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Astro Projects

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All Sky Camera Mark 7

Gina

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This is my latest generation of all sky cameras and based on the ASI178MM followed by ASI185MC CMOS astro camera and a Fujinon fish-eye lens of 1.4mm focal length.  Although rated at f1.8, this lens lets a lot more light through than this would imply.  Image capture is provided by a Raspberry Pi 3 in conjunction with INDI software.  This is used with KStars/Ekos client software running on a Linux Mint desktop indoors.  Communication is via Wi-Fi.  The Mark 6 ASC has proved inadequate after being in use for some time. 

This blog will describe the problems of the Mark 6 and report my progress in developing this new version.

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“Modern “ soldering irons never seem to last very long. I have one that I have had for more years then I care to remember, it has great heat distribution and warms quickly. Bought a new one from Maplin’s some months ago as I needed some needle point tips. You get more heat from a match stick, rubbish.

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Just thought, I shall want a rain sensor to close the lens cover if it starts raining.  In fact I have one on order, on a very slow boat from China, I reckon :D  That's to add to my weather station.

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Made ring bracket to hold the electronics and wired up the buck converter to the HAT and the power supply for the RPi.

5a43e3582c27f_ElectronicsonBrackets01.thumb.png.8e811aeb84739e4d2a77fa9545a7969d.png5a43e35462204_ElectronicsonBrackets02.thumb.png.41d8652bdfa9abb0eefdd056c57816bd.png

 

 

Edited by Gina

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Connectors soldered to RPi HAT for the Hall sensors and mating parts crimped onto the wires from the Hall devices.

5a43f1e8a80da_HallSensorsConnections01.thumb.png.f3eac14e1f8ab708cf7b299528bdda08.png

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I think I have everything connected ready to start testing but there are some modifications needed to the INDI code.  Firstly, I need to check where I was.  I'm still hoping to get imaging tonight - still plenty of time before moonset at around 2am though there is plenty I can test before then :D

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These are the current GPIO allocations :-

// Lens Cover Motor
#define DIR RPI_BPLUS_GPIO_J8_07	// GPIO4   DIR
#define STEP RPI_BPLUS_GPIO_J8_11	// GPIO17  STEP
#define STEP RPI_BPLUS_GPIO_J8_12	// GPIO18  SLEEP
#define IN1 RPI_BPLUS_GPIO_J8_29	// GPIOO5  Lens Cover Hall Switch

// Power lines
#define IN2 RPI_BPLUS_GPIO_J8_31	// GPIO06  Dew Heater
#define IN3 RPI_BPLUS_GPIO_J8_33	// GPIO13  Camera Cooler

// Focus Motors
#define IN1 RPI_BPLUS_GPIO_J8_13	// GPIO27  DIR
#define IN1 RPI_BPLUS_GPIO_J8_15	// GPIO22  STEP
#define SLEEP RPI_BPLUS_GPIO_J8_16	// GPIO23  SLEEP

#define M0 RPI_BPLUS_GPIO_J8_35		// GPIO19  Motor A
#define M1 RPI_BPLUS_GPIO_J8_37		// GPIO20  Motor B
#define M2 RPI_BPLUS_GPIO_J8_40    	// GPIO21  Motor C

There are no longer three focus motors and the single focus motor can be allocated to the standard pins for the Astroberry Focuser.  All focussing can be handled by the standard Astroberry Focuser INDI driver.  So the focus motor pin allocations are :-

// Focus Motor
#define DIR RPI_BPLUS_GPIO_J8_07	// GPIO4   DIR
#define STEP RPI_BPLUS_GPIO_J8_11	// GPIO17  STEP
#define STEP RPI_BPLUS_GPIO_J8_12	// GPIO18  SLEEP

Now to the other controls.  These will be handled by a modified Astroberry Board INDI driver.  There are two simple ON/OFF controls for the dew heater and camera cooler.  To allow use of GPIO 6 on pin 31, with pull-up, for one of the Hall sensors, the control for the dew heater has been moved to GPIO 12 on the adjacent pin 32.  So the ON/Off functions are allocated thus :-

// Power lines
#define IN2 RPI_BPLUS_GPIO_J8_32	// GPIO12  Dew Heater
#define IN3 RPI_BPLUS_GPIO_J8_33	// GPIO13  Camera Cooler

Now to the lens cover control.  Hall senors are on GPIO5 and GPIO6 and motor on pins 13, 15 and 16 (GPIOs 22,27,23).

// Lens Cover Motor Hall Switches
#define IN1 RPI_BPLUS_GPIO_J8_29	// GPIOO5  Open
#define IN2 RPI_BPLUS_GPIO_J8_31	// GPIO06  Closed

// Lens Cover Motor
#define IN1 RPI_BPLUS_GPIO_J8_13	// GPIO27  DIR
#define IN1 RPI_BPLUS_GPIO_J8_15	// GPIO22  STEP
#define SLEEP RPI_BPLUS_GPIO_J8_16	// GPIO23  SLEEP

 

Edited by Gina

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I think I have the focuser code sorted out but the Astroberry Board driver is a different matter as I had it all set up for three motor selection control so I think I shall have to leave that for another day.  I'll have to cut that out of the compiling process for now. OK commented out the Astroberry Board from CMakeLists.txt.  Now to find what I do to compile stuff...

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"Huston - we have a problem!"  Plugged SD card back into RPi and applied power.  DISASTER!  Smoke started appearing from somewhere!! :(  I don't think I shall be imaging tonight after all :(  Maybe I'm rushing things too much.

Edited by Gina

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Had a cuppa, had a think and decided to do a bit of fault-finding.  Disconnected everything including HAT from RPi and RPi power connection from buck converter.  Gradually applied volts to the buck converter while measuring the output voltage.  All fine.  Plugged in the RPi power connector and the rig started drawing lots of current - just under an amp.  Switched off again.  Checked RPi processor chip and slightly burnt my finger!!  Seems I've blown up the RPi :(  I have spares but I need to find the fault before trying another RPi - at £30 odd a "pop" it could get expensive!  So that's it for tonight.  Some very careful circuit checking to do tomorrow!

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Inspected connections etc. and can see nothing wrong.  Checked with DMM for possible shorts and again didn't find anything.

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Thought I'd gamble £32 on possibly popping another Pi - I lost :eek:  This is silly!!! This Pi popping has to stop!  I've already wasted what I've gained from dumping BT "services"!  Though I'm very happy to have saved so much money and frustration from Blooming Terrible so-called broadband :D  Now where's my knitting wool and needles?

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Had another really close inspection of the HAT with sunlight on it and powerful magnifier plus reading glasses and found a fine strand of wire that could have been intermittently shorting the +3.3v line to Gnd.  It didn't show a short on the DMM but it could have just touched when I was testing I guess.  This seems unlikely but, as I believe Sherlock Holmes said "Once you have eliminated the possible what seems impossible must be true" or something like that.  I suppose if the 3.3v regulator had been destroyed the full 5.1v could be applied to the processor and blow it up.  But I'm by no means convinced this is what has happened.

EDIT - Found the quote 

Quote

Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.

 
Edited by Gina

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Looks like the whisker of wire shorting out the 3.3v supply was the problem.  Took the new RPi out of it's substantial packaging, plugged in the micro SD card and the power plug and gradually increased the supply voltage.  Current of under 0.4A and no smoke :)  Nothing plugged into the HAT.

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New RPi was working but I couldn't get a LAN connection from my Linux Mint desktop so I decided to add the human interface devices and see what was going on.  Tried without the HAT.  Powered up but no display from the HDMI and the LEDs on the RPi no longer came on :(  Has this one died as well??? :eek:  If so that's it - no more RPis in stock!!  New one should arrive tomorrow but...

Edited 9 minutes ago by Gina
Edited by Gina

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Well, I dunno!!! Been searching in various boxes but I seem to be totally out of Pies!  I think there's on in my imaging rig in the observatory but I'm not touching that.  Seem this project is on hold now though maybe I could do some driver code editing.  I can put the card in my Linux Mint desktop and edit files.

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OK...  Firstly, to discuss what is required in the modified Astroberry Board driver.  This is divided into two groups - ON/OFF controls and the OPEN/CLOSE for the lens cover.  ON/OFF controls are already covered in the code but the lens cover control is totally different.  The GUI is quite similar though with a button for OPEN and a button for CLOSE.  The light will show Grey for CLOSED and Green for OPEN, plus Yellow for moving and Red for error/fault.  With the ON/OFF controls there is no delay in operation and no test for fault conditions so the light only shows Grey for OFF or Green for ON.

The code that operates the lens cover (stepper motor with Hall sensors) is quite different from the ON/OFF code.  On receipt of the move instruction the light is turned Yellow then a continuous stream of step pulses is be sent to the motor until the appropriate Hall sensor reports that the operation is complete.  Meanwhile, the pulses/steps are counted and if this count exceeds the number required to complete the operation then a fault condition exists and this is reported to the client and the light turned Red.  When a complete operation is detected the light is turned Green or Grey as appropriate.

Edited by Gina

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This code steps the motor once and will be included in a loop together with the step count and Hall sensor test.

        // step on
        bcm2835_gpio_write(STEP, HIGH);
        // wait
        bcm2835_delay(STEP_DELAY/2);
        // step off
        bcm2835_gpio_write(STEP, LOW);
        // wait 
        bcm2835_delay(STEP_DELAY/2);

Testing the Hall sensors is simply

if (bcm2835_gpio_lev(Hopen) == LOW ) 

Where Hopen specifies the GPIO pin for the OPEN sensor, and similarly for the CLOSED sensor.

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I have set up the standard RPi arrangement with human interface devices and the RPi power supplied from one of my bench PSUs.  The micro SD card is the ASC one and that is the only connection with the ASC - no electrical connection ATM.  I am taking the utmost precautions to avoid yet another dead RPi - the pile of dead ones is already far too high!!  I have already triple checked that I have the power plug wired correctly.  This photo shows the setup before applying power.

5a46411510c60_RPiTesting01.thumb.png.8c27dffade683bafff42c70b8dd750ab.png

Edited by Gina

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