AC Signal...

[Melanie]

Hmmm not quite an 'AC Power Source' ...

So you're telling us that the AC is really a dinky Audio Signal from a car radio and not a High-Voltage 'Power Source' ?

[Tear]

Well I havent measured so I dont know the exact voltage of the AC signal, but it is AC voltage signal that also powers the car speaker that it would feed off of.

~Michael

[Sharky]

Hi Tear,

Sorry to say it, but I think your on a slippery slope.

I agree that it is really fun to play and work with PIC's but I really think that there most be an easier way for you than to use a PIC for this job.

Are you sure that there is'nt a signal out from the car stereo for an electrical antenna or for the amplifier, this is quite normal when you have a lineout signal from the car stereo.

Sorry this is getting OT !

Sharky

Ps. Thanks Melanie your circuit is really something I can use, normally I use a two-coulor LED to check if a fuse it blown, but it will be very cool to let a PIC do something to indicate that a fuse is blown

[Tear]

Well there is the antena lead off of the head unit (stereo) but the problem when using it is that if you play CD's instead of listening to the radio using the antena the line will be low and turn the amp off. This is due to the fact that the antena only has power when listening to the radio.... as far as I know.

~Michael

[mister_e]

If it's the factory radio this is probably the an HONDA, or NISSAN.... and most of them will cut the power on the electric antenna wire when switching to CD, tape deck.

Well there's another way... just use the accessory wire at the ignition switch, then do a delay... or not. Many time i did it in the past.

As far as i remind, DEI do something like the unit you want to do.

Usually, 6V is present between each speaker lead and ground(drive BTL by TDA73XXXX amp or equiv). Easy way, use capacitor to remove the DC, pass it thru an OP-AMP/Voltage comparator/ADC and then activate/disable you Amplifier remote lead.

Many car have also external amplifier, if you give me the car model/year i can see if there's any possibility of external amplifier.

EDIT: Is the unit the original or aftermarket?? If it's an aftermarket, as previoulsy mention... many chances are that the Power Antenna wire will also send DC while the CD is running... case not you must have 2 of thes blue wire back to this unit...

[Tear]

what is an ADC? I tried googling it and couldnt find anything valid as to what this is.

~Michael

[NavMicroSystems]

what is an ADC? I tried googling it and couldnt find anything valid as to what this is.

~Michael

Analog to Digital Converter

BTW
Are you really willing to use a PIC 16F84 for this simple task?
any 8 pin 12F or even a 10F could do this.

Or even simpler: somethimg like the NE555
(does not even require any programming at all)


This thread is a good example of what you end up with if you don't give sufficient details in the first place.

[EDWARD]

you dude, ADC means Anologue to Digital Comparator or something. it basically will give you a decimal readout of a signal (usually 0 to 255) rather then 1 or 0. it it can be hard to set up beacuse you would likely need to build a transforming circuit.

do you even know what type of signal must be sent out the amp siganl line? is it 5 or 12 volts DC? does it stay at 5-12 volts dc or does it just sent a pulse?

this could be made without a pic. but if you must these are things to consider.

sound to me like all you need is a zener diode and resistor connected between the ac sound signal and a pics input. not sure how much power a deck can produce and not really sure the value or the components, but get one that wont allow more then 5volts and limited current. if the current is higher then extepcted then i would use an isolation relay like the one posted at the top, this will prevent frying the pic. if all you can find is a standard relay that should work too but will be clicking like crazy.


just write a code that is like this:

if pic recives pulse on input line then
turn on amp
endif


the pics input pin will be reciving random pulses as the music plays so youll ne ed to write a workaround like:

if no pulse is recived within 1 minutes then
shut off amp
endif

how do you plan on powering the pic?


google search zener diode, optical isolation relay, rectification

also, using you meter, meaure the ac signal out the deck with the volume all theway up. also measure the amp signal on your car. im not 100% sure but when you meause the amp signal line go from that wire to ground in dc mode. but when measuring the speakers go from speaker LF + to speaker LF - (left front ) in ac mode.

[mister_e]

That's an area i'm really experienced with. I did installation for more than 10 years as now. Still do some times..

do you even know what type of signal must be sent out the amp siganl line? is it 5 or 12 volts DC? does it stay at 5-12 volts dc or does it just sent a pulse?

100% of the aftermarket amplifier need a constant 12 volt to turn them on. Usally called PCon, Remote or Turn-on Lead. The amplifier will stay on as long as you send him a 12volt on the remote terminal.

not sure how much power a deck can produce and not really sure the value or the components, but get one that wont allow more then 5volts and limited current.

Those deck work on 12Volts and never use internal voltage shifter to raise te voltage. So a MAX of 14Volts amplitude will be on the Speaker terminal when the car is running. Simple Voltage divider built with 2 resistor will do the job. Let's say 10K in serie between PIC and Speaker, 5.1k(or a few less) between PIC input and gnd. We can skip the capacitor in serie.