 7 and it works perfectly. The board includes a built in battery charger that charges the battery over usb.

All you need to do is slide the switch to "Slave", pair it with your device and plug it into your mount. The default baud rate is 9600 but I haven't found a way to change it.

The transmit and receive pins are flipped on the DB-9 connector, so you'll need a null modem adapter to connect it to most mount serial cables.

The data sheet for the BT module is here:

http://www.electronc...Spefication.pdf

and the schematics for the board are here:

http://www.electrodr...O_schematic.pdf

I have no affiliation with this seller other than having bought one from them.

I searched for other posts about modules like these but found none. I have a hard time paying $50 - $100 for the same thing in a plastic case. I originally was going to design one myself, but after searching on ebay for a few minutes it became clear I couldn't have made one for less than double this.

Enjoy!


Thanks for the info! I just ordered one. You can't beat the price!

#17 bdg

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Posted 22 November 2013 - 12:00 AM

Does this device work with Orion Sirius EQ-G mount and Nexus 7 Tablet?

#18 bdg

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Posted 22 November 2013 - 11:32 PM

Huh!! since nobody responded I decided to take the risk and purchased this item from eBay, the seller has raised the price to $25, its not $16 anymore also got a null modem from Monoprice, now keeping my fingers crossed hoping it will work with myy Orion Sirius EQ-G

#19 bdg

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Posted 29 November 2013 - 07:01 PM

Update: I got the above mentioned devices and managed to slew the mount using SkySafari from an Nexus 7 tablet. Testing was done indoors and I don't see any reason why this wouldn't work outdoors.

#20 korborh

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Posted 13 December 2013 - 03:11 PM

I got this too but ran into a problem with my CG5 mount. When it first connects (using SkySafari), there is a random slew and it messes up the mount position. Seems like initial connect sending some data it should not. I could not get it to work normally i.e. connect and mount position is retained.

Anybody using seeing this issue with Celestron mounts?

#21 btschumy

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Posted 13 December 2013 - 05:17 PM

Korborh,

Are you by any chance running the mount and the SkyFi off the same power source? We have had a could of reports of problems with Celestron mounts when doing so. Try using separate power sources and see if that helps.

Bill

#22 The Mighty Mo

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Posted 13 December 2013 - 06:38 PM

I don't believe he's talking about SkyFi Bill. He's using a cheap Bluetooth adapter from ebay, see the link above in the thread.

FTR Korborh, I use the Roving Networks RN-270 adapter Bill recommends on his (SkySafari) website, and it works like a champ to connect my Galaxy Note 2 and my CG-5. Sounds like this ebay adapter is inconsistent from one application and interface to the next. I'd think you'd be better off buying the better, tested, and established adapter.

#23 korborh

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Posted 13 December 2013 - 11:18 PM

Yes I think the eBay adapter is quite flaky. Since it was so cheap I took the risk but it's in the junk pile now. I was trying to use it with my PC.
I got the SkyFi adapter for the iPad to drive the mount and that works perfectly.

#24 derelicte

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Posted 16 December 2013 - 12:37 PM

I have seen this but only when the battery in my mount isn't fully charged.

All of my alignment and connection issues with this adapter have been related to the battery in the mount.

#25 Oldskaterman

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Posted 06 January 2014 - 12:59 PM

Had trouble attaching the promised file. Here's another attempt.

Attached Files








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