The audio signal should likely be around 250mV, maybe up to 1V peak-to-peak if 'line level'. I would expect the suggestion in post #3 should work.The source actually from HDMI to Audio Converter, on a 3.5mm stereo jack.
Audio signals are usually AC so a meter will generally average them out towards 0V on a DC setting, and will unlikely register on a 230VAC setting.My multimeter must be playing up then, cause I cant seem to read anything over 0.2mV!!
That's good to hear. I've always been a fan of 'zero component' solutions. Or at least no more than PICAXE, resistors, diodes, capacitors and LED's.Just got to say, the circuit and code you told me to give a go, works an absolute treat, thank you
Probably easier to come from the other direction; USB provides 5V at up to 100mA ( and maybe more ). Really depends on what is supplying that USB power. The PICAXE will probably draw less than 20mA so the relay can draw up to whatever is left.How much power draw would the switch side of a relay use? Im wondering if I could power this the whole circuit from a USB port
Which model ? You should be okay for 100mA but earlier boards may need modding to bypass the USB polyfuses and I recall there may be ongoing issues with hot-swapping and in-rush currents resetting the entire PI and you might have to work round that.I would use the USB port of a Raspberry Pi
I think you need to check with the Pi manufacturer for a definitive answer.I think Ive found a relay with a lower current on coil. At between 72 - 80mA, so that should work on the GPIO pins
Activating the relay might have the same effect on the supply as hot-swapping a USB device with its initial in-rush current which could cause a Pi reset so you probably will have to experiment. The Pi forums may indicate what levels of in-rush current are acceptable.Do I still need to be careful of current overload if its only on for a few milliseconds, or is there more room for maneuver??
I think it is best to stop and step back, explain how you mean and what you are now doing, before something seriously untoward occurs.I see what I have done wrong now, I was usingthe Ipod from battery source, but it seems you need to be connected to a common ground (mains neutral) for the circuit to work
The design is using the on-chip comparator to detect small voltages on input pin 4. With no input connected pin 4 should be tied to 0V, albeit through a large resistance. Perhaps the resistance has become too high or something is introducing noise on pin 4 or within the chip which causes the comparator to activate. It could be that the amp is back-feeding voltage which is activating the comparator. Does disconnecting the cable to the amp make it work ?However, the audio lead is disconnect, the circuit just latches on.
Are you sure the resistor is both earthed and connected to the input line when the socket is empty? The pins of switch-type sockets can be confusing.I then also tried to lower the pull down resistor right down to 22k
That's the only case you have to worry about for now.Input Audio disconnected = LED Latched On
That seems to suggest the comparator is seeing some voltage on pin 4 rather than 0V. What if you connect a wire from pin 4 direct to 0V ?I also tried to connect the LED to pin 2, and the same as above occured