This Instructable is specific to making an electronic viewfinder for the Canon S95, but assuming your digital camera has video-out capability, and you can find the correct connector and pin-out, you can adapt for your specific needs. This viewfinder is USB has rechargeable batteries and can be recharged via a microUSB connection.
This is the Mark 1 version, with a Black & White LCD video module scavenged from a Wild Planet Video Spy Car. This viewfinder is larger than I wanted it to be, and is not color. The next version will use parts scavenged from a Vuzix/Icuiti Video Eyewear/Glasses unit.
The other components are avialble online and make this project fairly easy with only minor soldering required.
Why would you want a viewfinder for a digital camera when you have that nice LCD display on the back? It might be easier to shoot in the sun for one reason, but who really cares why... if you want one, here is a way to make one.
Step 1: Get Some Parts
I bought the following from sparkfun.com:
1 - Lithium Polymer Charger
2 - 3.7V 110mAH Lithium Polymer Batteries
I scavenged a small switch from a previous project to have a power off/on for the viewfinder.
I had a small plastic box from some old Polaroid Kids Instamatic camera film that fit almost perfectly.
I also ordered a mini HDMI adapter to hack and use to physically stabilize the attachement to the camera. The Canon S95 has a mini HDMI port just above the Extended USB port. I used this mini HDMI port to give the viewfinder a more solid physical connection to the camera. There are no electrical connections to the mini HDMI connector you see in this Instructable.
Step 2: Find a Small LCD Video Module With Lens
I bought a Wild Planet Spy Video Car replacement Headset on ebay. This was the easiest to hack in my opinion, but is Black & White. Another option that I will be using for the next version which will be both smaller and color, is components from the cheapest version of the Vuzix/Icuiti video glasses I found on ebay.
Step 3: Cut the Cord
Take your cameras AV cable and snip it! Try to keep track of which one of the wires is for video, but usually the internal wires are color coded in case you mix it up. The video cable should be yellow. This is the one you will connect to the LCD video module.
Step 4: Convert to NTSC If PAL Is Not Required
The video standard most used in the USA is NTSC, and my camera was NTSC. If you bought your camera in another country, check the manual to see if yours outputs PAL or NTSC video. This step is purely for the Wild Planet Spy Video Car Headset. Note the exploded view in red for the resistor locations. Move the resitor to the empty pads for NTSC. In this picture you can also see where I glued the mini HDMI connector to the circuit board to strengthen the physical attachment to the camera. The picture quality is poor and I apologize, but I could not retake it, since by the time I decided to do the Instructable, I had already glued the connectors to the circuit board and now the components are hidden. Since the box I put it in later worked nicely, I should have waited and glued the connectors to the box instead, but I was also testing the assembly outside of the box.
Step 5: Solder Video Cable to LCD Video Module
Solder the video cable you snipped to the LCD Video Module. The center of the video cable is the positive (+) signal connection, "VIDEO-IN" on the circuit board. The other wire is the ground (-) connection, "VSS" on the circuit board.
Step 6: Solder the Lithium Polymer Battery Charger to the LCD Video Module
I trimmed the Lithium Polymer Battery charger board by breaking off the end that has the battery connector on it. This was to allow me to fit it into the space I needed. I soldered the charger to the LCD video module with a switch in between to allow me to turn off the power when not in use and when charging. VCC is positive. VSS is negative. The picture here is before I removed the connector and added a switch, but you can see where I attach the power supply to the main board. Also shown is the video connection in a wider view than the previous step.
Step 7: Solder the Batteries to the Charger
Snip the leads to the batteries to the appropriate length for your project and solder the red leads to the (+) terminal on the charger and the black leads to the (-) terminal on the charger. Currently I have 2 batteries, but may add more depending on how much usage they give me. Since I made the device USB charge-able, the unit can also be recharged with most of the USB Cell Phone Boosters and other power modules that use a microUSB connector.
Step 8: Arrange, Glue, and Tape!
Arrange the components for your container and get it prepared to stuff into a container of some sort. For my version, I had to rotate the LCD Video Module's Eyepiece/LCD 90 degrees. This was so the LCD Module Board could be mounted vertically. Since the white LED the module used for a backlight for the LCD was centered on the back of the board, it worked out well. I just made sure the connecting tape cable reached the connector when it was rotated, then glued it to the board in the position I liked.
Step 9: Put It in the Box
Cut the necessary holes in the container of your choice and put the components inside.
Step 10: Make Sure Video-out Is Enabled, and Use It!
Whether I use it much or not, I made this for fun and to see if it could be done cheaply. The cheapest I could do it is around $50. If you have to buy the whole Spy Video Car kit or the Vuzix/Icuiti goggles are too much, then your cost will be higher.
This version works, but the low resolution, black & white, and size of the module make it less than perfect, even for a DIY project. My next version will be less than 1/3rd the size using the components from the Vuzix glasses.
I was still fun and cool to make :-)