Racepak Streetwire: how to share rear turn signal and brakes on a single bulb?

I'm using the SmartWire in a mid-'60s Nova that has two bulbs for three functions: Tail lights, turn signals & brakes. One bulb is brighter than the other and should be used for both turn signals & brakes. The key is that turn signals take priority over brakes; e.g., if the car is slowing to turn left, the left turn signal is blinking, and right side is a constant brake. Hope that makes sense. Can the SmartWire be programmed to handle this situation: A prioritized set of rules with different functions on a single output? Thanks!

I don't know about Smartwire, but as it's a very common set-up for US vehicles, I expect they have a built in option. If it's not in the manual/guide, give them a call/e-mail. I can think of a couple of ways of using a separe micro-controller, but it's bit finicky, and if not required?

If they have a FAQ section, give that a look, too.

I don't think there's a built-in option. I'll keep playing with the software, but I may have to do what this fellow did:

Racepak Smartwire Rear Light Setup (hpacademy.com)

He wired two outputs to the one bulb, which is a bit of a hack.

I can't think of any other solution other than to send two outputs to each bulb, and only turn on the "brakes" when the directional on that side isn't on. It's ugly and costs me four outputs, rather than three. I suppose I should blame GM, rather than RacePak, lol.

It needs a simple XOR* gate to the bulb, but haven't looked at Boolean Logic in around 30 years, so not sure how, now, to configure that from the options given "Programmed logic operations;
(Equal to, Not Equal to, Greater than, Greater than or Equal to, Less than, Less than or

Not Equal to)"

* EXclusively one OR the other. The gate, switch, has two inputs, A & B, and one output, O, with 4 states for the gate to operate in. ONLY when either A OR B is 'on' with there be an output at O - in either, or both are "on" then the output O is "off".

This operates as the brake, alone, turns the bulb on, the indicator, alone, flashes the bulb on when powered. When the brake is on, and the indicator on, the indicator turns the bulb OFF, not on, flashing the bulb.

Not what you wanted, but might help point you in the right direction.

Oh, if you haven't got them, you can d/load pdf's here https://www.holley.com/products/data_acquisition/power_distribution_modules/parts/500-KT-SWST?srsltid=AfmBOoq8dlrzcDGB32OBt6CPOXxtjvbRweHC08Zu9DtRodUa8ipoYO0X

Hmm, considering the vehicle's year, there may be a small, discrete, module to do this in the OEM wiring circuit that may be adaptable, if you're happy using it, if there is one?

Right, if I could provide logic to output, this would be easy. But you can’t, and you can’t share more than one behavior per output. Logic operations can only be done on inputs.

As far as a discrete box goes, I might be interested, but isn’t that why one utilizes a PDM? I should have used an ECUMaster PMU. I could habve this quickly with their gear.

Did a bit more checking, and can't find an alternative to an external logic controller, either OEM (if applicable) or custom made. If you have, or a friend has, some basic electronic skills you should be able to make a very small device in a sealed enclosure with a couple of gates (LH and RH), if the gate has the current capacity.

All the gates I can find are voltage and/or current limited, so a SS relay or OP-AMP for each may also be required?

However, as I said before, I'm VERY surprised such a common US tail-light configuration doesn't seem to be catered for - they certainly dropped the ball there! Then, again, it would need parallel outputs for the front and repeater lights so they wouldn't come on when the brakes were applied.

You might find some help in these discussions -

https://forum.allaboutcircuits.com/threads/12v-3a-high-side-switch-with-two-input-xor-logic.188532/

Gord, thanks for the help above, it got me to find this circuit, which I think will work. It requires 4 relays, 2 per side. Now to decide if I want to add 4 relays to my pristine PMU-based wiring.

I found it here: Utility trailer 12v solution

That would work, and you should be able to find suitable surface mount, solid state relays that can be used on a circuit board and, with a suitable enclosure, should make a tidy, discrete package, maybe a 3D printed enclosure.

There will probably be a variety of options for the device, so you can chose what fits best.