measuring across the IR sensor from output to ground on the IR sensor, do you have full logic level voltage swing and is it the same as when you use the IR remote to do the same thing. This may well require an oscilloscope to determine. I'm thinking that you don't have a good idea of how the IR sensor is connected to the CD player. Placing your finger from the sensor output point to ground does 2 things, 1, is to introduce some resistance from the contact point to ground and 2, is to place some small capacitance from the contact point to ground. A "Normal" "Dry" finger to finger measurement is about 20K give or take a few K (the usual range from the time when I made GSR "meters" for bio feedback was 10 to 30 K for "normal dry fingers". It is entirely possible that the pull down isn't small enough to pull the point low enough to work and measuring across the sensor for both conditions should point you in the correct direction.Bob
You can upload files with your post, just click on "Additional options" when composing your reply.If the IR sensor is something like this http://www.adafruit.com/datasheets/tsop382.pdf then you should feed the transistor just the modulation signal, not the carrier. If you post your sketch, I or someone else may be able to advise what changes you need to make to send just the carrier. You might get away we connecting a capacitor of a few hundred pF between the transistor collector and ground, but it is better not to transmit the carrier in the first place.
now i would like to understand why it works. especially as it is working with a modulated signal.
Quote from: NeX on Oct 15, 2012, 07:39 pmnow i would like to understand why it works. especially as it is working with a modulated signal. The transmitted signal comprises bursts of the modulation frequency to represent logic 1 and periods of no transmission to represent logic 0. (I have assigned the 0 and 1 states arbitrarily).When a logic 1 is transmitted, the transistor turns on and off at the modulation frequency. When the transistor is on, it provides a low resistance to ground, discharging the capacitor. When it is off, the capacitor charges slowly through a pullup resistor. However, it doesn't have time to charge much before the transistor turns on again. So the output never rises to a logic high.When a logic 0 is being transmitted, the transistor remains off, so the capacitor gets a chance to charge up to 3V and the mcu sees a logic high.So the transistor, resistor and capacitor form a demodulator.
so in theory, if i can get it to send just the data, it should work without the capacitor
Quote from: NeX on Oct 16, 2012, 06:53 amso in theory, if i can get it to send just the data, it should work without the capacitor That't right. You will still need the NPN transistor, so that it can share the mcu input with the IR sensor nicely.
If you've connected the Arduino pin directly to the IR sensor output, that's a bad idea. When the sensor tries to drive the output low and the Arduino tries to drive it high, you are likely to exceed the current rating of the IR sensor, the Arduino output pin, or both. Unless you've written the code very carefully to only make the pin an output when you drive it low, and make it an input the rest of the time. Also, you should consider what happens when the Arduino is powered down and you want to use the IR remote, unless the Arduino and the IR receiver are powered form the same source.