I'm having the same problem. My LCD flickers and sometimes even shows the sparkfun logo meaning it has shutoff or reset. It seems that I need to take more precaution in my setup to prevent a surge of current or voltage from the relay when it closes or opens. But I'm not sure how to go about this. Everything else works like I want it to except for this surge of current. I have re-soldered this relay circuit three times now even trying two IN4004 diodes in parallel, using other relays, etc... This project has to be solid. I want to add another relay to it to control something else but am afraid it will double the frustration...
I have an arduino Duem with a Serial LCD-09394. I have two TMP36 temperature sensors coming in on analog(0) and analog(1). I have a 5A, 12V relay and 2N4401 transistor WITH 1N4004 diode setup just like this however my relay circuit is opening and closing an 120V ASCO water valve. http://www.arduino.cc/playground/uploads/Learning/relays.pdf
My schematic is here:http://web.me.com/jaysettle/iweb
My program is here: please know that I am no programmer. not even really sure how to add code to this forum, guess I'll copy it to notepad and put it on a website:http://web.me.com/jaysettle/iweb/Site/code.html
To be clear, my question is: First of all, is my relay circuit surging the arduino or LCD? If so, how can I protect them better?
BTW, I do have a solid state 25A 120V Crydom relay that inputs 3V to 32V. It has each node labeled (1) through (4), check the picture. http://web.me.com/jaysettle/iweb/Site/Crydom.html
I couldn't get it to work though. I had a negative from arduino to the negative on relay(4), positive from digitalout on arduino to positive on relay(3), and i'm assuming (1) and (2) become closed when arudino sends a 5V to (3). but it no worky. any suggestions as I think this relay would be better.