Canon 1100D Mod: Filter Removal, Direct Cooling, Electrical Dew Control

[benzomobile]

Hi all,

I'm Giuseppe, from Como, Italy.
I'm finishing my tutorial resulted from modding work I performed on my Canon 1100D, I want to share with you.

My tutorial is currently in Italian, but soon I will present it in English. 
You will find at the following link:

https://sites.google.com/site/beppelastrofilo/home/canon-1100d-mod-filter-removal-direct-cooling-electrical-dew-control
 

The specific feature of my mod consists in preventing the formation of moisture on the sensor surface, by placing small silica gel granules in the groove  on the black plastic frame, where the LPF#2 filter  was placed, before I've removed it.

Thus,  very low relative humidity is created inside the sealed thin chamber, delimited by LPF#1 filter (put back in its place)  and the sensor surface.

A resistive wire NiCr (384 ohm/m) was stuck on the plastic frame, at a small distance from the edge of the filter.

The nichrome wire, in series with a 120 ohm resistor, is fed to a voltage of 12V. 

Therefore, the wire dissipates approximately 1/5W (2.7V x 78mA) heating good the LPF#1, whereas no significant heat is transferred to the air within the chamber.

I realized through various tests that the power dissipated by the NiCr wire should not be too high.

In this case, in fact, the temperature inside the chamber  increases too much, causing the formation of some  (little) frost filament on the sensor surface.

With a wire dissipated power of around 0.20-0.25W, I have completely solved the problem of condensation, even a temperature sensor lower than -10 ° C.

Notes that in this way the sensor surface is not directly heated, therefore the sensor total cooling  is not diminished by excessive heater power.

The current flowing into the Peltier cell is controlled efficiently by the PWM supply circuit, low-pass filtered (I designed it myself). This is not a standard thermostat that turns on and off the TEC, but it is a power source that varies its voltage continuously - near real-time and with very small hysteresis - in response to the variation of the NTC resistance.

I wish you a merry Christmas!

[frostynixon]

Very nice!