Don K wrote:

wrote:

0.047 uF @400 V
1K || |
----www----||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

Unlike a wall-wart, it will require special precautions not to accidentally
touch anything when you go to change the battery...

And it has battery backup :-)

There's nothing to limit the current when capacitors fail, so that failure
will cause a fire.

I doubt that. The diodes will probably open, and I used really skinny wire.

There's no transient voltage protection, so the odds of capacitor over-voltage
failure is pretty high.

Or diode damage. So... I added a 1K series resistor. This would also work:

0.022 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
| |
10K | |
-----------www----------------------------------

*Digikey's $29.95 M400-KIT-ND 400 V capacitor assortment contains
10 of these, along with 10 of 14 other values from 0.001 to 0.1 uF.

Nick