Turn Signal/Brake Light/Hazard Circuit

Thread Starter

CSspeed225

Joined Jan 25, 2024
6
Hello. Been browsing on here for a while without making an account. I'm working on a PCB fuse/relay center for a project car. I'd like to integrate a turn signal/hazard flasher right into the circuit. In the world of wires and relays I could definitely get this done, but on the electronics side I'm not sure. I've made basic circuits, but I'm green, so I'd appreciate any guidance. I've attached a PDF of the schematic Im working on and I'll explain what I'm trying to do.

1. 12vdc automotive circuit peaking at around 14.5vdc when running

2. I will not be running an external flasher for this circuit.

3. Not drawn into the schematic yet, but Pin 4 on K1-K6 will all have 12v at pin 4

4. Will be using 2 "filament" LED bulbs, 1157 style led bulbs

Here's what I'm looking to accomplish:

1. When 12v is applied to Pin 10 on U3 pulsing 12v will be sent to K1 and K3 activating Left Turn Signals

2. When 12v is applied to Pin 9 on U3, pulsing 12v will be sent to K2 and K4 activating Right Turn Signals

3. When 12v is applied to Pin 8 on U3, 12v will be supplied to K1 and K2 activating brake lights

4. When 12v is applied to Pin 10 on U3 and Pin 8 on U3,12v will be applied to K2 for right brake light and pulsing 12v will applied to K1 allowing Left turn to flash, overriding the constant 12 v applied to K1

5. When 12v is applied to Pin 9 on U3 and Pin 8 on U3, 12v will applied to K1for left brake light. Pulsing 12v will apply to K2 allowing Right turn signal and overriding brake light.

6. When 12v is applied to Pin 3 on U3, pulsing 12 will be applied to K1 - k4 allowing operation of front and rear "hazard" lights.

I can't wrap my head around this, like I said I'm new to this. Thanks in advance for any suggestions.
 

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Ron H

Joined Apr 14, 2005
7,063
You say " In the world of wires and relays I could definitely get this done." In your schematic, that's all I see. What am I missing?
 

Thread Starter

CSspeed225

Joined Jan 25, 2024
6
I am. I did some serious digging and found a circuit skematic that id like to replicate. Its exactly what i need. See the schematic on the attachment. Where can i get relays that operate like that?
 

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sghioto

Joined Dec 31, 2017
5,388
Here's an all transistor circuit that will meet the requirements 1 thru 6 using standard 12 volt 5 pin auto relays.
The IC1 is a basic Flasher circuit, probably needing some modification.
EDIT: needs further review!
 
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Thread Starter

CSspeed225

Joined Jan 25, 2024
6
also i'm just slightly confused as to why #9 and #10 repeat in the revision. they are at the top and the bottom. Just curious as to what this is doing. thank you
 

sghioto

Joined Dec 31, 2017
5,388
also i'm just slightly confused as to why #9 and #10 repeat in the revision. they are at the top and the bottom. Just curious as to what this is doing. thank you
Just means they are connected together. I edited the schematic in post #9 with starter values for C1 and R1.
 

MisterBill2

Joined Jan 23, 2018
18,440
Just think that in years not that far past this was all achieved by te actual turn signal switch assembly, no relays and no processor. And at least in the seventies Plymouth products I owned I never had to replace the switch. But it did use two flashers, not just one. And the flashers did eventually need replacement.
 
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