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  1. #1
    Good Citizen
    Join Date
    Aug 2008

    Default Interfacing LI to Aux or Autocom mod.

    Hello everyone!

    As you all know I purchased a laser interceptor to protect my bike from lidar speed measurements.

    The design of the LI allows you to hear the alerts spoken in voice. The LI was designed for a car in mind but I wanted to adapt it to a motorcycle.

    I also have an Autocom unit. Unfortunately, due to the way the LI was built. You can't interface the two directly. Connecting the LI to an autocom directly will fry the LI CPU's preamp circuit. Autocom is designed for single ended inputs. The LI is designed with a differential output. I originally fried my LI preamp trying to bring these two devices together. I eventually went with a LED notification but lost the ability to hear the names of the gun.

    I set out on a quest to bring these two devices together and found a solution to this problem. So I bring to you my first publicized LI mod.

    Hooking up a LI to your Autocom. *I posted this on the LI forums so it's a copy/paste job. Bear with me*

    This mod kills 3 birds with one stone.
    1. Allows you to hook up your LI to your autocom.
    2. Provides ground isolation so if the 3.5MM plug is disconnected and touches ground. No damage will occur.
    3. Removes engine whine and noise that was associated with my first version of this mod (this is v2).

    Fully tested, works perfectly!
    The transformer is rated at 300hz-5khz. It's meant for telecom applications where quality in the vocal range is required. It's not a HI-FI solution but works perfectly for the LI's voice skinning feature.


    Ok!, I figured it out! My problem was I was interfacing a differential speaker to a single ended input (my aux input)

    In my brainstorming I thought that a GLI would solve my problem. Unfortunately I was unsure how to hook up a differential output to a GLI since you can't ground the wire.

    Well turns out, a GLI approach is exactly how you convert BTL audio to single ended..

    Now I will teach you how I wired my LI to the CPU. I will explain at the end of the tutorial how you can do it without soldering or voiding your CPU. To do so you will mount the transformer externally. I chose to do a internal install because it's safer, Remember, A speaker wire to ground is death to the preamp. This is why I don't want anything mounted externally that shouldn't be.

    What you need is the following.

    LI CPU (Of course)
    Small Philips Screw Driver (only needed to place the transformer inside the CPU, If you wish to mount it externally you can do that as well)

    1 Radioshack 6FT Stereo cable extension. Item#42-2387
    1 Radioshack Isolation 1:1 transformer. Item#273-1374
    A voltmeter/continuity tester *optional
    Electrical Tape

    *Internal Install*
    Open up the LI cpu case,
    Remove the isolation transformer from the packaging. Set aside for now.
    Remove stereo cable from packaging.

    Now take your stereo cable and cut the cord with scissors. (halfway, far end, it doesn't matter. You only need one side (so close to one end is better)

    There are three wires inside. Two are colored, one will be silver stranded uninsulated. Take the two wires with insulation and strip a quarter inch. Next twist these two together (this will turn the li mono output into a stereo output).

    Get out your transformer and unwind the wires, there should be 4. Black/White/Red/Yellow

    Ok find the 8 pin junction block on the li.
    Place your LI on a desk. You should see this....
    Back of unit facing you (as if you were looking at the pins directly)
    [electronics inside]
    [Electronics inside]

    White goes to pin 1 Differential Positive
    Black goes to pin 5 Differential Negative
    Yellow goes to the two wires you twisted together (there should be three together now)
    Red goes to the silver uninsulated wire (ground)

    I put in side adhesive tape to support the transformer to prevent it from banging around. It's a 3M automotive tape. The same stuff I use to secure my heads to my bike (the stuff is magic it won't go no where once you put it back together)

    Make sure you don't block the screw holes for when you reassemble the unit. Also very important, put electrical tape on your exposed contacts so they don't short out. Electrical tape around the transformer as well (I added this after I took the pics just to be safe).

    Use needle nose pliers to make a conduit to route the audio cable out of. Reassemble CPU, plug in the device and you're all set.

    You can remove and connect the LI cpu to the aux unit as you wish. Powered or unpowered as there is no physical ground connection to the speaker wires.

    External install*
    Ok I got a few comments about warranty issues etc. You can very well void the warranty doing an internal install (the points that the wires connect to are big, there are no surface mount connectors nearby to which you can damage so an internal install is safer IMO due to sensitivity of the speaker wires being unable to ground. I've blown a preamp before from grounding a blue speaker wire (external install) and I voided my warranty to fix it since I knew that it was my fault. Cost to fix was about 7$ but I still bought a second cpu anyway. I use my fixed cpu to do my testing, then I implement it on the newer 7.06 cpu I have on my bike once it's finished. (I don't trust using my previously damaged cpu in real world conditions).

    If you wish to do an external install here's how.
    Prepare the stereo cable as described in the internal install. When you wire the insolator. Just use the blue speaker wires coming out of the back of the unit. That's it. I can't give any more information as I don't recommend an external install. The isolators wires are very small so make sure you mount the transformer to something sturdy so it doesn't rattle around. Place tape on the stress points of the cable (solder joints etc) so they don't break under vibrations.

    Here's a picture of my setup.

    Oh I forgot to mention this on other boards but you are using the external speaker points to drive the transformer (thus you need to set your unit to external speaker mode) sorry bout that!

    one additional note. This was designed to hook up a LI to a mixer unit device that mixes the LI voice into the audio system. If your AUX on your unit does this then you're all set.

    If your deck only outputs aux to speakers when selected then you won't hear LI alerts unless you're on internal speaker mode or your radio is selected to AUX (thus you'd be listening to silence until you had an alert)

    You can also interface your 3.5mm jack to a fm transmitter so you and your group riders nearby can hear the alerts.

    I may post the mod that shows how to have your autocom transmit the LI alerts via GMRS radio to your group riders in another post. Not sure if I want to do this just yet.
    Last edited by Darkflame; 11-26-2008 at 05:18 PM.

  2. #2
    Join Date
    Mar 2006

    Default Re: Interfacing LI to Aux or Autocom mod.

    Man i would like the LI to play thru my factory stereo speakers..

  3. #3
    Radar Fanatic
    Join Date
    Feb 2007

    Default Re: Interfacing LI to Aux or Autocom mod.

    LI could add blue tooth to the LI interface and by doing they they could make it so you don't have to run anymore wires into the cabin. You can control the LI through the blue tooth signal and it could play though your radio because most new cars come with blue tooth for your cellphone. They way they could weather proof the control box and make it easy to install and interface with the car.

  4. #4
    Join Date
    Mar 2006

    Default Re: Interfacing LI to Aux or Autocom mod.

    I'm thinking if i mount the cpu right by my column the internal speaker might just cut it.

  5. #5
    Good Citizen
    Join Date
    Aug 2008

    Default Re: Interfacing LI to Aux or Autocom mod.

    It's possible to add a audio mixer to combine the LI and the RADIO outputs and mix them to your amps input to be driven to the speakers. This requires a lot more work then it's worth to some. You can build a mixer with just 2 resistors and a few parts but I am unsure how the quality of the stereo would be going to the amp. I use a autocom system which mixes my cellphone, ipod, gps and LI. Everything sounds cherry.

    I think a dedicated mixer would be safer then building the resistor method but I can't give anymore info as I don't have experience in this area.

    I've tested my GF's LI in the aux port of our sony deck and it works fine to produce sound to the speakers in the car but like I said her unit doesn't mix w/ radio or take over when sound is detected. So it's either listen to music and have li on internal speaker mode. or listen to silence and amplify the li to the cars speaker system.

    All decks are different, maybe your deck might have a feature that activates aux when ground is detected. Like a mute wire but activates aux instead. I'm sure vehicles with in car hands free kits will do this. You can tap the LI mute wire to this point then convert the 3.5mm to RCA or if you have the older screwed on points, just screw the yellow and red wires appropriately.

  6. #6
    Old Timer
    Join Date
    Apr 2007
    New Jersey

    Default Re: Interfacing LI to Aux or Autocom mod.

    way to complicated for me but nice set up

  7. #7
    Good Citizen
    Join Date
    Aug 2008

    Default Re: Interfacing LI to Aux or Autocom mod.

    It's really simple honestly.

    I was thinking of doing a video tutorial of an external mod that requires no soldering and has no questionability of voiding the warranty. It's as simple as cutting a 3.5mm jack, twisting a few wires together and that's it.

    The internal install is harder then the external install. It's just more secure due to the solder connections and protection from ground..

    Maybe on friday i'll pony up a video tutorial on doing this mod for those interested.



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