Physical assessment device
An instrument head is provided for attachment to a plurality of instrument handles having different power profiles. The instrument head contains an illumination assembly including at least one LED as well as a drive circuit for detecting a power profile of an attached instrument handle and converting variable voltages received from the attached instrument handle to a constant current for powering the at least one LED based on the power profile. Accordingly, the instrument head enables use with a plurality of instrument handles, including those originally configured for use only with incandescent light sources.
1. An instrument head for attachment to a plurality of instrument handles having different power profiles, the instrument head comprising:
an illumination assembly including at least one LED; and
a drive circuit comprising a controller, the controller being configured to:
detect power up signals from an attached instrument handle of a specific type;
determine a power profile of the attached instrument handle based on the detected power up signals, the power profile including a voltage calibration curve; and
convert variable voltages received from the attached instrument handle to a constant current for powering the at least one LED based on the voltage calibration curve of the power profile to illuminate the at least one LED with a specific brightness.
2. The instrument head of claim 1 , wherein the drive circuit outputs a pulse width modulation (PWM) of the constant current to illuminate the at least one LED, wherein dimming of the at least one LED is achieved by varying a duty cycle of the PWM of the constant current responsive to changes in the variable voltages received from the attached instrument handle.
3. The instrument head of claim 2 , wherein the drive circuit outputs the PWM of the constant current to power the LED at a given illumination level when connected to either a first of the plurality of instrument handles with a first power profile and first variable voltages or a second of the plurality of instrument handles with a second power profile and second variable voltages, wherein the first and second power profiles are different power profiles.
4. The instrument head of claim 1 , wherein the drive circuit comprises a buck/boost circuit, the buck/boost circuit outputting a constant voltage notwithstanding an input voltage from the instrument handle being above or below the constant voltage.
5. The instrument head of claim 1 , wherein the drive circuit comprises a rectifier, the rectifier comprising field effect transistors (FETs) for converting an alternating current input from the instrument handle to a direct current for powering the at least one LED.
6. The instrument head of claim 1 , wherein the controller further detects a polarity of the instrument handle attached to the instrument head.
7. The instrument head of claim 6 , wherein the drive circuit comprises a buck/boost circuit, the buck/boost circuit outputting a constant current notwithstanding an input voltage from the instrument handle being above or below the constant voltage, and the controller further controls the buck/boost circuit to output the constant current with a pulse width modulation (PWM) at a duty cycle selected to illuminate the at least one LED at a specific brightness.
8. The instrument head of claim 6 , wherein the controller detects a vibration or idle state of the instrument head and responsive thereto powers up or powers down the instrument head.
9. The instrument head of claim 6 , wherein the controller uses a lookup table to determine the power profile of the attached instrument handle based on the power up signals received when attached.
10. The instrument head of claim 1 in which the instrument head is part of a physical assessment device.
11. The instrument head of claim 10 , in which the physical assessment device is an otoscope or an ophthalmoscope and in which at least one of the instrument handles used with the instrument head are typically configured only for use with an incandescent light source.