Separate Brake Light From Turn Signal

[ThomsCircuit]

Does your truck's flasher lights look to flash equal time on/off?

Yes. Thank you. I will modify my circuit and replace the pot with a 100k resistor.

 

[eTech]

I adjust the pot to match my trucks turn signal rate of 85 cycles per minuteView attachment 147361

You might try this 555 circuit configuration. It will maintain 50% duty cycle regardless of frequency.
You can use the same LED configuration in this circuit, I just didn't show it.

 

[ThomsCircuit]

Does your truck's flasher lights look to flash equal time on/off?

I made the change, setting the pot to 100k and the circuit has improved.
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with both inputs flashing the output flashes.
with RTB flashing and LTB solid there is no output
with LTB flashing and RTB solid the output flashes
with both inputs solid there is no output.
EDIT
with RTB flashing and LTB out there is no output
with LTB flashing and RTB out there is no output
--------------------------------------------------
I will continue to check and compare my breadboard to yours and the schematic.

Thank you for the improved 555 circuit.

 

[eTech]

Here is a table that lists the input and required outputs.
It is based on a vehicle approaching an intersection.
"RT APPR", as an example, means "approaching an intersection with intent to make a right turn".
"RT WAIT" means "at intersection with intent to make a right turn, brake applied".
etc..

Please review and comment.

 

[ThomsCircuit]

Please review and comment.

This is exactly how it should function.
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Cleaning up after the storm. Trees down, neighbors need feeding as I seem to be the only one with power.

 

[ThomsCircuit]

Once I realized that the diodes and capacitor could be connected to the BB like this it made connecting everything else a bit easier.
I have not powered this up yet as some neighbors still have no power so I'm cooking for the older folks. I did this last night and it did not take too long. I have realized and learned a great deal. I still plan on testing all pins and junctions as you have laid out in post #152

 

[ThomsCircuit]

2C. When +12V volts is applied to both U1-14 AND U1-6, the voltage at U2-1 should be +12V.

While I was performing these tests I ran into a short in U1 and the IC smoked at pin 4.

I got this far
----------------------------------
To test this function, remove the connections to pins U1-5,6,13,14,
then temporarily connect these pins to 0V (ground). Pins U1-5,6,13,14
will be called the "input pins" from here on for testing purposes.
1. Apply power to circuit.
1A. Check the voltages at pins U2-3,4,8,9,10,11,12,15. Each pin voltage should be ~0V (ground)
1B. Check the voltages at pins U2-2,7,16. Each pin voltage should be +12V.
1C. These voltage measurements should remain constant throughout this test.
2. Check the voltage at U2-1.
2A. With 0V volts at ALL input pins, the voltage at U2-1 should be 0V.
2B. When +12V volts is applied to U1-14, the voltage at U2-1 should be 0V.
-----------------------------------
all was well but when I moved pin U1-6 from ground to power the chip smoked.
2C. When +12V volts is applied to both U1-14 AND U1-6, the voltage at U2-1 should be +12V.

-------------------------------------------------------------------
Before I began these tests this was the state of the circuit

Output for each
1 L
2 L
3 L
4 L
5 L
6 F
7 L
8 L
9 F
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I will post some breadboard photos. After making this 4 times and comparing mine with yours I could find no differences except for the 3 diodes at the circuits input that were not in yours. I will post a few BB photos.

Thank you for your assistance.

 

[ThomsCircuit]

BB of circuit.
I apologize for so many photos but I think at this point finding mistakes in my BB might be helpful.

Memo: The last few folks in my neighborhood had their power restored yesterday after being knocked out by H-Milton Last Wednesday night.
This wide shot may be the most useful

 

[ThomsCircuit]

Additional info that may help understand why the chip failed.
You said...
"To test this function, remove the connections to pins U1-5,6,13,14,
then temporarily connect these pins to 0V (ground). Pins U1-5,6,13,14"

What happened...
In order to do the above it was easy enough to set 5& 6 to ground but for 13 &14 I removed Rx2 & D2 but I left the cap C2 connected to pins 14&15.
I want you to know I have no intention of giving up on getting this right. I do want to perform the tests that you took the time to document. I have 18 more 14538's I am just a bit stuck and need advice on how to avoid blowing another chip before I repeat the tests
------------------------------------------------
I also (before the smoke signals) re-did the test you outlined in post #142. I may have mis-understood just how much of the tests to perform but I did each junction block repeating 2A-2B. The results were

#142
1. Disconnect LTR wire from Q3-collector while leaving R12 connected to Q3-C.
Then apply 12v supply power to the circuit.
2. Check the voltage at Q3-Collector.
2A. With ~0V volts at "LTB" input, the voltage at Q3-C should be ~ +12V.
2B. With ~+12V volts at "LTB" input, the voltage at Q3-C should be ~ 0V.
If "Left Blink Input" block passes these tests, it works, then move to the next block.
----------------------------------------------
LTB
J1 WORKS
J3 WORKS
J5 STAYS HIGH

RTB
J2 WORKS
J4 STAYS HIGH
J6 WORKS

NOTE:
I did use the new 555 circuit you posted for the tests

 

[ThomsCircuit]

1. Apply power to circuit.
1A. Check the voltages at U1A-4,1,8. The voltage should be ~0V (ground)
1B. Check the voltages at U1A-3,16. The voltage should be ~+12V.
1C. These voltage measurements should not change and remain constant throughout the test.
2. Check the voltage at U1A-5.
2A. With ~0V volts at "LTB" input, the voltage at U1A-5 should be ~ +12V.
The voltage at U1A-7 should be ~12V.
2B. When ~+12V volts is applied at "LTB" input, the voltage at U1A-5 should be ~ 0V.
Simultaneously, the voltage at U1A-7 should fall to ~0V, remain at 0V for about 2.5 seconds, then rise to ~12V.

Replaced the IC and ran this test again.
----------------------------------------------------------------------------
Disconnected RTB input and the connection at the RTB collector
Connected collector for LTB. Applied power to circuit.
voltages at U1A-4,1,8 = 0v
voltages at U1A-3,16 = 12v
voltage at U1A-5 = 12v with 0v at LTB input (output at mosfet blinks once when i touch with probe)
WITH CONSTANT INPUT AT LTB
voltage at U1A-5 = 0v with 12v at LTB input (output at mosfet flashes OUT of sink or erratic)
voltage at U1A-7 = constant 12v with 12v at LTB input (does not fall to 0 after 2.5 seconds)
---------------------------
EDIT: [Simultaneously] I was not reading the voltage at U1A-7 at the instant that 12v was applied to LTB. I set up the MM with a few clips to hold the probe so I could observe pin7 when I performed the test. Now I see that Pin7 is at 12v when LTB is 0v and drops to 0v when I apply 12v to LTB. However the duration that pin7 remains at 0v is not 2.5 seconds. On my meter its more like a fraction of a second but that may be because of a limitation with my cheap meter.
---------------------------
WITH FLASHING INPUT AT LTB
voltage at U1A-5 rises and falls with 555 output
voltage at U1A-7 rises and falls with 555 output (does not last 2.5 seconds)
output at mosfet flashes IN sink with 555 output
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I will wait for reply's before I perform other tests

 

[simonbramble]

How modern is your car? If it is less than a couple of years old, be careful. Modern headlamps have detection circuitry that lets the driver know if light bulbs have failed or if there has been some comms failure to the headlamp unit. You might upset this circuitry. Just a word of warning. The older or the more basic the car, the safer you will be

 

[ThomsCircuit]

How modern is your car? If it is less than a couple of years old, be careful.

Thank you and I agree but this is for the trailer lights. Its for an aftermarket third brake light that will be attached to the trailer. This circuit should not interfere with the vehicles circuitry.

 

[eTech]

Hello TC,
Sorry for the delay....I've been getting over the flu..

I found a problem with the circuit. When both brake lights are on (no turn signals) the third brake light flashes once, but should be steady on. I found this during a bench test.

The way to fix is to make some wiring changes, and use AND (1 chip) and NOR gates (1 chip), instead of the CD4048B. If there is another way to fix, I'm open to suggestions.

See below:

Notice that every time the brake is applied (either, or both, inputs steady), the 3rd brake light is steady on. The 3rd brake should only flash during emergency mode (both inputs flashing).

I still need to bench test this new circuit configuration.

 

[ThomsCircuit]

I still need to bench test this new circuit configuration.

Thank you.
I will order the 4081B and the 4000B

 

[eTech]

Thank you.
I will order the 4081B and the 4000B

Hi,
It’s up to you, but I would prefer you wait until I confirm it works. It will be a few days before I can test.

 

[eTech]

BTW-
I couldn’t find CD4000B so I’m going to use a CD4025B

 

[ThomsCircuit]

I found a problem with the circuit. When both brake lights are on (no turn signals) the third brake light flashes once, but should be steady on. I found this during a bench test.

During my tests I had the same results. The output would flash once but it did that for a number of scenarios. I could never produce a high steady output. Only a flash output. If my IC's are not flawed and the circuit is setup correctly then the only thing that is different is my simulator circuit. I studied your BB and adjusted mine to match yours. Even removed the diodes. Still my circuit remained unchanged. The mystery continues...

 

[eTech]

During my tests I had the same results. The output would flash once but it did that for a number of scenarios. I could never produce a high steady output. Only a flash output. If my IC's are not flawed and the circuit is setup correctly then the only thing that is different is my simulator circuit. I studied your BB and adjusted mine to match yours. Even removed the diodes. Still my circuit remained unchanged. The mystery continues...

Hi
One thing to keep in mind when testing.
The CD14538 is configured to be "re-triggerable" where successive triggers will extend the delay time. As such its sensitive to "bounces" at the trigger pins. So, manually connecting a wire to the trigger pin to produce a trigger might cause it to trigger multiple times, producing a longer delay than anticipated. The transistors and caps at the inputs help prevent this.

 

[ThomsCircuit]

The transistors and caps at the inputs help prevent this.

It was a desperate attempt to find out what could be the problem. Regardless, I have learned and to me that is more important than the circuits success. Although a working circuit is always a good thing and your dedication to the group and its members is greatly appreciated.

 

[eTech]

Hi

Getting back to you on this circuit.
The circuit will need to be much more sophisticated that originally thought.
The single flash is caused by the "detector's" attempt to determine if the
input pulse is the result of a "turn" or a "brake". Resolving this makes a
solution more complicated. Detecting the state of static switches, like a
turn signal switch, or brake switch, is much simpler, but isn't useful for
the solution you want. I recommend searching for a commercial solution.