Jump to content

sgl_imaging_challenge_2021_4.gif.6a323659519d12fc7cafc409440c9dbf.gif

Power Distribution & Focus Control Box for MN190 Imaging


Gina
 Share

Recommended Posts

I'm thinking of having the MN190 only on my EQ8 mount and the 400mm FL triple imaging rig as a separate system.  In consequence I shall need a new power distribution and focus control box and keep the much more complicated multi-scope power and focussing system just for the triple imaging rig.

Here is the circuit diagram.

post-13131-0-85550100-1423951664_thumb.j

  • Like 1
Link to comment
Share on other sites

Small (but crucial) correction to the circuit diagram - missed the Nano Gnd connection.  Gets power from the USB but needs Gnd to stepper motor driver Gnd.  Not good to rely on the USB Gnd IMO.

post-13131-0-06829200-1423998370_thumb.j

Link to comment
Share on other sites

I might add automatic dew heater control dependent on the dew point, as measured by a DHT22 digital humidity and temperature measuring device.  A DS18B20 digital thermometer would measure the temperature of the telescope near the dew heater.  The Arduino sketch would have a section that determines dew point and controls the power to the dew hearter such that the dew heater heats the telescope to a few degrees above dew point.  This prevents dew with the minimum of heating.  One of the PWM outputs controls the MOSFETs in the circuit below to control the power to the dew heater.

Here is a modified power and focus control circuit diagram with added auto dew heater control.

post-13131-0-24571400-1424025729_thumb.j

Link to comment
Share on other sites

I have made up the simpler circuit as in post #2 and designed and printed a box to contain it.  The box fits onto the ADM dovetail that's used to mount the MN190 scope, between the dovetail and the scope and sticking out to one side.  It is retained by a lug that fits into one of the holes in the dovetail.  No screws or bolts needed :D

The 5v regulator is bolted to the dovetail to provide cooling.  The tab is the ground connection so no insulation required.  A slot in the box enables the regulator chip to be bolted directly in thermal contact with the dovetail.  Part of the box is covered by the scope, the rest has a clip-on lid.

post-13131-0-76895000-1424537071_thumb.jpost-13131-0-86506500-1424537076_thumb.jpost-13131-0-12827400-1424537081_thumb.jpost-13131-0-23877800-1424537085_thumb.j

  • Like 2
Link to comment
Share on other sites

Next stage will be to modify the Arduino sketch that I used when I had the four scopes controlled by the Arduino Mega to work with the different data pins on the Nano for the focus control and test it.  I shall also produce a modified VB app to run on the laptop to control the Arduino.  I think I'll do all the development and testing indoors (I now have the MN190 indoors) and make sure it all works properly before moving it all out to the observatory.

With a forecast of several hours of clear sky tonight I was hoping to have everything ready for imaging but now I think that is asking too much.  I don't want to rush things - that always seems to lead to trouble :grin:  I have been delayed by a problem with the observatory roof that took a while to sort out this afternoon.

One problem is that everything seems to take longer now than it did years ago when I was younger :(  Oh well, not to worry, I'll be imaging again one day, it's just that I can't say when...

Link to comment
Share on other sites

Just realised I also need to find a timing pulley to fit the stepper motor.  Previous focus control on this scope was a DC motor and manual remote control with a separate cable.  When using the other scopes, the MN190 was only used for guiding and I used manual focus.  I'd forgotten I hadn't added the stepper motor focussing :D

Edited by Gina
Link to comment
Share on other sites

Here is the Arduino sketch (untested).

// Gina's single remote focussing system using PC control - 2015-02-21 2000.// File name - astro_focuser_half_step_single_01//// Stepper motors used are 28BYJ-48 with ULN2003A drivers// 4 phase, 8-beat motor, geared down by a factor of 64. // Step angle is 5.625/64 degrees.//////////////////////////////////////////////////declare variables for the motor pinsint motorPin1 = 2;	// Brown to driver   - Blue   - 28BYJ48 pin 1int motorPin2 = 3;	// Red to driver     - Pink   - 28BYJ48 pin 2int motorPin3 = 4;	// Orange to driver  - Yellow - 28BYJ48 pin 3int motorPin4 = 5;	// Yellow to driver  - Orange - 28BYJ48 pin 4                        // Green to driver Gnd                         // Blue to driver 12v - Red   - 28BYJ48 pin 5 (VCC)////////////////////////////int incomingByte = 0;   // for incoming serial dataint FocusSpeed = 1;int motorSpeed = 1200;  //variable to set stepper speedint lookup[8] = {B01000, B01100, B00100, B00110, B00010, B00011, B00001, B01001};//////////////////////////////////int focusCount = 0;  // int stepSize = 5;  // how many motor steps correspond to one focussing step - this may need changing after testing//////////////////////////////////////////////////////////////////////////////void setup() {  //declare the motor pins as outputs  pinMode(motorPin1, OUTPUT);  pinMode(motorPin2, OUTPUT);  pinMode(motorPin3, OUTPUT);  pinMode(motorPin4, OUTPUT);  Serial.begin(9600);}////////////////////////////////////////////////////////////////////////////////set pins to ULN2003 high in sequence from 1 to 4//delay "motorSpeed" between each pin setting (to determine speed)void moveBackward(){  for (int s = 0; s < stepSize; s++) {    for(int i = 0; i < 8; i++)    {      setOutput(i);      delayMicroseconds(motorSpeed);    }  }  focusCount--;//  sendFocusCount ();}///////////////////////////void moveForward(){  for (int s = 0; s < stepSize; s++) {    for(int i = 7; i >= 0; i--)    {      setOutput(i);      delayMicroseconds(motorSpeed);    }  }  focusCount++;//  sendFocusCount ();}////////////////////////void setOutput(int out){      digitalWrite(motorPin1, bitRead(lookup[out], 0));      digitalWrite(motorPin2, bitRead(lookup[out], 1));      digitalWrite(motorPin3, bitRead(lookup[out], 2));      digitalWrite(motorPin4, bitRead(lookup[out], 3));}///////////////////////void moveManyF(int count) {    for (int i = (count -1); i >= 0; i--) { moveForward(); }  sendFocusCount ();}   //void moveManyB(int count) {    for (int i = (count -1); i >= 0; i--) { moveBackward(); }  sendFocusCount ();}   ///////////////////////void sendFocusCount (){  Serial.println(focusCount);}///////////Single focuser control ASCII codes :-//53 - Single Step//54 - 10 Steps//55 - 100 Steps//56 - Down//57 - Up//void loop() {  if (Serial.available())  {  incomingByte = Serial.read();  switch (incomingByte) {    case 53: //     Serial.println("Single Step Focussing");      FocusSpeed = 1;      break;    case 54: //     Serial.println("10 Step Focussing");      FocusSpeed = 10;            break;    case 55://      Serial.println("100 Step Focussing");      FocusSpeed = 100;      break;    case 56://      Serial.print("< ");      moveManyB(FocusSpeed);      break;    case 57://      Serial.print("> ");      moveManyF(FocusSpeed);      break;    default:       // if nothing else matches, do the default        // default is optional      Serial.print("Unrecognised Command: ");      Serial.println(incomingByte, DEC); }  }}

Operation is controlled by ASCII codes received on the serial port (USB).

53 - "5" - Single Step

54 - "6" - 10 Steps

55 - "7" - 100 Steps

56 - "8" - Down

57 - "9" - Up

If anyone wonders why the codes start at "5", it's because this is designed to be compatible with the multifocuser versions and other codes select the particular focuser.

Edited by Gina
Link to comment
Share on other sites

Tried with the Blink example sketch and got the same result so suspect a faulty Nano.  Tried with another Nano and that works fine also tried with a cheapo Nano with CH340G USB to serial chip and that also works fine both with the Blink sketch and my focus controller :)  The apparently faulty Nano has an FTDI USB to serial chip.

Anyway, I have working Nanos so I'll swap the dodgy one for one of those.

Link to comment
Share on other sites

Thank you Damian :)  Yes, the printer is showing signs of wear.  ATM it's still working well and producing accurate prints but if/when the print quality deteriorates or fails I'll take the covers off and see what's what.  Once I've got something working well for imaging, I'll get back to the RepRap style experimental 3D printer project - I could do with a backup printer and also the bigger printing volume would be very useful.

Link to comment
Share on other sites

Testing continued...

Using the triple imaging VB app that I developed for my widefield triple imaging rig (3x 460EX plus 3x SLR prime lens), I'm getting the correct response from the Nano through the serial connection (USB), (ignoring the focuser selection which doesn't apply).  Test successful :)

Next stage will be to connect power and connect a stepper motor to the driver and check that the motor responds correctly to the various commands.

Edited by Gina
  • Like 1
Link to comment
Share on other sites

Got a problem :)  I've been developing the VB app on my Win 7 desktop and now need the application itself on my obsy laptop.  But how to do it????  Should be simple but...  This is Microsoft so...  Tried Publish from the Project menu - went through the options in a couple of ways and got to this point :-

post-13131-0-38936500-1424605146.jpg

As you can see, I tried a simple path from which I thought I could copy everything across to the laptop with TeamViewer but it came up with this :-

post-13131-0-78298200-1424605350.jpg

I thought "Ah, maybe it wants the laptop address on the network" so I tried browsing to that (tried to open "homegroup" from the Browse window) but VB crashed - all it said was that it encountered a problem and was shut down :(

What to do now???  I don't really want to publish it to a web site or burn it to a CD or DVD.  Nor do I want to set up VB development on my laptop.  I'm sure there must be a simple answer to this, but what?  Anyone any ideas, please?

Link to comment
Share on other sites

Until I sort this out, this project's on hold.  I could add an analog input and use my manual control box I suppose but would rather use computer control.  Meanwhile I'm progressing the other two imaging projects - triple imaging with 3 lenses and the other with 3 scopes.

Link to comment
Share on other sites

SORTED!  :)

As I suspected the answer was simple.  Did some Googling and found several examples of publishing to web sites and CD-ROM.  Turns out that publishing to CD-ROM does NOT actually burn the CD - it just places the files in the previously specified deploy or Publish location on local HD and you have to burn the CD as a seperate operation. 

SO... Publish to CD-ROM - does exactly what I want - puts the required files in the folder on the local HD.  Then using TeamViewer, transfer files to laptop into a suitably created folder, run Setup.exe and it installs the app on the remote laptop :)  Job done. Simples :D

Edited by Gina
Link to comment
Share on other sites

Connected up the MN190 power and focussing box to laptop USB, power and stepper motor fitted with a crude pointer (piece of solder).  Ran the triple focussing VB app (haven't done a specific single focuser app yet) and it all works.  With the current settings, the motor output shaft rotates between 3 and 4 degrees per focussing step.  100 steps gives slightly less than one revolution.  10 lots of 10 steps does the same.  1, 10 and 100 steps tested in both directions and operation is perfect :)

RESULT!! :) :)

Now to put it all on the scope :)

Here's a screenshot of the TeamViewer window showing the Triple Remote Focussing System VB app running.  (Click image to see full size.)

post-13131-0-83797400-1424692020_thumb.j

Edited by Gina
Link to comment
Share on other sites

Power and Focus Control Box fitted to dovetail and MN190 attached plus focuser stepper motor and timing belt added.  VB app controlled focussing has been tested and working :)

Here's a photo.  Not the best I'm afraid :grin:

post-13131-0-45571500-1424715185_thumb.j

Link to comment
Share on other sites

The 13.8v supply on the 12v stepper motor causes it to run rather warm and currently one phase is left on continuously so I'll be adding a bit of code to the Arfuino sketch to switch the stepper off in periods of inactivity.  No holding current is required as the stepper motor's gearbox holds position anyway.  I though I had already included this code but apparently not :D

Link to comment
Share on other sites

I now have the MN190 and all its kit mounted on the EQ8.  Balanced and all connected up.  The remote PC controlled focussing is working perfectly - I had the scope pointing at the trees on the far hill and started with the focus way off.  I started with 100x and gradually got a clearer and clearer image.  Once I could tell roughy where I was I aligned the scope onto the top of one of the trees and gradually refined focus, using the x100 then the x10 and finally the x1 and zooming in on the display until I was within one step.  Nice sharp image unbinned and zoomed in to show the pixels.  I'm very happy with that :)

However, I'm AGAIN having problems with the EQ8 mount not working a few seconds after connecting with CdC :(  The only thing I've done is to add a fuse in the power line to the battery and connect the mount cable directly (rather than using a cig lighter adapter) with a 4A fuse.  The battery is not fully charged and is drawing about 2A of charging current and reading 13.0v.  So the cable from the PSU in the warm room is dropping 0.8v.  13.0v should be fine for the mount.

It's the same battery as I was using before when it was working fine.  Instead of using crocodile clips to connect the battery, I am now using proper battery terminals with nice thick cable doubled up so that good connection is obtained with the twin connection screws.  All this mount power stuff has it's own thread so I'll continue with my efforts to fix this in that thread...

Drat I thought I was set up for imaging tonight :(  Mind you, despite the forecast for clear skies there are dirty great black clouds gathering so they may well be wrong!

Link to comment
Share on other sites

  • 2 weeks later...

Having sorted out the EQ8 mount problems I now have a working imaging system using the MN190 scope and have been tackling the PA tonight until cloud stopped play.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.