Removing all unwanted parts of a DSLR to make a minimal weight and volume astro camera

[Gina]

The purpose of this thread is to describe as succinctly as possible how to convert a Canon EOS series DSLR to it's absolute minimum for use as a cooled astro colour camera.  I have described parts of this in various threads that include other information not directly related to this, making the wanted stuff difficult to find.  This new thread will, I hope, make the conversion information more concise and to the point.

The objective is to take off all camera parts not required for astro imaging under the control of a computer.  The resulting assembly can then be mounted in a new casing that can be dehumidified (that's just a fancy word for "dried") using silica gel and well sealed so that damp cannot get in from the surrounding air.  We will also be running the camera from an external power supply rather than the battery.

[Dave_D]

great stuff. i was thinking about removing the rear display on mine... for starters. that, and external power is my next project.

[knobby]

What a cracking idea...

[libraryman]

Yep, that is exactly what's needed, look forward to this, can you cover the electrical connection also, that's where I struggle mostly?

Ray

[Gina]

Yep, that is exactly what's needed, look forward to this, can you cover the electrical connection also, that's where I struggle mostly?

Ray

Yes, I plan to do that.

[libraryman]

Yes, I plan to do that.

Then I'm glued to this thread

Ray

[Davey-T]

Thanks Gina, you're a star.

Dave

[Gina]

Here we go ...

First job will be to remove all the screws that hold the various parts of the case together and onto the innards.  For this a Philips 000 screwdriver is required.  It's well worth buying a good one as there are dozens of tight little screws to undo and some of these on the inside you will want to reuse so you won't want to drill them out if you damage the slots.  Some toothpicks and plastic faced tweezers are useful for removing and replacing ribbon cables.

I am using an 1100D (called Rebel T3 in the USA) to illustrate this stripdown but other models are similar and I shall show variations where appropriate.  I will be taking the stripdown right from a standard camera with all the screws in place and go right through the process.  I could have referred you to the excellent work elsewhere for filter removal/replacement but thought it would be better to have it all in one place.

So we start with the camera and here are photos from all angles showing all the tiny screws.  (Except that I have already removed the screws that hold the from part of the case )

Remove the strap to access two screws.

And slide the eyepiece off to show screws behind including one that holds the eye correction knob.

All the screws have now been shown and these may be removed.  When I want to know where to put screws back and get the right ones in the right places I store them on double sided tape on a piece of paper with labels to show where the screws came from.  In this project, these screws will NOT be replaced but I have saved the screws this way in case anyone wants replacement screws.

To be continued...

[Gina]

[Dave_D]

Gina, you said that these LM2596 modules are good for powering the camera from a 12v source:

can they be built into the same box as the camera or do they need to be external? not sure how much heat these produce. also, would i need the heatsink to go with it?

[beamer3.6m]

For ease can we leave questions till the end so the thread flows...

... awaiting the next installment.

[Dave_D]

For ease can we leave questions till the end so the thread flows...

 Easy to say when your finger isn't hovering over the 'Buy Now' button 

[Gina]

It may be a good idea to make a couple of menu settings before dismantling the camera as it's easier on the camera menu with the LCD.  (Forgot to mention this earlier.) 

1. Release shutter without card - Enable
2. Image review - Off
3. Auto power off - Off
4. Auto rotate - Off

I think that's the lot but if anyone knows others please say.

First part of the case to come off is the back.  This should be carefully eased apart from the rest of the camera as there are ribbon cables connecting this to the main circuit board.  Some models have one cable and some like the 1100D have two.  In most cases ribbon cables have a connector consisting of gold contacts (usually inside) and a tiny hinged plastic clip to hold the cable in.  These are very fragile and need care to flip up with something sharp.  The ribbons usually have a small hole moulded in just behind the end that assists removal and reinsertion.  This is where the toothpick comes in.

Once the back  is separated sufficiently, flip up the little clip(s) and remove the ribbon cable(s).  The back may then be put aside - we do not need it for an astro camera as all functions are controlled from a computer via the USB cable.

Next part to come off is the front.  This is being held in place by a hole that is hooked over the tripod bush.  Take a screwdriver or other thin flat object and lift the plastic casing up and over the tripod bush - remove the front case part.  This also will not be required.

Next and last past of the case is the top but before we remove that it would be wise to deal with a hazard on the power board at the front of the camera.

Be very careful not to touch the connections to the large electrolytic capacitor on the power board (black cylindrical object) as the capacitor may still be charged to several hundred volts and capable of giving a nasty shock or burn.  These connections are partly protected by a plastic tab but be particularly careful with screwdriver, pointed nose pliers, wire cutters or anything metal.  I was going to deal with discharging and removing the capacitor later but if it's discharged now it won't end up "biting" you.

Here's a photo of the capacitor showing the connections.

I'll describe the method used to discharge the capacitor next (once I've found my multimeter!).

[Davey-T]

It may be a good idea to make a couple of menu settings before dismantling the camera as it's easier on the camera menu with the LCD.  (Forgot to mention this earlier.) 

1. Release shutter without card - Enable
2. Image review - Off
3. Auto power off - Off
4. Auto rotate - OffI think that's the lot but if anyone knows others please say.

How about shooting without lens attached ? unless you're using a camera lens I suppose.

Dave

[Gina]

How about shooting without lens attached ? unless you're using a camera lens I suppose.

Dave

Setting the Mode to "M" solves this.  Manual mode.  Later on I shall be describing bypassing the Mode and ON/OFF switches with solder bridges.

[Gina]

When charged the flash capacitor showed 310V and with the multimeter connected it was discharging at a volt in several seconds.  Without the multimeter on it would probably discharge at a slower rate.  The only safe way to discharge the capacitor is with a suitable resistor.  Shorting out the wires risks welding the metal to the wires or even making the capacitor explode - there is a lot of energy stored in the capacitor!

By firing the flash and then switching off and taking the battery out the capacitor read 250v so I calculated that a 180K resistor would not be fried connected across the capacitor wires (about 350mW initial dissipation, rapidly falling).  I simply wrapped the resistor wires round the probes of the mulitmeter, switched it on and set it to DC volts and applied the probe tips to the capacitor wires.  With this setup it took a couple of minutes to discharge the capacitor to a few tens of volts.

Here's a couple of photos of my simple discharge rig.  The second photo shows the probe tips placed beside the capacitor wire (with just two hands I couldn't take a photo and hold the probes onto the wires).

Next part will describe removing the top part of the camera.  This has to be done before there is access to the battery connections to connect an external power supply.

[Gina]

Next job is to remove the camera top section.

Two connections to the main board - a tiny plug and socket that connects the microphone, and a ribbon cable.  These are pointed to by arrows in the photo below.  The mic connection can be just pulled out but the ribbon cable needs careful treatment as we will be using this in the final assembly.  As with the back, carefully lift the little plastic clip and pull the ribbon out with a toothpick.



The whole top section may now be separated from the rest.  Two pairs of twisted wires remain which connect to the power board and power the flash unit.  We won't want the flash so these wires may be cut to remove the top section.  But don't throw the top section away yet - we haven't finished with it.

Next will be connections for external power.
 

[Gina]

Connecting external power to replace the battery.

Here are two photos of the power board with the camera base at the top of the photo.  The battery connections are near the edge of the board partly covered by the ribbon cable.  This needs disconnecting as shown in the second photo, which also labels the connections. 

External power is connected to the +V and Gnd and the sense connection is also connected to Gnd.  Grounding the Sense connection indicates that the camera is on external power and this is displayed in imaging software such as EOS Utility or APT.

To be continued...

[Gina]

These photos show the power wiring.  If the power wires are more than a few inches it would be worth adding a decoupling capacitor across the connections - something like a 100nF ceramic capacitor.

Solder added to the connection pads

Wire ends prepared

Power wires soldered onto the pads and the ribbon cable reinserted into its connector and the clip pressed down to hold it

The flash capacitor is not required or used so to avoid any risk of it being charged I would recommend cutting the wires and removing it.  It is lightly glued to the power PCB so just break the bond, lift it up and cut the wires.

Next part will describe stripping part of the ribbon cable out of the top and applying solder bridges to the switch base to emulate the Mode and ON/OFF switches.

[Gina]

This part shows the stripdown of the top to access the part of the ribbon cable we will require for the finished job.  All the rest of the top is not needed. 

First photo shows the underside of the top with arrows pointing out the screws to be removed.

Firstly the screws marked in blue which hold a plastic frame

To get the frame out take the wires to the flash unit from their clips and prise off various bits of ribbon cable from pips on the plastic frame

Next remove the screws that hold the moving contacts of the Mode and ON/OFF switches

The ribbon cable is now free at one end and here we see it spread out against a piece of paper.

The only part we need is the base contacts of the switches and the "offshoot" that went to the main board.  The ribbon cable can be cut as shown by these red lines

The final thing we need to do to use this ribbon cable as a pair of preset switches is to add solder bridges to emulate the moving contacts set to a fixed position - viz. "M" and "ON"

That is all we need from all that top section of the camera and the rest is surplus to requirements.

[RAC]

You may also need to short the pop up flash-open switch wires. You may find the shortest exposure you can take is 1/200th as it thinks the flash needed. This is what my 1000d did anyway.

[tekkydave]

Wonderful so far Gina, I'm watching with excitement. I wonder if it would be wise to pop on a body cap. If I was doing it I would have broken the mirror by now with a dropped screwdriver - sausage fingers you see

[Gina]

A few questions have arisen as I have been posting so I'll take a break now and answer these.  This may also be a suitable point to talk about other camera models as there are a few small variations.  There is more to be removed from the body of the camera such as the viewfinder and mirrors.  The mirror assembly is worth removing to reduce any vibration problems though not essential.  We have already reached a stage where we have removed a considerable amount of camera and saved plenty of weight and space.

[Gina]

Gina, you said that these LM2596 modules are good for powering the camera from a 12v source:

can they be built into the same box as the camera or do they need to be external? not sure how much heat these produce. also, would i need the heatsink to go with it?

I have a few of these which I have successfully used to power the cameras from my main 12v supply.  Being switch mode they give off very little heat so I don't see a problem putting one in the same box as the camera.  I think it would produce far less heat than the camera.  Even a linear voltage dropper like an LM 317T would generate less heat than the camera itself though if you used one of these I would suggest mounting it on the heat sink.

My main concern would be possible electro-magnetic radiation causing interference in the camera but if this were a problem the unit could be shielded with aluminium foil connected to Ground (be careful to insulate any shielding).

Edit...  Tell you what - I'll check this out with one of my LM2596 modules

[Gina]

You may also need to short the pop up flash-open switch wires. You may find the shortest exposure you can take is 1/200th as it thinks the flash needed. This is what my 1000d did anyway.

Thank you for that   I have not found any problem with 1100Ds but I'm only just starting to try the 1000D model so I'll check that out.  I've used 1/4000s exposures for flats with the 1100D in the past but this is the only model I've used so far for actual astro imaging.  I also plan to check out the 450D as I'm using this as well as the 1000D for my deBayering experiments.  (Please don't ask anything relating to deBayering aka CFA removal in this thread - use the appropriate thread - thank you.)