Custom 3rd Brake Light (Upd: 18th August)

[ph001]

Cool stuff! How does it all actually interface to the car in terms of braking, reversing, turning left & right etc? I assumed you were using some kind of acceleration sensor for the braking? Are you driving the individual leds with fets?

 

[IAmOrion]

Cool stuff! How does it all actually interface to the car in terms of braking, reversing, turning left & right etc? I assumed you were using some kind of acceleration sensor for the braking? Are you driving the individual leds with fets?

You simply tap into the bulb wires for each (Same way off the shelf products do, plus it's the easiest anyways)

The 12v-14v goes through a voltage divider (Just a 30k resistor and a 6.8k resistor) - the result of which connects to one of the Arduino Analog inputs. Then coded like this:

  value = analogRead(brake); vout = (value * 5.0) / 1024.0;
  brake_voltage = vout / (R2/(R1+R2)); if (brake_voltage < min_voltage) { brake_voltage=0.0; BRAKING=false; } else if (brake_voltage > min_voltage) { BRAKING=true; }

The min_voltage is pre-set at 3 ... this is to simply rule out any minor spikes ... those who have dabbled in Arduino and voltage into analog inputs like this will know that occasionally there's trace voltage and registers as like 0.3v or whatever... so that prevents accidental trigger.

The LEDs themselves and the Arduino is driven by a 5v buck converter. I've done it like this to make as DIY friendly as I can.
Also worth noting - 5v WS2812B LEDs are cheaper than their 12v version - sometimes as much as half the price when buying in bulk! - When there's only 20 like this, the brightness is EXACTLY the same - there's no difference. (There's loads of videos on youtube and info on the net to go into more detail of the comparisons) so it made sense to go with 5v LEDs and use a buck converter. Each LED uses a MAX of 60mA at full white brightness (White uses the most power). 20 x 60 = 1200 / 1000 = 1.2A . So with a maximum of 1.2A used by this, the 3A buck converter (which realistically is only reliable up to 2.5A) is still plenty enough to power the LEDs AND the Arduino 8)

This is my PCB design currently:



It looks more complicated than it is... but I've intentionally designed it this way so even newbies should be able to put it together since you just buy a buck converter and an Arduino Nano. There ARE some SMD Resistors for the voltage division however my plan (still depending on demand) is to get a batch of the PCBs made (Once I've finalised my design - I've some minor changes to make yet) and then sell them in a half built state - so I'll solder on the SMD resistors - and then others can DIY the easy parts .

I've yet to figure out exactly how I'll do it all... that's just a rough plan ha

 

[enuff_zed]

Yes I missed a point already mentioned , which I asked as an afterthought.
My main point was a query about the legality of the positioning for indicators. I don't know the requirements, but maybe it's ok as 'repeater' flashers. Perhaps someone has decent knowledge of the relevant construction & use regs?

I must admit, I never even thought to check that aspect. I mean, I know it’s fine as braking & reversing ... I’ll try and find out about indicators. In my head I didn’t think it’d matter since it’s not replacing indicators, but adding more.

I’ve seen loads of people install the cheap off the shelf strips (as someone’s mentioned earlier) without issue so I’d hope it’s not an issue

Currently working as Compliance manager and tech author for a company making trailer mounted wood chippers.
We have to adhere to strict measurements for all light positioning.
Found this for the indicators:

Colour Amber
Height position Between 350 mm and 1500 mm permissible
Width position Max. 400 mm from the outermost edge of the body. At least 600 mm apart

It would require a pretty bored, or over-zealous, plod to pick on you, but imagine if a car behind could, for whatever reason, only see the centre indicator set. How easily could they tell if you were turning left or right?

 

[IAmOrion]

Currently working as Compliance manager and tech author for a company making trailer mounted woodchippers.
We have to adhere to strict measurements for all light positioning.
found this for the indicators:

Colour Amber
Height position Between 350 mm and 1500 mm permissible
Width position Max. 400 mm from the outermost edge of the body. At least 600 mm apart

What's the point of reference for the height out of curiosity?

This would mean that the indicator function is perhaps a no-no however it's no more riskier I suppose than the off the shelf 120cm strips you can buy (since their placement would be against those regs too). Having a switch on the PCB as Jl-c suggested would give an easy way to turn on and off for MOT etc lol

 

[enuff_zed]

Currently working as Compliance manager and tech author for a company making trailer mounted woodchippers.
We have to adhere to strict measurements for all light positioning.
found this for the indicators:

Colour Amber
Height position Between 350 mm and 1500 mm permissible
Width position Max. 400 mm from the outermost edge of the body. At least 600 mm apart

What's the point of reference for the height out of curiosity?

This would mean that the indicator function is perhaps a no-no however it's no more riskier I suppose than the off the shelf 120cm strips you can buy (since their placement would be against those regs too). Having a switch on the PCB as Jl-c suggested would give an easy way to turn on and off for MOT etc lol

Height from the ground plane.
My point regarding plod was that they would be exempt from your MOT switch

 

[enuff_zed]

And if they did flash you to pull over, just flash your 'off-road' blue version and they'd assume you were on some covert op and let you go 8)

Or maybe not

 

[IAmOrion]

It would require a pretty bored, or over-zealous, plod to pick on you, but imagine if a car behind could, for whatever reason, only see the centre indicator set. How easily could they tell if you were turning left or right?

Height from the ground plane.
My point regarding plod was that they would be exempt from your MOT switch

Ha, that last bit wasn't there when I started my reply (I'm guessing you edited whilst I was still replying lol) - but yes they'd have to be bloody bored to pull you over for that - but still, there's always some newbie coppers on the beat who needs to meet their ticket target

I mean, I guess it depends on how blind the person behind is, since the indicators are clearly off center to the left or right depending on which side is indicating... BUT there's 0mm between the left and right so there's bound to be confusion for someone (hence the regs in the first place)

And if they did flash you to pull over, just flash your 'off-road' blue version and they'd assume you were on some covert op and let you go 8)
Or maybe not

Oooh, I like that though - although I'm not going to be the one to try it and see haha.

The Indicator toggle switch solution would keep both the MOT and the Plod happy as long as it was left OFF. 8)

 

[enuff_zed]

I mean, I guess it depends on how blind the person behind is, since the indicators are clearly off center to the left or right depending on which side is indicating... BUT there's 0mm between the left and right so there's bound to be confusion for someone (hence the regs in the first place)

At night, for example?

 

[enuff_zed]

I think the toggle switch idea should be used to manually select reversing light.
Should get the point across to all the numpties who don't know what a dipped headlight is :wink:

 

[IAmOrion]

At night, for example?

I mean, my opinion may differ once I've fitted it, and looked at it from behind at night - but given the normal lights will still function as normal - you'd still see the factory indicator flashing etc, so they'd have to be quite some distance away to get confused, it wouldn't confuse me - but I do believe you when you say it could cause confusion to some

I think the toggle switch idea should be used to manually select reversing light.
Should get the point across to all the numpties who don't know what a dipped headlight is :wink:

The toggle switch is purely to enable or disable a function - it does have 2 custom triggers though - eg, run a 12v feed to a switch (latching or monetary) then to one of the custom inputs and you could then activate a strobe effect or whatever you want to annoy people behind with high beam on haha

 

[mmm-five]

I think the toggle switch idea should be used to manually select reversing light.
Should get the point across to all the numpties who don't know what a dipped headlight is :wink:

I've got a 3000 lumens torch in the car for that :dizzy:

 

[IAmOrion]

Quick Update for anyone curious/following...

I've put into production 2 types of PCBs I've designed - designed as "external controllers" for want of a better word.

Variant A uses an Arduino Nano as the main controller, Supports 2 WS2812B connections (So you can use 2 LED strips independently - irrelevant for most, but it means that this PCB may also appeal to coders who want to expand on it - for example, you could use it to make custom DRLs, or Devil Eyes, Angel eyes etc etc but with the option of operating them differently > uses are endless I guess). It incorporates voltage divider circuits to handle the input signals.

Variant B uses an ESP-32 device. It offers the same functionality as above, except it ALSO allows to be WiFi hotspot so you could control various aspects of it via WiFi. (ESP-32s can connect to your home wifi etc, but for this usage case, it would be a captive hotspot - an independent wifi connection point). It also has bluetooth so you could add bluetooth functionality. This also uses optocouplers instead of voltage dividers since the ESP-32 devices don't have analog inputs (well, 1, but this needs 6) - so the optocoupler route allows for the input signals to be directed to Digital Inputs.

Both designs feature a Jumper for a Slide Toggle so you could easily enable/disable the indicators function. There's also a jumper to pick between Static Flashing or the Sequential flowing animation

More to follow soon 8)

 

[Jl-c]

I love this and want one BUT .............. I can't seem to find a cheap E86 third brake light. E85, yes, but not E86. Any ideas, apart from cutting up the original which is OK but it is red not clear so colours will not render correctly?

 

[IAmOrion]

I love this and want one BUT .............. I can't seem to find a cheap E86 third brake light. E85, yes, but not E86. Any ideas, apart from cutting up the original which is OK but it is red not clear so colours will not render correctly?

Someone asked me this on Facebook - I haven't yet found a cheap E86 3rd brake light either

 

[Grizzly9]

 

[Jteran5]

I created an account just to message you haha

Very very impressive work.

I am actually interested in replacing my 3rd brake light and was wondering what kind of bulbs are in the OEM housing originally? Are they some that are just plugged into each spot somehow? I've seen pics and vids of people replacing them but never get to see what they look like on the inside.

Reaksn I'm asking is that I've replaced my rear lights with LED's and now my 3rs brake light looks dull in comparison. I really would want just an oem setup but to be brighter (if that makes sense)

 

[IAmOrion]

I created an account just to message you haha

Very very impressive work.

I am actually interested in replacing my 3rd brake light and was wondering what kind of bulbs are in the OEM housing originally? Are they some that are just plugged into each spot somehow? I've seen pics and vids of people replacing them but never get to see what they look like on the inside.

Reaksn I'm asking is that I've replaced my rear lights with LED's and now my 3rs brake light looks dull in comparison. I really would want just an oem setup but to be brighter (if that makes sense)

I don't know what is in the BMW / OEM ones - I think they're LEDs too. The Chinese one I ordered has 20 small red LEDs - they are SMD type, 2 pin, roughly 2mmx3mm - so I don't think you'll be able to simply "change a bulb" for a brighter one so to speak.

 

[IAmOrion]

PCB Arrived! New post here: https://z4-forum.com/forum/viewtopic.php?f=2&t=117273

 

[Matty_Z4]

The 12v-14v goes through a voltage divider (Just a 30k resistor and a 6.8k resistor) - the result of which connects to one of the Arduino Analog inputs. Then coded like this:

  value = analogRead(brake); vout = (value * 5.0) / 1024.0;
  brake_voltage = vout / (R2/(R1+R2)); if (brake_voltage < min_voltage) { brake_voltage=0.0; BRAKING=false; } else if (brake_voltage > min_voltage) { BRAKING=true; }

The min_voltage is pre-set at 3 ... this is to simply rule out any minor spikes ... those who have dabbled in Arduino and voltage into analog inputs like this will know that occasionally there's trace voltage and registers as like 0.3v or whatever... so that prevents accidental trigger.

For the floating pin can you just not use the appropriately sized pullup / pulldown resistor to tie the signal high or low until triggered? Not sure how it would affect the inbound signal from the voltage divider.

Looks like a pretty good project, always love a good DIY electronic project.

 

[IAmOrion]

For the floating pin can you just not use the appropriately sized pullup / pulldown resistor to tie the signal high or low until triggered? Not sure how it would affect the inbound signal from the voltage divider.

Looks like a pretty good project, always love a good DIY electronic project.

Without getting into a huge electronics lesson, the short answer is no - you wouldn't / shouldn't do that when using voltage dividers. What I've done, and that code snippet is the best method to use.