Low energy data communication circuit for hazardous or nonhazardous environments
View Patent ↗The present invention relates to a data communication circuit and system for use in hazardous or nonhazardous environments. In the preferred embodiment, the system is a bi-directional, low energy, current loop data communication circuit primarily for high speed data communications via parallel or twisted pair conductors. The system of the present invention can safely transmit data across long distances (e.g., up to 1000 feet (300 meters)) in an explosive atmosphere.
1. A data communication system, comprising:
a first transmission circuit in a first location for transmitting a signal;
a first receiver circuit in a second location for receiving the transmitted signal, the first receiver circuit comprised of:
a. an averaging circuit receiving said transmitted signal through a switch for producing an average signal representing an average level of the transmitted signal received by the first receiver circuit; and
b. a comparator for comparing the average level of the average signal with the transmitted signal received by the first receiver circuit, wherein the comparator is turned on when the transmitted signal received by the first receiver circuit is above the average level and turned off when the transmitted signal received by the first receiver circuit is below the average level, wherein the switch is responsive to a feed back control signal from an output of the comparator that controls the switching of the transmitted signal received by the first receiver circuit through the switch to the averaging circuit;
wherein the output of the comparator represents the signal transmitted from the first transmission circuit.
2. A data communication system according to claim 1 , wherein the first transmission circuit is comprised of:
a switch between two positive low current levels so some current flows at all times through the first transmission circuit.
3. A data communication system according to claim 1 , wherein the first transmission circuit is comprised of:
a first switch connected to a first transmit loop line;
a second switch connected to a second transmit loop line; and
wherein the first and second switches are controlled by the signal to be transmitted, and wherein the first and second switches are switched at the same time so that the voltage between the first and second transmit loop lines remains the same.
4. A data communication system according to claim 3 , wherein the first transmission circuit is adapted to transmit signals at high speeds at current levels below standard ignition levels.
5. A data communication system according to claim 4 , wherein the first receiver circuit is adapted to reconstruct the transmitted signal from the first transmission circuit at a distance of 1000 feet between the first transmission circuit and the first receiver circuit.
6. A data communication system according to claim 1 , wherein the first receiver circuit is further comprised of:
an optical coupler for isolating the first transmission circuit from the first receiver circuit.
7. A data communication system according to claim 6 , wherein the optical coupler is further comprised of:
an optically isolated photodiode; and
a transistor coupled to the optically isolated photodiode.
8. A data communication system according to claim 1 , wherein the first receiver circuit is adapted to reconstruct the transmitted signal by negating the effect of cable resistance, capacitance, inductance and voltage noise.
9. A data communication system according to claim 1 , wherein the system is a bi-directional data communication system.
10. A data communication system according to claim 1 , wherein the transmitted signal is a TTL (transistor-transistor-logic) signal received from a TTL transmit device.
11. A data communication system according to claim 1 , wherein the system is adapted to transmit signals at high speeds from a hazardous location using low current levels.
12. A data communication receiver, comprising:
a first receiver circuit adapted to receive a transmitted signal sent from a first transmission circuit located remotely from the first receiver circuit, the first receiver circuit comprised of:
a. an averaging circuit receiving said transmitted signal through a switch for producing an average signal representing an average level of the transmitted signal received by the first receiver circuit; and
b. a comparator for comparing the average level of the average signal with the transmitted signal received by the first receiver circuit, wherein the comparator is turned on when the transmitted signal received by the first receiver circuit is above the average level and turned off when the transmitted signal received by the first receiver circuit is below the average level, wherein the switch is responsive to a feed back control signal from an output of the comparator that controls the switching of the transmitted signal received by the first receiver circuit through the switch to the averaging circuit;
wherein the output of the comparator represents the signal transmitted from the first transmission circuit.
13. A data communication receiver according to claim 12 , wherein the first receiver circuit is adapted to reconstruct the transmitted signal from the first transmission circuit at a distance of 1000 feet between the first transmission circuit and the first receiver circuit.
14. A data communication receiver according to claim 12 , wherein the first receiver circuit is further comprised of:
an optical coupler for isolating the first transmission circuit from the first receiver circuit.
15. A data communication receiver according to claim 14 , wherein the optical coupler is further comprised of:
an optically isolated photodiode; and
a transistor coupled to the optically isolated photodiode.
16. A data communication receiver according to claim 12 , wherein the first receiver circuit is adapted to reconstruct the transmitted signal by negating the effect of cable resistance, capacitance, inductance and voltage noise.
17. A data communication transmitter, comprising:
a first transmission circuit in a first location for transmitting a signal to a first receiver circuit in a second location for receiving the transmitted signal, the first receiver circuit comprised of:
a. an averaging circuit receiving said transmitted signal through a switch for producing an average signal representing an average level of the transmitted signal received by the first receiver circuit; and
b. a comparator for comparing the average level of the average signal with the transmitted signal received by the first receiver circuit, wherein the comparator is turned on when the transmitted signal received by the first receiver circuit is above the average level and turned off when the transmitted signal received by the first receiver circuit is below the average level, wherein the switch is responsive to a feed back control signal from an output of the comparator that controls the switching of the transmitted signal received by the first receiver circuit through the switch to the averaging circuit;
wherein the output of the comparator represents the signal transmitted from the first transmission circuit.
18. A data communication transmitter according to claim 17 , wherein the first transmission circuit is comprised of:
a first switch connected to a first transmit loop line;
a second switch connected to a second transmit loop line; and
wherein the first and second switches are controlled by the transmitted signal, and wherein the first and second switches are switched at the same time so that the voltage between the first and second transmit loop lines remains the same.
19. A data communication transmitter according to claim 17 , wherein the first transmission circuit is adapted to transmit signals at high speeds at current levels below standard ignition levels.