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?"

[Hillbilly]

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.

[Hillbilly]

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