flyboy
18-10-2012, 03:01 PM
Hi there !
I thought I'd write a bit of a DIY explanation of how the wiring in the 380 Bluetooth System works, and how to DIY mod it for volume issues.
If you aren't quite handy with a soldering iron, it's probably not worth the effort to make modifications and you'd be better off buying the patch cable from Mitsubishi, but it might be an interesting read for those with a little electrical knowledge. Who would have thought some electrical engineering during my Science degree would come in handy ;)
So, basically, here is how the stock BT system works:
1. Loom
A loom goes between the standard factory loom (14-pin) and the headunit. Most of the connections are just a straight through extension of the standard wiring, with the exception of the following
a) It taps into the power (12V) to also power the BT module and relay box in addition to the radio
b) It taps into the ground (0V) for the same reason
c) It taps into the illumination power (12V) to power the backlighting to the dial/hang up buttons when the dash lights are turned on
d) It taps into the left front speaker wiring (more about this in a minute)
2. Blue box
This is essentially the brain of the BT system. It contains the hardware for the wireless connection and software for the system. It has three connections on the side.
a) Front most square connection - power supply and ground from tapping into the factory harness
b) Middle blue connector - audio out, control of the black relay box, and wiring for the dial/hang-up buttons (also used for flashing the firmware)
c) Rear connector - microphone input
3. Black relay box
This is a tricky little customer. It is, in fact, not really required and is the reason for the majority of user issues with the system. Mitsubishi would have been wise to design the system without this.
It has two main functions.
a) It controls when the headunit is going in and out of "Phone" mode. It does this using a transistor and set of relays - and pulls pin #7 on the 10-pin headunit connector to ground. The headunit senses pin #7 going to ground, and enters "Phone" mode.
b) At the same time as grounding the head unit to enter "Phone" mode, it also does some trickery with the wiring for the front left speaker. It disconnects the left front speaker wiring from the headunit and directly outputs the BT audio to that speaker alone.
Now for the slightly more complicated bits:
1. The grounding of the other three speakers when in BT mode is actually a function of the headunit, NOT the BT system. Whenever the headunit enters phone mode, it stops outputting audio to the other three speakers. I always thought this would be a function of the BT unit, but it is most definitely not. Connect any off the shelf BT unit to the 380 using pins #7, #3 & #8, and you will get the same result - audio from the left front speaker only.
2. The black cable which goes between the blue BT box and the black relay box has 5 coloured wires inside.
Black - Ground
Yellow - 12V
Blue - sense wire for the BT on/off signal. It signals to turn on by sending about 1V to the black box
Red & White - BT audio output
3. The 380 headunit can actually take an audio input in phone mode (pins #3 & #8) and outputs it to the front left speaker, but the stock BT setup does not take advantage of this. The stock headunits also have the ability to amplify this signal, and retain the volume level in memory - independently of the volume for normal audio from the tuner or a CD. This is where the 380 BT "patch" cable comes in handy. This input is not suitable for audio input from say, an iPod, for several reasons
a) It is a mono input only - terrible quality for music
b) The headunit will only output it to the left front speaker (there is NO way around this, except for extensive wiring modifications to all speaker outputs and switching relays)
Now for the really hard bits:
1. The relay/transistor setup in the black box is poorly designed. Several users including me (particularly with the earlier BT software pre 3.19) used to get pops and thuds when turning the car off, or when the phone was connecting/disconnecting. The reason for this is fairly technical, but essentially it is caused by poor circuit design of the relay system inside the black box which manipulates the connections for the left front speaker.
2. The signal which comes off the BT system to trigger BT mode is only 1V. This makes DIY modifications fairly tricky, because 1V is not enough to trigger relays. If it was, you could simply connect the red and white from the black cable to the audio input on the back of the headunit (pins #3 & #8) and connect the blue wire to a relay which grounds the pin #7 to enter phone mode, and you'd be done.
3. The black box becomes a problem. We need it to get the headunit into "Phone" mode with only a 1V switching signal, but we don't want it to be controlling audio because of the quality issues and lack of volume control.
How to DIY a better system:
I wanted to mod the BT system for three main reasons - my interest in how it all worked, to allow volume control, and also solve the pops and thuds (which did partly go away with a firmware update mind you).
How did I do it?
1. Well, I cut into the black cable between the blue and black boxes, and cut all the wires near the end which goes into the black box. Insulated all the ones coming out of the black box, and just the yellow one (12V) coming from the blue box.
2. Remove the yellow wire from pin #3 of the 10-pin where it connects to the headunit and insulate.
3. I picked up a PN100 transistor from Jaycar and wired this up with the blue signal wire and black ground wire. I used this setup to trigger pin #7 on the 10-pin to ground. Hence, the headunit enters phone mode correctly using the small 1V signal. Very simple circuit which overcomes the problem of 1V not being enough to drive a relay.
4. I connected the red and white audio wires to pin #3 and pin #8 on the 10-pin. This means the audio output from the BT goes into the headunit phone input now.
The result - well, I have better quality BT audio - and volume control using the headunit to fix my low volume issue. And the stupid clunky black relay box is completely isolated.
Could it be done even better in hindsight?
Well, yes. Because this was a trial and error type experiment, now I know how the system works, the BT mod could be done even easier, without any parts other than some wire. The 5 wires in the black cable are fairly thin and difficult to solder, so leaving most of these alone would be a big improvement.
1. In the original 14-pin factory loom, pop pins #5 and #13 out of the connector. Extend the wiring and re-insert these pins into the same position on the BT 14-pin loom (which connects into the back of the headunit). This means the left front speaker output bypasses the black box. The ones you will have to pop out of the BT loom to replace can be then cut off and saved for step 3.
2. Cut into the sheath of the the black cable between the blue BT box and black BT box (leave the blue, yellow and black wires intact).
3. Cut the red and white wires and extend them directly to pins #3 and #8 on the 10-pin connector, using the pins you saved from step 1.
Voila! Hacked bluetooth low volume mod for the 380 which can be achieved without anything other than a pair of wire strippers, a sewing needle to remove pins from terminal blocks, and a soldering iron.
While the Mitsubishi patch cable is actually quite cheap ($65), I just had a huge moral objection to buying it from them... mainly because the bluetooth system is poorly designed and Mitsi should have acknowledged this and offered the cable for free to people having the volume issues.
Anyway, I hope someone finds this interesting. Maybe there's another electrical nerd on this forum! If someone decides to do the mod themselves, let me know and I'll give you any help I can.
I thought I'd write a bit of a DIY explanation of how the wiring in the 380 Bluetooth System works, and how to DIY mod it for volume issues.
If you aren't quite handy with a soldering iron, it's probably not worth the effort to make modifications and you'd be better off buying the patch cable from Mitsubishi, but it might be an interesting read for those with a little electrical knowledge. Who would have thought some electrical engineering during my Science degree would come in handy ;)
So, basically, here is how the stock BT system works:
1. Loom
A loom goes between the standard factory loom (14-pin) and the headunit. Most of the connections are just a straight through extension of the standard wiring, with the exception of the following
a) It taps into the power (12V) to also power the BT module and relay box in addition to the radio
b) It taps into the ground (0V) for the same reason
c) It taps into the illumination power (12V) to power the backlighting to the dial/hang up buttons when the dash lights are turned on
d) It taps into the left front speaker wiring (more about this in a minute)
2. Blue box
This is essentially the brain of the BT system. It contains the hardware for the wireless connection and software for the system. It has three connections on the side.
a) Front most square connection - power supply and ground from tapping into the factory harness
b) Middle blue connector - audio out, control of the black relay box, and wiring for the dial/hang-up buttons (also used for flashing the firmware)
c) Rear connector - microphone input
3. Black relay box
This is a tricky little customer. It is, in fact, not really required and is the reason for the majority of user issues with the system. Mitsubishi would have been wise to design the system without this.
It has two main functions.
a) It controls when the headunit is going in and out of "Phone" mode. It does this using a transistor and set of relays - and pulls pin #7 on the 10-pin headunit connector to ground. The headunit senses pin #7 going to ground, and enters "Phone" mode.
b) At the same time as grounding the head unit to enter "Phone" mode, it also does some trickery with the wiring for the front left speaker. It disconnects the left front speaker wiring from the headunit and directly outputs the BT audio to that speaker alone.
Now for the slightly more complicated bits:
1. The grounding of the other three speakers when in BT mode is actually a function of the headunit, NOT the BT system. Whenever the headunit enters phone mode, it stops outputting audio to the other three speakers. I always thought this would be a function of the BT unit, but it is most definitely not. Connect any off the shelf BT unit to the 380 using pins #7, #3 & #8, and you will get the same result - audio from the left front speaker only.
2. The black cable which goes between the blue BT box and the black relay box has 5 coloured wires inside.
Black - Ground
Yellow - 12V
Blue - sense wire for the BT on/off signal. It signals to turn on by sending about 1V to the black box
Red & White - BT audio output
3. The 380 headunit can actually take an audio input in phone mode (pins #3 & #8) and outputs it to the front left speaker, but the stock BT setup does not take advantage of this. The stock headunits also have the ability to amplify this signal, and retain the volume level in memory - independently of the volume for normal audio from the tuner or a CD. This is where the 380 BT "patch" cable comes in handy. This input is not suitable for audio input from say, an iPod, for several reasons
a) It is a mono input only - terrible quality for music
b) The headunit will only output it to the left front speaker (there is NO way around this, except for extensive wiring modifications to all speaker outputs and switching relays)
Now for the really hard bits:
1. The relay/transistor setup in the black box is poorly designed. Several users including me (particularly with the earlier BT software pre 3.19) used to get pops and thuds when turning the car off, or when the phone was connecting/disconnecting. The reason for this is fairly technical, but essentially it is caused by poor circuit design of the relay system inside the black box which manipulates the connections for the left front speaker.
2. The signal which comes off the BT system to trigger BT mode is only 1V. This makes DIY modifications fairly tricky, because 1V is not enough to trigger relays. If it was, you could simply connect the red and white from the black cable to the audio input on the back of the headunit (pins #3 & #8) and connect the blue wire to a relay which grounds the pin #7 to enter phone mode, and you'd be done.
3. The black box becomes a problem. We need it to get the headunit into "Phone" mode with only a 1V switching signal, but we don't want it to be controlling audio because of the quality issues and lack of volume control.
How to DIY a better system:
I wanted to mod the BT system for three main reasons - my interest in how it all worked, to allow volume control, and also solve the pops and thuds (which did partly go away with a firmware update mind you).
How did I do it?
1. Well, I cut into the black cable between the blue and black boxes, and cut all the wires near the end which goes into the black box. Insulated all the ones coming out of the black box, and just the yellow one (12V) coming from the blue box.
2. Remove the yellow wire from pin #3 of the 10-pin where it connects to the headunit and insulate.
3. I picked up a PN100 transistor from Jaycar and wired this up with the blue signal wire and black ground wire. I used this setup to trigger pin #7 on the 10-pin to ground. Hence, the headunit enters phone mode correctly using the small 1V signal. Very simple circuit which overcomes the problem of 1V not being enough to drive a relay.
4. I connected the red and white audio wires to pin #3 and pin #8 on the 10-pin. This means the audio output from the BT goes into the headunit phone input now.
The result - well, I have better quality BT audio - and volume control using the headunit to fix my low volume issue. And the stupid clunky black relay box is completely isolated.
Could it be done even better in hindsight?
Well, yes. Because this was a trial and error type experiment, now I know how the system works, the BT mod could be done even easier, without any parts other than some wire. The 5 wires in the black cable are fairly thin and difficult to solder, so leaving most of these alone would be a big improvement.
1. In the original 14-pin factory loom, pop pins #5 and #13 out of the connector. Extend the wiring and re-insert these pins into the same position on the BT 14-pin loom (which connects into the back of the headunit). This means the left front speaker output bypasses the black box. The ones you will have to pop out of the BT loom to replace can be then cut off and saved for step 3.
2. Cut into the sheath of the the black cable between the blue BT box and black BT box (leave the blue, yellow and black wires intact).
3. Cut the red and white wires and extend them directly to pins #3 and #8 on the 10-pin connector, using the pins you saved from step 1.
Voila! Hacked bluetooth low volume mod for the 380 which can be achieved without anything other than a pair of wire strippers, a sewing needle to remove pins from terminal blocks, and a soldering iron.
While the Mitsubishi patch cable is actually quite cheap ($65), I just had a huge moral objection to buying it from them... mainly because the bluetooth system is poorly designed and Mitsi should have acknowledged this and offered the cable for free to people having the volume issues.
Anyway, I hope someone finds this interesting. Maybe there's another electrical nerd on this forum! If someone decides to do the mod themselves, let me know and I'll give you any help I can.