Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_android_vs_ios_winners.thumb.jpg.803608cf7eedd5cfb31eedc3e3f357e9.jpg

MarsG76

DSLR Active cooling MOD process - Part 2

Recommended Posts

PS:

as Louise has remarked well, a winding diode in parallel to the cap is  absolutely essential because It prevents from damaging the final stage

of the controller (power) by reverse voltage spikes!

Beppe

Edited by benzomobile

Share this post


Link to post
Share on other sites

Four yrs ago, I projected and made by myself this controller for Peltier power & dew heather.

It controls sensor temperature within the range  of +/- 0.05° C.

The display shows the applied voltage and the current absorbed by the TEC.

Beppe

20190206_110658.jpg

20190206_110738.jpg

Edited by benzomobile
  • Like 1

Share this post


Link to post
Share on other sites

Why the multiturn precision pot?  Do you really need that resolution?

Edited by Gina
  • Like 1

Share this post


Link to post
Share on other sites
47 minutes ago, Gina said:

Why the multiturn precision pot?  Do you really need that resolution?

Hi Gina,

the pot is 20 turns one, linear.  I needed this resolution to explore the range  of the desired set point.

When we decide set point would be ever the same - for example  0° C,   we can substitue pot with small trimmer, definitely.

Beppe

 

 

Edited by benzomobile
  • Thanks 1

Share this post


Link to post
Share on other sites
12 minutes ago, benzomobile said:

Hi Gina,

the pot is 20 turns one, linear.  I needed this resolution to explore the range  of the desired set point.

When we decide set point would be ever the same - for example  0° C,   we can substitue pot with small trimmer, definitely.

Beppe

 

 

100 ohm!

Beppe

Share this post


Link to post
Share on other sites
15 minutes ago, benzomobile said:

This is my new one schematic. It differs from previous one you can see on my site.

Beppe

Cattura.PNG

 

Edited by benzomobile
  • Like 1

Share this post


Link to post
Share on other sites

Hi to all,

just two weeks ago, I sent my gerber files to EasyEDA as they can produce ten 'professional grade' pcb for me

(for the first one request you will pay only 8 $ ?, while the requests after the first, will cost just a four bucks  more)

I should receive the pcbs in two weeks at the most - at least I hope ? . Then I will test my new dew  & TEC controller.
If any of you there want it, I'm willing to share my gerbers with SG friends.

I attach rendering of controller.

Only one thing: you'll have to wait a few weeks yet ?

Beppe

 

3D.PNG

Edited by benzomobile

Share this post


Link to post
Share on other sites

Hello all....

Good news is that after I filled the inside of the camera with foam strips, sealed the cold finger entrance with expanding foam and placed silica gel into the card compartment, I could image all night for quite a few nights with no condensation problems....

 

With the on going quest to freeze my 40D sensor while exposing subs, I constructed the same setup to measure the temperature of the peltiers with the surrent setup... the result is that it did not got below 4.2 degrees (from an ambience of around 20), and that temperature was hit in about 20 minutes... the dilemma is that with the distance between the cooling system and the sensor, the cold finger passing through the inside of the camera, seems to heat up by around 20 degrees.. resulting in the actual sensor temperature hovering at around ambient temperature while exposing (give or take a degree or two).

Even though the system currently is a noticeable improvement over when the camera was uncooled, ultimately I would like to have the sensor at around 5 degrees.

As the next stage in experimenting, I got a bigger heat sink, the CoolerMaster 212X, added a second fan to it and attached two peltier stacked, the primary TEC powered with 12V and the secondary with 5V... the temperature drop was 44 degrees.. went down to -19 degrees from and ambiance of 25... at this level, even if the cold finger would heat up by 20 degrees, the sensor would still be at 4.. so my target would be reached....

The other problem is implementation since thee 212X is a lot bigger, but weighs the same as my current setup with the two TECs and two P4 heatsinks, so it seems like the heatsink might be unbalanced unless I stabilize it.

To be continued...

 

 

  • Like 3

Share this post


Link to post
Share on other sites
9 minutes ago, MarsG76 said:

Hello all....

Good news is that after I filled the inside of the camera with foam strips, sealed the cold finger entrance with expanding foam and placed silica gel into the card compartment, I could image all night for quite a few nights with no condensation problems....

 

With the on going quest to freeze my 40D sensor while exposing subs, I constructed the same setup to measure the temperature of the peltiers with the surrent setup... the result is that it did not got below 4.2 degrees (from an ambience of around 20), and that temperature was hit in about 20 minutes... the dilemma is that with the distance between the cooling system and the sensor, the cold finger passing through the inside of the camera, seems to heat up by around 20 degrees.. resulting in the actual sensor temperature hovering at around ambient temperature while exposing (give or take a degree or two).

Even though the system currently is a noticeable improvement over when the camera was uncooled, ultimately I would like to have the sensor at around 5 degrees.

As the next stage in experimenting, I got a bigger heat sink, the CoolerMaster 212X, added a second fan to it and attached two peltier stacked, the primary TEC powered with 12V and the secondary with 5V... the temperature drop was 44 degrees.. went down to -19 degrees from and ambiance of 25... at this level, even if the cold finger would heat up by 20 degrees, the sensor would still be at 4.. so my target would be reached....

The other problem is implementation since thee 212X is a lot bigger, but weighs the same as my current setup with the two TECs and two P4 heatsinks, so it seems like the heatsink might be unbalanced unless I stabilize it.

To be continued...

 

 

Keep us updated. Fascinating work. 

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)
1 hour ago, MarsG76 said:

resulting in the actual sensor temperature hovering at around ambient temperature while exposing (give or take a degree or two).

Don't trust the internal temperature given in the exif data, it isn't measured at the sensor, or is this from the sensor mounted thermistor?

Edited by Stub Mandrel
  • Like 1

Share this post


Link to post
Share on other sites

Hi

I actually bought a tec and did some investigations - just out of interest (I enjoy experimenting! :) ). I've not had time to do much but will be free to do more after next Thursday :). Still, it occurred to me that my Atik 383l+ cools the sensor with a delta of about 40 ie down to ~-18 from a similar room temperature. It runs from 12V and only draws, at most, 2A. I figure I should be able to achieve that with the parts I have got together but have to prove it! I've learnt that coupling between the sensor and heatsink has to be really high to take heat away i.e. needs high quality heatsink thermal compound. It also needs a fairly high tightness between the cold finger and the tec. Anyway, I'll post about what I've been able to achieve in a week or so.

Louise

  • Like 2

Share this post


Link to post
Share on other sites

Which model of Peltier TEC are you using Louise?

Share this post


Link to post
Share on other sites
3 minutes ago, Gina said:

Which model of Peltier TEC are you using Louise?

It's just a standard tec1-12706 :) I've tested it and it works fine :) 

Louise

 

Share this post


Link to post
Share on other sites

Ah yes, I know it.  Not the most efficient but nice and cheap for experimenting.  I'm sure you'll learn a lot from it ?  Have fun.

Share this post


Link to post
Share on other sites

One point that might help you, they are not at their best when run flat out, back off to about 2/3 the maximum current and that should give you the most cooling.

  • Thanks 1

Share this post


Link to post
Share on other sites
9 minutes ago, Gina said:

One point that might help you, they are not at their best when run flat out, back off to about 2/3 the maximum current and that should give you the most cooling.

I have the datasheet! :)

  • Like 1

Share this post


Link to post
Share on other sites
3 hours ago, Stub Mandrel said:

Don't trust the internal temperature given in the exif data, it isn't measured at the sensor, or is this from the sensor mounted thermistor?

I don't trust the EXIF, I have a thin NTC between the sensor and the cold finger giving me an actual reading.

Share this post


Link to post
Share on other sites
Posted (edited)
15 hours ago, Gina said:

One point that might help you, they are not at their best when run flat out, back off to about 2/3 the maximum current and that should give you the most cooling.

The problem number one is getting rid of the heat from Peltier warm side. 

Big power TECs require big dissipating system, so lower power TECs - due to the easier heat dissipation, often  perform better as higher power ones ?

Beppe

 

Edited by benzomobile
  • Like 1

Share this post


Link to post
Share on other sites

Very true.  Only if you have a lot of heat to get rid of, such as in a refrigerator, do you need larger TECs.  For cooling image sensors you only want a small TEC.

Share this post


Link to post
Share on other sites
9 hours ago, Gina said:

Very true.  Only if you have a lot of heat to get rid of, such as in a refrigerator, do you need larger TECs.  For cooling image sensors you only want a small TEC.

I guess that is the case if the peltier is sitting directly on the sensor... but what about when the heat extraction is by using a copper plate which constantly fights outside heating sources such as the circuitry.. I'm guessing that the colder the better... currently I have a 20 degree heat up simply to the copper passing through the camera in a 24/25 degree ambient temp... hence my aim for -20 at the peltier side.

 

Share this post


Link to post
Share on other sites

You need to add thermal insulation to the cold finger, though some uninsulated copper will attract moisture away from the sensor which will be warmer.

  • Thanks 2

Share this post


Link to post
Share on other sites
6 hours ago, MarsG76 said:

I guess that is the case if the peltier is sitting directly on the sensor... but what about when the heat extraction is by using a copper plate which constantly fights outside heating sources such as the circuitry.. I'm guessing that the colder the better... currently I have a 20 degree heat up simply to the copper passing through the camera in a 24/25 degree ambient temp... hence my aim for -20 at the peltier side.

 

IMHO, I suppose your goal is very difficult to realise ...  I've done many experiments in this area and  32° C  is my the maximum deltaT° .  No more chilling I ever reached, neither with more accurate insulation, nor with bigger Peltiers too ...

Beppe

 

  • Thanks 1

Share this post


Link to post
Share on other sites
On 16/03/2019 at 20:16, benzomobile said:

IMHO, I suppose your goal is very difficult to realise ...  I've done many experiments in this area and  32° C  is my the maximum deltaT° .  No more chilling I ever reached, neither with more accurate insulation, nor with bigger Peltiers too ...

Beppe

 

A 32° on the sensor would have me very joyous... even might be too much, since a hot night is around 30°C here but generally summer is around the 22-24°C and winter 9-15°C at night, so either way I'd have to use the temperature controller to keep the sensor at the 5°C for which I'm aiming. Don't want to fight frosted sensors.

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, MarsG76 said:

A 32° on the sensor would have me very joyous... even might be too much, since a hot night is around 30°C here but generally summer is around the 22-24°C and winter 9-15°C at night, so either way I'd have to use the temperature controller to keep the sensor at the 5°C for which I'm aiming. Don't want to fight frosted sensors.

What camera do you want to chill?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Adam J
      I have decided to create this thread to take anyone who is interested through the design and construction of my DSLR Cool Box over a series of posts.
      I made my start in astro-photography / DSO imaging about 18 months back using a Canon 1000D on a 130DPS / HEQ5pro.
      I have a very limited budget and so almost every piece of equipment I own is second hand or self built. Living in a yellow zone area I started out using a Astronomic CLS filter and this worked well for me for a short period. However, once I started guiding it became clear that I was limited by light pollution in longer exposures. To that end I decided that I wanted to try narrow band imaging, but I knew that I could not afford a mono CCD or CMOS camera to go with the narrow band filters and that with my DSLR I would suffer from low signal to noise ratio if I attempted narrow band imaging through the Bayer Matrix.
      I initially looked into debayering a DSLR in an attempt to get more signal and I did in fact manage to successfully remove the bayer matrix and create a good quality mono sensor.  However, extensive testing convinced me that this was not the way ahead and that I had in fact lost performance overall due to the loss of the micro lenses along with the bayer filters. As a result I decided to focus on the other side of the S/N equation and have a go at reducing the noise through cooling.
      All of this of course has been well covered by others in the past, however I would hope that my approach has proven to be a good one with some original design elements and so it sill worth sharing.
      I began by researching ‘do it yourself’ DSLR cooling, as I said I am certainly not the first to have attempt this and a wealth of information exists on the internet not least this forum. It was immediately apparent that no two approaches are the same, but it was possible to group DSLR cooling into two main methods both of which make use of Thermal Electric Cooling (TEC) modules, a TEC being a solid state heat pump that uses the Peltier effect to draw heat from one side of the module to the other. The module itself consisting of two ceramic plates sandwiching a semi-conductor matrix. When a voltage is applied across the TEC one side of becomes hot and the other cold. 

      Cooling Method 1: The first method is very similar to that used in commercially available CCD cameras and uses a copper plate or ‘cold finger’ in direct contact with the rear surface of the DSLR CMOS sensor to remove heat through conduction. This consists of a copper plate cooled by a TEC which is in turn cooled by a heat sink and fan. While this method is extremely effective in cooling the CMOS sensor it requires significant modification to the camera which carries a significant level of technical risk, problems can also occur with condensation inside the camera body due to the low temperature of the cold finger.
      Cooling Method 2: The second method leaves the camera body intact and places it within a ‘cool box’ enclosure (essentially a miniature fridge). This effectively lowers the ambient temperature of the air around the camera which in turn leads to the temperature of the CMOS sensor being lowered. The effects of this type of cooling on noise can be simulated by placing a camera into a fridge on a hot day and taking a long exposure dark frame before and after cooling. While this method is lower risk than the direct cooling method it does come at the expense of bulkier less efficient and less effective cooling. However, I selected this method for my cooling project as the primary goal is to improve performance with minimum expenditure, accidentally destroying a perfectly good DSLR camera would not aid me in this goal. The ability to seal a DSLR within an air tight box would be essential in preventing dew from forming.
       
      To be continued:-
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.