Carbon monoxide sensor for an engine assembly

1. An engine assembly comprising:

an internal combustion engine; and

a carbon monoxide (CO) sensor unit comprising:

a CO sensor controller comprising:

a CO sensing circuit configured to detect a level of CO; and

a shutdown circuit configured to:

receive a detected level of CO;

calculate a trailing window average of the detected level of CO, the trailing window average comprising an average of the detected level of CO over at least two consecutive sampling loops;

determine whether to initiate a shutdown of the internal combustion engine based on at least the calculated trailing window average and a predetermined trailing window average threshold; and

initiate the shutdown of the internal combustion engine based on determining that the trailing window average exceeds the predetermined trailing window average threshold.

2. The engine assembly of claim 1 , wherein the shutdown circuit is further configured to:

calculate an array value based on the trailing window average and a currently detected level of CO.

3. The engine assembly of claim 2 , wherein the array value is calculated to be one if the currently detected level of CO exceeds a threshold above the trailing window average.

4. The engine assembly of claim 3 , wherein the array value is calculated to be zero if the currently detected level of CO is less than the threshold above the trailing window average.

5. The engine assembly of claim 4 , wherein the shutdown circuit is configured to initiate the shutdown of the internal combustion engine based on determining that the array value exceeds a summed array value and the trailing window average exceeds a low trailing window average threshold;

wherein the low trailing window average threshold is less than the predetermined trailing window average threshold;

wherein the summed array value comprises a sum of the array values within a pre-sized array of array values;

wherein the array value and the summed array value are reset to zero upon detection of the currently detected level of CO less than the threshold above the trailing window average.

6. The engine assembly of claim 5 , wherein the shutdown circuit is configured to initiate the shutdown of the internal combustion engine only if an internal combustion engine runtime is less than an internal combustion engine runtime threshold.

7. The engine assembly of claim 1 , wherein the shutdown circuit monitors the trailing window average and the detected level of CO based on at least a continuous monitoring mode and a start-up monitoring mode;

wherein the start-up monitoring mode is used when an internal combustion engine runtime is less than an internal combustion engine runtime threshold;

wherein the continuous monitoring mode is used when the internal combustion engine runtime is equal to or greater than the internal combustion engine runtime threshold.

8. The engine assembly of claim 7 , wherein the shutdown circuit switches from monitoring in the start-up monitoring mode to the continuous monitoring mode upon a trailing window average value drop of more than a threshold drop between a first trailing window average value and a subsequent trailing window average value.

9. The engine assembly of claim 1 , wherein the CO sensor controller further comprises:

an alert circuit configured to:

receive an indication from the shutdown circuit to trigger an alert on the internal combustion engine; and

trigger the alert on the internal combustion engine.

10. The engine assembly of claim 9 , further comprising an alert battery configured to provide power to the alert circuit and the alert.

11. The engine assembly of claim 1 , wherein the CO sensor unit further comprises a sensor power supply configured to receive power from an alternator of the engine assembly and provide power to the CO sensor unit.

12. An engine assembly comprising:

an internal combustion engine; and

a carbon monoxide (CO) sensor unit comprising:

a CO sensor controller comprising:

a CO sensing circuit configured to detect a level of CO; and

a shutdown circuit configured to:

receive a detected level of CO;

receive an indication of internal combustion engine runtime;

calculate a trailing window average of the detected level of CO, the trailing window average comprising an average of the detected level of CO over at least two consecutive sampling loops;

determine whether to initiate a shutdown of the internal combustion engine based on at least (i) the calculated trailing window average and a predetermined trailing window average threshold and (ii) the internal combustion engine runtime and a predetermined runtime period;

initiate the shutdown of the internal combustion engine based on determining that the trailing window average exceeds the predetermined trailing window average threshold, wherein the predetermined trailing window average threshold is adjusted upon determining that the internal combustion engine runtime exceeds the predetermined runtime period.

13. The engine assembly of claim 12 , wherein the predetermined trailing window average threshold is adjusted to a higher value upon determining that the internal combustion engine runtime exceeds the predetermined runtime period.

14. The engine assembly of claim 12 , wherein the shutdown circuit is configured to initiate the shutdown of the internal combustion engine based on determining that the trailing window average exceeds the predetermined trailing window average threshold over at least five sampling loops within a start-up period of the internal combustion engine.

15. The engine assembly of claim 12 , wherein the shutdown circuit is configured to initiate the shutdown of the internal combustion engine based on determining that the trailing window average exceeds the predetermined trailing window average threshold over at least 120 sampling loops within a continuous operational period of the internal combustion engine.

16. A method of controlling an internal combustion engine, the method comprising:

sensing, with a carbon monoxide (CO) sensor, a level of CO;

calculating, with a CO sensor controller in communication with the CO sensor, a trailing window average of the sensed level of CO over at least two consecutive sampling loops;

comparing, with the CO sensor controller, the calculated trailing window average of the sensed level of CO to a predetermined trailing window average threshold; and

sending, via the CO sensor controller, a command to terminate operation of the internal combustion engine from the CO sensor controller to the internal combustion engine upon determining that the trailing window average of the sensed level of CO exceeds the predetermined trailing window average threshold.

17. The method of claim 16 , further comprising a step of:

receiving, with the CO sensor controller, an indication of current engine runtime;

comparing, with the CO sensor controller, the indication of current engine runtime against a predetermined runtime period; and

adjusting, with the CO sensor controller, the predetermined trailing window average threshold based upon the comparison of current engine runtime against the predetermined runtime period.

18. The method of claim 17 , wherein the predetermined trailing window average threshold is increased upon determining that the current engine runtime exceeds the predetermined runtime period.

19. The method of claim 18 , wherein the CO sensor controller sends the command to terminate operation of the internal combustion engine upon determining that the trailing window average exceeds the predetermined trailing window average over at least five sampling loops within a start-up period of the internal combustion engine.

20. The method of claim 18 , wherein the CO sensor controller sends the command to terminate operation of the internal combustion engine upon determining that the trailing window average exceeds the predetermined trailing window average over at least 120 sampling loops within a continuous operational period of the internal combustion engine.