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Help with a flip-flop circuit

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holabr

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I have an aftermarket remote start module in my car that has its own remote. The unit also has a test lead that will start the car when it is grounded momentarily. Since my car has an OEM remote to lock and unlock the doors built into the key, I would like to build a simple circuit possibly using CD4013 flip-flops to use a combination of lock and unlock pulses (like lock-lock-unlock-lock)within a set period of time to close a relay to ground the test wire. I would pick up the pulses from the 12volt lines going to the door lock solenoid in the drivers door. Logically, when the first lock pulse comes in, it would trigger the first flip-flop and start a timer. If the following pulses arrive within the time period in the proper order, the relay would energize. If not, the circuit would reset and wait for the next lock pulse. I found the attached schematic as a starting point but it does not allow using the same input pulse more than once. Any ideas? Is there another IC that steps the output to a different pin with every pulse of an input? That way the first "lock" pulse would look like SW2, the next like SW3 and the third like SW9.

 

HTA

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Hi,

I think you could change each level to multiple stages by adding more flipflops. E.g. if you have two 4013's in the first stage you have to press key two twice to pass on a "One" to the next stage. The circuit function is straight forward by passing a "One" to the next stage. The coding of the active keys/switches is just the wiring to Reset or a clock for the flipflop.
 

holabr

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I've been modeling a revised circuit and came up with the attached. It doesn't guarantee the exact combination (lock-lock-unlock-lock) but it does force two locks only before the unlock. I am still having a problem with the auto-reset after the solenoid is activated. According to the original lock circuit, the R12/C2 timer circuit is supposed to reset the lock through diode D1. If I close SW4, the circuit doesn't work at all. If I leave it open, the circuit works but does not auto-reset. Any ideas?

Also, what would be the easiest and/or best way to put a timer on the overall circuit that would require the proper input (lock-lock-unlock-lock) within 5 seconds or the circuit resets?

 

chuckey

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Going back to your first circuit, if you interpose gates in series with all the switch contacts, then after the first flip-flop has toggled it opens the gate to let the next input pulse to go to flip-flop2. The gate on the first flip-flop has to be arranged that it closes when any of the other flip-flops has triggered. Sort of steering the input pulse to the correct flip-flop.
Frank
 

holabr

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I've gone back to the original circuit to try and model it. I've attached an image of the modeled circuit however when I power it up, the solenoid immediately activates and the reset does nothing to change the state. Am I doing something wrong or am I missing something that I wired incorrectly? I'm really concentrating on getting the auto reset to work before I move on to changing the circuit to meet my original design criteria. I'm not very skilled in electronic circuit design but am trying to learn. Any help and direction is greatly appreciated.

 

HTA

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Hi,

According to the truth table of the 4013, the output Q will be low when Reset and Set is at a low level on Power-up. Then the relay is on and the voltage will charge C2 to generate a High on Set of the 4013's. This gives a Q=High on IC3a and turns off Q1.
The Reset buttom should work if the wiring is correct and the ICs are not damaged.

Have you build it in hardware or made a simulation? Maybe you can measure the level on Q of IC3a and recheck all wiring to it stays Low.

Good luck.
 

holabr

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I've been doing this all in simulation. The image is directly from the simulator software.
 

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