Anyone with an electrical clue in the house?

[Aiken Drum]

Last spring, I inserted an switch on the pink/white line (A6) that controls the antenna motor. This is spiffy, as I get decent reception in most areas and can just leave it down most of the time.

However, on mention by someone else that they found a "module" that lets you control the antenna height (and then they went away without giving details), I began to wonder if the antenna really is limited to fully-extended and fully-retracted or if you could put a variable resistor on that line and select an arbitrary height. That, or maybe select a different step to allow for the half-height we hear about Japanese NSXes having.

So, question to the clueful: Sound possible? Any idea what kind of resistor I'd need? Nothing in the service manual says what sort of current A6 carries, so I'm at a bit of a loss to progress further on my own.

(Edit: and, for that matter, what sort of lighted LED switch should I use? I obviously picked one that requires more juice than it's actually getting, since the switch works, but doesn't light.)

 

[D'Ecosse]

I began to wonder if the antenna really is limited to fully-extended and fully-retracted or if you could put a variable resistor on that line and select an arbitrary height. That, or maybe select a different step to allow for the half-height we hear about Japanese NSXes having...

A resistor in series is not going to do anything to the height position. (edit). If there is an electronic module available, without any feedabck of the actual position, it is at best merely a timer cct, that interrupts the power after "x" period. You could create a variable timer cct to emulate this behaviour for use with the drive to the antenna.

Edit: and, for that matter, what sort of lighted LED switch should I use? I obviously picked one that requires more juice than it's actually getting, since the switch works, but doesn't light.

If you are just using the switch as a single pole device to interrupt the power, that in itself will not light the LED - you must also supply a ground to apply voltage across the LED. Can you reference the switch you used?

 

[Briank]

The antenna is an all the way up all the way down setup a resistor will not make for a part way extension. As for the switch not lighting if it is truly a LED light the direction it is installed will make a difference. Also does the switch have 3 wires if not the led(light) can only work when in the off position connected on the supply side of the antenna motor.

 

[Aiken Drum]

A resistor in series is not going to do anything to the height position - it will merely slow down your motor.

No, this line doesn't supply power, just a signal. The power is on another line, since you still need power to lower the antenna. I was wondering if a lesser signal might have a different effect on the target height of the antenna. However...

From a closer look at the wiring diagram (page 1217), I'd say this line controls two simple relays that gate the real power lines. When the signal is low, power flows through the motor in the direction that lowers the antenna. When the signal is high, it flows the other way to raise it. There's a limit switch that kills the power when you reach the end of the range (raise to min or lower to max).

It looks like there's no obvious way to make the limit switch kick in at half mast. I'm assuming there would actually have to be a second limit switch. Maybe it's not in the North American mast module. That, or it's not in the diagram, since it's not used.

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As for the on/off switch, I want it to be lit when the signal going out of the switch is high (meaning the antenna should be up). That would happen when the head unit requests the up position and the switch is on/closed.

I don't remember where I got the switch, so I can't direct you to it, but I can confirm that it does have three wires/connections. When I first installed it, I did make sure I had it set up the way the little diagram on the box said to do it.

I think the problem is that I was assuming a stronger current running through it and what's actually there is considerably weaker (since it's only a signal) and not enough to light the LED. I probably need a switch with a more sensitive LED or something.

 

[Aiken Drum]

You also probably want to make sure the antenna fully retracts. A split second difference between the time going up and the time going down could leave the antenna out a quarter-inch and begging to be vandalized.

Is it possible to have these three states?

Inputs: signal high < N seconds, power to motor
Outputs: signal high, power to motor

Inputs: signal high >= N seconds, power to motor
Outputs: signal irrelevent, no power to motor

Inputs: signal low, power to motor
Outputs: signal low, power to motor

I'm one of those people they talk about when they say, "A little knowledge is a dangerous thing."

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As an aside, I did some looking around and noticed that some other cars include a half-height switch as well. It involves connecting a pin on the antenna module to ground. If ours are the same as the Japanese ones and use a similar method, we should look to see if there is an unconnected pin on the antenna's harness.

Edit: judging by this picture of the smartenna harness, I'd say there is indeed an unused pin.

 

[D'Ecosse]

Here is the antenna drive schematic for everyone's convenience.

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[Aiken Drum]

D'Ecosse--

I don't see where your circuit controls the white/blue +12V line. If you change the pink/white signal line, you only change the direction current flows through the motor.

We basically need a circuit that takes the pink/white and white/blue in from the radio and spits them back out to the antenna like this:

(Edit: as noticed by D'Ecosse, the "blue/white to antenna" should read "white/blue to antenna". Sorry, typo.)

 

[D'Ecosse]

Forget everything I said before - I realize as I started to explain how the antenna relay switching circuit works that I made a fundamental error - as soon as the power is removed from the pink wire, the antenna retracts, not stops. So the timer circuit, while interesting, will not work in that application. I refuse to give up just yet, may be able to integrate it into the relay logic - needs some more thought though.

Incidentally, re your state table above, There is no blue/white? If you mean the white/blue, however that is constant 12V - the switching happens within the relay logic of the antenna drive circuit.

Here's how the relay logic of the antenna drive works:

When the power first comes on to the pink/white, two things happen:
1: the motor relay is enabled (power from the pink/white; other side of coil permanent ground); 2: the "up" relay is enabled (power from the pink/white; ground through the limit switch down through the lower set of contacts on the motor relay to permanent ground.
This combination will transfer power from the white/blue to the top side of the motor (as shown in the diagram) via the now closed N/O contact of the "up" relay, while the bottom side of the motor will be grounded via the N/C contact of the "down" relay. This will drive the motor in the "extend" direction. When it reaches the upper limit switch, the ground will be inhibited from getting to the right side of the "up" relay & will stop the motor by placing ground on the top side of the motor as well as already on the bottom side.

Now - if you remove the power from the pink/white, the "up" relay will still be off (if at upper limit - or will turn off if in the process of being raised) & the contact will revert to the N/C condition, which will put "ground" on the top side of the motor. The motor relay will also drop out, which will remove the ground from the lower motor N/O contact & connect +12 from the white/blue through the now normally closed bottom contacts through the limit switch to the right side of the "down" relay coil; the left side of the "down" relay coil is connected to ground via the now N/C contact of the upper motor relay contact onto the top of the motor and also to ground via the now N/C contact of the "up" relay. So the "down" relay will energize & switch +12 from the white/blue through the N/O bottom contact to the bottom of the motor; this will result in the motor driving in the opposite direction & retracting the antenna. When it reaches the limit switch the power is inhibited & it stops driving.

It is probably easier to follow the volyage/current flow in these diagrams:
the red is the +12V circuit and the green is the ground circuit. First diagram shows how the relay logic applies power across the motor (until the limit switch cuts) to raise the antenna. Second diagram shows how the power is "reversed" across the motor and thus lowers the antenna (until th elimit switch inhibits)

 

[D'Ecosse]

OK - I think this will work - we put the timer circuit (no switch in the actual timer circuit) on the input of the "up" relay. Leave the original interrupt switch as before so the antenna can still be raised & lowered by control of that switch, except now will only raise according to the time constant when enabled.

Disclaimer: This circuit has not yet been tested. Undertake this at your own risk. I am not responsible for any issues or damage caused to your vehicle or others caused by use of this circuit or any problems associated with mis-wiring. Unless you possess rudimentary electronics knowledge I suggest you refrain from undertaking this directly, but consult a professional.

How it works:

The circuit works exactly as described before for the extend part of the drive - except when the timer toggles, the "up" relay will simply turn off & apply ground to the top of the motor, while the rest of the circuit remains as-is for the extend, also keeping ground on the bottom side of the motor.
For retract, by removing the power from the pink/white, the antenna will lower in exactly same fashion as described in prior post for normal condition.

 

[Aiken Drum]

Incidentally, re your state table above, There is no blue/white? If you mean the white/blue, however that is constant 12V

Yeah, I meant white/blue. Oops.

I'd agree with where you put the timer. I'll take it on faith that the timer section is correct.

Now, question is, who wants to crack open their OEM antenna unit in order to connect the timer in the right place?

By the way, I checked the antenna harness. There are indeed four wires coming off of the big bundle and going into the harness. However, only three come out of the harness and go into the antenna itself. I'm going to assume that the extra wire controls the half-height feature, but they cut a corner on the north american cars and used a cheaper antenna that didn't have a half-height feature.