US blinkers circuit

crutschow

Joined Mar 14, 2008
34,201
Okay, so how about this circuit?
It requires no connection the turn switch signal, only to the turn-signal blinker and running lights.

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Thread Starter

Laban9393

Joined Dec 3, 2020
17
The picture in post #11, what is the "blinker circuit"? Is that a signal that stays low while the bulbs are blinking, then goes normally high? Is it available as an input?

What signals are available as inputs to the new circuit?
No, that is supposed to be the output of the DRL circuit i need. The top line is the output from the car's controller to the bulbs. Add the DRL circuit output together with the output from the car's controller, then the last line is representing these combined, resulting in a DRL function at the start and end, and a in-sync flashing when blinking.
 

eetech00

Joined Jun 8, 2013
3,847
No, that is supposed to be the output of the DRL circuit i need. The top line is the output from the car's controller to the bulbs. Add the DRL circuit output together with the output from the car's controller, then the last line is representing these combined, resulting in a DRL function at the start and end, and a in-sync flashing when blinking.
See if this will work for you

Each circuit uses a 555 Timer configured as a Missing Pulse Detector to detect the blinker signal.
If the blinking signal is present, the timer output is high, and will allow the front bulb to follow the Blink signal.
If the blinking signal is absent, the timer output is low, and will override the blinking signal and light the front bulb steady on.

The simulation graph shows that the bulbs will flash in unison (synchronized).

I think you can make two circuits compact enough to fit where you need them.

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crutschow

Joined Mar 14, 2008
34,201
See if this will work for you
I think that main difference between your circuit's function and the one #21 is, yours has a faster turn-on after the turn signal pulses stop, which may be noticeable as a slightly slower turn-on of the lamp..
The TS will have to decide if the added complexity is worth a quicker turn-on.
 

eetech00

Joined Jun 8, 2013
3,847
I think that main difference between your circuit's function and the one #21 is, yours has a faster turn-on after the turn signal pulses stop, which may be noticeable as a slightly slower turn-on of the lamp..
The TS will have to decide if the added complexity is worth a quicker turn-on.
Yup. I mentioned to the TS there would be more complexity...
 

Thread Starter

Laban9393

Joined Dec 3, 2020
17
I like the 555 version you made, that way i have to try those chips out as well! Maybe ill learn something! It's so nice of both of you to take some time and help me, really appreciate it! I will try both of them out when i get home anyways
 

crutschow

Joined Mar 14, 2008
34,201
Just a small concern.
D3 and D4 should likely be higher current rated diodes since the bulb current goes through them when the blinkers are off.
(What is their purpose?)
 

eetech00

Joined Jun 8, 2013
3,847
Just a small concern.
D3 and D4 should likely be higher current rated diodes since the bulb current goes through them when the blinkers are off.
(What is their purpose?)
D3 and D4 are reverse voltage protection diodes. The operating current through them should be about the same D1 and D2 with the exception of a few additional milliamps (circuit operating current) thru D3 and D4. I think the TS mentioned 500mA for each bulb...
 

crutschow

Joined Mar 14, 2008
34,201
Just to show there's always another way, here's a circuit using two comparators (one LM339 or LM393 comparator package):
The two comparators have their outputs tied together to give the AND function (which works since they have an open-collector output).
It has a fast turn-on at the end of the blink sequence, similar to eetech00's 555 circuit, rather than the slower one of the post #21 circuit (if that's important).

If you wanted to build both left and right circuits on one board, you could use one LM339 quad comparator package for both circuits.

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Thread Starter

Laban9393

Joined Dec 3, 2020
17
See if this will work for you

Each circuit uses a 555 Timer configured as a Missing Pulse Detector to detect the blinker signal.
If the blinking signal is present, the timer output is high, and will allow the front bulb to follow the Blink signal.
If the blinking signal is absent, the timer output is low, and will override the blinking signal and light the front bulb steady on.

The simulation graph shows that the bulbs will flash in unison (synchronized).

I think you can make two circuits compact enough to fit where you need them.

View attachment 224250

View attachment 224162
Let's say i want to dim the DRL function, would that be possible via a potentiometer between the 555 out and 555 vcc rail?
 

crutschow

Joined Mar 14, 2008
34,201
Let's say i want to dim the DRL function, would that be possible via a potentiometer between the 555 out and 555 vcc rail?
Yes, you could put a resistor in series with the MOSFET outputs to the lamps in the 555 circuit.
But a pot would need to have a power rating sufficient to carry the current of the lamp.
Likely better just to experimentally determine the value for a fixed resistor.
 

Thread Starter

Laban9393

Joined Dec 3, 2020
17
Yes, you could put a resistor in series with the MOSFET outputs to the lamps in the 555 circuit.
But a pot would need to have a power rating sufficient to carry the current of the lamp.
Likely better just to experimentally determine the value for a fixed resistor.
Probably a stupid question, but is it not possible to have a resistor divider on the "lout" rail to pull the gate voltage a little higher on the mosfet? Would that not limit the S-D current of the mosfet?
 

eetech00

Joined Jun 8, 2013
3,847
Probably a stupid question, but is it not possible to have a resistor divider on the "lout" rail to pull the gate voltage a little higher on the mosfet? Would that not limit the S-D current of the mosfet?
If you put a series resistance or gate divider, it would dim the front bulb, but there would be inconsistent brightness between blink and steady brightness levels. Why would you want to dim DRL lights?
 

Thread Starter

Laban9393

Joined Dec 3, 2020
17
If you put a series resistance or gate divider, it would dim the front bulb, but there would be inconsistent brightness between blink and steady brightness levels. Why would you want to dim DRL lights?
The lights are quite bright, so to have the option to dim them to say 70% would be "nice to have" :) yes, there would be a difference between the blinking and drl function, but i don't mind that. Anyway, i just woundered if it was possible to regulate the mosfet using that method. Most likely not. Maybe it would be hard to match both side's brightness levels anyways. The bulbs are each 27w 1.93A according to what i find online (not able to check due to work). I have tried to make a pcb in easyeda (my first time making a pcb). I used a irf9530, hopefully that's going to work!
 

eetech00

Joined Jun 8, 2013
3,847
I used a irf9530, hopefully that's going to work!
Yes, that should work fine.

I've updated the schematic to show the IRF9530 mosfets.
Keep in mind that you can use an NE556 dual timer, if you want, instead of two NE555's. The NE556 is two NE555's in one package, but more expensive. You can also substitute a 2N3904 and 2N3906 for the 2N2222 and 2N2907 if they are easier to get (but I would substitute both, not just one of them). All resistors can be 5%, 1/4 watt. P1 and P2 are 500k trim pots used to adjust the 555 timing. Use tantalum caps, 16v minimum, for C4 and C2. Use electrolytic, 16v minimum for C5 and C6. The remaining caps can be ceramic.

In addition, I've updated the schematic to show an optional "brightness" resistor. The resistor value would be chosen through trial an error and then a fixed value used. I don't think there would be a need to have a switchable bright and dim setting since they are DRL lights and would only need to be adjusted once, but its your choice. I've shown the simulation graph with 5 ohm brightness resistors in place. Bulb current has been reduced by about 50%. If 5 ohm resistors were actually used, each would need to be about 10W. So the value would take some experimentation.

If we want to go further, we could add a second 555 to each circuit as a PWM driver to save power. But, again, this would further increase complexity.

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crutschow

Joined Mar 14, 2008
34,201
is it not possible to have a resistor divider on the "lout" rail to pull the gate voltage a little higher on the mosfet?
Yes in theory, but in practice the current is very sensitive to Vgs in the active region and can vary significantly with temperature and supply voltage, so it's not really a practical way to regulate the current.
Easiest is just to have a resistor in series with the lamp when it's in the DRL mode.
 

crutschow

Joined Mar 14, 2008
34,201
Here's the post #30 circuit modified to add a resistor in series with the lamp when in the DRL mode.
It uses a third comparator (of the four in an LM339 package) to control MOSFET M2 that shorts out the resistor when the turn signal is on.
Notice the lower lamp current (yellow trace) when the turn signal is off.
The value of series resistor R6 is selected to give the DRL brightness you want.
Note that this must be a power resistor with power rating determined by the current and the selected resistance.

If you wanted to save the use of a power resistor, you could likely use the last LM339 in the package to generate a PWM signal for M2 to dim the lights.

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Thread Starter

Laban9393

Joined Dec 3, 2020
17
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I have made the circuit according to the schematic above, but i have some issues. The output is high at power up, but when pulsed on the "in" input, the output goes low and does not recover. Where have i messed up?
 
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