DSI pro internal cooling and peltier power controller board

What is described below has allowed the cooling of a DSI pro to –60F from ambient (67F from heatsink temp) using fan-air cooling of the new heatsink.

Water cooling could take it really, really cold, basically 67F from the water temp.

(For me water cooling is too much work, previous project with water cooling modified webcam:

Water cooling modified webcam

On this page:

Test image @ 5F

Comparison darks over temperature

Camera head showing coldfinger and thermistor

Comparison images: raw, darks and raw-dark

Controller schematic

Pic of controller board

Thermistor References

Original project using micro sized pelt:

Micro sized peltier cooling of DSI (good for –20F from ambient)

Test image @ 5F

Image: center of M33, almost full moon, slight haze, not great focus.

20 frames, 60 seconds raw images aligned and stacked in Iris with NO dark subtract.

10 inch lx200 classic @ F3.5

DSI dark cooling comparison from 75 F to 20F versus 15F

The following animated GIF shows the differences in images for temps between 75F and 20F.

The dark for 15F was subtracted from the dark at the other temperatures then histogram stretched for 0-4096 range

The new generation cooling head on the DSI Pro before being buttoned up.

DSI pro image comparison

Below is an animation showing 2 frames. Both are 60 sec exposures of an out of focus light about 100 yards away shot through a window with a screen in it.

8X blowup, 0-16k histo stretched centered and copped around a nasty hot pixel my cam has.

The small circles are the hoarfrost on the CCD of the unsealed cam (optical window was in place).

One image is cooled to 15F, the other is 70F.

No dark frame subtraction done.

Here are dark frames of the region, again at 15F and 70F

And here are the images processed with the respective dark frames

Schematic for the peltier power controller

I have found it controls the temp from +0.1F/-0.8F to the set point.

Note: it is required to trim the power (see V-adj) based on the temp differential you are going for.

If looking for only 20F-30F and you run this at full power it will oscillate because the

cooling will way overshoot the set point on the rising cooling.

This has a very flexible supply requirements.

The Zener’s provide stable references for the temp reference and thermistor and the voltage regulator and 2N3055 transistor are good up to 36V input.

There is a voltage drop across the 2N3055, if you feed it 12V the max pelt voltage is ~8.5V. A higher voltage input will raise that level.

Heatsinks ARE required for the regulator and transistor!

XLS of part numbers versus vendor and prices

10K@25C Thermistor	RadioShack 271-110A (not stocked anymore)
2N3055	RS 276-2041
LM317T (I use K)	RS 276-1778
LM339	RS 276-1712
10k 15 turn trimmer	RS 271-343
5.1V Zener	RS 276-565
Transformer (closest RS has is 25.2 2A CT)	RS 273-1512
Rectifier	RS 276-1185
Peltier	AllElectronics PJT-1 (not carried anymore) 30mm 34.5W/15.9V/3.7A Note: this surplus pelt came with a 3/32inch think aluminum coldplate already attached to the cold side.
R1 – Vadjust	I used a 5K RS 271-343 is a 10k
4700uf	RS 272-1022 If not drawing more than 2.5A then can sub 2200uf RS 272-1020
Heatsink for 2N3055	Online
Heatsink for LM317T	RS 276-1363
Heatsink grease	I like ArticCooling Ceraminque, check out www.svc.com Non-conductive, non-hardening, non-capacitive
Switches - SPDT	RS 275-613
3/8 inch Aluminum coldfinger	I ordered a 3/8 square 6061 aluminum extruded by 12 inches from OnlineMetals