Sequential LED's (like the New Mustang's Turn Signals)

[Falcon69]

My nephew redid his truck, turning it into a flat bed.  He bought 6 LED lights, 3 on each side. He has asked me to make a circuit so he can have the lights flash in sequence like they do on the new mustangs when he turns his turn signals on.

Now, I've checked at the circuit box, pulled the flasher module, and jumpered it.  By doing that, it no longer flashes, but stays at a steady light when turn signals are on. So, there is a continuous supply of 12 volts going to the back of the truck to the lights via the factory wire harness.

I tried looking on google for a circuit that will work, but when i try to run a simulation, it doesn't seem to operate with transsistor/mosfets, resistors, and capacitors.

Some other images show using a 555 timer and a 4017.  what is a 4017? A decade counter?  Will that work? I am guessing that the outputs of the decade counter must be used with mosfets or transistors, as his LED lights probably draw too much power for the decade counter. My simulation program I am using does have a 555 timer circuit in it, and a decade counter circuit, but I'm not sure how to draw it up using those just yet.

Anyone have a simple circuit that will work for this application?  He wants them like this


Thanks in advance,
Jason

[theatrus]

What circuits have you tried, and what's your experience level?

If this were me, I would simply take the lowliest MCU I had sitting around to run the logic, and use three big enough FETs (or even relays for an authentic auditory experience) to drive the bulbs.

[Falcon69]

I found this

http://homemadecircuitsandschematics.blogspot.com/2011/12/how-to-make-car-led-chasing-tail-light.html

but, i'm not sure how to make it work with these

http://www.ebay.com/itm/2-Trailer-Truck-RED-LED-Surface-Mount-6-Oval-Stop-Turn-Tail-Light-Sealed-/160975575861?pt=Motors_RV_Trailer_Camper_Parts_Accessories&hash=item257ae45b35&vxp=mtr

Those are the lights he bought. 3 for each side.

[jlmoon]

www.engineeringshock.com is one of many places you can find a sequencer,  all you need to add would be some mos or hexfets to handle the power demand of those LED assemblies such as IRF44ZN on a small heatsink and your good to go.  Only reason I suggest this part is because I have shelf full of them.  You will need to allow for latching all outputs high when brake signal is present, in other words pull the three gates high (both sides) when brake signal wire is active and no signal light active.     Hope this makes some sense to you

[Falcon69]

what I dont understand is the 4017 has 10 outputs.  Do all the outputs need to be used?  Can i just use 3 of them, and hook them to a mosfet which controls the LED?

[jlmoon]

Since you're only using 3 led assemblies per side, you would only use output 0,1 & 2.  Two circuits required one for left and one for right.. unless your into some serious driver (mosfet) switching to drive each side with one sequencer.  Could be done tho, such as if a manufacturer were building millions of these.. then the cost savings would be quite significant.  One clock, one 4017 with some  enable gating logic (OR gates) and a mosfet for each lamp would do the trick.

[Falcon69]

that link i posted from homemadecircuits has one circuit to operate it both sides.

So, if the other pins of the 4017 are not connected, they are just ignored in the count?

[jlmoon]

yes.. or you could gate them if you don't desire the delay time between clock cycles from 3 - 9
0
    1
        2
             3(wait)
                 4(wait)
                    ....
                       9.. wrap around
0
see the idea?

[Falcon69]

oh, okay, so there would be a delay while it counted through the other 7 outputs.

What do you mean by gate?

Use an or/xor gate on the unused outputs and tie them to outputs Q0 (pin3), Q1 (pin2), Q2 (pin4) that will be working with the LED's?

[jlmoon]

Yes, using OR gates you can put 3 with 0, 4 with 1, and 5 with 2, as well 6 with 0, 7 with 1 and 8 with 2.. then let it rest for 9.  Best way to do this is breadboard it using actual leds or small bulbs with the actual mosfets and watch what happens.
Keep in mind you have to deal with the brake light scenario as well.  When the brakes are applied along with say the left turn signal .. you need to still have the left turn sequence working but the brake signal muted only to that side or the Brake light will mask the effect of your sequencer. Does this make sense?

[jlmoon]

IIRC, when using the brake with turn signal.. I think the brake 12v is applied to the signal flasher (for the turning side) and then routed to the bulbs on the turning side.  For this to work correctly you will need to remove the flasher and handle all this with gate logic.  Typically with OR logic routed to the gates on your mosfets, great thing about the parts you're using.. they will handle 12 nicely.  Just as a preventative measure be sure to put some over voltage protection/regulation on the supply to those ic's.  They can't handle much above 18volts, bad battery, jumping cars off can get a bit extreme on a cmos part. 

[Falcon69]

Yes,

I will work on drawing up the circuit now.

I will need to apply some kind of a mosfet/transistor switching so that when the turn signals are on, the running light is not on, meaning, the lights are are always dimmed to show the vehicle is on, so I will want that to switch off when the turn signals are working.

[Falcon69]

I will have to check his vehicle, but I believe there are 3 wires, Ground, Brake, and Turn Signal.

I took off the flasher module from his circuit board on the car, and jumpered it. It supplies a continuous 12volts to the rear lights (left or right) when a turn signal is activated.

There might even be a fourth wire for running light, for when the lights are turned on, if that is the case, should be easy to make it so the running lights turn off when the turn signals are activated.

[jlmoon]

Since you're in the U.S. as I am, the running lights are on an entirely different circuit.  I don't think the running light power is interrupted when turn signals are on.  Not on a late model car anyway
I presume you could sink a running lamp filament and control as you please as with any other lamp, but not sure you want to go through all that.

[Falcon69]

ya, I would just think it would look better if none of the LED's were dimmed during the turn signal operation. I might not look right when some are dim, while others are bright. 

[Falcon69]

I have a couple 7805's here, but I'm fairly a newb when it comes to electronics. Microcontrollers are out of my scope of knowledge.

Do you have a schematic of what you are talking about?

[jlmoon]

oh good point.. I'm still on the track of two different led board assemblies in the module..

I will have to check his vehicle, but I believe there are 3 wires, Ground, Brake, and Turn Signal.

I took off the flasher module from his circuit board on the car, and jumpered it. It supplies a continuous 12volts to the rear lights (left or right) when a turn signal is activated.

There might even be a fourth wire for running light, for when the lights are turned on, if that is the case, should be easy to make it so the running lights turn off when the turn signals are activated.

Think of the wiring in the concept of a trailer.. usually one ground lol.. sometimes (black) , clearance or running (brown), left turn/brake (green or yellow can't remember) and right turn/brake (green or yellow opposite of other side)
now that's a 4 wire plug
the 7 or 8 wire systems just add some extra stuff for electric brakes, charge wire for battery.. etc

[jlmoon]

A $5 microcontroller and six cheapass relays would work splendidly. All else you'd need would be a 7805 or something.

I like the microcontroller concept as well, provided one has the IDE to code the part.  lol.. then he could put a lcd display on the dash with a key pad and have a very dynamic sequencer.. 

[jlmoon]

You only need, what, six outputs and three inputs, right? So an ATTiny84 would work just fine. Literally $3, and you only need one.

For switching, these $2 relays should work. Oh, and add a bypass cap for good measure.

don't forget about the transient protection for both the controller and it's outputs?

[jlmoon]

coil current requirement for that relay.. @ 37.5mA.. pushing the limit on that ATTiny84 part.. only good for 40mA.. max.. .. for design reliability.. better do some buffering between them.

[Falcon69]

that gets too complicated for me.  I don't have the equipment to program the chips.

Those lights draw more then 40mA.

[jlmoon]

"That's why there's a relay. To program the chips you need a $10 arduino. "
yes.. but the relay is drawing 37.5 mA.. and that poor chip can only do 40mA maximum ratings.. thats pushing the envelope more than I would
as the device was designed they didn't intend on you loading it at over maybe 60% of it's rated output (generalizing of course).  I sure wouldn't if I desired reliability.

so do the LED assemblies have two or three wires per?

[Falcon69]

3 wires coming out of the led assemblies, GRN, Brake, and Turn

[jlmoon]

3 wires coming out of the led assemblies, GRN, Brake, and Turn

so... there's your answer.
the running lamps have their own board, so it is up to you if you want to mute the running light LED while in turn mode.  Add one more mosfet to the pot of parts for each side
then suppress the gate drive to that part when you're in turn mode.. so you don't see the dimmed LED, thinking you will need a XOR for that one.. wow.. going back to my karnaugh maps
.. I would need to do the logical operators on that one

[jlmoon]

all for L or R side:

Brake  & Running = Running Enable (1)
No Brake & Running = Running Enable (1)
No Brake & Turn Enable & Running Enable = Running Enable (0)
Brake & Turn & Running = Running Enable (0)
and it continues.....


now draw the schematic..

[Falcon69]

Drawing

I'm confused though, on the schematic here http://homemadecircuitsandschematics.blogspot.com/2011/12/how-to-make-car-led-chasing-tail-light.html

It shows pin 15 (MR) and Pin 5 (Q6) connected on the 4017.  I'm confused.  Q6 is one of the 10 outputs. 

Is it drawn wrong?

[Falcon69]

oh!  Wait, I think I understand.

In that schematic, they are using only 6 outputs, technically, Q6 is number 7, so, when it triggers the Q6, it goes to MR which resets the clock and starts back at Q0, therefore, no need to use gates on the other outputs.

Since I will only be using 3 outputs (1 for each LED assembly, left/right), I need to connect Q3 (pin 7) to MR (pin 15)

Is this correct in thinking?

[Falcon69]

oh

I just realized that if I take out that flasher module from the vehicles circuit board, the front lights won't flash right.  I'll need to trace the wires and run one all the way to the back, where my circuit will connect to the rear taillights.  bummer. more work.

[jlmoon]

no what the sequencer (4017) is being reset on count #6.. 0 - 5 then reset the pulse train at #6
so in effect if either on L or R.. you get 6 counts 0-5 and then a reset to start over
you could do the same after 0,1,2.. but then it might look funny to your eyes, there are so many ways to sequence a set of LEDs and depending on how you wire them is how they will appear.  Can play tricks on your eyes. 

The website diagram will work as well , they are using diode enable or logic instead of gates.. I prefer gates.. , something about the flexibility in them..

[tjb1]

I'm not sure what lights you have but its likely GND, PARK, BRAKE/TURN.



I've done a lot of wiring with those and the vehicles I have worked with use the same wire for the brake/turn and just flash or hold it steady for brakes.

[Falcon69]

tjb1

Yes, they are pretty much the same, just oval instead of round.  They just hook up to the battery for 12 volts.

So parking would basically just be the dimmed lights (white wire)

[jlmoon]

oh

I just realized that if I take out that flasher module from the vehicles circuit board, the front lights won't flash right.  I'll need to trace the wires and run one all the way to the back, where my circuit will connect to the rear taillights.  bummer. more work.

Yes, I was wondering when you were going to address that part of the project.  My solution was to OR (summing mode) the three outputs together and drive yet another gate of another mosfet for the front turn signal so when any one of the three turn signals are in (1) mode.. the front turn signal would be on as well and during the rest time somewhere between Output #3 and reset back to #0 the front lamp will be off. 
 
To do this project is not as easy as just hooking up some logic and relays.  Back in the early 60's if my memory serves me correctly they used to use a drive device to sequence those lights on the old Ford Thunderbirds.. I had one, but it has been so long ago now.. forgot if it was a stack of flashers or a drive motor that did that.  Maybe someone else on here will chime in on that one

[Falcon69]

I think what I am going to do is just tear the dash apart and find the switch wires of the turn signal and tap into those and run wires all the way back.  Place the flasher module back in for the front lights.

[jlmoon]

what type of vehicle is it.. year and model?
that still won't resolve the logic needed to sequence the turn signals, mute the braking signal and deal with the front lamp flash mode.. it's gonna be a    but you can do it!

[Falcon69]

it's a 2002 Dodge full size 4x4

Here's the schematic so far.  I figured no need for resistors after the LED's because I'm sure the assemblies have them built in already.

[jlmoon]

no resistors needed.. yes, they build those in on the boards

[jlmoon]

it's a 2002 Dodge full size 4x4

Here's the schematic so far.  I figured no need for resistors after the LED's because I'm sure the assemblies have them built in already.

what are those semi's.. Q1.... driving the LEDs.. and what are you going to do with the anodes on your diode trios on each side?

[Falcon69]

those are NPN transistors to power the LED's instead of powering them from the 4017. Should I replace those with mosFETs?  Each of those LED's shown are each of the 3 LED assemblies on each side.

[Falcon69]

oh, right, D6 and D9 should be connected for the brake light

[jlmoon]

actually on the Right LED group your anodes don't go anywhere
you will also need to use mosfets unless you're prepared to do some tricks with forward bias voltage drops on those transistors
need those Vds to be low so you don't loose any brightness due to voltage drop and you can use small heat sinks, and the calculations begin!

I wouldn't advise NPN.. , you loose .6 - .7 V across the B-E junction. , the mosfets drop like almost nill.. take a look at some of the mosfets.. IRFZ44.. or take your pick
at 10 Volts  Vgs.. the R_drain to source (Rds) is like in the milliOhms .. so very little power will be dissipated across that active junction.  Something to consider. 

[Falcon69]

Okay, i will try and find some surface mount mosfets that will work.

I ultimately wanted to design a circuit that i could just hook up the wires already at the rear, but, with the flasher module up front, not sure how to do that.  At this point, for me, i think this circuit will work, as long as I can tap in the turn signal shifter and brake light and parking light controls and run the wires back.

I may need to add a resistor as a dummy load for the flasher module so the front lights don't flash erratically.

I was recently in an accident, and my right turn signal on my car flashes super fast, and I'm guessing that's because the light on the rear no longer works, hence, the idea of a dummy load.

I will grab my nephew and head to Radio Shack and pick up some test parts.  I hope they have these chips in stock.  If all works well with this schematic, I will buy some surface mount components and design the PCB.  Since I have to make 10 boards, I might as well buy 10 sets of parts.  He can sell them to his buddies and get back his money and thus, basically, get a free circuit board for controlling his lights.

[jlmoon]

Okay, i will try and find some surface mount mosfets that will work.

I ultimately wanted to design a circuit that i could just hook up the wires already at the rear, but, with the flasher module up front, not sure how to do that.  At this point, for me, i think this circuit will work, as long as I can tap in the turn signal shifter and brake light and parking light controls and run the wires back.

I may need to add a resistor as a dummy load for the flasher module so the front lights don't flash erratically.

I was recently in an accident, and my right turn signal on my car flashes super fast, and I'm guessing that's because the light on the rear no longer works, hence, the idea of a dummy load.

I will grab my nephew and head to Radio Shack and pick up some test parts.  I hope they have these chips in stock.  If all works well with this schematic, I will buy some surface mount components and design the PCB.  Since I have to make 10 boards, I might as well buy 10 sets of parts.  He can sell them to his buddies and get back his money and thus, basically, get a free circuit board for controlling his lights.

the right signal is not working either because your right turn signal wire is shorted to ground (makes the thermal breaker - flasher) open and close much more rapidly than normal or you were hit hard enough the filament fused inside the bulb and created a direct short due to impact force while it was hot or active with current.

I would breadboard that circuit and get it working with LED's on a bench before going out and cutting / modifying any wires in that truck.. trust me on this one, you will be better off and learn alot in the process.
Good luck!

[Falcon69]

yes, I plan to bread board it.  I use to install car alarms, so tracing the wires to find the correct ones won't be a problem, just a pain.

I am going to check at radio shack today, to see if they stock those parts, though, I doubt they do.  They seem not to stock too many parts these days, like they used to.  I might have to drive out to Wilsonville, OR and buy them at Fry's electronics.  Long drive though from Vancouver.

[jlmoon]

Regarding those mosfets and how to use them, here is a link to help you out .. Enjoy!
https://www.youtube.com/playlist?list=PLjzGSu1yGFjUgTVkhb4WslOVDNAZ3K4yR

[Falcon69]

Okay, so, I tried this circuit on the truck that I found on this website http://homemadecircuitsandschematics.blogspot.in/2013/03/sequential-bar-graph-turn-light.html .

The sequencing of the LED's work as intended, just like they do on the new Mustangs.

However, When the brake pedal was applied, they still flashed.  Also, when turn signal (or brake) is turned off, they keep flashing but dim until they are lit no more.  When I turn on my headlights, NOTHING happens.

So, I took that schematic, and I redrew it with modifications.  I am not sure it will work, but seems to when I run a simulator.

The LED assemblies I am using have 3 wires: Red (Brake/Turn), Black (Park/Tail), & White (Ground).

I will be using 3 LED Assemblies per side: Right and Left.

I only drew the left side tail lights for the schematic.  The other side of the Hex inverter and Quad Nor Gate will be used for the right side tail lights.

I may need to replace all the Transistors with mosFET's, but will try it with Transistors instead, because of cost. Seeing how there will be a direct battery hook up and batteries usually put out 14.5volts, I should be okay on brightness for the LED's even with the voltage drop of the transistors. In theory anyway.

Do you see anything that I can change with this circuit?

I appreciate your help, and so does my nephew, who I am doing this for.

Jason

[Falcon69]

So, I modified the circuit I found, with some help, and this works, except for one problem.

I'm hoping someone can help me out on this one.  I'm stumped.

C1 (470uF capacitor) is there because the turn signals and hazards are connected to the vehicles turn signal switch, which flashes with the relay.  I have tried to find a direct connection with a continuous flow of 12 volts from the turn signal switch, and can't find one.  If I take out the flasher module, then the front lights on the truck do not flash.

So, C1 keeps power supplied during the 'OFF' times of the flashing, so it will keep Q1 turned on.

The problem I have is that when the turn signal is turned off, the LED's still flash for a few seconds and dims to nothing while the Capacitor discharges, and then finally turning off Q1. This poses a problem. When the brakes or park lamp are activated, they will not turn on Q4 or Q5 until the capacitor totally discharges and turns off Q1, allowing Q4 and Q5 to turn on (depending if brake or park lamp is activated).

Is there a way to fix this?  Anyway to discharge the cap quickly so the brakes will activate the LED lights?  This could cause on accident if there is a delay in the brake light turning on. I can't place a transistor in there, because it will just turn off and on as the lights flash.  I've tried change the values of R4 to 10k, 1k, and 100k. Anything larger than about 30k won't even turn on Q1.  This changes nothing, only makes LED's slightly brighter if anything.  I've tried changing the values of C1 to 4.7uF, 0.1uF, and 0.01uF and that really screws up the flashing of the LED's and I can't adjust the flashing sequence via R10.  So I'm stumped here, can't figure out how to fix this problem.

Also, one other thing, is a resistor needed between the collectors of Q4 and Q5 so that when the brakes are applied while the park lamp is on (the dimmed lights when headlights are turned on), the park lamps will turn off?  I'm just thinking if electrons take the path of least resistance, when Q4 turns on, the LED's would ground out through Q4 and not even go through Q5.  Or does this not even matter, since the LED's are the same LED's for both operations (no separate LED's).  I guess I could just simply move R8 to the collector side of Q5 to solve that problem, if there was one.

FYI, the circuit does work as intended, accept for the problem explained above which I beleive is in part because of C1 capacitor.  Other then a couple relays to change the polarity of the input connections, the circuit works fine, so I'd rather not mess with too much if it is not needed to fix the capacitor problem.

I appreciate your help with the capacitor problem.  Thanks in advance.

Jason

[nuno]

I don't know about the capacitor (I guess you would have to go get a turn signal control signal instead of just looking at the flashy signal, it's the only way to know if the turn signal is commanded on or off), but I think you have quite some simplistic "power supply" (and no fuse). The electrical environment on a car is noisy and spiky. With the engine on you have some 14.5V, and there are 2 versions of the CD4017 (and of the 4000 series CMOS chips in general), one that takes up to 12V and another that takes up to 15V. But even using the one up to 15V it's a very small margin and there are the spikes from other stuff connected to the 12V system. I have nothing more specific than a googled example of input power conditioning:
http://electronics.stackexchange.com/questions/76588/automotive-power-filtering-protection-feedback-needed

[Falcon69]

Yes, I checked the data sheet.

The 555 accepts up to 16 volts, as well as the 4017

The final circuit that will be in the truck permanently will have a 2 amp fuse.  I checked online and each of the 6 lights draw 243mA each.  So, a 2 amp fuse should be good.  I will also be putting in a 7812 regulator as well.

I may have found a fix for the flashing of the LED's after the turn signal is turned off.  I am trying to make a Missing Pulse Detector circuit work for the input of the turn signals.  That circuit uses another 555 and turns the pulse signal of the flashers into a continuous 12 volts. 

Jason

[Falcon69]

I tried to use a missing pulse detector circuit.  I tried to use several different kinds.

I can't make them work.

I have a truck that I need to change the flashing of the turn signals/hazard lights into a solid continuous 12 volts.  Not a flashing or pulsing. I have located the wires in the steering column that are connected to the switch.  I was hoping they were a solid 12 volts, then switched at a relay, but they don't. The switch connection also flashes.  I need to change that into a solid 12 volts and will need to switch on and off quickly for braking.



Anyone have any ideas?  I'm stumped, been working on it for about 30 hours (2 days combined).

[rs20]

It's very scary how you've got all these power transistors doing the logic work as well. This approach seems inadvisable (see below), but there are several specific problems with your circuit that jump out at me:
 -- There's no resistor between Q2's base and pin 7 of the CD4017 (which can be ground). See the little arrow in a transistor? There really is a diode there. This means a huge current will rush through Q2.
 -- Again, there's no resistor on the base of Q3. This means capacitor C1 will get very quickly discharged by Q3. This is why the capacitor isn't succeeding at keeping that signal high for a decent while.

(There may be more issues, but I don't think addressing them is the answer.) Another reason doing your logic in the power side is bad is because so much voltage is getting burned off by all these transistors. Looking at D6, current flowing through it has to go through Q2, D2, and Q4 just to get out. That's over a volt lost right there, assuming the transistors are biased correctly. You may well eventually succeed at this approach, but it's more difficult and you don't gain much.

I'd advocate using logic gates or transistors* (with the CD4017 and brake/park signals etc as inputs) to decide when the LEDs should be on, and then just having a simple, single transistor per LED to do the high power work. Much more neatly compartmentalised, much much easier to debug. Pic attached.

   * Even thyristors???

PS/  One other thing -- just like the way that the voltage supply is normally positive and at the top, and ground is at the bottom (you got these things spot on), schematics are generally laid out (where possible) such that "data" or "control" flows from left to right -- so the way that the 555 timer drives the CD4017 to its left, which in turn drives the transistors to its left, is a bit confusing. Just a stylistic thing.

[Falcon69]

Thank You rs20.

I will make those changes.

The SCR's are there so that the lights flash the way i want them too.  From my understanding, if they are not there, then one LED will light, turn off, move to next LED, turn off, etc.

I dont want that. I want them to turn on one by one, and NOT turn off until they've reached the end of the cycle, then all reset and repeat. Just like the new Mustangs.

Each LED will be on it's own transistor, I just have not drawn them in because that's not going to be on the circuit, but rather at the LED itself on the other end of the truck.

That 470uF capacitor is not working. It keeps the lights flashing until they dim to nothing when the turn signals are turned off. When brakes are applied, they won't stop the flashing and Light up solid until that cap has drained.  So the cap is working, as far as simulating a solid steady voltage from the flashing relay of the truck.  But, it isn't discharging fast enough.  Any cap value lower, and the flashing is just weird and is outside the adjust-ability of the Pot at pin 7 of 555. Any cap value higher, and well, the lights just flash even longer.  This could be dangerous having a delay in the lighting of the braking of the truck. Could cause accidents from behind.

So I need some help on trying to figure out how to change the flashing pulse from the turn signals themselves, into a solid steady voltage before it gets to the rest of the circuit.

Thanks in advance for your help.

Jason

[Falcon69]

I was doing alittle more research.

I found this schematic using and LM331.  A spendy little chip though compared to the 555.

Do you think this would get the job done?

I am not sure on f_IN. From what I was reading on the internet, vehicle light flashing is anywhere from 1Hz-4Hz, anything higher (or faster rate) could cause seizures to some people who have those conditions. I don't have the equipment to test what rate the truck is producing.

So, on this circuit, could I place a Pot in there somewhere to adjust that so the circuit matches the frequency of the flasher IN?

Also, this is a new one for me. What is that 5k resistor (R_S) with that arrow through it.  Is that another way of drawing a potentiometer?

[rs20]

That's a perfectly legitimate application of an SCR, but I think in this case it'd be more common to use SR flip flops. An SR flip flop is a device with two inputs: S and R. There's also one output called Q (there's almost always a complementary inverse-of-Q output as well). If S goes high, Q gets Set high. If R goes high, Q gets Reset low. If both R and S are low, Q remembers its previous state.  So wire S to the output of the 4017 that decides when it should turn on, R to whatever signal should cut it off, and wire Q directly to a simple, single transistor for each LED. Bonus: if you're using NAND gates for anything, you can make an SR flip flop from just two NAND gates (see google image search for "SR flip flop" to see how, beware though: the NAND variant of the circuit takes active low inputs, so Q gets set when S goes low, etc.)

Alternatively, perhaps you don't need a stateful (the behaviour of a thyristor and an SR flip flop depends not only on current inputs to the device, but its history, so it's said to be "stateful" or it "maintains state") solution. Can't you just say that led 3 is on if output 3 of the 4017 is on, led 2 is on if output 3 OR 2 is on, and led 1 is on if output 1 OR 2 OR 3 is on? This is just a couple (yes 2, not 3) OR gates, but I'm not sure if it's exactly the behaviour your after -- not sure if you want Leds 2 and 3 stay on even as 4017 continuously loops around.

I don't see brake lights as an output to your circuit, how is your circuit having any influence on brake lights? I feel like you should leave your brake wiring untouched, and just tap off a signal as a high-impedance logic input. I don't think LM331 is the right choice. An RC circuit like in my diagram, or a 555 in monostable single-shot mode, will both work just fine. Whether your subsequent logic a) is not interfering like Q3 is and b) is correctly making use of those signals is another question. Looking at your circuit, you have 470 microfarads with a 22 kilohm resistor taking it down, which works out as a time constant of over ten seconds (google calculation), so it will think the turn indicator is still on for 10-20 seconds after it's been turned off. A time constant of 0.25 to 2 seconds or so seems more appropriate.

If you switch over to using separate logic and power sections, you'll be able to ask much better questions -- "the turn signal is turned off, yet the very next NAND gate is outputting as if it's still on", instead of "my brake lights aren't coming on". Much easier for us to diagnose, much easier for you to understand and diagnose yourself too! Stick a little LED somewhere in the circuit (but not on the RC circuit itself because that'll spoil it) that indicates whether the turn signal is active or not -- that way you can debug that issue in isolation.

Yes, that resistor with an arrow through it is a variable resistor. Technically it's only called a potentiometer if it has three terminals. If you short together the middle pin with one of the outer pins of a potentiometer, you end up with a two-terminal device called a variable resistor and it has that symbol you see.

[Falcon69]

thank you rs20

good ideal on the led's to indicate which switch is on.  I will do that.

So shorting pin 2 with 1 or 3 on a three terminal potentiometer makes it a variable resistor and no longer a potentiometer. Thank you, that makes sense to me. Flip Flops Are one device I have yet to play around with. I will need to research into them and figure out how they work.  But sounds like a good idea.

On another note, I found out why I have been having so much problems with the circuit, and I think today I figured it out. Tomorrow I will finish the entire breadboarding and wire it up to the truck and see how it works.

The Problem I found today, and think I have fixed, is that when the left (or right) turn signal is on, the wire I have tapped into at the switch itself, pulses as the relay pulses, and then onto the lights to make them flash. Then I realized that when I then turn on the Hazard switch, the frequency of the pulses of the turn signal also changes.  And that is where the big problem is.  That Hazard flashing relay somehow is feeding through the turn signal flashing relay. The left (or right) turn signal and the Hazard switch use the same wire.  So, this is another problem I seem to have run into today when trying to make the Missing Pulse Detector circuit work. I get the pulse of the turn signals working just fine, spitting out a steady 12 volts, but, then I turn on hazards, and no more steady 12 volts, and vice versa.

But, I believe I have made it work today; after many hours of trial and error with resistor/capacitor changes.  I will test it on the breadboard tomorrow.  I hope it works.

And you mentioned the operation of the lights, this is how I want them to operate when the hazards or turn signals are on:

Flash - LED1 ON
         - LED2 OFF
         - LED3 OFF
Flash - LED1 ON
         - LED2 ON
         - LED3 OFF
Flash - LED1 ON
         - LED2 ON
         - LED3 ON
Flash - Resets the cycle.


Today, I had my nephew placing the jumpers and components on the breadboard.  So a 1 hour job turned into like a 4 hour job.  I was teaching him how to read the schematic and how to place the jumpers.  He was having fun and getting excited about how things worked. I don't think he exactly understood about the part where I was making him highlight the traces on the schematic as he was placing the parts.  Maybe I should have let him get an hour into the project first, and watched his frustration as he was trying to remember which parts he placed and where. Then, just maybe, he'd understand the importance of it.  LOL

I hope this thing works tomorrow.  If it does, I'll post up the schematic that worked for me, maybe it can help others, or maybe with help, can implement changes to make it less power drain.  I haven't quite got into working with logic gates or flip flops, but I'm learning.

Jason

[Falcon69]

SO, I couldn't get the Missing Pulse Detector working, SO I am tryin a new approach.  It seems that when I set the resistor/capacitor to work with the turn signals, it is fine, but when the Hazards are turned on, it goes all screwy again.  It seems that the Turn Signal and Hazard flash (pulse) at a different rate on his truck.  So I can't get it tuned correctly.

So, I am trying to use a relay to do it. 

Here is the new schematic, but I am having trouble.  Doesn't seem as if the transistors are all turning on correctly.

Ultimately, what I am trying to do with the relays is, the bottom relay takes the signal from the turn signals and hazards and turns it into a steady pulse. The 1000uF capacitor keeps the current flowing to keep the relay on.  However, at this time, I only had two 100uf Capacitors to work with and placing them in parallel is not enough to keep the relay active.  So I'm hoping the 1000uF is enough.  Also, when the relay is off, it activates the transistors for the brake/park to allow them to turn on.  I don't want the brake and park to go on while the flashers are on. The top relay is to deactivate the park lamp when the brakes are applied. No sense in having both on at same time, wasting current or supplying too much current to the LED's.

I know there are lots of transistors here, but I think if I have dawn it right, they all serve their purpose.

It was suggested to change the schematic to allow the transistors to turn on correctly.  That is the second schematic I have drawn up.  one single 10k resistor to turn on all transistors when the bases are tied together did not provide enough current to do so.  The consensus was to divide the 10k into how many resistors (10k resistor divided by 4 transistors = 2.5k resistor) and use a 2.5k resistor, which should allow enough current to each transistor to turn on. It was also suggested that placing a 10k resistor at each transistors base was probably a better idea.

Will the second schematic work properly?  I can hear the relays switch, but I get no LED's turning on (or sequencing) except for the first LED going into the bottom relay.

Thanks in advance for your input.
Jason

EDIT:  I know that everything from the SCRs to the right work correctly, as in the previous circuits, the sequencing of LED's worked as intended.  I just changed everything before that in these next two schematics.

[Falcon69]

Oh, I also have a question.

The Diode between pins 86 and 85 on the relays.  I understand that is needed to prevent flyback when the switch is turned off.  My question is, what amp/volt rating do those need to be?  Right now, I have them at 400v 3A.  I think that is overkill, and they are awfully large to place on the PCB.

[idpromnut]

I may have missed this piece of info, but does your circuit have access to a steady 12v other than the turning flasher?

[Falcon69]

yes, it is connected to the battery of the truck. Steady voltage.  I think with the engine running, it puts out 12.8 volts and could go up to 14.4volts.

But, the switch for the turn signals puts out a pulse of 12 volts. The wires to and from the turning switch all pulse. The flashing relay is the culprit.  I can't disconnect that, otherwise the front blinkers won't flash, unless I do a separate circuit for that, which I am trying to avoid.

[rs20]

The RC/555 monostable circuit will work, it's much easier to debug that than going down any other path. It does not need to be tuned precisely; it takes pulse gaps of any length and shorter and fills them in. So if you're trying to catch two different pulse trains with difference frequencies, "tune" it to the slower one, and you get the faster one for free. You should develop the RC circuit as a *separate* block, get it working perfectly, and then it's a black box you can trust -- or if it does fail, you know it's the surrounding circuitry that breaking it. Logic gates take away this concern about breaking other parts of the circuit because they have a huge input impedance (i.e., they claim tiny amounts of current) and can drive their outputs quite strongly. This is in contrast to BJTs, which provide output current in proportion to their base current, which makes biasing them to be strong enough to drive their output without breaking their input a non-trivial task.

I don't understand what the relay is supposed to be achieving here. Relay coils have low resistance, the coil of the relay is going to drain that capacitor in a fraction of a second, relay coils are not high-impedance devices. Use a high value resistor and a logic buffer that doesn't drain the capacitor (i.e., NOT a BJT), and hey look we're back to the RC circuit.

How are the turn signals and hazard signals just coming in through the same wire? Have you just shorted them together??

You're switching the ground of the CD4017!? Run! Run away!

At the risk of sounding like a broken record, this circuit is about 3 times more complicated now than it would be with clearly separated logic and LED drive sections. If you can get it to work like this, I take my hat off to you.

[Falcon69]

rs20

I've tried using a logic circuit with another circuit i am working on for a different purpose.  I can't get it working. Simulation shows it works, but when breadboarding, it does not. So I don't know how to work with logic gates either.

The problem with 'tuning' the 555 to work with the slower pulse is that pulse works fine (i.e. the Hazards), but when I turn the blinker on and off, then it stays on too long afterwards and there is a delay in the brakes when applied. That's dangerous.

I don't understand half of what is being said here I guess. I'm more of a visual person, if I can see it drawn, or see it work in a video, then I can understand for the most part.  I try to understand. I've spent over 2 weeks trying to make this circuit work. Been spending every waking moment trying to research and look for stuff on the net to help me understand.

Even if I could get logic gates to work, I still have to deal with the problem of the flashers.

Yes, it is one wire. Flip the switch for the left turn signal, you get a pulse through the wire that is tapped into at the switch. You flip on the hazards (whether turn signal switch is on or off, doesn't matter), you get a different pulse through that same wire, only difference is, now you get that pulse through TWO wires, the left and right turn signal switch.

So the only wires connected to the collector of the transistor should be the cathodes of the SCRs? The grounds for the 4017, 555, caps, etc. should be grounded normally?

[idpromnut]

The engineer in me says that it is time to step back and start at the beginning. Re-write your goals/requirements, draw up a thorough wiring diagram of the original truck's circuits, measure voltages to ensure you know what is connected to where and put it on the diagram. Measure any signals that you will need, such as the flashers (both voltages and blinking frequencies).
After this, then you can both post that info here to help us get a better understanding of the original system and you can start designing a block diagram of the circuit that you will need to get the turn signal effect you are looking for.

[rs20]

I must confess that I don't know what precise behaviour you've been wanting (although I'm 100% sure that every comment I've made is correct regardless of the details I haven't understood). If you want the brake light to always take precedence (a concept I heartily encourage), then you should make the logic consider the state of the brake light as more important than the turn signal/hazard light. What you want to happen when the turn signals AND brakes are on at the same time is an explicitly decision you make as a circuit designer, not something that falls out from the design that you have to live with and work around. The first step is to draw up a logic table (it's not as hard as it sounds) which describes how the LEDs respond to the various inputs, and which inputs take precedence over other inputs. For example,


        INPUTS                       |     OUTPUTS
Brake   Park     Hazard/Turn Signal  |      LEDs
--------------------------------------------------------------------
 On       X             X            |      Off
 Off     On             X            |      Off
 Off     Off         Flashing        |      Off
 Off     Off           Off           |   Cycling as described

( X means "Don't care")


So, for instance, this means that if the brake is on, the LEDs should be off, regardless of what the hazard, turn or park signals are doing. If the brake is off, but the park signal is on, the LEDs should also be off. Etc etc. If you could please correct this table to accurately state your intentions, then it will certainly clarify things for me, and maybe allow me to recommend specific fixes for your circuit (or indeed, as idpromnut just posted, we can think about taking what you've learned and doing a quick do-over based on distinct blocks).

Also, please clarify that you are leaving the brake lights, turn lights, etc etc all plugged in, and that you are only adding wires to these lines to your circuit to control 3 additional LEDs that are completely separate from the traditional stop & turn lights you find on any car.

[Falcon69]

I am leaving the factory wiring in the truck for two reasons.

One: In case he puts the bed of the truck back on, he can simply just plug his factory lights back in.
Two: Messing with the factory wiring harness could mess up the front lights, as well as the hitch lights for towing.

I am only tapping into the factory harness to get the 12 volts from the switches themselves.

I use a Snap-On 12v test light. It plugs into the cigarette lighter of the truck.  It has two built in LED's, one is red, other is green.  When it senses ground, it changes to green only, power it changes to red.  Pretty simple.

The wire from the brake switch is putting out 12 volts, ± 1 volt. When it is off, there is no signal, it does not alternate back to ground. (my test light shows both red/green LED's on inside it, indicating as if the wire was never hooked up to ANYTHING.)

The wire from the Park Lamp is putting out 12 volts, ± 1 volt. When it is off, the test light changes to green, indicating it is to ground.

The wire from each turn signal is putting out 12 volts, ± 1 volt, however, it alternates from voltage to ground. I don't know the frequency of the pulse, but from what I've been reading, it is about 1.5 hz (90 flashes per minute). I do not have a scope to test that. When the switch is off, the test light shows the wire then goes to ground. When the hazards are turned on, both the left and right turn signal alternate from power to ground, however, it is at a slower frequency, maybe at 60 or 70 Hz.

Rs20, this is what I am after:


The table above is per side, left or right.  For instance, when the turn signal is on the left, and brake is applied, the right side will have the brake light, but the left side will be flashing.

The way I want the LED's to work when the turn signal/hazard is activated is like this:


I played around with this last night:


G1, G2, and G3 would be connected to the Anodes of the BT169's in the original circuit.

I would still need to figure out how to change the pulse into a steady for the Turn/Hazard.

This circuit would use one Inverter, two NOR gates, and one 3-input Nor Gate.

I would still need the 4017 and 555 and the BT169's to do the sequencing.

The 470 resistors would not be needed and the 1.2k need to be reduced, as the LED assemblies have them built in.  I just needed those values for the simulation using single LED's for the visual. So please disregard those.

Jason