I had the same problem and had caught two snakes in my coop. This began as my girls had just started laying for the first time. I put out golf balls to stimulate them to lay and one day all my eggs were missing from under my banty and so were two of the golf balls in the other nest boxes. The snakes ate them. Since then, I have had no more problems with missing eggs and last weekend I found the remains of one snake (just vertebrae, a few ribs) with the golf ball laying in the center. So it can't hurt to put out of few golf balls.
There are also snake traps you can make that seem pretty simple if you go a search. After the missing golf balls, I have had no need to make one.
The problem is, once they find the egg buffet, they will continue to return.
I am sure the light bulbs would work but my girls get a little clumsy getting in and out of the boxes so I could see them getting broken.
Just a note of nostalgia: a friend of mine recently went to an auction at an old farm and there was a box of old porcelian door knobs without the hardware in the barn. When she asked what they were for, she was told that in the old days, farmers put those in the nesting boxes for snake control. Sad thing is, she did not bid on them for me!!!!!!