Turning a single relay into a sequenced one?

[barjebus]

I'm very new to electronics and recently have been wiring up remote car starters to GSM modules.

My current problem is likely very basic to all you experts The GSM module I have has 7 relays, one of which is activated by a phone call, the rest by text message.

My remote car starter key fob must do the following for the vehicle to start:

-Press lock button
-Release lock button
-Press car start button
-Release car start button

The problem is I only have one programmable relay at my disposal when it comes to phoning the device. The only control I have over it is how long the relay is opened for. Is there a way I could make it perform that sequence of events through only one phone call to my device?

My first thought was to use a capacitor to delay the car start button from activating, but then how would I turn off the flow to the lock button? Any advice or thoughts would help greatly!

 

[MikeMl]

You need a sequencer which can be built using some CMOS logic, or a cascade of 555 timers. You can use the relay output to control the lock button directly, and then that would be followed by two delays, one before the start button, and the second for the duration of the start button.

 

[barjebus]

Thanks Mike! I'll start looking into that. Does such a thing like this come built and ready to go or does it take some assembly/programming?

 

[MikeMl]

Peruse "Time Delay Relay" on DigiKey or Mouser. These are usually quite spendy, or you can do it yourself for $5 worth of parts.

How are the existing buttons wired? Does the relay closure connect to ground, or to 12V?

 

[barjebus]

The two contacts for the battery are wired into the 12 V cigarette lighter supply that powers the GSM device. Then the two contacts for the push button are connected to the relay. Here is a hi-res overhead shot:

**broken link removed**

Thats my starter, but the one for my friend will require two buttons to be wired up to the sequencer or 555 timers.