Quickcam cooling 2
The first test platform for Peltier cooling was a mixed success. The cooling worked, but the CCD kept dying. The success of this version indicates it was lead length, and not cooling, which caused the demise of the CCD. Where on the previous incarnation the leads had to get around, or rather through, the heat exchanger, this time, the heat exchanger is in front, and the camera head PCB is attached to the back, having only the 1/8" copper cold plate and 1/8" styrofoam insulation to pass through.
The styrofoam has proven to be too fragile in practice, so when I rework it, perhaps I'll make a mold, and use non-expanding foam in a spray can.
Version 1. A failure.
Front view of the heat exchanger
The square hole in the center allows access to the CCD. You can see the CCD mounting area, on the back plate through the hole. The wire-wrap socket pieces were epoxied into more or less rectangular slots cut in the cold plate. Frosting was an issue, so I tried a microscope slide cover over the hole. This stopped the frosting, but caused incredible reflections and a loss of transmission which were both at unacceptable levels..
End view of the heat exchanger
The back is toward the top of this image. You can see the camera head board mounted in its final position. The thicker copper plate is the cold plate, while the thinner one, with the tubes on it , is the heat exchanger. You can also see the TEC in between the plates. The thin plate looks curved here, but it isn't.
Interior of the enclosure
This camera is much larger than any of its predecessors. I got tired of working in cramped spaces. Rather than solder all of the connections between the boards, I have shortened the OEM cable to around 8". This is so I can take the unit apart and service it without risking damage by repeated soldering. The voltage regulator is not installed in this picture, and the connector board is a dead one.
Heat exchanger in place
There are two holes on the left side, and two slots on the right side. In retrospect, they should both be slots. I have to take the hoses off of one end to get the heat exchanger out of the package.
Exterior of the enclosure
The camera is mounted to the scope using T-threads. The 15mm extension from a Meade SCT to T-thread adapter is epoxied to the front of the enclosure. A 2" diameter optical window from Edmund Scientific is RTV'd to the back.I have a 1.25" barrel to T-thread adapter, and an Apogee T-Thread extension tube set. Between these devices, I can get about any focal ratio from the f/0.63 and f/0.33 focal reducers. I'm also on the list for one of Andy Saulietis' filter wheels. Originally designed for the CB-245 camera, he will build them to suit your needs. Mine will have a female T-thread front and rear, and comes with a male T-thread adapter. Total thickness is <16mm, so it is exactly the right thickness to get between the f/0.33 reducer and the camera at f/3.3.
The switches, from top to bottom are ABG, Camera Power, Peltier 1, and Peltier 2. The coolant tubes protruding from the right side are for the loop-back tubing. The two on the left are the inlet and outlet which go to the pump and reservoir. The heater, which keeps the CCD from frosting over during cool-down, is controlled by another switch, which isn't mounted yet.
The QC electronics, TECs, and pump are all powered from a 12V, 12.5 A switching power supply I found at MPJA for US$45.00. I have yet to add an outlet for the LX-200 power supply. I set it up so that I could run the whole thing off the battery in the van when I'm remote.
Update: You should have seen this thing when the 12V pump quit. One of the hoses exploded, and by the time I figured it out, the styrofoam in the box had incinerated, and the TECs had unsoldered themselves. Pretty cool.