My wife purchased a fairly expensive outdoor clock that is supposed to light up at night. It uses a ring of LEDs illuminating the plastic dial face, using a photo-resistor based circuit powered by C cells. The clock will only light up when there is a fast transition from light to dark, like turning off the porch light after sunset. It will not turn on from the slow sunset darkening. We contacted the supplier who immediately sent a new clock, telling us to just keep the original one. The new one behaves the same, and I found many reviews of the clock with this issue noted, so it led me to believe just a poor design.
I removed the control card to do some debug but am stuck trying to identify the IC that the manufacturer blacked out.
What has me stumped is this chip has the positive voltage on pin 1 and the return or ground on pin 8.
The positive rail from the battery connector loops around the top of the pcb and under the IC to connect to pin 1, when they could have simply connected the C1 bypass cap to the adjacent connector pin.
The photo-resistor pulls pin 7 low when in the dark and pin 3 goes low to sink the current for the LED string.
The remainder of the pins are floating.
In a slow light to dark transition, there seems to be a glitch or noise burst with the LED array flashing on then remaining off. With the fast transition LEDs light and stay on. This makes me think the IC is some latching comparator with a floating reference pin, but I have not been able to find such a device. I do not have a scope, so I'm doing this debug only with a DVM.
Any ideas what this part is?
I removed the control card to do some debug but am stuck trying to identify the IC that the manufacturer blacked out.
What has me stumped is this chip has the positive voltage on pin 1 and the return or ground on pin 8.
The positive rail from the battery connector loops around the top of the pcb and under the IC to connect to pin 1, when they could have simply connected the C1 bypass cap to the adjacent connector pin.
The photo-resistor pulls pin 7 low when in the dark and pin 3 goes low to sink the current for the LED string.
The remainder of the pins are floating.
In a slow light to dark transition, there seems to be a glitch or noise burst with the LED array flashing on then remaining off. With the fast transition LEDs light and stay on. This makes me think the IC is some latching comparator with a floating reference pin, but I have not been able to find such a device. I do not have a scope, so I'm doing this debug only with a DVM.
Any ideas what this part is?