I have this camera OV0706: https://learn.adafruit.com/ttl-serial-camera?view=all
I tested it with arduino mega and arduino uno and duemilanove and works perfect by the use of the library and wiring showed in the previous webpage.
What i want to do is to integrate this camera in my project, what consiste on a stand alone device measuring different temperatures by ds18b20. In order to reduce the power consume, better than to connect continuously the sensors to power pins in arduino mega, i use a 4n35 optocoupler. I connected all the grounds from sensors to the optocoupler, what is activated by a digital pin. This is the general scheme of the wiring: http://fritzing.org/projects/powering-sensors-by-4n35/ Not showed in that scheme there is a microswitch to connect the grounds from the sensors directly to ground pin, jumping the optocouper. This is only for debuging task.
The problem is that if i turn on the switch, all the sensors and the camera works correctly, but by the use of the optocupler, the temperature sensors works well, but the camera is not found...
In the diagram showed in the first link about how to wire the camera, there are a couple of 10K resistors in the RX and TX wires., one of them connected to ground. I tried both things: 1) to connect it to the other grounds connected to optocoupler, and 2) connect it directly to ground. In any of both cases, the arduino find the camera. Only if i jump the optocoupler and wire the camera directly to ground (independantly to were is connected the RX-TX resistor), it works.
I also tried by adding a 0.1uF capacitator to stabilize the power in the 5v-ground pins f the camera, by it still don´t want to work...
Any idea about what could i do to solve this issue? Thanks!