All Sky Camera/Weather Station build

[Gina]

Does the library source code need compiling first or does the Arduino IDE handle it?  I'll look for that Metro library.

[Gina]

Found the Metro library   And it seems just putting the folder with the source files in the Arduino Library folder is all that's required

[angryowl]

Yeah, the two libraries just need to be in the Libraries folder under the Arduino installation folder, no compiling required

[angryowl]

Finally got the chance to look over the assembled strip board and after a few modifications all connections/components work. Not the prettiest to look at but it does the job!

Ended up still using the 12V supply I had planned for the stepper motors with the addition of an LM2940 fixed voltage regulator which outputs 5V for the steppers. This works beautifully and saves me the trouble of having to source a separate 5V supply. 

I was also planning on using two optoisolators as switches for the camera fan and TEC, but turned out they had too much of a resistance across the switch end for them to be suitable for this job. So I've used two 12V relays which have virtually no resistance across the output switch end.

Also did an overnight leak test of the dome and enclosure lid assembly with only the two silicone sheets. No leaking whatsoever and this is without the additional acetoxy silicone so I think I'll be fine. I regret not doing a leak test when the enclosure was intact to test the effectiveness of the enclosure gasket but it's rated waterproof so I think it should withstand rain fairly well.

[Gina]

Beautiful birds nest

[angryowl]

Well, it turns out that the anemometer magnet is not strong enough to trigger the Hall Effect sensor so I'll have to either reprint a new magnet holder and install a stronger magnet or move the sensor closer to the existing magnet but for that I'd have to reprint an entire half of the anemometer.

Also don't like how the ASA dome spacer has turned out, lots of printing issues, so will be building a spacer out of a 12mm thick high pressure laminate sheet.

[Gina]

I've sometimes found that ASA doesn't print as well as ABS.

[angryowl]

9 minutes ago, Gina said:

I've sometimes found that ASA doesn't print as well as ABS.

I've never printed ABS so wouldn't know, but I do think ASA can be rather dificut at times. 

Unless I get my bed levelling spot on and use PVA glue on the build plate I can't get the part to stick and it usually lifts off and ruins the print. When I can get it to stick I have major issues with holes. I know this is probably user error, but never had this problem with PLA. I get what looks like under extrusion at every hole and I've tried adjusting flow rate, infill and skin overlap and retraction settings to no avail. 

Another thing which anoys me is when using PVA glue the part REALLY sticks to the glass build plate. So much so that even a bath for several hours in warm or hot water doesn't guarantee that I can remove the part without chipping the glass. Therefore my build plate is full of chips and soon will need to get a new one! ?

[Gina]

I've never used PVA glue on my glass build plates.  I find ASA needs a bed temperature of 120°C and I use a hot-end temperature of 260°C and brim on anything of more that a few mm height or I get curl and lifting off.  Another thing is that the glass needs to be scrupulously clean.  Isopropanol (IPA) works well for cleaning.

[angryowl]

Yeah, I always use a brim with ASA and clean the glass with alcohol after every print. My temps are 235 and 100 degrees for the nozzle and bed respectively. Have tried increasing both nozzle and bed temps but never gone that high so next time I do a print I will try this, thanks.

[angryowl]

It's now almost ready to go up the pole for a quick test and getting excited

However before that can happen I have to sort out a few electronic issues, namely the three steppers acting up, dew heater controller not working and the funniest one of all, when I turn on the PC fan, the case fan turns on too. I'm sure most of these are down to connections on the strip board as it was quite a job connecting them all in that tight space. If I ever do something similar again, in fact in any project involving the use of strip boards I will have the following thought in the forefront of my mind, leave ample space for the strip board and its connections. I under estimated the amount of space I would need for this and getting all the cables connected due to the tight space was I can say the hardest job in this project.

[Gina]

Great - good luck

[angryowl]

Thanks Gina, how's your going? Are you going to try a new HAT module or work around it?

[Gina]

Not well!  A new HAT won't be arriving for weeks so I've repaired the old HAT.  I've removed all the circuitry for dew heater and camera cooler and decided to use optocouplers to eliminate the possibility of microamps pulling up a GPIO and destroying the RPi as seems to have happened before.  The 28BYJ-48 stepper on the focuser stripped a gear in it's gearbox (tiny nylon gears really not up to the job) and I've decided to use better stepper motors - NEMA 11 motors on order.  NEMA 8 are even smaller but more than twice the price.  Project has been on hold until I get the new parts - optocouplers arrived this morning and just waiting for the motors.

[angryowl]

On 07/11/2017 at 10:16, Gina said:

For anyone interested in using the little 28BYJ-48 geared stepper motor for fine control I offer this modification.  The diagram below shows the coil connections for the 28BYJ-48 stepper motor.  The centre-taps on the coils are joined on the connecting block behind the blue cover.  This prevents the motor being used in bipolar mode with microstepping drivers such as the A4988, which requires electrically separated coils.  The modification involves cutting the PCB track that connects these centre-taps as mentioned above and not using the red wire.  The whole of each coil/winding is used rather than half, which doubles the voltage required to drive it and since the microstepping drivers limit the current it is perfectly safe to run the 5v version from 12v or more (eg. 13.8v).

 

I may have to turn my focus and aperture steppers to bipolar using the above modification and run them off 12V. In theory they'd need 10V but I'm hoping 12 will only get them slightly warmer.

The cover stepper seems to have enough torque as it is and I'll probably not modify it as it's in an awkward position and removing it now would prove too difficult.

When I was running them on 12V they worked fine but switching to 5V they have lost a lot of torque and am hoping this modification will bring some of that back.

[angryowl]

I knew there was a way to drive bipolar steppers from the ULN2003 boards but it's a very inefficient setup and some work involved. Don't know if I'll go down this path. http://elabz.com/driving-a-bipolar-stepper-motor-with-arduino-and-uln2803ag/

I think I'm better off just buying some 12V 28BYJ-48 steppers and run them in unipolar mode with the current ULN2003 boards but I can't find them anywhere that ships from the UK as I don't really want to wait 2 weeks to get them from China.

Does anyone have any sources for 12V steppers within the UK? Or any other suggestion as to what I could try to increase the torque?

[Gina]

Yes, using 12v motors and ULN2003 drivers that you're already using would probably be your best solution.  I have done this for some of my telescope focusers.

Using the A4988 bipolar driver you can adjust the current applied to the motor coils.  These drivers provide current drive rather than voltage and a more consistent drive (no problem from the back EMF from the inductance).  The only problem I've found is that the increased power can be too much for the gearbox if the output is mechanically stopped or overloaded.  Should be possible to solve by turning the current right down on the driver but not sure.  They don't get hot when run this way.

[angryowl]

Yeah, I think I'll go for the 12V version and use them with the ULN2003 boards and see how it goes, hopefully that should provide enough torque for the focus and aperture mechanisms. I may even replace the lens cover one as it too is struggling a bit while lifting the cover on and seems like it's skipping lots of steps.

If I still can't get them to work, I'll get the A4988 drivers and modify the steppers.

Now to find some 12V steppers that won't take a month to get here...

[LightBucket]

21 minutes ago, angryowl said:

I knew there was a way to drive bipolar steppers from the ULN2003 boards but it's a very inefficient setup and some work involved. Don't know if I'll go down this path. http://elabz.com/driving-a-bipolar-stepper-motor-with-arduino-and-uln2803ag/

I think I'm better off just buying some 12V 28BYJ-48 steppers and run them in unipolar mode with the current ULN2003 boards but I can't find them anywhere that ships from the UK as I don't really want to wait 2 weeks to get them from China.

Does anyone have any sources for 12V steppers within the UK? Or any other suggestion as to what I could try to increase the torque?

How many of those 12v motors do you need as I may have one new one I don’t need...?

[angryowl]

1 minute ago, LightBucket said:

How many of those 12v motors do you need as I may have one new one I don’t need...?

That's a really generous offer so thank you, but I would at least need two and three ideally. I'm thinking of changing all three steppers. I'll see if I can find somewhere to order them from.

[LightBucket]

56 minutes ago, angryowl said:

That's a really generous offer so thank you, but I would at least need two and three ideally. I'm thinking of changing all three steppers. I'll see if I can find somewhere to order them from.

No problem, I may have 2 but I know I haven’t got 3...

[angryowl]

Have found some with UK delivery so put an order in. I think these 12V ones should have enough torque but we'll see...

[LightBucket]

1 hour ago, angryowl said:

Have found some with UK delivery so put an order in. I think these 12V ones should have enough torque but we'll see...

I have to say, when I built my focuser I bought 4of these motors 2x5v and 2x12v and did not see any difference between them and so used the 5v as I already had a 5v supply on my mount..but for your use they may be fine, but for a focuser they were rubbish to be completely honest.

[Gina]

I've found these stepper motors quite adequate for my telescope and lens focusers.  Though I've used either the slo-mo scope drive or around 5:1 reduction either with gears or timing belt/pulleys.

[angryowl]

2 hours ago, LightBucket said:

I have to say, when I built my focuser I bought 4of these motors 2x5v and 2x12v and did not see any difference between them and so used the 5v as I already had a 5v supply on my mount..but for your use they may be fine, but for a focuser they were rubbish to be completely honest.

Hmm, I am hoping the 12V version has more torque than the 5V one. According to this it does (170-190 pull in for 5V and 370-400 for 12V) but that remains to be seen.