DSLR mod (fan) super simple and surprisingly efficient ! Canon 550D / Rebel T2i

[FrenchyArnaud]

As my 2007 canon 450D (Rebel T1i) is beginning to show signs of decay (hanging randomly, data corrupted...) I treated myself to a serious upgrade (just kidding) , a 2010 canon 550D (Rebel T2i / Kiss X4). Sold for spares or repairs. For £50. S&R because the flash is stuck but guess what? I don't really need that, do I.

I did the full spectrum mod and decided to deactivate the back screen and buttons and not even put it back on the camera to help with heat dissipation. At that point it occurred to me that the main problem with DSLRs, cooling, is due not to the heat produced by the sensor, but to the heat not being evacuated because the skin of DSLR is a thick plastic and the heat just accumulates.

The problem here is obviously that the thermal noise increases significantly between the first and the last exposure; considering that dark/thermal noise doubles for every extra 6C, it follows that the noise increases to 800% of its specifications value. It becomes a mess to calibrate out and the dynamic range of the sensor crashes down several steps. Because of that, some time ago I built a cooled box for my modded canon 450D. It works beautifully and gets the sensor a solid 12C below ambiant, but there are a few caviats, so I use it only on really warm days

And that got me thinking.
All it would take is a proper ventilation of the INSIDE of the camera (instead of outside cooling in a box) to prevent the temperature from rising in the first place. Limiting the increase to 10 or 12 C above ambient instead of 15 or 20, I could cut thermal noise by half or more.

So I did just that, without real conviction because it looked so obvious and simple that I could not really believe it would make a notable difference – but even 3 or 4C less would be a positive thing and the mod seemed really very, very easy so what is the downside?

After a few tests and tinkering I saw that :

- the sensor temperature in a stock DSLR tends to increase by about 1C per minute of sensor activity and settles usually around +15C to +20C (considering ambient temperature as the base line) In other words, with 60s exposures, at 15C air temperature at night, typically the first sub will be at 16C, the second at 17C, 18... all the way up to somewhere between 30C and 35C. At that point, the temperature curve flattens because the difference between inside and outside the camera is enough for equilibrium, so your telescope does not spontaneously catch up on fire.

- The temperature increases the fastest in the enclosed camera unsurprisingly, but decreased the fastest with a ducted fan, that is, decreases faster with the back on but air forced through than with a totally open back, even fanned. I guess it's because the forced air when ducted also seeps under the electronics.

The first results were encouraging so I just went ahead. (Vertical : temp of sensor above ambient, fan started at exp #12, red : cooling effect) 

Before reassembling and after I had tested that everyting was working fine, I disassembled everything within the back, including the buttons, and marked the opening of the fan.

 

 

I chose a 40mm, 5V, 160mA fan mostly because I have a bunch of these in my electronics drawers. On a 3.7V, 5000mA 18650 battery it can run for days at once.

Then I dremel'd it open

I separated the buttons and discarded the round selector (that will be the air outlet)
I glued the fan in place, and glued the other buttons to plug all holes (but NOT the round selector)

Then I painted a thick black coat on each side or the glass and behind the buttons (to avoid light leaks)

I also installed 2 tiny heat sinks on the shield of the sensor. Not sure they'll help a lot but it cannot hurt. 

Then I pushed the back into place and plugged a temporary battery to test the efficiency of the air circulation.

 

finally I glued a battery holder to make it neat(ish).

 

And now it's time for measures. This is the first set of measures.

The temperature floor ( zero) is in fact the ambient temp here. Namely 24C (it was muggy yesterday). Each exposure was 120s at 800iso. You can see that after 12 subs, the temp flattens out at around +14C. By the end f exposure #12, I turned the fan on. The red bars actually show the decrease in temp. The first sub was still at the same temperature but after that, decreased rapidly to settle at around +4 ,+5C. That is -10C from normal functioning temperature!

Needless to say, I was well chuffed with that. But then it occurred to me, look at the blue bars : clearly the fan is cooling FASTER than the electronics are heating. So I made a NINA sequence to redo the SAME test but this time, with a mandatory 30s pause between exposures, hoping to keep the sensor as close to ambient as possible. So, 120s exp at 800iso, 30s wait, repeat 20x, switch the fan half way through.

Here are the final results :

Clearly this little fan offers a MASSIVE thermal advantage - the temperature now settles almost 12C below normal functioning temp, 1 or 2C above ambient, which is obviously a surprisingly massive improvement!!!

Does it translate into less dark noise? Here are two 400% zoomed in, +4 stops darks made on my desk (23.5C ambient), 120s, 800iso. One is fan'd and consequently at 25C (+1.5C) the other not fan'd, and consequently at 38C (+14.5C)
No cigar for guessing which is which. 

 

The only difference is the 40mm fan. 

That's a very simple mod; it's not for everyone of course as it precludes using the dslr any other way than as a computer-piloted astro camera but on the other hand, it is surprisingly efficient and costs pretty much nothing (the camera itself can be bought on MPB for under £100)

Edited August 13, 2023 by FrenchyArnaud

[FrenchyArnaud]

For the curious, here is the full log after complete reassembly. 

20x 180s with 30s interruption in between exposures, iso 800, fan off,

followed by a 3mins pause with fan on,

20x 180s with 30s interruption in between exposures, iso 800, fan on.

I think the figures speak for themselves. 
Ambient : 23C throughout. 

 

2000/01/01 00:04:07 2023-08-13_15-38-27__25c_180.00s_0000.cr2 : M    181s ISO:800                 Canon 550D  Temp:25C NR:off 
2000/01/01 00:07:39 2023-08-13_15-42-00__29c_180.00s_0001.cr2 : M    181s ISO:800                 Canon 550D  Temp:29C NR:off 
2000/01/01 00:11:13 2023-08-13_15-45-33__31c_180.00s_0002.cr2 : M    181s ISO:800                 Canon 550D  Temp:31C NR:off 
2000/01/01 00:14:46 2023-08-13_15-49-06__32c_180.00s_0003.cr2 : M    181s ISO:800                 Canon 550D  Temp:32C NR:off 
2000/01/01 00:18:19 2023-08-13_15-52-39__33c_180.00s_0004.cr2 : M    181s ISO:800                 Canon 550D  Temp:33C NR:off 
2000/01/01 00:21:52 2023-08-13_15-56-13__34c_180.00s_0005.cr2 : M    181s ISO:800                 Canon 550D  Temp:34C NR:off 
2000/01/01 00:25:26 2023-08-13_15-59-46__34c_180.00s_0006.cr2 : M    181s ISO:800                 Canon 550D  Temp:34C NR:off 
2000/01/01 00:28:59 2023-08-13_16-03-19__35c_180.00s_0007.cr2 : M    181s ISO:800                 Canon 550D  Temp:35C NR:off 
2000/01/01 00:32:32 2023-08-13_16-06-53__36c_180.00s_0008.cr2 : M    181s ISO:800                 Canon 550D  Temp:36C NR:off 
2000/01/01 00:36:06 2023-08-13_16-10-26__36c_180.00s_0009.cr2 : M    181s ISO:800                 Canon 550D  Temp:36C NR:off 
2000/01/01 00:39:39 2023-08-13_16-13-59__34c_180.00s_0010.cr2 : M    181s ISO:800                 Canon 550D  Temp:34C NR:off 
2000/01/01 00:43:12 2023-08-13_16-17-32__37c_180.00s_0011.cr2 : M    181s ISO:800                 Canon 550D  Temp:37C NR:off 
2000/01/01 00:46:45 2023-08-13_16-21-06__37c_180.00s_0012.cr2 : M    181s ISO:800                 Canon 550D  Temp:37C NR:off 
2000/01/01 00:50:19 2023-08-13_16-24-39__37c_180.00s_0013.cr2 : M    181s ISO:800                 Canon 550D  Temp:37C NR:off 
2000/01/01 00:53:52 2023-08-13_16-28-12__38c_180.00s_0014.cr2 : M    181s ISO:800                 Canon 550D  Temp:38C NR:off 
2000/01/01 00:57:25 2023-08-13_16-31-45__35c_180.00s_0015.cr2 : M    181s ISO:800                 Canon 550D  Temp:35C NR:off 
2000/01/01 01:00:58 2023-08-13_16-35-18__38c_180.00s_0016.cr2 : M    181s ISO:800                 Canon 550D  Temp:38C NR:off 
2000/01/01 01:04:31 2023-08-13_16-38-52__38c_180.00s_0017.cr2 : M    181s ISO:800                 Canon 550D  Temp:38C NR:off 
2000/01/01 01:08:05 2023-08-13_16-42-25__38c_180.00s_0018.cr2 : M    181s ISO:800                 Canon 550D  Temp:38C NR:off 
2000/01/01 01:11:38 2023-08-13_16-45-58__38c_180.00s_0019.cr2 : M    181s ISO:800                 Canon 550D  Temp:38C NR:off 

2000/01/01 01:24:23 2023-08-13_16-58-43__31c_180.00s_0000.cr2 : M    181s ISO:800                 Canon 550D  Temp:31C NR:off 
2000/01/01 01:27:56 2023-08-13_17-02-17__29c_180.00s_0001.cr2 : M    181s ISO:800                 Canon 550D  Temp:29C NR:off 
2000/01/01 01:31:30 2023-08-13_17-05-50__28c_180.00s_0002.cr2 : M    181s ISO:800                 Canon 550D  Temp:28C NR:off 
2000/01/01 01:35:02 2023-08-13_17-09-22__27c_180.00s_0003.cr2 : M    181s ISO:800                 Canon 550D  Temp:27C NR:off 
2000/01/01 01:38:34 2023-08-13_17-12-55__27c_180.00s_0004.cr2 : M    181s ISO:800                 Canon 550D  Temp:27C NR:off 
2000/01/01 01:42:07 2023-08-13_17-16-27__26c_180.00s_0005.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 01:45:39 2023-08-13_17-19-59__26c_180.00s_0006.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 01:49:11 2023-08-13_17-23-32__26c_180.00s_0007.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 01:52:44 2023-08-13_17-27-04__26c_180.00s_0008.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 01:56:16 2023-08-13_17-30-36__26c_180.00s_0009.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 01:59:49 2023-08-13_17-34-09__26c_180.00s_0010.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:03:21 2023-08-13_17-37-41__26c_180.00s_0011.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:06:53 2023-08-13_17-41-13__26c_180.00s_0012.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:10:25 2023-08-13_17-44-46__26c_180.00s_0013.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:13:58 2023-08-13_17-48-18__26c_180.00s_0014.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:17:30 2023-08-13_17-51-51__26c_180.00s_0015.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:21:03 2023-08-13_17-55-23__26c_180.00s_0016.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:24:35 2023-08-13_17-58-55__26c_180.00s_0017.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:28:07 2023-08-13_18-02-27__26c_180.00s_0018.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
2000/01/01 02:31:39 2023-08-13_18-06-00__26c_180.00s_0019.cr2 : M    181s ISO:800                 Canon 550D  Temp:26C NR:off 
 

 

 

Edited August 13, 2023 by FrenchyArnaud

[Gasman]

What an excellent and helpful post Frenchy, just shows what can be achieved with a bit of thought ( and a bit more expertise obviously).

Many dslr's on eBay sold as 'not working'  for a song and well worth having a try with. Not sure what the black goat made of it 😄

Thanks for the info 👍

Steve

[FrenchyArnaud]

19 minutes ago, Gasman said:

Not sure what the black goat made of it 😄

Ooops. Corrected 🤭

[happy-kat]

The mod you did looks to have been very effective, I'm used to seeing similar mottled noise like your starting point.

[ElOr]

Hi everyone from Spain

I think it's a great improvement, amazing

I have a doubt, can it get dust on the sensor? have you tried it several times?

thanks in advance.

César

P.S. sorry if my English is not good enough, I'm learning it...

[FrenchyArnaud]

Hi César, 

Dust on the sensor - yes I guess it's possible but that does not sound like a big problem to me. Flat frames are designed for that and cleaning is not difficult. So far, no issue with this though.

Yes, the camera is permanently on the telescope, itself on a pier, and has been continuously in service since this post, without issues. 

Your english is at least as good as mine, (I am french) I guess in those days of international internet and world-wide hobbyist collaboration noone will care if you make a language mistake (noone ever said anything to me anyway!)

Edited January 14 by FrenchyArnaud

[ElOr]

Hi Arnaud

13 hours ago, FrenchyArnaud said:

Dust on the sensor - yes I guess it's possible but that does not sound like a big problem to me. Flat frames are designed for that and cleaning is not difficult. So far, no issue with this though.

I have in mind to do your improvement, I've an old EOS 500D that I've removed IR filter and I think I shouldn't touch the sensor many times...

 

13 hours ago, FrenchyArnaud said:

Yes, the camera is permanently on the telescope, itself on a pier, and has been continuously in service since this post, without issues. 

This puts me at ease, I'm sure I'll try it but I don't let the camera into the telescope I have to disassemble everything after imagin...

 

Thank yo so much to take time to answer me.

Clear skies

César