Method and apparatus to control bi-color LEDs on enterprise and datacenter solid state drive (E3) form factor
Systems and methods are disclosed for controlling the operation of visual indicators, such as light emitting diodes (LEDs). A novel circuit may be employed to energize one indicator while de-energizing a second indicator, and vice versa. The novel circuit uses at least one switching component to perform a switching operation on the indicators.
1. An electrical circuit comprising:
a first light emitting diode (LED) having a first color responsive to being energized;
a second LED having a second, different color responsive to being energized, the second LED and the first LED having a common anode;
a first switching device, an output of the first switching device coupled to the common anode of the first and second LEDs; and
a second switching device, a control input of the second switching device coupled to a cathode of the first LED through a first predetermined impedance and an input of the second switching device coupled to a cathode of the second LED through a second predetermined impedance, such that when the first LED is energized the second LED is de-energized and when the second LED is energized the first LED is de-energized.
2. The electrical circuit of claim 1 , further comprising a source voltage lead coupled to an input of the first switching device via a third predetermined impedance.
3. The electrical circuit of claim 1 , further comprising an LED control lead configured to transmit a switching control signal arranged to energize the first LED or the second LED, based on a value of the signal, the LED control lead coupled to the control input of the second switching device via the first predetermined impedance.
4. The electrical circuit of claim 3 , wherein the LED control lead is coupled to the cathode of the first LED.
5. The electrical circuit of claim 3 , wherein the second LED is energized and the first LED is de-energized responsive to the switching control signal having a voltage value of at least a first predetermined voltage, and wherein the first LED is energized and the second LED is de-energized responsive to the switching control signal having a voltage value of less than a second predetermined voltage, the second predetermined voltage being less than the first predetermined voltage.
6. The electrical circuit of claim 1 , further comprising a blocking diode coupled in parallel with the first LED, the blocking diode having a polarity opposite to the first LED.
7. The electrical circuit of claim 1 , wherein the first LED and the second LED have a common package.
8. The electrical circuit of claim 1 , wherein the first predetermined impedance and the second predetermined impedance comprise first and second resistors, respectively.
9. The electrical circuit of claim 1 , wherein the first and second impedances are selected such that a maximum circuit current is less than 20 mA.
10. An electrical circuit comprising:
a first visual indicator having a first color responsive to being energized;
a second visual indicator having a second, different color responsive to being energized, the second indicator and the first indicator having a common anode;
a first transistor, an output of the first transistor coupled to the common anode of the first and second indicators;
a second transistor, a base or gate of the second transistor coupled to a cathode of the first indicator via a first predetermined impedance and an input of the second transistor coupled to a cathode of the second indicator via a second predetermined impedance; and
an indicator control lead configured to carry a switching control signal to the base or gate of the second transistor via the first predetermined impedance, the switching control signal arranged to trigger the first or second indicator to energize, based on a value of the signal.
11. The electrical circuit of claim 10 , further comprising a source voltage lead coupled to an input of the first transistor via a third predetermined impedance.
12. The electrical circuit of claim 11 , wherein the second indicator is configured to illuminate independent of the presence of a voltage at the source voltage lead.
13. The electrical circuit of claim 11 , wherein when the first indicator is energized the second indicator is de-energized and when the second indicator is energized the first indicator is de-energized.
14. The electrical circuit of claim 10 , further comprising a blocking diode coupled in parallel with the first indicator, the blocking diode having a polarity opposite to a polarity of the first indicator.
15. The electrical circuit of claim 10 , wherein the electrical circuit consists of a minimal number of discrete parts, including one dual light emitting diode (LED) with common anode, one dual NPN bipolar junction transistor (BJT), four resistors, and one diode.
16. An electrical circuit comprising:
a first illuminating indicator having a first color responsive to being energized;
a second illuminating indicator having a second, different color responsive to being energized, the second indicator and the first indicator having a common anode;
an indicator control means, a first lead of the indicator control means coupled to the common anode of the first and second indicators;
a first voltage dividing resistor coupled in series with the first indicator;
a second voltage dividing resistor coupled in series with the second indicator, and a cathode of the second indicator being coupled to the indicator control means via the second voltage dividing resistor; and
an indicator control lead configured to carry a switching control signal to the indicator control means, the signal arranged to trigger the first or second indicator to energize, based on a value of the signal, such that responsive to the control lead being asserted the second indicator is energized and the first indicator is de-energized and responsive to the control lead being de-asserted the first indicator is energized and the second indicator is de-energized.
17. The electrical circuit of claim 16 , wherein the first voltage dividing resistor is disposed between the first indicator and a control input of the indicator control means.
18. The electrical circuit of claim 16 , wherein at least one of the first and second indicators comprises a light emitting diode (LED).
19. The electrical circuit of claim 16 , wherein the indicator control means comprises a programmable logic device.