# Double push OEM keyfob to activate trunk solenoid

#### Berszan Peter

Joined Feb 11, 2018
7
Hi, im new with IC project and a need some help
Im trying to make a circuit that mounts in the car and can activate a solenoid if remote button is pushed twice in short sequence.
The car has a negative -12v signal as a push the "open" button, the ideea is that at the first push a relay is opened and kept open by the frist 555 IC and at the second push the second 555 timer active the solenoid to open the trunk. I want to stick to OEM keyfob, trying to avoid multiple remote controls.
i made a circuit using 555 timer IC in falstad but i have some problems:
- can 555 timer switch the 12v needed for the solenoid?
- in the simulation i see a spike at the first push of the button, can it happen in real life?
- what kind of signal is needed for solenoid activation?
Cuircuit simulation http://tinyurl.com/y97bqmjp
If anyone have a simpler solution im happy to hear it

#### Dodgydave

Joined Jun 22, 2012
10,591
Why do you need to have two presses, will one not do the job?

#### Berszan Peter

Joined Feb 11, 2018
7
Not good one single press, i havem a car remote with 2 buttons OPEN / CLOSE
I dot want to pop the trunk everytime i open the car, so i need to interpret a sequence. single OPEN > door lock | double OPEN > trunk pop
Push Open > the car opens and if i want the trunk to open i push twice fast.
Only thing is that i wont be able to open the trunk without opening the doors, but this is not a problem.

#### dl324

Joined Mar 30, 2015
15,458
Are you really willing to hack your remote lock circuit to do this?

Your circuit will have to tap into the signals generated to activate the locks. Modifications could cause problems.

Is the feature you want a hidden feature? My car has software that lets me customize settings that aren't accessible from the usual controls. My radio has hidden features that let me change things like automatically changing the volume according to vehicle speed and controlling how much the volume changes.

#### Berszan Peter

Joined Feb 11, 2018
7
Are you really willing to hack your remote lock circuit to do this?

Your circuit will have to tap into the signals generated to activate the locks. Modifications could cause problems.

Is the feature you want a hidden feature? My car has software that lets me customize settings that aren't accessible from the usual controls. My radio has hidden features that let me change things like automatically changing the volume according to vehicle speed and controlling how much the volume changes.
Yes i will tap into it. It need to be a clean look.
No my feature is not hidden in any ways, I think you dont understand me, now to open the trunk i need to unlock the doors (1 step) and second step is to pull the handle to open it (2 step). The second step can be done by a solenoid, so i dont need to pull the handle with my hand.
The signal is -12V i found the cable responsible for the "UNLOCK" button and i need the circuit to activate the solenoid if i press the UNLOCK again. This i what i simulated in the link, but im not sure if it works in real life.

#### dl324

Joined Mar 30, 2015
15,458
No my feature is not hidden in any ways, I think you dont understand me, now to open the trunk i need to unlock the doors (1 step) and second step is to pull the handle to open it (2 step). The second step can be done by a solenoid, so i dont need to pull the handle with my hand.
When the car is unlocked, you can't open the trunk using the latch/button/whatever on the lid?

#### Berszan Peter

Joined Feb 11, 2018
7
I can like everybody, but i don`t want to do that I want to be able to do it from remote, in the future the latch/handle/button on the lid will disappear, and a solenoid will do the work. Yes this usually is activated from inside with a custom/hidden button, but in this case i cant open it from outside, this is why i need to create the second function.
In the video below is a guy that did it with LOCK-UNLOCK sequence, but if i lock it from mistake and than open the car the trunk will pop so i need UNLOCK-UNLOCK circuit.

#### philba

Joined Aug 17, 2017
959
To implement double click semantics, you will need some sort of timing mechanism to distinguish between two separate single clicks and a double click. How does your circuit see the fob button presses? assuming you have a way to do that, you will need a flipflop and a timer.

On power up, make sure flipflop is clear (reset)
If you see a press and flipflop is set, open trunk.
If you see a press and flipflop is not set, set flipflop.
If timer ends, reset flipflop.

Set up your timer for the max time between presses for a double press.

#### philba

Joined Aug 17, 2017
959
The solenoid for the trunk should have a driver somewhere in your car. You just need to find the signal that activates it and tap into it. Youi'll have to figure out what kind of a driver is needed for that (to drive the driver).

#### Berszan Peter

Joined Feb 11, 2018
7
To implement double click semantics, you will need some sort of timing mechanism to distinguish between two separate single clicks and a double click. How does your circuit see the fob button presses? assuming you have a way to do that, you will need a flipflop and a timer.

On power up, make sure flipflop is clear (reset)
If you see a press and flipflop is set, open trunk.
If you see a press and flipflop is not set, set flipflop.
If timer ends, reset flipflop.

Set up your timer for the max time between presses for a double press.
I used a timer to keep the first signal "live" and drive a relay that conects to the second timer IC
1 press the first one activates for ex. 2sec and if a second press happens the second timer IC is activated thru the relay. The second timer output will activate the solenoid driver.
Signal is -12V when button press, when release is 0V, this is the same in the circuit on link.

#### Berszan Peter

Joined Feb 11, 2018
7
In the graph look like is working okay, i have a problem with a 12v spike (marked yellow) at the first unlock push, and the spike is measured on the second IC output what seems impossible, at the first push the second IC trigger line is connected - no signal should flow thru it. When the second push happens the signal on the output is visible, not like the spike, the spike is my problem

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#### AnalogKid

Joined Aug 1, 2013
10,176

Press once and release
Circuit waits 1 second to see if there is going to be a 2nd press
If there is no second press, circuit unlocks doors, but not the trunk.
If there is a 2nd press within one second of the first press, circuit unlocks trunk, but not the doors.

Is this what you want?

ak

#### Berszan Peter

Joined Feb 11, 2018
7