Elk KP2 Flashes to Full Bright Intermittently

coppercox

Member
I've noticed that my keypad will flash bright for a split second every now-and-then. The keypad is normally set to level one brightness but flashes to full for a fraction of a second then returns to normal. There is no set time when it does this but it has caught my attention several times in the darkened room and am wondering if anyone has had this happen? Any ideas why it is doing this?
 
I've noticed that my keypad will flash bright for a split second every now-and-then. The keypad is normally set to level one brightness but flashes to full for a fraction of a second then returns to normal. There is no set time when it does this but it has caught my attention several times in the darkened room and am wondering if anyone has had this happen? Any ideas why it is doing this?


The keypad I have in the master bedroom is also set to one and it does the same thing. I have four other KP2's in the house that I have not noticed it on, but it would be easy to miss as the bedroom is very intermittent.
 
I can only guess what could cause a flash in the keypad backlight:

The dimming of the backlight LED's are pulse width modulated, PWM. If for any reason the processor's time is in another interrupt routine longer than normal, the PWM might not get serviced and the backlight LED's would go full bright for a fraction of a second.

Thanks for the input, and I will look into the issue.
 
I can only guess what could cause a flash in the keypad backlight:

The dimming of the backlight LED's are pulse width modulated, PWM. If for any reason the processor's time is in another interrupt routine longer than normal, the PWM might not get serviced and the backlight LED's would go full bright for a fraction of a second.

Thanks for the input, and I will look into the issue.


FYI Mine does the same thing as its located in the Master bedroom....It could be even as much as once/hour. I only notice it because i'm staring right at it when I fall asleep....

thx
kev
 
We looked into the brightness of the backlight on the LCD screen changing when set to a low level. The backlight is controlled by a software Pulse Width Modulator that blinks the LED's on the backlight very fast which appears to be dimming the brightness of the LED's. If the right set of processor interrupts occur at the right time and the Pulse Width Modulator has turned on the backlight LED's, the LED ON time may be extended that appears as a brightness change. We have improved the interrupt latency time, but have not totally resolved the issue. Setting the backlight level to 0, should stop the quick blink. A backlight level of 1 to 3 is more noticable for the infrequent blink.
 
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