February 2020

Clock Radio Hacking

Nice little clock radio with a docking station for charging a cellphone. I bought it through One Day Only or something.

One big problem, though. The display is so flippin’ bright that it keeps you awake at night. Draws moths, even. Not ideal.

The large PCB at the top holds the buttons. All the work is done by what one would have thought is the display board.

Clock, radio, everything. One would have thought they could have put an LDR in there to make the thing dim automatically when it gets dark. Philips is not what they used to be.

The 330 ohm resistor is not like the other resistors. Specifically, it’s a higher-wattage 0805 package and not 0603 like all the other resistors on the board*. Figuring that there must be a reason for this, this is where I started.

Replaced it with a 1k and sure ’nuff, the display is now bright enough to still read indoors in daytime, but dim enough to not outshine the street lights when we have them

* OK there are other 0805 resistors on the board. They bridge two or three traces, so I figured that’s why they chose bigger resistors in these positions. Also, 330 ohm is sort of the right value for an LED current limiter. Yea, it’s all gut feel. Sometimes it works.