Hi All,
First post here! I've got a project in mind for the old-school stereo system on a car I'm restoring. The stereo that's in it now is an older in dash AM/FM/cassette that I plan to keep there for the time being. I have an under dash 8 track deck that I'd like to use with the same rear speakers. (The in dash radio operates 4 speakers; the 8 track deck only the two rear ones).
My thought is to use a 5pdt relay for this. Four of the poles would be for the + and - for the rear speakers. The fifth would be for the power line for the in dash radio. The rear speakers would be connected to the center contacts and the outputs from the radio would be to the NC contacts. The power to the radio would be on the center and NC contacts of the 5th pole. So in the unenergized state, the radio would play normally - it would have power and its rear speakers would be hooked up. Its front speakers would always be hooked up because they are wired directly to the radio. The outputs from the tape deck would be conntected to the 4 NO relay contacts.
When the relay is energized, the rear speakers would be switched to the tape deck and power to the radio would be cut, automatically silencing the front, radio-only speakers. I'm pretty sure all this would work with an A/B switch. Where I need help is with the trigger for the relay. I'd like to be able to "sense" current going to the tape deck and use that to energize the relay. The tape deck normally doesn't draw any current at all when it's off. It's turned on by putting in an 8 track and turned off by pulling the 8 track out. My thought is to somehow use a transistor on the power line to the tape deck, to drive the relay but I don't know the specifics. I'm also wondering about other components that I'm overlooking. E.g. would I need diodes and/or caps somewhere to protect the radio or tape deck from spikes when switching back and forth, etc.?
All this stuff is pretty low-power, too, by the way. I don't have the specs. in front of me but I would guess speaker output below 30W max, probably closer to 7-10W. No giant amps involved. Again, guessing, I believe the radio and tape deck would draw between 2-5A max.
Any help on the triggering part of the circuit would be appreciated, as well as component selection/sources.
Thanks!
Pat
First post here! I've got a project in mind for the old-school stereo system on a car I'm restoring. The stereo that's in it now is an older in dash AM/FM/cassette that I plan to keep there for the time being. I have an under dash 8 track deck that I'd like to use with the same rear speakers. (The in dash radio operates 4 speakers; the 8 track deck only the two rear ones).
My thought is to use a 5pdt relay for this. Four of the poles would be for the + and - for the rear speakers. The fifth would be for the power line for the in dash radio. The rear speakers would be connected to the center contacts and the outputs from the radio would be to the NC contacts. The power to the radio would be on the center and NC contacts of the 5th pole. So in the unenergized state, the radio would play normally - it would have power and its rear speakers would be hooked up. Its front speakers would always be hooked up because they are wired directly to the radio. The outputs from the tape deck would be conntected to the 4 NO relay contacts.
When the relay is energized, the rear speakers would be switched to the tape deck and power to the radio would be cut, automatically silencing the front, radio-only speakers. I'm pretty sure all this would work with an A/B switch. Where I need help is with the trigger for the relay. I'd like to be able to "sense" current going to the tape deck and use that to energize the relay. The tape deck normally doesn't draw any current at all when it's off. It's turned on by putting in an 8 track and turned off by pulling the 8 track out. My thought is to somehow use a transistor on the power line to the tape deck, to drive the relay but I don't know the specifics. I'm also wondering about other components that I'm overlooking. E.g. would I need diodes and/or caps somewhere to protect the radio or tape deck from spikes when switching back and forth, etc.?
All this stuff is pretty low-power, too, by the way. I don't have the specs. in front of me but I would guess speaker output below 30W max, probably closer to 7-10W. No giant amps involved. Again, guessing, I believe the radio and tape deck would draw between 2-5A max.
Any help on the triggering part of the circuit would be appreciated, as well as component selection/sources.
Thanks!
Pat