Delay between ignition and headlights coming on

Hey.

It's regulation to keep the headlights on AT ALL TIMES where I live. This is extremely draining on the battery during ignition, as the battery is just not designed to supply that kind of amperage.

What i'm trying to do is to make a circuit which delays the headlights coming on by maybe 10 to 12 seconds. As this is a real life application, even if any components fail, it should stay on.

Right. What i've currently brainstormed is to splice a SCR gate (Something like the NTE5461 - NTE5468?) along the power lines to the headlamps (12v, 5amps), then connect the gate to the output of a frequency divider. That SCR gate should stay open until crystal to generate a clock signal, then CD406 to divide the frequency to something more maneagble at 0.1 hz. Or one pulse per 10 seconds.

That should ensure the SCR gate stays closed, and the headlights stay on - but only when the clock pulses 10 seconds after ignition

Feasable? And keeping in mind that i'm a complete newbie - so i'm modifying circuits on the internet to suit my needs. Main questions I have is about the crystal - how do you connect it to the frequency divider? One line to 12 volts and one line to the clock input? And how fragile are crystals?

I would have used a 555 timer, but according to a post I read, that would be extremely innacurate. At the 20 second range, at least.

Thanks for the feedback in advance.

Zephyr said:

Hey.



I would have used a 555 timer, but according to a post I read, that would be extremely innacurate. At the 20 second range, at least.

Thanks for the feedback in advance.

Click to expand...

hi,
For this application ie: 10 to 12 seconds a 555 timer would be ok.
I guess you mean headlights ON when engine running.?

I assume you have the battery negative connected to the chassis and you plan to put a SCR in the high side of the headlamps.??

Precisely. Would that work?

Yeah, headlights must be on while the engine's running. We don't even have a switch to switch it off - which makes it extremely draining on the battery when the headlights are on and it tries to ignite the engine.

I have to replace the battery every year or so, which is annoying.

I'll look up the circuits for 555 timers and draw one up later, and you guys can poke me about missing components. Sound good?

**broken link removed**

Something like that, R1 being 10k, R2 being 20k, and the capacitor being 100microFarad. 14.5 second cycle time.

Regardless, two related question.

How should I start learning ICs? And RC circuits, while i'm at it. Messing around with a bread board?
And what program do you use to draw these circuits?

Zephyr said:

Precisely. Would that work?

Yeah, headlights must be on while the engine's running. We don't even have a switch to switch it off - which makes it extremely draining on the battery when the headlights are on and it tries to ignite the engine.

I have to replace the battery every year or so, which is annoying.

I'll look up the circuits for 555 timers and draw one up later, and you guys can poke me about missing components. Sound good?

Click to expand...

hi,
As the SCR is going to be in the high side of headlights supply ie: +12V I would suggest a opto-coupler from the timing circuit to the SCR Gate.

Its possible to get 10 to 12 seconds using other types of timers.

Are you located in Scandinavia .??

Scanda... Oh, you mean the regulations? Nah, nowhere close. Keep guessing.

But an optocoupler sounds good. Do I need to connect that to a power source, or does that run fine on it's own? From what I read on wiki, it just electrically isolates two things.

And, erm, that picture of the circuit up there would work, right? All I need is another SCR from the ignition lines to the 9v power line.


How reliable are SCRs anyway? At staying on above their holding current?

ericgibbs said:

hi,
For this application ie: 10 to 12 seconds a 555 timer would be ok.
I guess you mean headlights ON when engine running.?

I assume you have the battery negative connected to the chassis and you plan to put a SCR in the high side of the headlamps.??

Click to expand...

Hi Eric,

a 10-12 second delay between ignition on and headlights on doesn't necessarily mean the engine is running.

I'd go for sensing of engine rpm which is 700-900 rpm at engine idle. Sensing can be done using a reflective IR-sensor (CNY70) or a Hall-sensor (TLE4905L). Both can be interfaced with a missing pulse detector which puts out a "GO" for the headlights if engine rpm is attained.

This method won't require an scr and take care of 'headlights off' if the engine has stopped for reasons other than shutdown. (At engine shutdown the circuit should be deenergized as well.)

Regards

Hans

Hm.

If I remember correctly, it's when the engine is ignited. Regardless.

So once ignition goes, headlines go on. And stay on until you turn the key, regardless of whether you're moving or not.

Zephyr said:

Hm.

If I remember correctly, it's when the engine is ignited. Regardless.

So once ignition goes, headlines go on. And stay on until you turn the key, regardless of whether you're moving or not.

Click to expand...

hi Z,
The 555 circuit you have posted will not work as you expect.
I guess you know that the negative side of the headlamps is the chassis, so your SCR is in the positive 'high' side of the headlamps.
This means the SCR gate is on the 'high' side.

A simple way to over come this is to use a opto-isolator to trigger the gate.

On my truck the headlights are relay controlled and I believe here in the US many vehicles have the headlights running off a relay. You may want to take a good lookie at how the headlights are switched.

Something I have been giving thought to is in the US state I am in a new law was just passed that anytime the windshield wipers are in operation the headlights (all lights) must be on. I may start thinking about looking at how the wipers are configured to make something so anytime the wipers are on the lights relay is pulled in.

Anyway, before I went hacking into the headlight lines directly I would see if they are under a relay control and work from there.

Ron

Oh, have I put "Headlights" on the wrong end of the SCR?

Sorry. Of course, i've just contacted the shop I usually go to for my parts and they do have Optocouplers, so yes, I will be using that to protect my 555.

The Optocouplers need a power rail?

Edit: @Ron, Good idea. You mean to just to replace that relay with a delay-on relay or something?

Why not just sense the battery/alternator voltage? With vehicle parked, battery will be <12.6V. Key on, prior to start, it will drop lower. During cranking, it will go <11V. Only after engine is running at fast idle or faster will the battery voltage come up to >13.0V. During driving, the voltage will always be from 13.2V to 14.5V.

I own two vehicles (2004 and 2006) which have always on headlights. They both still have their original batteries, so I think you are solving a non-existant problem.

If your battery can't start the engine with the headlights on it's probably an indication you need to change your battery.

On my truck, '98 Silverado, the daytime running lights (DRL) can be shut off by simply applying the emergency brake enough to open the switch on the pedal. The wire going to that switch could be used for the delay circuit, see if yours works the same..

hi Z,
If you decide to go for IGN ON SW triggering the 10~12secs delay timer, this is a simple option using a res/cap charge circuit with a FET. Ref image.

If you went the relay route, the FET could be used to operate the relay.

I agree with the previous posters regarding the expected battery performance.

Indeed - except i'm changing my batteries yearly.

Eric, IGN ON SW? As in Ignition on switch?

And I was leaning away from a RC circuit because that Capacitor means an extra drain on the battery. Would that matter?

Ron, since I'm also in Ohio, would you please make a new post of your circuit when you make it? I was going to tap into the relay coils between the headlights and wipers(mine have relays for both). Putting a diode in the wire between the relays would keep the wipers from coming on with the lights. cary

PS, sorry to hijack thread!

Zephyr said:

Indeed - except i'm changing my batteries yearly...

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Then you have another problem, like a parasitic drain when the vehicle is parked, or a diode out of your alternator. My 2004 K1500 GMC Pickup is driven infrequently (once a week, on average) and still has the original battery. My 2006 Toyota is driven daily, and still has the original battery.

It sounds like the OP has an electrical problem or weak alternator and/or battery. Have you taken it to a local mechanic?

MikeMl said:

Then you have another problem, like a parasitic drain when the vehicle is parked, or a diode out of your alternator. My 2004 K1500 GMC Pickup is driven infrequently (once a week, on average) and still has the original battery. My 2006 Toyota is driven daily, and still has the original battery.

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Hi Mike,

I guess the ambient temperature has quite some influence on battery lifetime.

Back in Germany the batteries of my cars were still good after 5 to 6 years of use.

Here in Thailand where temperatures rise to >40deg/C the SLA batteries of my motorbyces are usually finished up within one year, meaning they don't have enough power to crank the starter.

When parked unprotected from the sun the temperature of the body rises to as much as 80deg/C (Oh, what a feeling when climbing the byce! )) - and with it also the battery temperature.

Cars usually have the same problem here, although my friends take good care of sufficient water/acid level.

That's probably the reason why batteries are so cheap here. An SLA battery 12V/7.5Ah is about US$10.

Boncuk

Boncuk, Our temps run 95 to 105degF (35 to 40degC) in the summer, so not that much cooler.