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Connecting arduino to car...

Diy1995

Member
Hello, I need to connect arduino to my car and I need a little bit of help because I don't want to fry the stereo.

I have no remote wire because stereo is controlled via can bus and my lighter socket is always on, but I have electric antenna out on my stereo and I already have my amp connected to it and it works.
Now arduino can take up to 1A of current so this is a no go for antenna out.

Can I use e-antenna out for powering relay's coil so I can use a relay to turn arduino on and off?
And I have read somewhere that it is good idea to connect flyback diode to the coil to provent popping from speakers and risk to damage stereo because of voltage spikes? (I have seen them turned right way + to + and - to -, and some of them reversed, how I should turn it)?



How many current can electric antenna out provide?

Thank you for anwsers!
 
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MikeMl

Well-Known Member
Most Helpful Member
Draw a detailed block diagram of what you are trying to interconnect.
The "amp" likely already requires several A of current, depending on its power level.
An Arduino (with little connected to it) draws less than 60mA.
 

Diy1995

Member
Draw a detailed block diagram of what you are trying to interconnect.
The "amp" likely already requires several A of current, depending on its power level.
An Arduino (with little connected to it) draws less than 60mA.
Hello, thank you for anwser.
Amp's remote is connected to it. Several amps would fry that output for sure hehe.
I will use arduino as vu meter (5 leds) and to control little dc motor attached to pot. I will draw schematic when i get home.
 

MikeMl

Well-Known Member
Most Helpful Member
...
Amp's remote is connected to it. Several amps would fry that output for sure hehe.
I will use arduino as vu meter (5 leds) and to control little dc motor attached to pot. I will draw schematic when i get home.
So the "Amp's remote" is just a logic signal input that tells the amp to turn on?

If the original "e-antenna" output from the head unit is intended to power an auto-extend/retract motorized antenna, then likely you could draw a couple of amps from it. If the motorized antenna input is like your amp (where the control input is just a logic signal), then it is possible that the "e-antenna" output from the head end can supply only a few tens of mA, maybe even not enough to power a relay coil directly.

Do you have an installation manual on the head end? It should specify what the "e-antenna" output is intended to drive.

Does the power amp already have an output that has 12v on it only when it is powered up? If not, can you bring a wire out of it that would?
 
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Diy1995

Member
So the "Amp's remote" is just a logic signal input that tells the amp to turn on?

If the original "e-antenna" output from the head unit is intended to power an auto-extend/retract motorized antenna, then likely you could draw a couple of amps from it. If the motorized antenna input is like your amp (where the control input is just a logic signal), then it is possible that the "e-antenna" output from the head end can supply only a few tens of mA, maybe even not enough to power a relay coil directly.

Do you have an installation manual on the head end? It should specify what the "e-antenna" output is intended to drive.

Does the power amp already have an output that has 12v on it only when it is powered up? If not, can you bring a wire out of it that would?
Hello,
Amps remote is just a logic signal input yes (it's a classic subwoofer amp that has +12 gnd and remote inputs).
It' original opel/vauxhall/saturn astra head unit, so I dont belive that it's e-antenna output is intended to extend antenna, because none of opel's/vauxhall's/saturn's from that year have extendable antenna.

I will try to find manual for HU.
Thank you
 

MikeMl

Well-Known Member
Most Helpful Member
So your "e-antenna" signal may just be an output to power a remote-mounted antenna RF preamp, so might be good for driving only a few mA.

Here is what I would do: First choice: a high-side transistor switch using a NPN driving a PNP or PFET. Second choice, an NPN driving a small relay coil. I would not try to drive the relay coil directly as you show above.

47.png 47p.png 47r.png
 

Diy1995

Member
So your "e-antenna" signal may just be an output to power a remote-mounted antenna RF preamp, so might be good for driving only a few mA.

Here is what I would do: First choice: a high-side transistor switch using a NPN driving a PNP or PFET. Second choice, an NPN driving a small relay coil. I would not try to drive the relay coil directly as you show above.

View attachment 106338 View attachment 106339 View attachment 106340
Hy, thank you for schematics, I will go with second option. I also wrote an e-mail to blaupunk service and thay anwsered that they have no info about pin's output current.

Thank you again
 

mojozoom

Member
Could you just connect a keyed positive from the fuse box to the Arduino? If the stereo is off there'll be no action on the VU meter, so essentially equivalent to having it off. But you'd also have the Arduino available all the time then, instead of only when the stereo is on.

Then you could use the Arduino to lock the doors when you get above a certain speed, shut off the A/C when you are accelerating, trigger a shift light, cook you breakfast....
 

MikeMl

Well-Known Member
Most Helpful Member
Could you just connect a keyed positive from the fuse box to the Arduino?...
Good idea! The "e-antenna" signal can be run through a suitable voltage divider, and applied to an Arduino port pin as an input so that the Arduino knows if the radio is on or off.
 

Diy1995

Member
Hello,
Those are some clever ideas. But fusebox is in engine bay, there is no interior fuse box. I would rather not hack electronics too much (astras are known for electronics problems -i didnt have one yet thankfully), im reffering to door lock, ac controll, ...
I can turn my stereo on witout key in ignition and my radio turns off after I take key off. So connecting it to radio itself would be much more intergrated.
Thank you
 

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