Hey,
I'm looking to build a device that will turn on LEDs if my car reaches particular G-force rating. I will have connected an arduino Uno, some LEDs (6) and a 3-way Accelerometer. I was hoping this would be battery powered but I can't see this lasting more than a few days. I want it to be low maintenance (no on/off switch) and have the battery last as long as possible.
What can I do to the device that will increase the battery life? Any advice would help.
Thanks
Assuming the device is located in/on your car, why not use the 12v car power available in the power port (what used to be called a cigarette lighter) instead of a battery? You will need to have a good voltage regulator (better than the normal Arduino, since car voltage can spike somewhat higher than 12v).
I was hoping to go for a more of a quick and easy DIY job, I was going to give there to other people and was hoping to make it easy for a lay-man to install and forget.
It will be externally mounted on the rear of the car. Any ideas? what about solar charging?
Deriving power from the on-board battery would have to be the smartest and simplest part of your project. Indeed somewhat smarter and simpler than a solar device, which would likely require a voltage regulator anyway - quite likely the same regulator.
Nick_Pyner:
Deriving power from the on-board battery would have to be the smartest and simplest part of your project. Indeed somewhat smarter and simpler than a solar device, which would likely require a voltage regulator anyway - quite likely the same regulator.
By "on-board" are you referring to the car's battery? as I said it will be mounted at the back of the car. Which is difficult for a lay-person to run power to from the car's battery source.
If you mean the battery included in the device? then from what I can tell, the device would run for a day before it does flat. I'm looking for ~6 months etc.
HI, are you making a brake sensing device, the harder the braking the more LEDs come on.
Any reason why it has to be mounted externally.
Tom....... 
One of the instructors at the local TAFE College proposed and idea to the state motor vehicle dept, have the HI level Brake Lights flash when you apply the brake, the faster the flash the harder the braking. Went on deaf ears.
TomGeorge:
HI, are you making a brake sensing device, the harder the braking the more LEDs come on.
Any reason why it has to be mounted externally.Tom.......
One of the instructors at the local TAFE College proposed and idea to the state motor vehicle dept, have the HI level Brake Lights flash when you apply the brake, the faster the flash the harder the braking. Went on deaf ears.
Something very similar yes, but something individuals could install without an auto electrician, i.e no Electrical work needed to be done the car.
ricadam:
I want it to be low maintenance (no on/off switch) and have the battery last as long as possible.
What can I do to the device that will increase the battery life? Any advice would help.
Those two requirements are necessarily mutually exclusive.
Batteries means maintenance. Always. And daylight visibility means serious power use. So just forget the battery idea for a start.
ricadam:
Something very similar yes, but something individuals could install without an auto electrician, i.e no Electrical work needed to be done the car.
This means it runs from the "lighter" socket. Recent vehicles have more than one, including one in the rear tray or boot. Or you get an extension cable.
Actually, what you really want is something powered by the brake light. Now if a car has a towbar, you already have a socket with the brake light circuit connected.
TomGeorge:
One of the instructors at the local TAFE College proposed and idea to the state motor vehicle dept, have the HI level Brake Lights flash when you apply the brake, the faster the flash the harder the braking. Went on deaf ears.
Well, it would have been the (multi-)hundredth "inventor" of such - variations of this are in the project magazines such as Silicon Chip.
Now as to the "eye-level" brake lights themselves, there are a lot that are not actually at eye level. The problem with this idea in the first place is that people did "studies" showing that there were fewer (rear-end) accidents when cars were fitted with these lights. What is obviously wrong with that? Well, when you introduce something novel and some cars have them fitted and are unusual, that will increase their visibility. When however, all or just most cars have them, they lose the novelty and it is highly improbably that their presence makes any difference at all.
Relates to my favourite gripe about having headlights on in daylight. If many people practice this, it entirely loses the alert value for motorcycles and emergency services and becomes nothing more than a nuisance on roads with a centreline as it obscures the behaviour (such as overtaking) of cars following.
Paul__B:
Now as to the "eye-level" brake lights themselves, there are a lot that are not actually at eye level. The problem with this idea in the first place is that people did "studies" showing that there were fewer (rear-end) accidents when cars were fitted with these lights. What is obviously wrong with that? Well, when you introduce something novel and some cars have them fitted and are unusual, that will increase their visibility. When however, all or just most cars have them, they lose the novelty and it is highly improbably that their presence makes any difference at all.Relates to my favourite gripe about having headlights on in daylight. If many people practice this, it entirely loses the alert value for motorcycles and emergency services and becomes nothing more than a nuisance on roads with a centreline as it obscures the behaviour (such as overtaking) of cars following.
I can understand this statement, but I still see merit into such a device fitted onto a car. What I was thinking is having the light come on AFTER the normal break lights have already come on. Sort of like a secondary break light. This secondary light would cause a reaction in the driver behind because they were not expecting another light to come on and hopefully in turn cause them to become more aware of the situation.
I was thinking the secondary light would come on under heavy breaking load only (ie. greater than a specific g-fore threshold), so normal breaking would not trigger it. But say, a kid walks out onto the road causing someone to slam on the breaks would trigger the secondary lights. I was thinking of it flashing as well but it may be more of a distraction, I don't know.
Thanks for your input, I think I might need to look into powering the device from the car's power source instead of it being independently powered.
ricadam:
I was hoping to go for a more of a quick and easy DIY job, I was going to give there to other people and was hoping to make it easy for a lay-man to install and forget.It will be externally mounted on the rear of the car. Any ideas? what about solar charging?
Look at the third party backup monitor field that mounts a video camera on the back of the car, and many of these are meant for the end user to install. For example, here is one of the first links that were found by a google search: http://www.youtube.com/watch?v=BqbxyvP3u8A
MichaelMeissner:
Look at the third party backup monitor field that mounts a video camera on the back of the car, and many of these are meant for the end user to install.
Most of the "install" details - not surprisingly - being how to wire the reversing camera unit to the reversing light circuit of the car. The system - many of these are integrated into a GPS - switches into camera mode when the "wireless" camera is powered up by engaging reverse, and the monitor detects the presence of the wireless signal.
Which is of course, precisely what you would do in the system proposed, but connecting instead to the brake light.
The accelerometer can provoke the flashing to occur more rapidly and of course sooner on heavier braking. Essentially the delay before the first flash is the same as the delay between flashes and that is primarily what varies.
I'm surprised to know that the are spare connections in the break lights! is this normal?