Using 12v at base of transistor

Hello Nico,

Here's a better design - two extra diodes but the relay only needs to be DPST so will be cheaper and easier to find.

I think this nearly does what you want - if only one input is high the appropriate turn light comes on, if both inputs are high the relay energizes and the brake lights come on (but so do the turn lights), the brake lights stay on until both inputs go low because the c terminals on the relay hold it on so long as there is power through either diode.

I don't really like the turn lights coming on at all when braking but this gets much harder since you need quite a lot of 'statefullness' in the controller - are you up for a micro ?

MK

That's really good, Michael!

You're right about the turn lights coming on when braking being a bit annoying, and might be confusing to other drivers.

It's similar to hooking up the wires directly to the red and orange lights together, but gains the benefit that signals are only using the orange.

...this gets much harder since you need quite a lot of 'statefullness' in the controller...

That's the conclusion I came to as well.

It seems that the only way to tell if it's a turn signal is by the flashing action.

are you up for a micro ?

But of course! That's probably where I'm most comfortable. My worries are that the micro would have to start up very fast, or else be kept powered up by an alternate source. I'm guessing that a capacitor would keep it running long enough between blinks though. After that it should be possible to determine when a light has been on and off, and then flash the orange indicator on the transition from 0v to 12v, maybe missing the first flash, but that's ok.

ps, the trailer does have it's own 12v power source too, so that could be used to power it, however, the failure mode (ie, no trailer power available) should provide safe function still (maybe just using the red lights, as would be the usual for trailers).

Maybe the easiest way to handle it is to add two lines from the car turn indicator wires to directly control the orange turn indicators.

Thanks,

-Nico

Hello Nico,

Simple micros with on chip RC oscillators can be up an running in under 1mS quite easily - I don't think you need store power between blinks because if the brake is on there is always at least one turn signal high to provide power.

Do you have  a micro preference - almost anything would do (PIC, AVR, ARM) and do you need it to be in a DIL package or are you OK with SO which would need a board. The whole thing will be much more reliable with a board of course.

MK

Hi Michael,

...up and running in under 1mS quite easily

That's really good to know.

For the between-blinks power store I was thinking that would be needed for the case where it's just a turn indicator flashing (no brakes). Out of curiosity I might test to see how long one will run on a capacitor.

Do you have  a micro preference

I do have a micro preference, mostly due to laziness   Because my stuff is pretty much all hobby I've decided to focus on Arduino and Raspberry Pi - I found that otherwise I end up spending my time learning new tools instead of building projects. I also have TI MSP430, and CCS isn't too bad, but Energia makes using those super simple too.

I'm still at the DIP stage. I have a few surface mount ATTiny13 chips because I needed one for an art project (it's glued to a rock and "wired" with conductive glue).

I haven't created any PCB's yet. A lot of my projects never go beyond breadboard, and the ones that did I've used perf board - a bit messy but worked well enough.

I do have some nice little 3x2x1 inch project boxes that include perf board in it, that I bought from Radio Shack when they were clearing out all that stuff before they became "The Source" here in Canada. One of those might work well for this.

In terms of controllers inventory, I have a couple of DigiSparks (ATTiny85 based) that might work well for this, or maybe one of the TI MSP430 chips because their DIP format would make them easy to add to a board.

Cheers,

-Nico

Note to self, because I'll probably need it later...

Removing 5 second startup delay for Digispark

Maybe there is a POTS soln:

How To Install A Trailer Light Taillight Converter In Your Towing Vehicle

I am not quite sure how the brake light signal is derived from turn signals.

If you can come up with the FSM I am sure this can be configured with a coupla logic chips

I'm not sure this state table is what you have, but once the states are populated, the logic to derive each state can be determined.

It the table your vehicle controls (in blue) generate control signals (in green) and you want the output signals in yellow and red.

The output signals must be derived from the green control signals. there are only 2 control signals, but they each have five states (off, on dim, on full, flashing off-on and flashing dim-on) The darker colours indicate flashing on-dim. If I have it right, there are 14 input states and 11 output states.

This doesn't need a microcontroller to sort out as your yellow turn signals only have 2 states and your tail lights follow the green control signals, except when the yellow signals are flashing. The dim condition doesn't matter if you use the green signals as power rails for your tail lights. etc.

Some states are not possible because, for instance, the left and right turn controls cannot indicate both at the same time.

In order to figure out the state it is necessary to detect flashing. The two types of flashing don't matter, but it is harder to detect flashing because it isn't always the same.

Note the brakes can be flashing if you pump the brakes - you don't want this to cause turn signals to come on unless the turn signals are also on.

I am not sure there is enough information in the control signals to know what is going on if you pump the brakes at the same rate as the turn signal flashes - while they are flashing.

If you use a flashing detector, it will delay your turn signal activation.

I hope this doesn't look too confusing and complicated - it is just trying to set up a way to document what you and Michael have been saying in words, and in translating to a circuit, it should simplify to something similar to what you and Michael have been designing.

Thanks for all that, Douglas!

It's after midnight, so I'll keep it quick, and check in more detail later, but we can reduce the table a little bit: there is no "Dim" - the lights have a separate wire and separate bulbs/LEDs on the trailer, so we can ignore anything to do with night-lighting for the logic. The signals get a full 12v when on.

Thanks!

-Nico

No much time today but just a couple of quick thoughts.

1) I would go for the AVR processor but code in C - I just don't trust the Arduino code environment for precise timing, start up etc. The Atmel software tools are free and nice.

2) @Doug - I'm used to classic state diagrams which show how events cause transitions in the machine's state - I don't see quite how your table can show how the reaction to new input conditions is affected by the state the system is already in.

MK

You might consider implementing this in PROM.