Audio Triggered Switch Help

[CBB9]

I'm hoping someone here can help lead me in the right direction on an experiment of mine.

In my car I have an automatic starter that includes a wire that when given the 12v negative connection will trigger the automatic starter. What I would like to do have this negative connection activated when an audio clip (constant 14khz) is played from an audio device such as an MP3 player. I attempted using a TIP31 following this schematic but that did not seem to do the trick (I believe this is because the 12v positive connection and LEDs are eliminated in my setup). My next attempt will be to use this device, replacing the mic with a 3.5mm audio jack, but ultimately I would like to build my own using as simple as a configuration as possible. Any ideas are greatly appreciated!

 

[CBB9]

Limited success with the light controller. I was able to wire it into the automatic starter and when setting it to a constant light setting everything worked as expected. When in audio pulse mode the voltage jumps all over the place even when given a constant sound file. The automatic starter doesn't trigger cause the voltage doesn't hold long enough. I plan to try this next.

 

[spec]

Hi CBB, what you are trying to should be quite simple to implement, but the design depends on how much current and what is being switched to 0V (battery negative) to start.

Can you define what current flows when the starting circuit is switched to ground?

Also, can you define what is being switched- is it a relay for example?

spec

 

[CBB9]

Unfortunately I have not been able to locate that information. The best I found from the vendor of the starter was this. In my testing I connected the wire directly to the negative of the accessory charging port and the car started and continued running until the connection was broke. I'm open to any way of switching, transistor, relay, whatever is easiest and cheapest (and ultimately using parts I could grab quickly from my local radio shack). I'm out of my level of expertise here, took a few classes in high school and can figure things out with enough time, so any direction is greatly appreciated.

Flow: Headphone Jack (NOT Line Out) --> Circuit --> Starter Wire
When audio plays from audio device the circuit should connect a 0V (Battery Negative) to the wire coming off my starter. When audio stops disconnect.

I hope that helps.

 

[spec]

Unfortunately I have not been able to locate that information. The best I found from the vendor of the starter was this. In my testing I connected the wire directly to the negative of the accessory charging port and the car started and continued running until the connection was broke. I'm open to any way of switching, transistor, relay, whatever is easiest and cheapest (and ultimately using parts I could grab quickly from my local radio shack). I'm out of my level of expertise here, took a few classes in high school and can figure things out with enough time, so any direction is greatly appreciated.

Flow: Headphone Jack (NOT Line Out) --> Circuit --> Starter Wire
When audio plays from audio device the circuit should connect a 0V (Battery Negative) to the wire coming off my starter. When audio stops disconnect.

I hope that helps.

Yes that does help.

Have you got a multimeter. If so can you switch the multimeter to the highest DC current range, at least 10 Amps, and connect the leads of the multimeter from the start terminal to OV (battery negative). Then note the current indicated on the multimeter.

spec

 

[cowboybob]

In my testing I connected the wire directly to the negative of the accessory charging port and the car started and continued running until the connection was broke.

(My emphasis).
This implies that the engine starts (and runs) so long as the "A13" connection is grounded. Removing the ground from A13 causes the engine to stop. Is that correct?

Reason I ask is because this link indicates that the temporary grounding of the A13 connection has alternate effects: Engine OFF - briefly ground A13 - engine startes and stays ON. While Engine ON - briefly ground A13 - Engine is turned OFF. In other words, alternate grounding of A13 toggles the engine On and Off.

Whichever sequence is right will dictate the kind of circuit you need, i.e., a continuous connection or a pulsed connection. This, in turn, will greatly affect either the "remote" triggering circuit's design and its response to a sound, and/or the duration of the sound itself.

 

[CBB9]

spec - I do. At 10A the current is .01

 

[CBB9]

cowboybob - Correct. Thank you for taking the time to explore that. Yesterday I had experienced a couple pulse starts while trying things and didn't make much of it. After seeing your post it clicked with me and I checked and wouldn't ya know, we are both correct! A quick pulse starts the car and keeps it running, and repeating that stops the car. A constant connection starts the car and leaves it running until the connection is broke. Given this "starter" wire exists to interface with older or otherwise incompatible remote/security systems it makes sense to me that it's setup to handle both use cases. The unit is a software based device so it doesn't seem out of the realm of possibility to me.

I'm glad you pointed that out, it builds on my original idea by cutting it down from a long running audio file and managing that remotely to a quick blip. I'm thinking that would make for easier circuit design too?

 

[spec]

spec - I do. At 10A the current is .01

Thanks CBB,

0.010A (10mA) is a much lower current than I feared and is good news.

spec

 

[spec]

cowboybob - Correct. Thank you for taking the time to explore that. Yesterday I had experienced a couple pulse starts while trying things and didn't make much of it. After seeing your post it clicked with me and I checked and wouldn't ya know, we are both correct! A quick pulse starts the car and keeps it running, and repeating that stops the car. A constant connection starts the car and leaves it running until the connection is broke. Given this "starter" wire exists to interface with older or otherwise incompatible remote/security systems it makes sense to me that it's setup to handle both use cases. The unit is a software based device so it doesn't seem out of the realm of possibility to me.

I'm glad you pointed that out, it builds on my original idea by cutting it down from a long running audio file and managing that remotely to a quick blip. I'm thinking that would make for easier circuit design too?

I wish all posters were as prompt, informative, and definitive as you CBB9.

From what you and Cowboybob have said, there seems to be three options:
(1) Short audio and short A13 (engine start) low starts engine. Another short audio and short A13 low stops engine
(2) Short audio and A13 goes low and stays low until another short audio when A13 goes open circuit and stops engine. A3 remains open circuit.
(3) A13 goes low whenever audio is present and A13 goes open circuit otherwise. If I have understood your post #8, this means that the engine would start and run while an audio signal were present and the engine would stop when the audio signal ceased.

From an implementation point of view (1) and (2) are identical and are the simplest, but (2) is no big deal to do.

Would you like to chose which approach you favor?

spec

 

[CBB9]

spec - The same goes to you! I appreciate how supportive this community has been to me as a new member.

I think option #1 makes the most sense if the implementation is less than or eqaul to #2. The reason for that being I assume there is more chance of random pulse from the alternator kicking on/up when the car starts or goes under load. With that said, if #1 requires components that would need to be ordered (not available at a local Radio Shack in my situation) and #2 does not, #2 works too.

Thanks again for all the support.

 

[MikeMl]

CBB9, Are you trying to start a car parked outside from inside your house? That is what we do in snow country(Flagstaff), or in extreme heat country(Phoenix).

If so, why use "sound", rather than IR or radio (keyfob)?

 

[cowboybob]

For the effort and cost, this rig strikes me as an ideal solution when coupled with this. (Don't know why they sell them separately... ). The receiver will need a small buck power supply (12VDC to <=10VDC) but a super simple LM317 (from Radio Shack) circuit will do the trick. Also, the receiver's outputs go HIGH with a signal from the fob, so you'll need to add a transistor "switch" to take the A13 connection to ground - also parts that are available at RS.

Any one of us can provide the necessary schematics for this system.

I've purchased a fair amount of Adafruit stuff (mostly Arduino related) in the past and I like their products.

Not a totally DIY solution, but RF circuitry design and construction can be (and usually is) frustrating to get all the pieces parts to all play nice with each other.

 

[spec]

Hi CBB9

spec - The same goes to you! I appreciate how supportive this community has been to me as a new member.

I think option #1 makes the most sense if the implementation is less than or eqaul to #2. The reason for that being I assume there is more chance of random pulse from the alternator kicking on/up when the car starts or goes under load. With that said, if #1 requires components that would need to be ordered (not available at a local Radio Shack in my situation) and #2 does not, #2 works too.

Thanks again for all the support.

No problems from me about the support.

OK option (1) it is.

There are normally many ways to do a job and various aspects and there are many members on ETO, so often you will get many approaches. But at the end of the day, it is up to you to make the choice.

So, with this in mind, I will do a circuit for option (1).

Just one point, do not worry about the details of the design or the performance- hopefully, I will take care of that, including the effects of battery voltage drop on starting.

What we find helpful is a complete and specific description of what you want the design to do and you have done this.

spec

 

[cowboybob]

... The receiver will need a small buck power supply (12VDC to <=10VDC) but a super simple LM317 (from Radio Shack) circuit will do the trick. ...

I should have also noted that the receiver will operate with as little as 4VDC. Thus, you could easily use the 5VDC and ground provided by the car's USB port for powering the the receiver, without modification. That depends, of course, on the USB port remaining "hot" (also the cig lighter, if you go the LM317 route) when the ignition key in the OFF position.

... Just one point, do not worry about the details of the design or the performance- ...

Rest assured, CBB9, spec's designs are very good.

... I will take care of that, including the effects of battery voltage drop on starting. ...

Spec, that shouldn't be a problem, should it? Engine start only occurs after the A13 connection has already been taken to ground by the remote start circuit(s).

 

[spec]

Rest assured, CBB9, spec's designs are very good.

Wow cowboy- thanks a lot. I am blushing.

Spec, that shouldn't be a problem, should it? Engine start only occurs after the A13 connection has already been taken to ground by the remote start circuit(s).

Ah yes good point.

But I I do think it is wise to put a simple filter on the 12V supply to the circuit- you an get all sorts of goings on on the 12V supply line of automobiles.

spec

 

[CBB9]

MikeMl cowboybob - My apologies, I mentioned automatic starter but failed to indicate that it was remote. I'm covered on short range wireless. The addition of an audio source trigger to the starter opens this solution up to many devices.

 

[CBB9]

spec - Having spent many years competing in car audio competition I can attest to all the random goings! With that said, I'm somewhat curious to find out. I like to tinker and test and I'm opening to trying it unfiltered as well as filtered.

 

[cowboybob]

MikeMl cowboybob - My apologies, I mentioned automatic starter but failed to indicate that it was remote. I'm covered on short range wireless. The addition of an audio source trigger to the starter opens this solution up to many devices.

OK.

The most reliable (and least likely to respond to an errant audio signal ) is a simple audio circuit that uses an LM567 Tone decoder. This device has been around for a very long time. Basically behind the touch tone phone signal decoding. Its output goes to ground when activated. With an electret mike and a small, medium gain OpAmp amplifier in front of it and, wahla, you have your audio fired switch.

I've had very good success with this device when I needed rock solid audio detection of a specific audio frequency, especially in an environment with a lot of spurious, extraneous and random "noises".

If you're interested, I'd be glad to provide a schematic.

 

[CBB9]

OK.

The most reliable (and least likely to respond to an errant audio signal ) is a simple audio circuit that uses an LM567 Tone decoder. This device has been around for a very long time. Basically behind the touch tone phone signal decoding. Its output goes to ground when activated. With an electret mike and a small, medium gain OpAmp amplifier in from of it and, wahla, you have your audio fired switch.

I've had very good success with this device when I needed rock solid audio detection of a specific audio frequency, especially in an environment with a lot of spurious, extraneous and random "noises".

If you're interested, I'd be glad to provide a schematic.

It doesn't look like they stock the LM567 at Radio Shack as far as I can tell. Not a deal breaker by any means, it just eliminates the shipping wait and cost. If you have a schematic handy I'm happy to take a copy. I'll include the LM567 in my next order to anywhere that stocks it and explore that option as well. Thanks!