Cooled DSLR History 5

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copper skiving fin heat sink…………………………………….06. 05. 27

To make removable cooling unit more compacted I looked at the coolers for the computers that are distributed in the market place. First the CPU coolers were getting bigger as clock is getting higher and more heat is coming out, and heatpipe products were getting main product. There were few product of VGA cooler which is small and cool but after testing it’s functions were not good enough. So I finally came up with the Taiwan’s Cooljack slim cooler product after looking at CPU with copper heat sink with great functions. With 3~4mm thick plate and soldering the cooler pin to a copper plate is normal ways of making this but this company used thick copper plate and cutted off the cooler pin to high the function of heat delivery.

Removing the heatpipe cooler and placing the Cooljack’s JAC313C cooler(60×60mm)(as seen in right picture) I tested and as the results CMOS goes up 1.5℃(2.7˚F) compared to when using heatpipe cooler. This is satisfying enough and I decided to use this.

Coolers thickness lowered to 2.3cm from 7cm and center of gravity moved toward the center of the camera.

To solve the problems of dew condensation of the peltier module I put this inside the airtight chamber and at the outer side I put copper block to deliver heat to the heat sink. and I removed the pin which caused heat delivery from cold finger to airtight chamber so the direct heat delivery won’t be caused. And the biggest problem to be handled is to make the optic axis leveled. I solved it by making CMOS and lens mount surfaced leveled directly.

 

I lapped cafully the surface of copper block & contacting face of cold finger and used the thermal compound to cement these to higher thermal conduction. With copper block and airtight chamber housing and made high thermal conduction, so the most far end fo the airtightchamber got up to -5℃(-9˚F) on the basis of ambient teperature and it got safe from dew condensation. The lid of the airtight chamber changed from copper to 2mm alumium and painted thermal compound at boundaries with the chamber to even higher the thermal conduction.

I used DSUB Connector to connect USB, Remote controller, Thermometer, Power of Peltier Module from inside the camera to EXcooler. All the jacks are placed at bottom of the EXcooler.

When taking pictures of stars CMOS cooling temperature has to change as the external temperature changes, and that’s why we need temperature control system. The Basis is to control current of the peltier by linking with the CMOS system. But to do that the powers have to be seperately supplied to the fan and peltier and have to put current controller on power supply, but this causes another cable and have to make 5 jacks at EXcooler.

After considering I came up with the idea to use a easy method. First use only one power and than inside the EXcooler let 12V out to the peltier and use variable resistance to change voltage from 5V~12V to control the fan speed. This helps to control the heat sink’s cooling effectiveness to vary CMOS temperature.

Test showed that CMOS temperature varies about 2.5℃(4.5˚F). This shows that it works out when shooting a object for 1~2 hours.

To make CMOS sensor equal to optic axis I made three hole in the rear lid of airtight chamber and put legs in so that the it lands on the rearside of the CMOS. And put leveler just as in pictures, then put camera on the glass then level the lens mount and CMOS surface. control the washers thickness in three supporting points in mirror box to level it.

Taking the actual pictures of the stars they are in good shapes without bending.

Right now camera is using self driving batteries, I am considering to change the power system to use the battery power from the 12V external power supplied by the cooling system.

 

 

 

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