Peltier Cooling Of Modified Canon Digital Rebel XSi

I have been imaging for a few years with Canon astrophotography DSLRs and have found that there is a noticeable improvement in dark frame noise when imaging below 50 degrees Fahrenheit. In 2004 when I first modified a Canon 300D, I prepared plans for cooling the camera’s imaging chip directly with a peltier device, but never built the system for two reasons:

Most of my imaging in Northern PA is during nighttime temperatures of 50 degrees Fahrenheit or less and noise is not a problem.
For direct peltier cooling of the imaging chip, the chip should be isolated in a sealed chamber to avoid frost and that would be difficult to do without major modifications to the camera.

When I modified a Canon 450D and began imaging with it, I found that the camera is completely controllable with Canon provided software for astro imaging via the USB connection to a computer. This means that the camera can be completely enclosed in a whole camera cooling system and still be used for remote astro imaging. The Canon 450D (XSi) with its plastic body is relatively light and along with its small size allows a light weight whole camera cooling system to be possible. I built Version I and Version II of a whole camera cooler and learning from those two projects, completed Version III of the camera cooler for which detailed assembly instructions are provided beginning on this page.

If you want to learn about peltier devices and their cooling effect in general Click Here.

Since the 450D (XSi) and the 1000D (XS) have the same height and depth, this cooler fits the 1000D (XS) as well.

Objective:

Build a whole camera peltier cooling system with these requirements:

Temperature drop of at least 30 degrees Fahrenheit (This was exceeded)
Low cost
Made with readily available parts and materials.
Only simple hand tools needed.
Size and weight appropriate for use on a typical telescope focuser.
Sealed cooling chamber to avoid frost and condensation

Warning:

These assembly instructions detail how I built a whole camera peltier cooler. The cooler is working well for me. If you damage your camera in the process of building or using the cooler, I am not responsible. Although measures are taken to avoid condensation and frosting, the results with your camera and cooler may differ based on your local conditions. Care should be taken when using AC in the field. The Vector AC/DC Converter has these warnings: “Risk of Electrical Shock”, “Dry Location Use Only” and “Do Not Use Outdoors”, among other warnings.

Parts:

1. Rubbermaid 5 Liter / 9 can Thermo-Electric Travel Cooler – Model No. VEC 222RB

This cooler is branded “RubberMaid”, but the cooler is made by Vector and branded under other names as well. I bought the cooler at Target on sale for $25. Besides stores, these coolers are also sold at truck stops and from online sources. Vector was acquired by Black and Decker in 2006.

The cooler operates on 12 volts DC and Vector also makes a 6-Amp AC/DC converter to operate the cooler using 120 volts AC. The converter is Model No. VEC004A.

We will be using the Peltier/heatsink, fan, on/off switch and DC cable from the travel cooler. The size of the peltier device is 40mm X 60mm. This information on the peltier is provided in the owner’s manual: “Amperage draw: 4 Amperes (approx. 48-Watts”). UPDATE: In 2011, I did testing of three travel coolers in order to determine which might be best to use for building a whole camera peltier cooler. The three cooler comparison is HERE.

2. Styrofoam Cooler. I bought a light styrofoam cooler from Kmart for $3. Pieces cut from it are used to insulate the aluminum cooling chamber. The walls of the cooler I used are one-half inch thick. Pieces are easily cut using a hack-saw blade.

3. Expanding Foam Sealant. I used a low cost sealant sold by Walmart called MaxFill.

4. Aluminum Sheet. Be careful when buying aluminum sheet. There are many types of aluminum alloy sheets and they can vary greatly in heat conductance properties. See the listing HERE. You want an aluminum sheet with a High Thermal Conductivity rating. Aluminum 1199 is the highest purity aluminum (99.99% Al min.) and has a high thermal conductance. Using an aluminum sheet with high thermal conductivity will provide the best and quickest cooling chamber that will be connected to the peltier device. I bought a 24″ by 24″ sheet of .025″ thick Aluminum Sheet by Steelworks (#11238) from my local Lowes Hardware. This aluminum sheet can be found from many online sources as well, here is a 12″ X 18″ piece that sells for $7.88.

A piece that measures 12″ X 18″ would be sufficient for making this cooler, but only the larger 24″ by 24″ piece was available at my local Lowes.

5. Plastic Radio Shack project box; size: 3″ X 2″ X 1″. Radio Shack No. 270-1801.

6. For helping to circulate air inside the cooling chamber, a small 12 volt heat/sink fan is useful. I got this small blue heatsink/fan from a local computer store for $15. The manufacturer, StarTech has the specifications and sells it directly online HERE. The model number is: FANCSORB and it can also be found on ebay. It has a sticky thermal pad that makes it ideal for using inside the cooling chamber since no screws or drilling is required.

7. 18-gauge speaker wire from Radio Shack. Radio Shack Part No. 278-567 and 24-gauge speaker wire from Radio Shack. Radio Shack Part No. 278-567.

8. Small tube of thermal paste (optional). Radio Shack Part No. 276-1372.

Tools:

Screwdriver, razor knife, hacksaw, epoxy, soldering iron, solder, pop-rivet gun, small pieces of wood, file, sand paper, 1 3/4″ and 2 1/4″ hole saws, and hot glue gun.

Assembly Instructions:

1. Remove four screws as shown from cooler and remove grey plastic housing from cooler:

2. The warm/off/cool switch slides out of the grey plastic housing:

3. Remove four screws from the fan assembly:

4. Remove three screws from switch circuitboard and lift off switch cover. Unsolder DC electric cable going to warm/off/cool switch circuit board. Mark cables for polarity before removing (I used red tape as shown in photo below).Remove black strain cable relief. Route DC electric cable out of grey fan assembly part hole for later resoldering to circuit board.

5. The switch will be placed four feet away from the cooler instead of mounting it on the cooler. The reason for this is to keep the cooler light in weight. Four conductors will need to be routed from the switch to the cooler. I used 18 gauge speaker wire for the cooler pair of wires and 24 gauge speaker wire for the fan pair of wires. Unsolder peltier black and red wires from circuit board. These are marked P+ for red and P- for black on the circuit board. Solder four feet of 18 gauge speaker wire in its place. Be sure to maintain correct polarity. Unsolder the fan black and red wires from the circuit board. These are marked M+ for red and M- for black on the circuit board. Solder four feet of 24 gauge speaker wire in its place. Be sure to maintain correct polarity. We will connect these two pairs of wires later in Steps 24 and 35.

6. Drill a one-half inch hole in end of plastic project box for cable strain relief. Pass the black DC power cord through hole and install with cable strain relief. Solder wires to circuit board. Cut a small slot on the edge of the other side of the project box with a razor knife for the peltier/fan cables. Mark center of project box face plate and use grey switch cover removed in the above step (#5) as a template to drill holes in the face plate for the switch and two LEDs. Install circuit board in project box and fasten face plate with four screws provided.

7. Remove the peltier device from inside the cooler by removing four screws as shown on the metal peltier mounting plate. Be careful of the peltier/heatsink assembly so that it doesn’t fall when the screws are removed:

8. Below is a photo of the removed peltier/heatsink and metal peltier support plate with 4 screws and 4 small rubber washers that will be reused. If the travel cooler is new and you haven’t used it yet, you will be able to reuse the white thermal paste on the peltier, or you can buy a small tube of thermal paste at a computer store or at Radio Shack (Part No. 276-1372).