Question: I want to take some video of a friend with a motor disorder while he is sleeping. We are doing this to help get information about what happens while he sleeps. 

I have a tripod and set up my iPad to video tape. But as soon as I turned off the light, the iPad could record nothing. I thought the iPad camera mode might have some way to brighten the image so that I could record, but nothing happened. 

What is the least costly way to film my friend in the dark?

Answer: 
If trying other cards has not worked ([as indicated in comments](https://photo.stackexchange.com/q/81698/75526#comment140065_81698)), then the problem is not the card, it's the camera. You will need to get it repaired or at very least disassembled and cleaned by a specialist.
I was dealing with the exact same problem. I took a Q-Tip and wiped the contacts off on the card. Worked like a champ!! The camera would read other cards and my computer would read the one the camera didn't like. So give it a try. Seems the camera may be a little more sensitive to the condition of the contacts. Good Luck!