blindspot monitor buzzer addition

[notaGolfR]

I was all prepared to have an auto-electrician tap into the wiring to add a couple of LEDs to my dash which would light up if someone was in the blind spot. He no as he thought the "Can bus " might be upset and problems created.

Can anyone confirm if he is correct please, or is there a way to do it without upsetting the Can bus?

[notaGolfR]

I was all prepared to have an auto-electrician tap into the wiring to add a couple of LEDs to my dash which would light up if someone was in the blind spot. He no as he thought the "Can bus " might be upset and problems created.


Can anyone confirm if he is correct please, or is there a way to do it without upsetting the Can bus?"

[Guest001]

I was all prepared to have an auto-electrician tap into the wiring to add a couple of LEDs to my dash which would light up if someone was in the blind spot. He no as he thought the "Can bus " might be upset and problems created.


Can anyone confirm if he is correct please, or is there a way to do it without upsetting the Can bus?"

Why dont you just buy the lights that fit in the mirror housings.

Black For VW Golf 7 GTI R GTE GTD MK7 MK7.5 2013 2019 Touran Jetta MK7 Side Wing Mirror Indicator LED Dynamic Turn Signal Light|Mirror & Covers| - AliExpress

[notaGolfR]

Why dont you just buy the lights that fit in the mirror housings.

Black For VW Golf 7 GTI R GTE GTD MK7 MK7.5 2013 2019 Touran Jetta MK7 Side Wing Mirror Indicator LED Dynamic Turn Signal Light|Mirror & Covers| - AliExpress

Thx for trying to help Hillbilly but that link comes up as turning indicator & I'm on about a blindspot monitor.

I know you previously chastised me for not using the exterior mirrors & turning my head & not relying on noticing the BSM & I agreed and I used to do that. However, probably because of neck-ache I am failing to do that nowadays.

Although I have yet to try 2 leds on the dash I am pretty sure they would be good.

[Guest001]

Thx for trying to help Hillbilly but that link comes up as turning indicator & I'm on about a blindspot monitor.

I know you previously chastised me for not using the exterior mirrors & turning my head & not relying on noticing the BSM & I agreed and I used to do that. However, probably because of neck-ache I am failing to do that nowadays.

Although I have yet to try 2 leds on the dash I am pretty sure they would be good.

LOL Yes you would need the whole housings so I will go back to sleep

[notaGolfR]

Hi DV52 / Don. Your helpful post yesterday (19/5/2021) seems to have been taken down from this thread (maybe 'cos of your comment about advertisements). Luckily I had made a copy.

The tip to use pins "accessible on pin#3 and pin#4 of the 8 x pin connector on the BSM module. These pins are the supply points for the 2 x LEDs on the mirrors." sounds good if they are easy to get at. I presume they are in the rear bumper. Alternatively are the coupling points TTIV or TTV ok?

As for using the circuit like
you supplied, can that be avoided by (as a poster on a rival forum said) "if you first measure the resistance of the o.e. led then disconnect it and replace with another led (on the dash) with the same TOTAL resistance (i.e. resistor plus new led = that of the o.e.) then the "module" will not throw errors as it will not know the difference. " ?

[DV52]

Hi DV52 / Don. Your helpful post yesterday (19/5/2021) seems to have been taken down from this thread (maybe 'cos of your comment about advertisements). Luckily I had made a copy.

No, nothing as clandestine as big-brother intervening - I deleted my post because of a fat-finger syndrome (mine). I didn't have the mental fortitude to re-write it, so good that you kept a copy!!

The tip to use pins "accessible on pin#3 and pin#4 of the 8 x pin connector on the BSM module. These pins are the supply points for the 2 x LEDs on the mirrors." sounds good if they are easy to get at. I presume they are in the rear bumper. Alternatively are the coupling points TTIV or TTV ok?

Yes, J1067 is located in the left-side rear quarter panel. The "TTxxx" coupling points are on the inside of the left/right (see reference to "L" & "R" on the diagram) door skins. - so these are probably the most convenient splicing points for the new LEDs

As for using the circuit like you supplied, can that be avoided by (as a poster on a rival forum said) "if you first measure the resistance of the o.e. led then disconnect it and replace with another led (on the dash) with the same TOTAL resistance (i.e. resistor plus new led = that of the o.e.) then the "module" will not throw errors as it will not know the difference. " ?

hmm...... I've not read the post in the "rival forum" - but how do you "measure the resistance of the o.e. led"? By definition, an LED is a semiconductor device so it has a non-linear relationship between voltage and current. I guess that you could generate a graph like this:



And use ratio of dv/dI (i.e. the mathematical first derivative of the slope of the curve) - but it would be lots of work and I'm not sure that the answer would be accurate. So I can't comment on the suggestion from the other forum (but it seems mighty odd - to me at least!!).

The single-transistor driver in my deleted post might look scary to anyone who is not familiar with these circuits - but it really is the stuff of electronics 101.

The problem that the auto electrician will have for this project is that he/she knows nothing about the internal circuits inside the module that are connected to the 2 x pins that drive the OEM LEDs. So he/she doesn't know the designed wattage of the driver circuits, or if these pins are auto-protected against overload.

The additional load of the new LEDs should not be high, but it really depends on the chosen LEDs (especially if you want high intensity LEDs)

One option is to just add the new LEDs in parallel with the OEM LEDs and hope for the best. This seems like a "courageous" and very blunt approach - to me.

A far better way (IMO, of course) is to provide a degree of electrical isolation between the driver circuits inside J1067 and the load from the new LEDs. My transistor suggestion does this.

But there are countless other ways of achieving the objective of electrical isolation - so I have no doubt that a competent auto electrician will have other suggestions

Don

PS: I'm not sure how your car is fitted-out, but some MQB platform vehicles have the following adaptation channel in the hexA5 module:

[notaGolfR]

No, nothing as clandestine as big-brother intervening - I deleted my post because of a fat-finger syndrome (mine). I didn't have the mental fortitude to re-write it, so good that you kept a copy!!



Yes, J1067 is located in the left-side rear quarter panel. The "TTxxx" coupling points are on the inside of the left/right (see reference to "L" & "R" on the diagram) door skins. - so these are probably the most convenient splicing points for the new LEDs



hmm...... I've not read the post in the "rival forum" - but how do you "measure the resistance of the o.e. led"? By definition, an LED is a semiconductor device so it has a non-linear relationship between voltage and current. I guess that you could generate a graph like this:



And use ratio of dv/dI (i.e. the mathematical first derivative of the slope of the curve) - but it would be lots of work and I'm not sure that the answer would be accurate. So I can't comment on the suggestion from the other forum (but it seems mighty odd - to me at least!!).

The single-transistor driver in my deleted post might look scary to anyone who is not familiar with these circuits - but it really is the stuff of electronics 101.

The problem that the auto electrician will have for this project is that he/she knows nothing about the internal circuits inside the module that are connected to the 2 x pins that drive the OEM LEDs. So he/she doesn't know the designed wattage of the driver circuits, or if these pins are auto-protected against overload.

The additional load of the new LEDs should not be high, but it really depends on the chosen LEDs (especially if you want high intensity LEDs)

One option is to just add the new LEDs in parallel with the OEM LEDs and hope for the best. This seems like a "courageous" and very blunt approach - to me.

A far better way (IMO, of course) is to provide a degree of electrical isolation between the driver circuits inside J1067 and the load from the new LEDs. My transistor suggestion does this.

But there are countless other ways of achieving the objective of electrical isolation - so I have no doubt that a competent auto electrician will have other suggestions

Don

PS: I'm not sure how your car is fitted-out, but some MQB platform vehicles have the following adaptation channel in the hexA5 module:

I'm persisting Don.
I am mindful that the whole blind spot system involves the turning signals, lane assist, and goodness knows what else.
Therefore, whatever I do I must not cause inappropriate triggering of those.

As I understand your “far better way is to provide a degree of electrical isolation betw the driver circuits inside J1067 and the load from the new LEDs using the transistor (NPN) suggestion”.


Here's Jaycar's Search NPN transistors | Jaycar Electronics
so which would you suggest?
I would put the circuit on a small bit of circuit board & conceal under the door sill trim.


I do not intend to tailor R1 for brightness as I would go for maximum and dim by experiment by applying black texta to suit. If it helps, the Jaycar specs for the LEDs I bought are
“Typical fwd voltage 3.2V
Typical fwd current 30mA,
Resistors for 5,9 & 12 VDC are 62, 200 & 300ohm respectively.”
Therefore I gather 300 ohm gives brightest?


For R2 I would start with 2k but then what would I be looking for before going higher?


I have perused the circuit diagrams in the manual and am bamboozled by the changing of wire colors along the paths to the O.E leds and how I see J1086 appears to be wired to J1087. Also I can't see pin # 3 & pin # 4


I have removed the door “cards” and the trim covering the connectors inside the car and
connecting in both places looks very awkward.
Are there wires I could use in the door sill harness which runs from the back of the car but before they reach the connectors? If so, which ones would I cut to join to R2 and which would I spice into R1, bearing in mind to not change the turning signals, lane assist, and goodness knows what else?
I will do the passenger side first, and I don't care if the O.E. Leds are disabled..

[DV52]

notaGolfR

OK- Rather than simply give the answers to your questions - I'll describe how to calculate the resistor values and let you decide how you want to proceed.

Most folk think that transistor design is "magic" - but it's not; it's dead easy. Transistor manufacturers have made the process simple so that design engineers with an IQ <100 can manage the math. In truth, the only formula needed (mostly) is Ohm's law (Volts = Resistance x Current)!!

So - the first task is to choose a transistor: because this is a circuit in which the transistor acts like a simple switch, it's probably prudent to select a "switching transistor" (i.e. a transistor that is designed to be either OFF, or ON -the latter state is called "saturation")

You have indicated that your chosen LED has a nominal current =30mA, and a nominal voltage = 3.2V (i.e. Watts=V x I = 0.1) and the circuit diagram shows a NPN transistor.

I've opted for a 2N3904 (see the JAYCAR spec sheet HERE) for no other reason than I've used lots of these low-power, switching-transistors before'

Here is the basic circuit showing the calculation parameters:



As you can see, I've used a nominal car rail voltage of 13.8 V. Also, note the transistor voltages; these are the voltages that typically appear when the transistor is "saturated" (i.e. when the transistor is switched-ON) - I've simply thieved the values in my diagram from the Jaycar spec sheet and I've added the LED voltage that you have quoted (i.e. 3.2 V).

To calculate R1 - we need to calculate VR in the diagram like this:

VR = 13.8 - (3.2 +0.2) Volts = 10.4 Volts
R1 =Volts/Amps = VR/(LED nominal current, 30 mA) = 10.4/0.03 = 347 ohms
To choose the power rating of R1: Watts= V x I =10.4 x 0.03 = 0.3 Watts
R1=347 ohms

To calculate R2 - I need to introduce the concept of DC Current Gain (called "hfe"). You can think of this as the transistor "amplification factor" when switched-ON. Or said another way, it's the amount of transistor Base current (let's call this "Ib") needed to make the required current flow through the Collector/Emitter junction ( let's call this "Ic" - which is 30mA in this case)

By definition hfe= Ic/Ib. Or Ib = hfe/Ic

If you look at the spec sheet, you will find that the minimum hfe when the Collector/Emitter current=50mA is 60. Let's use hfe=60 since 50mA is close to our circuit current of 30 mA.

So, this means that Ib needs to be 30 mA/60 = 0.5mA

Now, assuming that the nominal voltage of Input in my diagram= 12V, the voltage across R2 = 12-0.9 = 11.1 Volts. And since we need Ib to be 0.5 mA, R2 = V/I =11.1V/0.5mA = 22.2K. For the sake of reliability, let's choose 20 K ohms

R2 = 20 K ohms

That's it - I think, except for one further suggestion. I'm not sure that I entirely agree with your "black texta" solution for varying LED intensity. A perhaps more elegant solution (IMO, of course) is to replace R1 with a fixed and variable resistor as I've shown in the lower part of my diagram. R1a = variable resistor & R1b = fixed resistor

So maybe choose R1b = 300 ohm and R1a = 100 ohm (Spectrol 25 x Turn Trimpot) initially for your prototype. This means that at your quoted LED current of 30mA, the trimpot should be about half-way in its travel - because if R1b=300 ohms, 47 ohms (about 50% of the trimpot resistance) is needed to make-up the calculated 347 ohms).

However, you may need to tweak my suggested values once you have experimented with your test unit.

A word of warning if you alter my suggestion: the critical factor in changing these resistor values is to ensure that the current flowing through the LED does NOT exceed it's maximum rated value when the variable resistor is wound all-the-way-"in" (i.e at the extreme trimpot travel where the resistance of the trimpot is zero). If you think about this situation, if the trimpot resistance is zero, the current through the LED will be solely limited by R1b

So using the same numbers as above for the calculation of R1:

• R1b should NOT be lower than 10.4V/(Maximum permissible LED current) - see the JAYCAR spec. sheet for your chosen LED to find the maximum permissible current

Don

PS: Doubtless you are asking yourself: what does this design achieve in respect of the "electrical isolation" objective? Well......... with the circuit values as calculated, the additional "load" on the BSM module will be the extra current draw from "input" as shown in diagram - which as calculated should be slightly higher than 0.5 mA!!!

[notaGolfR]

Thx for your detailed reply Don. I have been poring over the 1964 pages of wiring in the Golf manual pdf. I repeat 1964 pages.

I found pins 3 & 4 and now. here's how I understand the arrangement:
From J1087 unit 2, pin 3 goes to lamp K303 by way of a yellow wire to a 27-pin terminal TTVL for the front left door. Then that yellow goes to a 2-pin terminal TTIVL IN the front door, then a (red+green) wire goes to the LED in the mirror.


It looks to me that only J1087 does the leds but also goes to J1086 and thence to the CAN bus, thus using pins 3 & 4 avoids CAN bus involvement.
Only J1087 is for the LEDs but I can't see how J1086 "tells" J 1087 to light up K304 when it detects a vehicle.

I have removed the door “cards” and the trim covering the connectors inside the car and connecting in both places looks very awkward.
Could I use wires in the door sill harness which runs from the back of the car but before they reach the connectors?



In the passenger-side sill, I can only find a yellow that is twisted/paired with blue & there are no blues from J1087. Is that yellow the one I want?
Would the green wire I need for the driver-side be in the driver door sill?

Thanks

[DV52]

Thx for your detailed reply Don. I have been poring over the 1964 pages of wiring in the Golf manual pdf. I repeat 1964 pages.

I found pins 3 & 4 and now. here's how I understand the arrangement:
From J1087 unit 2, pin 3 goes to lamp K303 by way of a yellow wire to a 27-pin terminal TTVL for the front left door. Then that yellow goes to a 2-pin terminal TTIVL IN the front door, then a (red+green) wire goes to the LED in the mirror.


It looks to me that only J1087 does the leds but also goes to J1086 and thence to the CAN bus, thus using pins 3 & 4 avoids CAN bus involvement.
Only J1087 is for the LEDs but I can't see how J1086 "tells" J 1087 to light up K304 when it detects a vehicle.

I have removed the door “cards” and the trim covering the connectors inside the car and connecting in both places looks very awkward.
Could I use wires in the door sill harness which runs from the back of the car but before they reach the connectors?



In the passenger-side sill, I can only find a yellow that is twisted/paired with blue & there are no blues from J1087. Is that yellow the one I want?
Would the green wire I need for the driver-side be in the driver door sill?

Thanks

Yes, I believe that you have interpreted the wiring diagram correctly.

In terms of how the comms happens, whilst J1087 is indeed the module that drives the lamps (they are indicated as incandescent, not LED in the wiring diagram - yes, I was surprised too), it's J1086 that has full CAN status and it's this module that has direct participation in communications with the rest of the car's CAN network.

As you have observed, J1087 is connected to J1086 in what seems to be sub-CAN arrangement (so J1087 is a kind of "slave" to J1086). I assume that instructions like "light up K304" happens over this sub-CAN link between J1086 and J1087.

As for the best place to splice the connections, here's my cut-down version of the relevant information:



As you can see and as you have said - the BSM lamp wires travel along the bottom sills from the rear of the car (where J1087 is located) to the 27 x pin coupling points TTVR & TTVL. The wires then enter the door cavities at these coupling points. I agree that the car interior side of these coupling points is probably the best place to make your connections.

You should see a green wire connected to pin#1 on the right-side coupling point. This is the wire that connects to Input on the right-side transistor circuit and a brown wire on pin#2 connects to Earth in my transistor circuit

The left side connection points are the same for the yellow wire on pin#1 of the coupling point which connects to Input on the left-side transistor circuit. It depends on where you mount the new LEDs - but if it's convenient, you don't need to run another earth - just use the same brown wire connection from the right side.

If this was my project and before I reached for a blade to cut the wire insulation, I would borrow a small sewing needle from my current life-time partner (wife). Pierce the insulation on the yellow, or green wire so that the needle touches the copper wire, then using a multi-meter, check that a voltage (to an earth point) appears on the needle when the BSM lamp illuminates - both of the native BSM lamps turn-on as part of a test-cycle at ignition switch-on.

Again, before any permanent wiring changes are made and assuming the check above is OK, I would temporarily hook-up my prototype transistor circuit to the needle (and earth) and check the operation of the additional circuit- as proof-of-concept

Don

PS: I'm not sure about your mention of a "blue wire" on TTVL. I can't find any such colored wire on my wiring diagram - but if it's physically there on your car - it almost certainly isn't related to your project

[notaGolfR]

nbg

Yes, I believe that you have interpreted the wiring diagram correctly.

In terms of how the comms happens, whilst J1087 is indeed the module that drives the lamps (they are indicated as incandescent, not LED in the wiring diagram - yes, I was surprised too), it's J1086 that has full CAN status and it's this module that has direct participation in communications with the rest of the car's CAN network.

As you have observed, J1087 is connected to J1086 in what seems to be sub-CAN arrangement (so J1087 is a kind of "slave" to J1086). I assume that instructions like "light up K304" happens over this sub-CAN link between J1086 and J1087.

As for the best place to splice the connections, here's my cut-down version of the relevant information:



As you can see and as you have said - the BSM lamp wires travel along the bottom sills from the rear of the car (where J1087 is located) to the 27 x pin coupling points TTVR & TTVL. The wires then enter the door cavities at these coupling points. I agree that the car interior side of these coupling points is probably the best place to make your connections.

You should see a green wire connected to pin#1 on the right-side coupling point. This is the wire that connects to Input on the right-side transistor circuit and a brown wire on pin#2 connects to Earth in my transistor circuit

The left side connection points are the same for the yellow wire on pin#1 of the coupling point which connects to Input on the left-side transistor circuit. It depends on where you mount the new LEDs - but if it's convenient, you don't need to run another earth - just use the same brown wire connection from the right side.

If this was my project and before I reached for a blade to cut the wire insulation, I would borrow a small sewing needle from my current life-time partner (wife). Pierce the insulation on the yellow, or green wire so that the needle touches the copper wire, then using a multi-meter, check that a voltage (to an earth point) appears on the needle when the BSM lamp illuminates - both of the native BSM lamps turn-on as part of a test-cycle at ignition switch-on.

Again, before any permanent wiring changes are made and assuming the check above is OK, I would temporarily hook-up my prototype transistor circuit to the needle (and earth) and check the operation of the additional circuit- as proof-of-concept

Don

PS: I'm not sure about your mention of a "blue wire" on TTVL. I can't find any such colored wire on my wiring diagram - but if it's physically there on your car - it almost certainly isn't related to your project

Hi Don,
Long story short I had no luck.

I know I have the correct yellow as I see a voltage with the needle test. I cut the yellow and get ~ 9.7 V for a few seconds when I press the ignition. For 11.1 V you calculated R2 as 20 K ohms & I tried 20 K and then 10K for 9 V input.

I have quadruple checked connections, checked correctness of resistors in the circuit & confirmed correctness of transistor connections (don't know why they don't mark which is the Collector). What happens is that the LED lights very bright, but stays on, whereas the driver side comes on briefly as expected. I have the wire for power to the led connected to + on a blank plug I bought into the cigarette lighter socket then to the long leg of the led.

It's as if power to the led then R1 (resister + pot) is going thru the transistor to earth whenever the ignition is on and the signal from the yellow via R2 is doing nothing.

Any ideas?

When you say use 20 K oms for R2 instead of 20.2 "for reliability" can you explain please?

[DV52]

@notaGolfR: hmmm........ I just "bread-boarded" my design using an old 2N3094 that I found in the junk box and the resistor values in my calculations (and a bog, standard LED) - worked perfectly!!!

Clearly- if you want to persist, you need to resolve what's keeping the LED switched-on. Of course anything is possible and remote problem solving is fraught with difficulties. But, to my mind - two possibilities arise:

1. Without intending any offense, the circuit has been incorrectly wired (yes, I know that you "have quadruple checked connections, checked correctness of resistors in the circuit & confirmed correctness of transistor connections (don't know why they don't mark which is the Collector)" Incidentally, the 2N3094 from my junk box actually has the Base, Emitter, Collector leads marked on the housing!
2. The nature of the voltage that drives the native BSM light (on the mirrors) is not as I expected. My design assumes that the waveform of this trigger is a "square" pulse - meaning no-voltage (at all) when the BSM lamp is off and a positive voltage when the lamp is switched-on.

So- to confirm that option 1 (above) is not a problem , do this - Remove the Yellow wire from your device and connect the point that I have labelled Input in my diagram to earth. With this arrangement, the Transistor switch is "crow-barred" into the OFF state because the voltage to the Transistor Base is forced to zero - is the LED on your device off with Input earthed?

If the answer is NO (i.e. the LED is still turned-on) -clearly something is wrong with the construction, or the transistor is blown.

If the answer is YES - using a good multi-meter, check the voltage between the Yellow wire AND THE TRANSISTOR EMITTER pin with the native BSM lamp switched-off.

let me know your findings and we can think about the next steps

Don

When you say use 20 K oms for R2 instead of 20.2 "for reliability" can you explain please?

As you have probably observed, the design calculations for the Transistor Base resistor was very inexact - because it relied on a hfe value (remember this was the "DC current gain") that came from the specification sheet. I used hfe=60 which applied for a typical transistor collector-emitter current of 50 mA. Your circuit has a collector-emitter current closer to 30 mA depending on the position of the slider on the variable resistor.

Truth is that my choice of Base resistor was pretty-rough! However, the value of this resistor ain't that important because in a transistor switching circuit - all that is needed is sufficient base current to saturate the transistor (and the hfe value that I used was a guaranteed "minimum" value - so the actual hfe on a real world transistor will be higher anyway).

And in any event, your device clearly has full transistor saturation because the LED is illuminated (all the time)

Don

[notaGolfR]

There's no worries offending me by thinking I may have incorrectly wired the circuit. As I guess you have suspected I did get the C & E the wrong way round previously


I just re-read an earlier post of yourswhere you said to trial by connecting to the needle i.e. with the oe included. Maybe that'swhere I've been going wrong as I cut the yellow. It would be good to have both o.e. lamps and my mod asdrivers can tell by the oe's if they are in one's blindspot.

I measured V between yellow and collector with the oe off & I got 0.52 V. Then on the actual forum I noticed you said to the Emitter, so you must have edited. That was a trick . I get 0.58 V to the Emitter. That is by the needle in the yellow.


Out of interest I also measured with the yellow cut, and oe off,between yellow and collector I get 0.463 V and yellow to Emitter Iget 0.535 V

When testing I have been using a seat bolt as I haven't got around to tracking which brown out of several in the sill harness.

[DV52]

^^^ hmm.... not sure what you are telling me (have you found the problem?) - but those low voltage readings should not be sufficent to light-up the transistor LED when the native BSM lamp is not illuminated!

And just for clarity, I had assumed that it was understood that you need to construct 2 x identical new circuits; one for each side of the car!! Please re-read my previous post in which I identify a "left-side transistor circuit" AND a "right-side transistor circuit"

And, again as I said in my earlier posts, you should use the brown wire from the loom as the earth for both transistor circuits. Don't use a "bolt" or any another earth wire - because depending on how the modules are earthed, using a totally different earth point can generate earth loops from the noisy environment of a car (which can cause problems).

As for which brown wire to use - look at my wiring diagram. You can see that there is a brown wire on pin #2 which is immediately next-to the pin for the yellow wire on TTVL. Or you can use the brown wire on TTVR pin #2


Don