Hi,
I want to be able to stick a photodiode on my LCD screen and when the screen changes color from black to white for instance then I get this change (really fast under 1ms) and send it through rj45 connection to my EEG amplifier.
I am having trouble knowing what photodiode to use for fast response and for lightining/color changes on the LCD screen. moreover, I will be using an Arduino Uno and I am planning to buy an Ethernet Shield because my EEG amplifier only accepts such an input. So ultimately I want to be able to send a pulse through the rj45 connection that indicates with under a 1ms precision the onset/offset of different light levels/colors coming from my PC screen.
Thank you,
Rani
Split your project into color detection and data transmission. An opamp may be required, to amplify the photo diode signal. Take care that ambient light will not be detected as a screen "white" signal.
For the data transmission you have to specify a message format, and transmit that message when a color change is detected. You also have to specify the IP address of the EEG amplifier as the message target. The target device has to know what to do, when such a message is received. Consult the manual of your EEG amplifier for all accepted messages, and pick the right one for your message. Or update the EEG amplifier code to handle your new message.
Thanks Doc for your help.
I need more advice on the hardware. Specifically, what photodiodes are suitable for this project (particullarly regarding the fast time response required).
Regarding sending the signal to EEG. The EEG expects this and I know how to handle it. I am worried on whether ethernet shield enables me to use it to send data over UDP to the EEG.
I think that photo diodes react much faster than an Ethernet transmission takes, Also an amplifier reduces the response time, so that a photo transistor may be a better and simpler solution.