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+9V on RX/TX ??

PostPosted: Fri Mar 04, 2011 8:13 pm
by gloob
Hello. Today I started my Merlin and something strange happened. Now I can measure +9V betweet RX/TX and ground. Is this correct? Because my Arduino also could not communicate with the merlin. The SynScan AZ is working without any problems. Also Papywiz via SynScan AZ and rs232 is running.

PostPosted: Fri Mar 04, 2011 8:55 pm
by gloob
Now I tried it with a external power supply and now I get +5V on the RX TX wire.

PostPosted: Fri Mar 04, 2011 9:22 pm
by fma38
???!!!???

PostPosted: Fri Mar 04, 2011 9:24 pm
by gloob
Okay. The question is:

Is it normal that there is +9V between the RX/TX wire and the Ground when I plug in a cable into the HC port and power on the merlin.

PostPosted: Fri Mar 04, 2011 10:52 pm
by gloob
Now it seams that there is 5V between the signal wire and the ground. Is this normal when using batteries?

PostPosted: Sat Mar 05, 2011 8:51 am
by fma38
The Merlin DATA line (on RJ12 connector) is TTL, so you should have 5V, not 9V. If you are watching the RS232 port of the GOTO controller, you may have 9V, as it is pure RS232. But you can't connect the RS232 line to the TTL lines of your arduino.

PostPosted: Sat Mar 05, 2011 6:17 pm
by claudevh
Hello Gloob,

Could-you explain a little bit more what you want to achieve with the Merlin and the arduino ?
If we know more, we will be able to help you !

Anyway, as allready answered by Fr├ęderic ...

This isn't not normal (not possible normally !!!) to get 9 V into the Merlin !

The only value you can get is :

- 12 volts from the batteries (more or less according type and charge,up to 15.4 volts = maximum tolerance !)
- 5 volts on the TTL transmissions lines.
- If you have a "Goto hand controler" (the one with a display), the RS232 line (RJ connector on the bottom) could show up a 9 to 12 volts ... BUT DON'T mix all that stuff you will kill the Merlin !!!

The arduino will accept TTL signals (5 volts) but NOT RS232 signals !
A last precaution... don't attach a external power supply without REMOVING THE BATTERIES !
The external power supply should be attached to the "IN" plug (NOT THE OUT!)
Never reverse the polarities !!!

Have fun !

PostPosted: Sun Mar 06, 2011 5:15 pm
by gloob
Do you know any possibility to check if the rx/tx connection is still okay in the merlin and I did not destroy it? Is it okay if I can connect to the merlin using the SynScan AZ and the merlin on a PC?
If it is okay I have to check my Arduino, I want to use to control the merlin instead of a PC.

PostPosted: Sun Mar 06, 2011 5:34 pm
by claudevh
If the TTL line is OK, the hand-controler will work as usual ! ;)
This is not recommanded to connect at the same moment the hand controler on one RJ connector and a PC or other Arduino on the other one !
The instructions given by to way of several controlers (e.g. a PC and a hand controler) will be "inconsistant" for the Merlin head.

So, this the one OR another !!! :mad:

PostPosted: Sun Mar 06, 2011 5:37 pm
by claudevh
If you want to control the Merlin via a Arduino, you can read the next explanations:
http://dynamicperception.com/?main_page=wordpress&page_id=334
In fact, a Arduino library for the Merlin allready exist ...

PostPosted: Sun Mar 06, 2011 6:24 pm
by gloob
claudevh wrote:If the TTL line is OK, the hand-controler will work as usual ! ;)
This is not recommanded to connect at the same moment the hand controler on one RJ connector and a PC or other Arduino on the other one !
The instructions given by to way of several controlers (e.g. a PC and a hand controler) will be "inconsistant" for the Merlin head.

So, this the one OR another !!! :mad:

Sorry that it was not clear what I did.

I have two options to connect the merlin to a device:

1: Merlin -> Handcontrol -> RS232-USB Converter -> PC

2: Merlin -> RX/TX and Ground -> Arduino RX/TX via 220Ohm resistor and ground to ground

PostPosted: Sun Mar 06, 2011 6:31 pm
by claudevh
OK understand ....

But not the 2 connected in the same time ... OK ?

PostPosted: Sun Mar 06, 2011 7:02 pm
by gloob
No no. Just one at one time.