Sequential brake light hardware ??

cordless · Joined: 12 Oct 2005 Posts: 29

I am wanting to add sequential brake lights to my 68 Camaro.

I have 2 12V inputs (right and left turn/brake signal). How would I connect them as inputs to a 2313?

Any help is appreciated!

On the code --

input right would do ...
input left would do ...
both inputs same time ...

Got that part, just need help on hardware inputs.

Thanks!!!!

(BASCOM-AVR version : 2.0.7.1 , Latest : 2.0.7.6 )

aphawk · Joined: 23 Jan 2010 Posts: 156 Location: Brazil

You must use two resistive divider. The voltage from car can be as high as 14 V , then you must calculate one divider to reduce from 14 volts to 5 volts. By example , use the values 12k and 22k for the divider. The 22k goes to to your signal from car, and the other pin goes to the 2313 input. And the 12k goes one pin to the 2313 input, and the other pin goes to ground.
This will maintain the 2313 input in safe. And only to have more assurance, please use one 100nF ceramic capacitor in parallel with the 12k resistor.

Excuse my bad english...

Paulo

cordless · Joined: 12 Oct 2005 Posts: 29

I was thinking of using the an opto-isolator but the divider is simpler.

Any ideas on the code?

I pretty much got the right and left turn signal but if brake is used, both input lines are used.

And the turn signals being used during braking? The turn signals only last about 1 sec. then off then on, etc.

How would I write the code?

aphawk · Joined: 23 Jan 2010 Posts: 156 Location: Brazil

I'm considering that you will use one more input : the brake signal !
Then will be 3 inputs, and the logic will be more simple.

If only right turn is on, you will initiate the sequential from right side only; if is the left turn on, will make the same only in the left side. But if the brake is on, you will initiate the two sides sequential at the same time, independent of the left or right turn signal.

Are this the work mode that you are thinking ? And how many lamps you will have in each side to make the sequential ?

Paulo

cordless · Joined: 12 Oct 2005 Posts: 29

Actually there are only two signals, right and left. Brake goes thru steering column and uses same turn signal wires. If brake is pressed, both signals stay on. With brake and one of the turn signal, the opposite side stays on while the other goes thru flasher and does it thing. There are 2 bulbs each side for the RS Camaro. Everything is old school mechanical on a 68.

Arera · Joined: 23 Sep 2007 Posts: 375 Location: Wuppertal, Germany

The voltage in a car is far from being clean! You will encounter noise and spikes of unpedictable shape an voltage. Recon 100V spikes at least. That means, a simple R-R divider is not an option. Also you need to take a lot of care to regulate and filter VCC for your micro.
I have no opportunity to draw a circuit right now, I just like to prevent you from making a PCB that misses parts you really need.
Just my quick idea for the inputs:
First a serial R of 1k, this one is important to keep energy from incoming spikes low.
Next a pull up or pull down R, depending on which level the input is pulled to when active.
Next two fast diodes. One from our signal to +12V, one to GND. Both in reverse direction, to drain energy from high or reversed input spikes. The diodes should have a low foreward voltage and should be able to survive 200V reverse voltage.
Next a z-Diode with voltage of about 80-90% of the micros VCC, GND-bound.
A 100nF in parallel to the Z-Diode could do no harm.

IMO an opto coupler is of no use, as the supply on the Led-side is still the same as on the load-side. So what shoul it seperate? And the input of the opto needs protection as well.

This are my late-night-thoughts, take them as ideas to think about yourself. But definetly you need to think further than a simple V-divider.

Marc

Deanus · Joined: 26 May 2006 Posts: 188 Location: Adelaide

I agree with Arera,
and I would go even further, as to put 78L05 regulators on each of the inputs.
This guarantees that the voltage getting to the 2313 input IS the correct voltage.
I always use this for inputs where the source voltage can change wildly.

Regards

Deanus

Paulvk · Joined: 28 Jul 2006 Posts: 1197 Location: SYDNEY

I would use opto-couplers but would not use a common ground I would run through one or two diodes the power to the lamps thus generating a constant voltage for the opto-couplers and supply the micro with power and ground of its own. I have used this to sense power in many circuits through the years and have had nun fail. It does mean you need to run two light duty wires to each LED of the opto-couplers from each diode but the diodes can just be spliced into the car wiring then have heat shrink over them, 3 amp diodes are cheap enough.

Regards Paul

Evert :-) · Joined: 18 Feb 2005 Posts: 2114

Paulvk · Joined: 28 Jul 2006 Posts: 1197 Location: SYDNEY

I forgot to mention the other reason I used the diodes was to let me know when no current was flowing which means a blown bulb.

Regards Paul

aphawk · Joined: 23 Jan 2010 Posts: 156 Location: Brazil

People, see this AN from ATMEL :

http://www.atmel.com/images/doc2508.pdf

Why you are worried with 100 volts spikes ???? I have seen this kind of circuit conected with 220V from many and many years, and works perfectly. If Atmel recomends this usage in your own AN, there must be a reason for that ! The reason is that input protection is implemented in the AVR line.

Atmel uses only a resistor to limit the current in inputs. And in page 7 they told that we must only observes that the maximum current flowing in the clamp diodes can't pass 1 mA ....

From datasheet you can see that the AVR line has input protection. Sure, we can help to better this protection, because with this high impedance any noise can be induced and can make false level change. This is resolved lowering the input impedance with one resistor to ground.

I have used this method in my motorcycle, an Yamaha Dragstar, from more than one year. And every day I use whitout any problem.

There is no reason for use optocouplers, or 78L05, or zeners, or fast diodes. Only a resistor. I put one small capacitor too to resolve interference problem with my alarm, that uses RF and is very close to my circuit. This can happens in the car too.

Excuse my bad English.

Paulo

Matrixx · Joined: 30 Nov 2005 Posts: 158

I agree with aphawk, there is no need of optocouplers and 7805's in the inputs.

A couple of simple resistor dividers and a small ceramic capacitors 0.1 is what you need.
I have a ciruits working like this for years.