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DSLR Active cooling MOD process - Part 2


MarsG76

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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
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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
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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
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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

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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
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  • 1 month later...

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...

 

 

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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. 

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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
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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

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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.

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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.

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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
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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.

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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.

 

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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.

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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

 

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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.

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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?

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