Determination of round count by hall switch encoding
This disclosure describes systems, methods, and apparatus for detecting and displaying a number of rounds in a firearm magazine comprising a maximum number of N rounds. The magazine may comprise a follower, magnets on the follower, and <N magnetic-field-sensing sensors arranged along a path of the magnets when the follower moves along a length of the magazine, the sensors generating round count data based on a position of the one or more magnets relative to the <N magnetic-field-sensing sensors, and a first substantially flat antenna arranged on an inside of the magazine and configured to wirelessly transmit a round count indication to a second substantially flat antenna on the firearm, the round count indication based on the round count data, the second substantially flat antenna affixed to an inside of a magazine well of the firearm and mostly overlapping with the first substantially flat antenna.
1. A round counting system for a firearm, the system comprising:
a detachable magazine comprising a follower, the follower comprising one or more magnets, and the magazine comprising:
<N magnetic-field-sensing sensors arranged substantially along a path of the one or more magnets when the follower moves along a length of the magazine, where N is a maximum number of cartridges that can be loaded in the magazine, the sensors generating round count data based on a position of the one or more magnets relative to the <N magnetic-field-sensing sensors; and
a first antenna on the magazine arranged in a region of the magazine that is configured to fit at least partially within a magazine well of the firearm, the first antenna configured to wirelessly transmit a round count indication from the magazine to the firearm via a second antenna on the magazine well or a trigger guard of the firearm, the round count indication based on the round count data.
2. The system of claim 1 , further comprising a magazine processor configured to convert the round count data to the round count indication for wireless transmission to the firearm via the first antenna, wherein the round count indication represents a number of cartridges remaining in the magazine.
3. The system of claim 2 , wherein the processor correlates positive signals from two adjacent magnetic-field-sensing sensors as a follower position between those two sensors.
4. The system of claim 1 , further comprising a reader processor configured for coupling to the firearm and in electrical communication with the second antenna, the reader processor is configured to receive the round count indication from the second antenna, the round count indication comprising the round count data from a plurality of the <N magnetic-field-sensing sensors, wherein the reader processor is configured to determine a number of cartridges remaining in the magazine from the round count indication.
5. The system of claim 1 , wherein the first antenna receives power from the firearm.
6. The system of claim 5 , wherein the power from the firearm is used to power a magazine processor of the magazine and the <N magnetic-field-sensing sensors.
7. The system of claim 1 , wherein the magnetic-field-sensing sensors are Hall effect switches.
8. The system of claim 7 , wherein the magazine comprises N/2, N/3, N/4, (N+1)/2, (N+1)/3, or (N+1)/4 of the magnetic-field-sensing sensors.
9. The system of claim 1 , further comprising a reader processor configured for coupling to the firearm and in electrical communication with the second antenna, the reader processor including a tangible computer readable medium encoded with computer readable instructions for:
reading a radio frequency signal from the second antenna; and
controlling a user interface to indicate a number of cartridges remaining in the magazine to a user.
10. The system of claim 9 , wherein the user interface is selected from the group consisting of a frequency of a blinking light, a color of one or more lights, a number displayed on a multi-pixel display, a number of LED lights lit up on an LED display, an audible signal, a fuel gauge indicator, and a bar graph indicator.
11. The system of claim 1 , wherein the first antenna is on a rear of the magazine.
12. A firearm with a round counting system, the firearm comprising:
a barrel;
a receiver;
a trigger guard coupled to the receiver;
a magazine well coupled to the trigger guard and the receiver and configured to releasably receive a magazine;
the magazine configured to carry up to N cartridges and comprising:
a follower comprising one or more magnets;
<N magnetic-field-sensing sensors arranged substantially along a path of the one or more magnets when the follower moves through the magazine, the magnetic-field-sensing sensors generating round count data based on a position of the one or more magnets relative to the <N magnetic-field-sensing sensors; and
a first antenna on the magazine located so as to align with a second antenna on the magazine well or trigger guard of the firearm when the magazine is fully inserted into the magazine well, the first antenna configured to pass the round count data, or a round count generated from the round count data, to the second antenna.
13. The firearm of claim 12 , further comprising a display configured to display the round count.
14. The firearm of claim 12 , further comprising a processor configured to correlate positive signals from two adjacent ones of the <N magnetic-field-sensing sensors as a position of the follower between the two adjacent sensors.
15. The firearm of claim 12 , wherein the <N magnetic-field-sensing sensors are Hall effect switches.
16. The firearm of claim 12 , wherein there are N/2, N/3, N/4, (N+1)/2, (N+1)/3, or (N+1)/4 of the magnetic-field-sensing sensors.
17. A method of determining a number of remaining rounds in a magazine in a firearm, the method comprising:
providing a magazine configured to carry up to N cartridges;
providing a follower of the magazine having one or more magnets;
providing <N magnetic-field-sensing sensors in a line or arc within the magazine;
generating a voltage sufficient to exceed a threshold at two of the <N magnetic-field-sensing sensors when the one or more magnets of the follower are substantially equidistant from at least one of the two of the <N magnetic-field-sensing sensors;
passing the voltage, or a signal derived from the voltage, across a wireless interface between the magazine and the firearm; and
displaying an indication of the remaining number of rounds in the magazine based on the voltage or the signal derived from the voltage.
18. The method of claim 17 , wherein the display is remote from the firearm.
19. The method of claim 17 , further comprising wirelessly passing power from the firearm to the magazine.
20. The method of claim 17 , further comprising generating a voltage sufficient to exceed the threshold at only one of the <N magnetic-field-sensing sensors when the one or more magnets of the follower are substantially aligned with the only one of the <N magnetic-field-sensing sensors.