#181  
Old 19-08-2016, 11:56 AM
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wasyoungonce (Brendan)
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Just have to post this...new toy to play with, 3D render of PCBs. Much better than the old eagle3D and POV Ray.

You can look between the layers, pads etc and imports BOM etc. Apparently the netlist file is IPC-D-356 format and it contains way more than just connections. Obviously some of my parts are not correctly rendered correctly. I have to work on this. Also my colour selection is.."I chose poorly"!
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  #182  
Old 20-08-2016, 12:21 AM
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Congratulations on successfully freeing the sensor!!! Excellent work

So the black plastic frame and the glass stayed glued to the sensor. Interesting...
Rowland, in his Canon 450D cold finger mod, glued few SMD resistors around the front glass and was passing low current through them to keep the glass warm to prevent fogging. From memory it raised the sensor temperature slightly but it was nothing major.
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  #183  
Old 20-08-2016, 07:42 AM
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wasyoungonce (Brendan)
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Hi Luka

The IC package, sensor glass & glue, totally unaffected by the DMSO. Even the copper wire I used as shorting wire between the pins...everything unaffected except the glue.

I have no idea what's in DMSO apart from what GOOGLE tells me. Suffice to say...the sensor fell off the carrier in ~3.5 days!

I agitated the sensor from time to time to pick off softened glue and also rotated the sensor in the solution face up/down. I put a saucer over the container to contain the solution. Quite a bit of solution evaporated and was on this saucer after 3 days.

Dew mitigation...hard to tell. One side we are cooling the other side heating....poor old sensor will be split for choice! We will probably have to do something like resistor dew control.
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  #184  
Old 21-08-2016, 10:03 AM
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wasyoungonce (Brendan)
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2nd sensor free from carrier. Took around 2.5 days for this. Just has some cleaning spray on it in pics.

In the mean time...kids have used all out internet data allowance so I'm throttled back to dialup speeds...Grrrrr. Painfully slow. Where is my NBN oh that's right I'm on pair gain so I won't be getting it until they remove my copper....in other words "never".
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  #185  
Old 25-08-2016, 11:12 AM
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Sorry I was slow to reply, had quite a few things to sort out. Roughly, what size Peltier are we after so I can start looking around. I assume we want to get it as cold as possible?

Also, the SIL sockets I ordered on Aliexpress just arrived. HUGE >10cm x 7cm x 7cm box with tons of bubblewrap with 4 tiny sockets inside. I first thought it was another DSLR with a new sensor that I forgot that I ordered :-)

The pitch looks OK (measured by ruler) but I don't have a free sensor to try. Things just got too busy recently...
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  #186  
Old 25-08-2016, 06:16 PM
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wasyoungonce (Brendan)
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Hi Luka...sorry I don't know the Peltier size. I would expect probably no bigger than the Mill cut-out for the cold finger. Also probably no more than 3A, 12V...probably best 2A @12V.

Sorry I cannot help till tomorrow...kids used all my internet data allowance and even loading this page took 5 mins....Grrrr. Data resets tomorrow.
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  #187  
Old 27-08-2016, 04:47 PM
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The Peltiers...
There are few cheaper ones at Jaycar around $20, all 40x40mm. The smallest one may be able to run at our power levels.
Then we move a step up to RS/E14 and similar shops and the prices start at $40. Large range of Peltiers to chose from, even stacked ones for over $100.

After lots of reading it looks like running the Peltier at about 70% of max power is the best for long life. This means that we should look for about 15V Peltier that runs at less than 4A.

For example, something like this at 12V will give us around 3A max current. The max temperature differential will be about 40deg.

Or there is a fancy dual-stage Peltier here. A bit pricey at $100 but it should be able to achieve temperature differential of 95C!!! However, the cooling power is 8W only... I suppose that will be the main question, how much cooling power do we really need.
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  #188  
Old 28-08-2016, 06:22 PM
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wasyoungonce (Brendan)
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Hi Luka...been absent for a few days. Enjoyed the break...fixing soldering stations. Now I want anything but soldering stations!

I agree on Peltiers...we don't ant to over kill...but ...seeing that beauty from E14.....my testosterone levels went up a notch! I would have thought a 40mm sq unit is a bit big for our needs. Looks like the Ukrainians (and others) are looking at a much smaller 3A unit. Notice its 8V? What's the deal here? Odd voltage rating? Or is this an avg voltage?

Those TEC units are a little pricey, nice, but pricey. Might have to revert to fleabay. From my understating of TEC units (I may be wrong) they:
Are best run at a slightly lower voltage than specified;
They don't like PWM but hey this is probably the easiest method of controlling average cooling capacity (depends on what PWM freq used in the firmware);
Current draw for our application is limited ~3A'ish;
The centre PCB hole for the cold finger is 20mm dia which might limit TEC sizes to around this dimension;
A dual unit wins hands down over a single unit;
What cooling capacity do we need? Hard to tell...I noticed my Canon 450D pretty much plateau'd off noise wise at around 5ºC and below. meaning the noise floor had been reached. That said...what to QHY run their units at?

I'm not fussed atm...I'll start looking now and get back on this.

Brendan
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  #189  
Old 28-08-2016, 09:20 PM
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Haha, I knew you would like the E14 dual stage Peltier. Interestingly it is only 7W so it may not have enough capacity to get the heat out. Also the dual stage Peltiers are extremely inefficient... single stage has about 10% efficiency and dual stage then 1% efficiency.

Regarding the temperature, the colder the better. QHY8L (same sensor as us) goes down to -40C while QHY8-Pro goes down to -45C.

I have cooled 450D as well and, as you said, the noise plateaus around 5C. However, this is only part of the story:
  1. Canons do some heavy processing even on RAW files which probably explains why the noise plateaus. I believe Craig Stark had some excellent articles on this, I can find the links if you are interested.
  2. The ~5C plateau applies only for relatively short exposures. I tested it for 3 min exposures and the dark frames were identical to the bias frames at 2C exactly (for my camera/cold finger build).
  3. Going colder at 3 minutes exposure may not reduce the thermal noise but it definitely reduces the intensity of the hot/cold pixels.
  4. I recently tried doing 10 min exposures and things are very different compared to the 3 min exposures. At 10 min the noise definitely gets less when colder than 5C. There is still a significant noise even at -3C when compared to the bias files (-3C is my limit due to my insufficient power supply). I suppose that Canon's manipulation of the RAW files works differently for such long exposures.
Also I was unable to find any 20x20mm 12V Peltiers on ebay. Only ~3V and ~5V versions exist.

Few of the larger and possibly suitable 30x30mm Peltiers are here, here and here.
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  #190  
Old 29-08-2016, 05:57 PM
Gary47 (Gary)
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Sensor size

Hi,
The cameras I have looked at all have a larger TEC unit and the cold finger reduces in size to fit the sensor or through the PCB. The lump of copper I have for this project is about 35 mm diameter so we can use a sensor that will cover that. As well it would be no drama to add a larger flange to the cold finger to fit a larger TEC, I would only have to find a piece of copper plate, a bit of old bus bar or similar would do the trick and we could have full coverage for a wide range of TECs.
Does anyone know how much power the sensor outputs?
Need to look at the TEC specs because TECs only achieve their rated deltaT when they are operating at maximum efficiency which is not actually moving any heat. Two stage TECs are notoriously inefficient.
An "over size" TEC will operate at better efficiency and give a faster cool down time.
Gary
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  #191  
Old 29-08-2016, 06:39 PM
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Fully agree with you Gary, the larger the Peltier the better, if we can fit it. We are probably limited to about 30W max power due to 12V input with <3A max current due to our connector.

By the way, QHY8L (same sensor) uses 3.6W-30W, i.e. about 4A of current at max cooling. Advertised delta T is -35 degrees and it has a single stage Peltier.
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  #192  
Old 29-08-2016, 10:31 PM
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12V/3A/36W, dual stage, 30x30mm Peltier on ebay here. Max temp difference is 80 deg.

I don't like the ebay cheapies as they don't really have much details compared to, for example, the RS/E14 Peltiers.
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  #193  
Old 31-08-2016, 11:18 PM
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Did you see the Ukrainian forum. There is talk of a new camera with ICX613AQA sensor. Read noise is 4eV, half of our current build.

edit:
ICX493AQA, not ICX613AQA
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  #194  
Old 01-09-2016, 08:33 AM
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wasyoungonce (Brendan)
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Hi Gents

yes I saw the work done by Ruslan. Very nice. He's been doing this camera for awhile but obviously gained enthusiasm to continue from the CamXX project. he's done some fine work and indeed a whole new range of DIY may come from this.

Just think...all those 2nd hand cameras on ebay are about to get more expensive!

I'd be up to building one...but after we get this one running.

As for TECs..I'm going to buy some 3Amp vers and as Gary said around 40mm square. Actually 40mm sq is a little large for the case? We are cutting the case so the TEC clears it!
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Old 01-09-2016, 09:26 AM
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I am in as well for building the next version

See if you can find any 12V 40mm square Peltiers on ebay. I retract my word when I said we can/should use >12V Peltier so it does not run at 100%. PWM will do this for us and we should not limit ourselves from the start to reduced performance.

Also if looking on ebay, the descriptions of Peltiers have lots of incorrect/misleading information. It looks like lots of descriptions were copied/pasted and some corrected and some not.
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  #196  
Old 04-09-2016, 10:00 AM
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wasyoungonce (Brendan)
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Ordered qty 2 30mm sq TECs, one 3 Amp one 2Amp (fleabay). They might take awhile to arrive.

AstroCCD.ord has posted ASCOM for Cam86.

The Camera C45, 1uf ceramic, grim was replacing this with a higher capacity ~10uf or up to 22/33uf 20V in 1206 size. I'll leave ours atm but probably need change it.

Others are building their PCBs and noticed +5V/+3V regulators getting a little hot. They are within temp specs (but the 3.3 is hot) and the I draw is in specs but probably on the upper end of what they can supply. We probably need to maybe look at a slightly higher rating regulator, especially for 3.3V.

I'm keen to resolve this "regulator issue" and get on an build our PCBs...but its good we waited somewhat. But I feel we won't be far off.

Brendan

edit:
Ok we might get away wit han 3.3V LDO with a more narrow voltage input range than the current LDOs LP2950XX. These have a wide voltage input range (up to 29V in) but I think the trade off for this is a limit of power dissipation. Where as MCP1702XX is rated for 13.2V in and has 250mA I out in TO92 package. not so sure atm have to read the pdf on this device, but it appears to use a pass FET thus can handle I flow with less heat.

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  #197  
Old 05-09-2016, 12:50 AM
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Brendan, no matter what kind of regulator you use, dissipated heat will always be the same because it is function of the input/output voltage difference and amount of current through regulator. That's how all linear regulators work.
What can be done is better thermal management, for SMD parts that means using larger area of PCB for heatsinking.
Off course, one should not exceed maximum allowed power dissipation of used voltage regulator.
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  #198  
Old 05-09-2016, 12:56 PM
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Actually you're right Flip. I was quickly looking at MCP1702 specs and saw it using a pass FEt in lieu of more traditional transistor array for the device. I was thinking hey this will have less V drop across it.

When in fact its exactly the same as a traditional device P = (Vin -Vout) x Iout. Reading the TI tech paper on this, SBVA027, details lots of info on the SOA of these devices.

I have to now go back and look at the current thru the regulator. No use chasing tails if it's in the SOA of operations.
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Old 05-09-2016, 11:28 PM
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Saw this posted by Glen in this thread. May be useful for the camera/sensor alignment, it is way cheaper than any other devices I saw before.
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Old 10-09-2016, 09:27 PM
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From the Ukrainian forums, it looks like the camera will work with voltages over 7V. Regulating 7V will definitely produce less heat than trying to drop down 12V.

Either we find TEC that works between 7V and 12V or we could have a separate power for TEC? 12V or more depending on the TEC. It would require an extra pin...
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