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556 Question for GSM Car Starter

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barjebus

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So I've only really gotten into actual breadboarding, etc. in the last two weeks so I'm an absolute noob when it comes to this kind of thing, so please forgive my ignorance, and be clear with any advice you've got handy!! Here goes...

Building a GSM remote car starter for someone. The key fob for the remote starter has a lock button and a start button. The lock button must be pressed for 1 second (approximate) and then released for one second. After these two seconds have passed, the start button must be pressed for 4 seconds.

I at first was going to use two 555 timers and then instead began playing around with a 556 timer. My first thought was to just use both timers as astable, but the problem is that both go high as soon as current is applied, and then go low. I needed to delay the second timer by those two seconds before going high for 4 seconds.

So then I thought perhaps a monostable one shot timer on one side (go for one second) which would be connected to the second timers trigger pin such that when it goes low, the second timer would then be activated high. However, it seems that monostable timers seem to require a switch be pressed to flip its state, so I'm not sure how I could make that happen.

The entire setup would have a programmable window of time, say 6 seconds, so its not imperative that both timers turn themselves off etc. as power will be lost after whatever time works best. I have a 556 on my hands and two 555's available at the moment, but if needed I can purchase whatever components you guys recommend.

Anyways, any information or ideas would help this very new, aspiring young person to pursuing more projects in electronics!
 
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You really should have kept this to one thread........

Are you actually using GSM? Most remote car lock / unlock devices are direct RF so that the key fob transmits directly to the car.

GSM phones can only communicate with the cellular system, they cannot talk directly to each other. I you phone or text someone who is close to you, the data still has to go via the cell towers, and you still have to pay.

If you are using RF, with a simple transmitter in the key fob and a simple receiver in the car, then you should be looking at security. I suppose if you are making a one-off, nobody will bother hacking it.

OK, so assuming that you are connecting by GSM, you should put all thoughts of using a 556 out of your head. You need a programable device, like a microcontroller, to handle all that is needed for the GSM communication, and that can do all the timing that you need.

If you are wanting to make this sort of device commercially, I might be able to help as I have made vehicle tracking devices that also have remote outputs.
 
Sorry, let me clarify.

The car starter device is RF, as you said, but I've got a GSM relay device that opens and closes relays based on either a phone call or text message for a programmable length of time.

The GSM relay is connected to one of the RF key fobs that you have on your key chain. When I call or text the device, it opens the relay allowing power to complete the connection on one or more of the buttons on the key fob.

The problem is that for this car starter, it requires a sequence (1 second on the lock button, then 1 second of nothing, then 4 seconds on the start button). I just need something to create that sequence once the relay is opened. Should I be looking at something programmable? If I got rid of that 1 second gap, would I still be able to do it with a single 556 do you think?

Thanks for your reply!
 
Ok, so the only reason that the starter device is RF rather than wired directly is that you are using something that comes with the car anyhow?

Leaving a car unattended on the public roads with the engine running is against the law here, I think, so cars don't come equipped like that in the UK. The key fob unlocks the car, opens the boot or windows and moves the seats etc, depending on the model of car and the whim of the designers.

I think that you want something programable anyhow. You need 3 timers, and it could be done with a few 555s, but it very soon starts to get complicated, difficult to get the timing right, and unreliable.
 
Interesting, I had no idea it was illegal to leave a running car on the road in the U.K.

I'm from Canada and I'd say that at least %60 of the vehicles here have remote starters.

I do plan to buy a few car starters sometime soon and crack open their brains to see if I can wire the GSM relay in directly, but in the mean time, some people who have car starters already would like theirs to be "upgraded" if you will such that they can start their vehicle from anywhere in the world due to the limitations of RF signals (buildings, distance, etc.).

If I was to go with something programmable, do you know of anything off the top of your head? Like I said, I'm rather new at hardware, but I do embedded software as my job so I should be up to the task of programming.
 
I was speaking with a friend today who mentioned a PIC might be the way to go? Does anyone know of a good two output PIC thats cheap and quite common?
 
I'm from Canada and I'd say that at least %60 of the vehicles here have remote starters.
I am also in Canada and my son is a car dealer in Canada. Only 2% of cars have remote starters. Most cars are started with the key inside the car. Maybe you are near the North Pole where it is extremely cold all the time.
 
I live in Saskatchewan, so maybe we just like warm cars I guess.

Regardless, is a PIC the solution to my problem? Does anyone have recommendations as to a certain model, etc.?
 
I've got a GSM relay device that opens and closes relays based on either a phone call or text message for a programmable length of time
Why cant you wire the relays to the key fob switchs and use the GSM relay timing? Andy
 
The remote starter that I'm working on requires that the lock button be pressed for one second, released for one second, and then the start button pressed for 4 seconds unfortunately. Most other car starters that I've done can be done the way you suggest (just wiring the start button to the GSM relay).
 
So let me understand. You want to generate the sequence lock on 1 sec. lock off 1 sec. start on 4 sec. Then something else recognizes the sequence and starts the car? Not to hard if that's it. Just low power outputs? No relays?
What is GSM?
 
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