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Gina's Observatory Roll-Off-Roof Automation


Gina

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Just been out to the observatory to look at the best place for the Power Distribution Box and ROR Control and it would appear that the best place for the PDB is on the south wall of the warm room at the back of the bench.  Best place for the ROR Control box is on the partition wall near the doorway at the top.  Two separate boxes then.

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It would be nice to have a single digital meter for the main battery V/A display but these devices measure the current in the negative rail so the battery negative cannot be connected to observatory ground line.

Edited by Gina
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1 minute ago, Gina said:

these devices measure the current in the negative rail

That's the bit that worries me, its sooo easy somewhere else in the system where you could short 0v & GND thereby by-passing the meter.

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Yes, that's why my present design uses separate voltmeter and ammeter - the problem is avoided in the ammeter by using a separate supply for the logic.

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Here is an circuit that uses the V/A digital meter for the battery voltage and total current load.   The PSU has an ammeter that shows the supply current (load plus charging current), otherwise I would have liked a centre zero ammeter for the battery to show charge/discharge current.  As long as the battery and PSU negative are boxed away from any other wiring, I think it should be pretty safe.

657385630_PowerDistribution7.thumb.png.4a3817af4f2c7318d2046871107ccef1.png

Edited by Gina
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Most of the wiring done and been looking into the Arduino sketch for the Nano.  Have a problem - can't upload from the Arduino IDE to a brand new Nano (or to a couple of others).

Quote

Arduino: 1.8.7 (Linux), Board: "Arduino Nano, ATmega328P"

Sketch uses 950 bytes (3%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
An error occurred while uploading the sketch
/home/gina/arduino-1.8.7/hardware/tools/avr/bin/avrdude -C/home/gina/arduino-1.8.7/hardware/tools/avr/etc/avrdude.conf -v -patmega328p -carduino -P/dev/ttyS0 -b115200 -D -Uflash:w:/tmp/arduino_build_776651/Blink.ino.hex:i

avrdude: Version 6.3-20171130
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/home/gina/arduino-1.8.7/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/home/gina/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyS0
         Using Programmer              : arduino
         Overriding Baud Rate          : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

 

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Oh well, plenty else to get on with.  Dismantled part of my observatory to run concealed cables.  Just the interior door and panels on the middle wall on the scope room side.

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Wired cable to the limit switches.  Now to feed the cables to the position of the control box.  I can also route the cable from the rain detector through to the control box.

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Since I'm using an RPi for remote roof control I can easily add a webcam to watch the imaging rig.  This will be supported by the KStars/Ekos/INDI system same as imaging cameras.

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More low voltage, high current twin cable has arrived.  This is for the power suppl;y and the feed to the motor.  The high current rating is not for carrying a high current but for minimal resistance and hence volt drop.  A genuine Arduino Nano is due to arrive tomorrow - I've gone right off cheapo Chinese clones!!  False economy - I want something that works and continues working!

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18 minutes ago, Gina said:

More low voltage, high current twin cable has arrived.  This is for the power supply and the feed to the motor.  The high current rating is not for carrying a high current but for minimal resistance and hence volt drop. 

A genuine Arduino Nano is due to arrive tomorrow - I've gone right off cheapo Chinese clones!!  False economy - I want something that works and continues working!

I am surprised that it is only 2 x 0.75mm^2.
I use 2 x 2.5mm^2 stranded speaker cable when I want something with a bit of "welly" for my DIY subwoofers.
Inexpensive in long rolls from discount car spares outlets. Clear with a blue coloured line for polarity.

How do you tell a Genuine Arduino Nano from a "Dolly?" 
You can't. They all look exactly alike until they die young. :wink2:
 

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This Nano is being shipped from Arduino in Italy so should be the real thing.

I use thicker cable for speakers.  This smaller cable is adequate for astro use with around 3A and 13.8v supply.  I measured the resistance of this cable and the 10m length (2x5m) measured 0.2 ohms.  I estimate under a meter from power box to ROR control box and maybe 1.5m from control box to motor.  Total 5m for the round trip.  Motor current is about 2A - maybe 3A at startup giving a volt drop of 3x0.02x5 = 0.3v.  That won't slow the roof movement much!  I used a thicker version for the 4m run from warm room to pier head - 16.5A and that was one side only - the earth is good thick house earth bonding cable (10mm^2 I think).

Edited by Gina
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On 04/09/2019 at 15:23, Gina said:

Most of the wiring done and been looking into the Arduino sketch for the Nano.  Have a problem - can't upload from the Arduino IDE to a brand new Nano (or to a couple of others).

 

Thats because they have changed the IDE and you now need to use the Processor marked (OLD BOOTLOADER) . Problem came in on IDE 1.8.7 I think.

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Genuine Arduino Nano has arrived but that won't allow upload either!  Tried several versions of the IDE but no joy.

Went over to my W7 laptop and still no joy.  Device Manager said device was working properly on COM16.  Then tried the new Chinese clone and it reported as being on COM13 with DM saying device working so tried edited Blink sketch on that and it worked!! 

I always use the example Blink sketch to test an Arduino though it needs editing to show an actual change as Arduinos come with Blink already installed.  All the Nanos I've tested had a working Blink sketch.  The new genuine Arduino Nano Blinks and W7 Device Manager reports the USB-serial chip as working on COM16 so I don't know if the Nano is faulty or something else is wrong.  I suppose that as far as this project is concerned, I can program the working Chinese clone.  Can't say I'm happy though.

Edited by Gina
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Cable runs for the limit switches completed and middle sliding door replaced.  Also run cables for the power and motor.  Both now need connections to the control box.  The power and motor cable runs were shorter than estimated with both being about 2ft.

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Looking into connecting the limit switches I can see a possible problem.  I have used a common Gnd for the data and LED switching but with the LEDs running from the main supply of 13.8v it should have a separate power Gnd.  As an alternative I could have the LEDs powered from the Nano.  With only one on at a time and running at 10mA this should be alright.

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On second thoughts, I don't like that either.  The LEDs drop 2.8-3v and with the logic 1 Arduino voltage being 5v, that doesn't leave much for the current limiting resistor.

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NO!  I think I'll do the job properly and replace the 3 core limit switch cables with 4 core.  Also, since these cables will be carrying data it might be a good idea to use screened cable.

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