Fail safe control circuit for a vehicle barrier security system
A fail-safe circuitry for a vehicle barrier security system prevents accidental raising of the barrier due to inadvertent closing of an activation relay causing power to be provided to an activation mechanism raising the barrier. A latching relay, having a latched state and reset state, is placed in series between the activation relay and the activation mechanism. The latching relay is reset whenever the OPEN switch is pressed for lowering the barrier or an automatic reset relay is energized by a controller whenever passage of a vehicle is sensed. Prior to raising the barrier, the latching relay must be reset, which can occur by pressing the OPEN switch or by the controller detecting passage of a prior vehicle and activating a automatic reset relay. Accidental raising of the barrier due to malfunctions of the activation relay due to vibrations is prevented by latching and resetting the latching relay.
1. A vehicle barrier security system for controlling a barrier at a security checkpoint comprising:
a power source providing power;
a CLOSE switch connected to the power source and configured to provide power from the power source to raise the barrier when the CLOSE switch is activated;
a vehicle detection relay configured to receive the power from the CLOSE switch at a first contact of the vehicle detection relay and provide the power to a second contact of the vehicle detection relay when a vehicle is not detected at the checkpoint;
an actuation relay comprising an actuation relay coil, the actuation relay configured to receive the power from the second contact of the vehicle detection relay thereby energizing the actuation relay coil and providing the power from a first contact of the actuation relay to a second contact of the actuation relay;
a latching relay connected in series with the second contact of the actuation relay and configurable to be in a latched state or a reset state, wherein the latching relay is configured to receive the power from the second contact of the actuation relay at a first contact of the latching relay and provide the power from the first contact of the latching relay to a second contact of the latching relay when the latching relay is in the reset state;
an actuation mechanism electrically connected to the second contact of the latching relay and configured to raise the barrier when:
the actuation relay provides the power to the second contact of the actuation relay,
when the latching relay is in the reset state, and
when the power is provided from the first contact of the latching relay to the second contact of the latching relay thereby providing power to the actuation mechanism; and
an automatic reset relay configured to receive power at a first contact of the automatic reset relay and provide power to a second contact of the automatic reset relay when energized, thereby providing power to a reset coil of the latching relay and resetting the latching relay.
2. The system of claim 1 , wherein the vehicle detection relay is configured to provide the power to a latch coil of the latching relay to latch the relay when a vehicle is detected.
3. The system of claim 1 , further comprising an OPEN switch configured to provide power to the reset coil of the latching relay.
4. The system of claim 1 , wherein the automatic reset relay coil is energized in response to detecting passage of a vehicle past the security checkpoint.
5. The system of claim 1 , wherein the vehicle detection relay is configured to be in an open condition when the vehicle is detected at the checkpoint.
6. The system of claim 5 , wherein the barrier comprises a plurality of bollards.
7. The system of claim 1 , wherein detection of a vehicle uses a buried wire in a road to detect the presence of the vehicle on the road.
8. The system of claim 5 , wherein the vehicle detection relay comprises a double pole relay.
9. A system for avoiding inadvertent positioning of a barrier at a checkpoint in a vehicle barrier control system, comprising:
a power source;
an input switch configured to be activated by a user thereby generating a signal to raise the barrier;
an actuation mechanism configured to raise or lower the barrier, the actuation mechanism configured to raise the barrier when receiving power to raise the barrier;
a first vehicle sensor detecting the presence of a vehicle at a checkpoint;
a second vehicle sensor detecting the passage of the vehicle past the checkpoint;
a controller generating a second signal indicating the presence of the vehicle detected by the first vehicle sensor, the controller using the second vehicle sensor to generate a third signal indicating the passage of the vehicle;
a first switch in a normally closed state and configured to be opened when receiving the second signal indicating the presence of the vehicle;
a second switch in a normally opened state and configured to be closed when the input switch generates the signal to raise the barrier;
a latching switch having a reset state wherein the latching switch is closed, the latching switch also having a latched state wherein the latching switch is open,
wherein the input switch and the first switch are connected in series to provide the signal to the second switch, thereby providing power from the power source through both the second switch and the latching switch to the actuation mechanism to raise the barrier when:
the input switch generates the signal to raise the barrier,
there is no second signal indicating the presence of the vehicle detected by the vehicle sensor, and
the latching switch is reset; and
an automatic reset relay configured to receive the third signal from the controller and provide power to put the latching switch in a reset state.
10. The system of claim 9 , wherein the latching switch comprises a latch coil that when energized puts the latching switch in a latched state, and a reset coil that when energized puts the latching switch in a reset state.
11. The system of claim 10 , wherein the latching switch is reset in response to an OPEN switch being pressed.
12. The system of claim 11 , wherein pressing the OPEN switch causes the actuation mechanism to lower the barrier.
13. The system of claim 12 , wherein the power source comprises a 24 volt power source.
14. The system of claim 13 , wherein the first switch and the second switch comprise a relay switch.
15. The system of claim 14 , wherein the first switch comprises a double pole relay.
16. A method of controlling movement of a barrier in a vehicle barrier security system, the method comprising:
detecting passage of a vehicle past a checkpoint;
generating a signal to an automatic reset relay thereby causing power to be providing to a latching switch, wherein the latching switch is placed into a reset state;
receiving input from a user at a switch for raising the barrier at the checkpoint thereby generating a first signal;
receiving a second signal at a second switch in a normally closed state, wherein the second signal indicates the absence of a vehicle over the barrier;
receiving the first signal at a third switch in a normally open state thereby closing the third switch;
providing power from a power source through the third switch in response to closing the third switch;
providing the power from the third switch to the latching switch, wherein the latching switch is in a normally closed state when in a reset state, and the latching switch is in the reset state; and
providing the power from the latching switch to an actuation mechanism causing the barrier to rise.
17. The method of claim 16 , further comprising:
changing the state of the second switch from a normally closed state to an open state; and
energizing a latch coil of the latching switch based on changing the state of the second switch.
18. The method of claim 17 , further comprising:
receiving input from the user at an OPEN switch for lowering the barrier at the checkpoint thereby providing power to a reset coil of the latching switch and changing the state of the latching switch to the normally closed state.
19. The method of claim 17 , generating a signal to an automatic reset relay thereby causing power to be providing to a reset coil of the latching switch.
20. A non-transitory computer readable medium storage device comprising instructions which when executed cause a computer to:
receive a first input signal from a sensor associated with a vehicle barrier at a checkpoint for receiving a request from a user to open a barrier at a checkpoint;
ascertain using the first input signal that the user authorized to pass the checkpoint;
receive a second signal input wherein the second signal indicates the absence of a vehicle over or under the barrier;
provide a third signal to an activation switch in a normally open state thereby closing the activation switch,
thereby providing power from a power source through the activation switch in response to closing the activation switch,
thereby providing power from the activation switch to a latching switch, wherein the latching switch is in a normally closed state when in a reset state, and the latching switch is in the reset state, and
thereby providing the power from the latching switch to an actuation mechanism causing the barrier to move so as to allow entry of the vehicle;
detecting the passage of the vehicle past the barrier at the checkpoint; and
generating a fourth signal to the latching switch in response to detecting the passage of the vehicle, wherein the latching switch is reset to a normally closed state.