#421  
Old 20-12-2016, 01:53 AM
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And another one without the sensor. As the reading of the sensor is slow (it takes about 2 seconds), during this time I disconnected the P19 (input of the opamp), then grounded it and then disconnected it again.

This simulates different voltages going into the ADC circuit. The pattern is obvious in the image.

Any thoughts?
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  #422  
Old 20-12-2016, 04:40 AM
pat30 (Patrice)
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I am at home I see the pictures better than on the gsm.

It seems even problem I had in the first photo

What value is C40? Make test with greater value.

Well wait between the images 5 seconds mini and turn off all the software on the PC. But I find it unusual for the CCD to send anything.

Send a message to Rome to see if he has an idea.
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  #423  
Old 20-12-2016, 07:29 AM
flolic (Filip)
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Luka, do you have an oscilloscope? If all supply voltages are ok, next thing to check are waveforms as per timing diagrams here: http://astroccd.org/2016/10/cam86/#more-1345

It looks like your ADC works as it should.

I made two mistakes while assembling my camera. First, I installed C15 and C16 capacitors because I was looking at schematic and not part list. Those capacitors are not needed , in fact camera was not working with them installed (no H1 output from horizontal driver).
Second mistake was C12, C13 and C14 where I mistakenly put capacitors with 10x needed value. Again, those capacitors control timing and camera produced only garbage.
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  #424  
Old 20-12-2016, 08:14 AM
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wasyoungonce (Brendan)
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Quote:
Originally Posted by flolic View Post
Luka, .....I made two mistakes while assembling my camera. First, I installed C15 and C16 capacitors because I was looking at schematic and not part list. Those capacitors are not needed , in fact camera was not working with them installed (no H1 output from horizontal driver)....
Great pick-up Filip.....Hey Luka...guess what...I also have them on the schematic and brd. Its possible you put these on the PCB? I would have also!

Brendan

Last edited by wasyoungonce; 20-12-2016 at 09:09 AM.
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  #425  
Old 20-12-2016, 05:00 PM
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It is alive!!!
Photos and tests later tonight, no time right now.

Filip, you were right, removing C15 and C16 solved the problems. Thank you and everybody else very much!!! And special thanks to the people from the Ukrainian forums who designed it in the first place.
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  #426  
Old 20-12-2016, 05:23 PM
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wasyoungonce (Brendan)
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It is alive!!!
Photos and tests later tonight, no time right now.

Filip, you were right, removing C15 and C16 solved the problems. Thank you and everybody else very much!!! And special thanks to the people from the Ukrainian forums who designed it in the first place.

Ugggghhh...another screw up by me!

FWIW...I was worrying so went thru the entire schematics this morning...suffice to say they were alright!

Congrats Luka! When you get some pics....post up in the Ukrainian forum, thanks Grim...them all. I know he was watching Filip's debayering with interest! Filip you're famous! (edit sorry hyper link does not work with language translation, see page 126).

Last edited by wasyoungonce; 20-12-2016 at 08:06 PM.
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  #427  
Old 20-12-2016, 05:58 PM
pat30 (Patrice)
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YESSSS,
Congratulation Flolic I forgot C15 and C16
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  #428  
Old 21-12-2016, 04:24 AM
pat30 (Patrice)
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After the good news of luka, I give you a little of mine, finally if you are interested, if not, tell me !

I tried to make the best photo of the matrix, it seems to be leave

http://www.webastro.net/upload/image...1482257349.jpg

http://www.webastro.net/upload/image...1482257385.jpg
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  #429  
Old 21-12-2016, 07:39 AM
flolic (Filip)
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Congratulations to Luka for successful camera build!

@pat30, great images! Have you scraped Bayer mask off, or is that just result of chemicals?
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Old 21-12-2016, 08:13 AM
flolic (Filip)
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Another observation. In my camera I used AD811 opamp from China (ebay). Based on price (US$2.99) and how it looks, I am quite sure it is not a genuine part.
Today I tried another opamp that I had lying around, THS4031 that came from Farnell few years ago and is for sure genuine. Comparing bias frames between the two, and without sensor, standard deviation for AD811 is 19ADU, and for THS4031 is 10ADU. That is clear and massive improvement.
I was in a hurry doing the tests, so for now take this with a grain of salt.

Those two opamps should be comparable in performance, with slightly lower noise on THS part. But who knows what is really encapsulated in a AD package...

More tests will follow
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  #431  
Old 21-12-2016, 03:39 PM
pat30 (Patrice)
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Congratulations to Luka for successful camera build!

@pat30, great images! Have you scraped Bayer mask off, or is that just result of chemicals?

Just chemical, but one would have to try on another sensor to be able to validate the method, I would give the products tonight if you want.
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  #432  
Old 22-12-2016, 01:24 AM
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Hi guys, thank you. Sorry it took so long to do some testing but I was not feeling well...

My cam86 works well but there are few "things" I noticed. Initially I thought it had problems but I just spent 2h reading 50-ish pages on the Ukrainian forums and collecting notes and I believe I have found lots of answers. I have included the comments below as Brendan and Gary may have the same questions:

Note that all my tests were done without any cooling at ambient temperature of about 25C.

1. There is a strong vertical line on the left hand side. Actually there are other weaker vertical lines throughout the images. See attached image 1. On the Ukrainian forums it was noted that the vertical lines should go away once the sensor gets cooled. I am not sure about the big line. Pat, from memory you fixed this by using a larger capacitor C30=330uF, 6.3V. We have used 3x100uF ceramic capacitors so hopefully we are in the clear. If needed we could even boost this to 3x200uF ceramic (E14 has stock of those).

2. If you run the camera for a while you will notice that the standard deviation for the frames goes up. This is because the sensor warms up and the thermal noise goes up.

3. The 0ms exposure is not dark if there is any light shining on the sensor (image 2). I found this comment on the Ukrainian forum explaining what is going on:
Quote:
This occurs for the following reason. When any simple charge accumulates in the sensor.
The firmware provides cleansing it in the formation of the frame pulse SUB. The method works, but not completely. We need to do a single frame preview frame "empty" before shooting. then it is becoming normal. This also applies to other versions of the cameras.
4. Every now and then the camera goes nuts and the reading takes 3.8 seconds instead of the usual 2 seconds. It will do this for several images and then go back to normal. See attached image 3.
There were few comments on the Ukrainian forums to change the USB cable, to check feet 8 of DD6, to make sure the CPU on the computer is not overloaded or to change the resistor R12.
My problem is likely my temporarily USB cable which has a large section of unshielded wires.

And my final image has been taken through hand-held Nikkor 50mm f/1.8D @f/5.6
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  #433  
Old 22-12-2016, 04:16 AM
pat30 (Patrice)
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I am surprised that with C30 300μf there is the band on the left !!!

For the Horizontal band, I had to turn off Windows defender and service "Superfetch" it seems resolved the problem, but I did not try an evening because of bad weather
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  #434  
Old 22-12-2016, 04:54 AM
flolic (Filip)
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Quote:
Originally Posted by luka View Post
1. There is a strong vertical line on the left hand side. Actually there are other weaker vertical lines throughout the images. See attached image 1. On the Ukrainian forums it was noted that the vertical lines should go away once the sensor gets cooled. I am not sure about the big line. Pat, from memory you fixed this by using a larger capacitor C30=330uF, 6.3V. We have used 3x100uF ceramic capacitors so hopefully we are in the clear. If needed we could even boost this to 3x200uF ceramic (E14 has stock of those).
Horizontal driver (DD8) is not routed correctly on your board(s). What is wrong is component placement. Decoupling capacitors should be placed the shortest electrical way to supply pins (pin 9 and pin 16). On your board the ground is totally messed up.
You can put ten more capacitors parallel to C30, C46 and C47, and that will not help anything. Those capacitors must be placed where they need to be.
Try to solder 100uF ceramic directly to DD8 supply pins with shortest wires possible.


Weaker vertical lines will disappear when sensor is cooled.
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Old 23-12-2016, 02:33 AM
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Problem is fixed.

I added 100uF capacitor next to the pin 9 of DD8, going between the pin 16 and 12 track and GND. Image 1 shows the location of the capacitor.

Interestingly adding a capacitor next to pin 16 on the top of R16 to GND did not have any effect. In this position it is even closer to pin 16 as in the example above. Image 2 shows the location of the capacitor.

Also it should be noted that the quality of the power supply plays an important role. I tried several and some had vertical stripes which were not visible with other power supplies.

Finally, image 3 shows noise for 0ms exposure of the improved Cam86. It was kept in the fridge for few minutes to cool down but not for too long as I didn't want to have condensation on it. My guess is that the sensor was at 10-15 degrees C. Also the sensor was not in complete darkness (light leaking from the left hand side on the image).
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  #436  
Old 23-12-2016, 02:44 AM
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And one more image, M42 through 10" dob, 1s exposure. Camera was not cooled, ambient temperature was about 20 degrees C. Custom made 3D printed plastic housing.

Still have to figure out what to do with the gain and offset
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  #437  
Old 23-12-2016, 03:23 AM
pat30 (Patrice)
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Still have to figure out what to do with the gain and offset
I had difficulty understanding "GAIN and OFFSET".

In France we say "EXPOSURE and CONTRAST" to regulate the gain it is necessary to make several picture with different times of poses, to make simple to regulate the GAIN to the highest being careful that the stars is not saturated, if not to lower a little and for OFFSET I do not touch.

We understand better using real acquisition software; I chose ASTROPHOTOGRAPHYTOOL, it is really good and free.

The top stars seem oval, right ?

Last edited by pat30; 23-12-2016 at 06:52 AM.
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Old 23-12-2016, 08:35 AM
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Problem is fixed....I added 100uF capacitor next to the pin 9 of DD8, going between the pin 16 and 12 track and GND. Image 1 shows the location of the capacitor....I.
Excellent...but its counter intuitive. If it was a noise issue then right at the pin would fix it. I wonder if it's acoustic oscillations. I also wonder if the data sheet capacitor values should have been used.

We may have to "fine tune" each camera?

Well done, 1s exposure M42...well done indeed. You have been good for Christmas...Santa will be pleased.

Brendan

edit:
oh meant to say...making notes for next iteration already especially wrt bypass caps and maybe even leaving a few extra pads for extra bypass caps. And I'll try my PCBs with the data spec caps, an electro and ceramic just to see what happens. It appears Filip was pretty spot on...curse him I was muttering under my breath but have to acknowledge he was pretty spot on and I salute that! Well done Filip!

Also...the issue could relate back to the 6V supply, maybe this needs a chip inductor on the output! I can try this on my boards! Further to this Intersil AN1108 mosfet drivers talks of mosft driving high freq capacitive loads (such as the CMOS sensor) and talks of using ferrite bead on Vs+ in parallel with a small ohm resistor as well as the 4.7uf electro and ceramic bypass caps. maybe I can do some experimenting...suffice to say...try to take the easiest route.

Lots of work ahead!

Looking fwd to this. And indeed glad its ok ATM and well we have achieved something that works!

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Old 23-12-2016, 01:04 PM
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Pat, I have been using APT with my DSLR but didn't even think to try using it with the new Cam86... good thing to know that it will work, thanks. The test image of M42 was a very quick one. The Dobsonian was not properly collimated or cooled (and there was no coma corrector), the focusing was very rough etc. I just wanted to get my first DSO image with the Cam86

Brendan, I did lots of testing of the effect of capacitors.
1. The extra capacitor over R16 did not make any difference. This is weird as it sits directly on pin 16 and it has almost identical distance to pin 12 as compared when it is placed next to pin 9.
2. When I removed one capacitor from our three I did not notice any difference (200uF total capacitance).
3. When I removed another capacitor there was obvious ringing of the vertical stripe (100uF total capacitance).
4. Adding capacitor next to pin 9 solved the problem.
5. Adding back two removed capacitors did not improve anything. I think I will need to cool the sensor to reduce thermal noise before making any conclusions here.

Again the proximity of the capacitor does not clear up the picture completely, as in my point 1 above. The "sweet spot" for C30 seems to be next to pin 9, just like in Grim's and Filip's circuits. Actually placing the capacitor "above" the DD9 and not "to the right of it" would probably make it even better as it is closer to the power pins.

Furthermore, once the stripe was there I could see a definite effect of different power supplies. Perhaps increasing C29 before DD11 (6V regulator) would help stabilise the power even more.

Also, if I was doing the schematics I would place the bypass capacitors next to the actual chip that they are used with instead of next to the power regulators. This will make their function immediately obvious. For example, I think it is slightly misleading to have the bypass capacitor C30 next to power regulator and not next to the actual chip DD11 (in the schematic).
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Old 23-12-2016, 06:23 PM
flolic (Filip)
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Luka, I'm happy that you've solved the issue

About capacitor placement and their effect on circuit behavior, that's important. But when you are designing high speed/fast rise time circuit like this, you have to look wider. You have to look at power supply (DD11), driver (DD8) and image sensor (DD14) as a single circuit. And that mean optimizing current paths from the supply through the switch to the load. The most important thing here is ground that connect all these parts.
If you look at the layout of my board, you will notice that I tried to place components and tracks in a way that there is a shortest possible distance between them. And for a ground, I used ground fill everywhere, on a both layers, and with strategically (!) placed vias that connect top and bottom grounds.

I must confess that even my board is NOT ideally routed. The most important reason for this is that I used existing design and tried to improve it. In a process you can (and will) overlook something...
As in your example, only real life tests will show all the problems with the design. So, standard thing to do next is to redesign the circuit and try how that works. Or you can bodge few parts here and there and call it done
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