led schematic help- auto motive

[ryan_larue]

so i am trying to build a set of front turn signals for the front of my car, and this is the sequence i would like to duplicate
YouTube - 79 - 81 TA Sequential LEDs Taillight Upgrade Kit

i figure it shouldnt be this difficult, but then again ive never done this before

this is the schematic i drew up
**broken link removed**

is this correct and will this work?
also, how would i make the 555 timer work with the CMOS 4017?

 

[Diver300]

The idea is OK. A 555 will drive a 4017 fine.

You need to connect the number 4 or 5 output of the 4017 to the reset line so that the off period isn't too long.

The transistors as shown will sink current so that the other side of the LEDs should be at +ve. Each LED needs a current limiter if it isn't built in.

If you want brakes lights as well you have a whole new level of complexity.

 

[magnatro]

this may work !


555 Timer Astable Multivibrator Circuit; Pulse Generator Circuit

 

[Diver300]

Don't put the LEDs in parallel. Use a separate resistor for each one.

 

[Dr_Doggy]

is that one single turn signal? What are you expecting your LED's to do?

 

[magnatro]

yes.. see the youtube video, he needs that kind of signaling.
turns ON
led bunch 1
led bunch 1,led bunch 2
led bunch 1,led bunch 2,led bunch 3

 

[ryan_larue]

Magnatro: that is exactly what i am looking for!

led bunch 1
led bunch 1,led bunch 2
led bunch 1,led bunch 2,led bunch 3

Diver300: this is only a rough schematic and i thought that would work but i wasn't sure, i am a total n00b on this stuff,
now, should i run a reset for the 555 as well?

oh and these will for the front of my car, so brake light circuit is needed

 

[magnatro]

now, should i run a reset for the 555 as well?

i think its not necessary

oh and these will for the front of my car, so brake light circuit is needed

its included, see the circuit diagram,(J1) the timing of the 555 is your choice

 

[ryan_larue]

ok

i ment to say its not needed, my bad

 

[magnatro]

simply remove the j1

 

[Dragon Tamer]

I would recommend that you double check that this isn't illegal in which ever state you live or commute to. In Pennsylvania, it isn't illegal, but it will get you stooped by the cops and you will be asked a lot of unnecessary and drawn out questions. Maybe put in a bypass so that you can turn it off if you need to.

 

[RMMM]

I would agree with a bypass.

If you do not use serious transient suppression for the circuit, you will kill the 555, 4017, and the LED.

When you turn your headlamps off, when your windshield wiper motor starts and stops, fan motor, etc.. You can get upwards of 70v on the system.
This is called a LOAD DUMP. The inductance in the alternator is still full of operating current when a device is switched off. The larger the load, the larger the dump.

TVS to ground at input buss for each "blinker". (Use automotive rated TVSs)

Take a look at what a standard automotive diode is rated at:
https://www.electro-tech-online.com/custompdfs/2010/12/Littelfuse_TVS-Diode_SLD.pdf
50,000W !! 76amps. 1 pS

Automotive environments are some of the hardest for a little IC.

ALSO, reverse battery protection. IF you have your hazard lights on, and give someone a jump start, a reversed battery connection can spell the end for your circuit.

These are some of the reasons that they are illegal in many many places.

If you get pulled over, or you loose a circuit, the ability to "reintroduce" the old bulb with a flick of a switch would be nice.

 

[Diver300]

When you turn your headlamps off, when your windshield wiper motor starts and stops, fan motor, etc.. You can get upwards of 70v on the system.
This is called a LOAD DUMP. The inductance in the alternator is still full of operating current when a device is switched off. The larger the load, the larger the dump.

You only get serious load dumps when the battery is missing, or is totally broken. When you turn off headlights or the heater or something, the alternator cannot respond quickly so the current that you have just stopped using ends up in the battery, for a second or so.

A battery that can hold more than 8 V when cranking the engine at 300 amps is only going to rise by 0.5 V or so when a 30 A surge is put into it.

You can also get short inductive spikes with the battery working fine, but they have a much shorter duration and a modest capacitor will absorb them.

However, none of that is a good reason not to have load dump protection. A load dump will almost certainly destroy 18 V rated ICs.

 

[Dragon Tamer]

The battery is acting as a giant capacitor. It would still be good to have a suppression circuit just in case, but it's not really needed if the battery works fine.

 

[RMMM]

Sorry, friend that is not exactly correct.

The BATTERY is supplying the current during cranking.. NOT the alternator. The BATTERY stabilizing is the cause for the change.

And a SECOND is a lifetime to an electronic component.

I dont know your definition of "serious load dumps" but even a load dump of 5 volts:

13.8 x .02 = 276ohms 13.8 volt average automotive operating voltage (ish)
18.8 / 278 = 68mA add 5 volt load dump giving 18.8 on the system

Gives your 20mA LED 68mA

at 45v load dump: 7.28A PER LED.

Load dumps NEED to be dealt with and designed into an automotive circuit.

There REALLY should not be any objection to this.

Would you have your family in a car with LED breaklights designed by a DIYer who never heard of load dumps? Or didn't think they would matter?

AND how many vehicles do you know of thats battery stays in perfect condition over the life of the car?

SO, there will be times when a LOW battery will help exacerbate even larger load dumps into the system. Do you agree with that?

 

[Dragon Tamer]

My Grand AM is about 10 years old now and the battery is still going strong (though it may have been replaced before I got the car). However, the battery is noticeably strained when certain electrical devices are used together. Such as the radio on any volume setting over 7 (splits ear drums though) the head lights, and the whippers.

 

[Diver300]

I dont know your definition of "serious load dumps" but even a load dump of 5 volts:

13.8 x .02 = 276ohms 13.8 volt average automotive operating voltage (ish)
18.8 / 278 = 68mA add 5 volt load dump giving 18.8 on the system

Gives your 20mA LED 68mA

at 45v load dump: 7.28A PER LED.

I don't follow your calculations.

If there are 4 LEDs in series in each string, that gives about 8 V across the LEDs.
That leaves (13.8 - 8) = 5.8 V across the resistor.
The resistor is chosen to give 20 mA, so it is 5.8 / 0.02 = 290 Ω

If the voltage rises to 18.8 V, there is 10.8 V across the resistor. The current is then
10.8 / 290 = 37 mA

Even at 45 V, the voltage across the resistor is 37 V and the current is 127 mA. That might well damage the LEDs and I agree that load dump protection is a good idea. Also voltage fluctuations will get worse as the battery ages.

However, the big load dumps that are over 30 V and over 500 ms can't happen if the battery is capable of cranking the engine. Alternators are current limited by the inductance of their windings, and putting 50 - 100 A into a car battery won't increase the voltage more than a couple of volts.

A big load dump happens when a battery is low, and is being charged by the alternator, and the battery becomes disconnected. Then the current that was charging the battery has nowhere to go and the voltage can be very large.

It is also impossible to test for load dump by using a car, because you are very likely to damage other components on the car.

 

[magnatro]

i have an LED flasher in my bike and it uses a 555 .. it works fine for 2 years and counting.. and my bike is yamaha fz that need to have that much initial transient current to start the bike and there have been no problem!