sorry for my ignorance but i have spent a full day trying to work out whats happening and i am at a loss.
here is what i am trying to do:
i have a car CD player, powered by a car battery, i want to control it with my laptop. i have used the arduino IRremote library to learn the codes of the infrared remote, and with an infrared LED on the arduino and sending serial data from the laptop to the arduino i can control the CD player,
but what i would like to do is hardwire it, so that i have a small arduino inside the CD player, and a wire directly from the arduino to the infrared sensor on the CD player, so no optics involved.
the infrared is inverted, so the output from the arduino drives a transistor which is across the IR sensor in the CD player, the arduino is also grounded to the CD player to complete the circuit.
here is where the problem starts. this setup only works if i have one hand on the battery negative and one hand touching the IR sensor output pin.
obviously this seems to be a ground issue, so i soldered a thick ground wire from the CD player, to the arduino (to the exact same place as the transistor is wired) but that didn't work.
i thought that maybe the output pin of the IR sensor (active low) wasn't going low enough, and maybe the internal pull up resistor of the IR sensor was some how keeping it from going fully low. but putting a 10k pull down resistor between the output pin and ground, also did nothing.
so now i am at a loss, the project is so close to being complete, but for some stupid ground issue. i have tried capacitors to filter any noise, pull up and pull down resistors, loads of ground wires, nothing changes.
the only way to get it to work is to hold the output pin and touch something grounded, then it works fine. it only works if i touch the output pin as well.
please help, i am at the limit of my knowledge here and i could use the advice of some smarter people.