Step 1: How this project came about
Step 2: How the circuit works.
For remote controlled operation I added a 12 volt DC power supply power supply, remote control receiver, chime (to let her know it activated), power relay and a LED power on indicator. When you press the button on the remote control transmitter a small relay in the remote control receiver operates (RCR1). When the relay's normally open contacts close, the voltage from the power supply turns on the chime (CHM1) and the power relay (RLY1). One set of normally open contacts in the power relay turns on the main power to the coffee maker and a second set of normally open contacts act as a relay latch by bypassing the radio receiver relay contacts so the power relay will stay on even after you remove your finger from the transmitter button. There is a diode (D5) between the receiver relay (RCR1) and the power relay (RLY1) to prevent this bypass voltage from activating the chime when you take your finger off the transmitter button. Without this diode the chime will continue to sound the entire time the coffee maker is on. Believe me when I say that is not a pleasant experience. The kick-back diode (D6) prevents the relay coil's (RLY1) induced voltage spike from frying the LED (LED1) when the relay turns off. In order to turn the coffee maker off you simply press the normally closed push button (PB1). This interrupts the relay latching voltage coming from the bypass contacts in the power relay (RLY1) and the coffee maker turns off.
Step 3: The parts list
1 - Single Channel 12 volt DC Remote Control Receiver and Transmitter (RCR1)
1 - Miniature 120 to 12 volt transformer (T1)
6 - 1N4007 general purpose diodes. (D1-6)
1 - 1000 mf 25 volt electrolytic capacitor (C1)
1 - LED (any color) (a mount is optional) (LED1)
1 - 470 Ohm 1/4 watt resistor or a resistor close to this value (R1)
1 - 120 VAC 15 amp DPDT relay with a 12 volt DC coil. [A socket is optional] (RLY1)
1 - NC (normally closed) push button switch (PB1)
1 - One electronic doorbell chime from Radio Shack - one with 3 wires coming out of it. (CHM1)
2 - Small perforated boards
1 - plastic project box ( the largest Radio Shack sells)
Assorted screws and nuts for mounting
Small gauge hookup wire (various colors)
Large gauge electrical wire (a lamp cord will work)
Nylon Wire Ties
A few inches of small heat shrink tubing.
Step 4: Getting started
Step 5: Wiring up the coffee maker.
Solder one wire of the lamp cord to each of the two terminals on the original power switch as shown in the picture. The other terminal on the switch is for the power light built into the switch and is not needed for the remote control.
Drill a hole and mount the normally closed push button switch beside the main power switch. Solder a pair of wires to the terminal.
Solder the 470 ohm resistor to one lead of the LED. Solder a wire to the other end of the resistor and a second wire the the other LED lead. Use heat shrink tubing to insulate the bare wire and resistor. Drill a hole on the other side of the original power switch and mount the LED in the hole. I used a small amount of hot glue to secure the LED.
Cut the coffee makers power cord in two and use wire nuts to add an additional set of leads to feed the electronics in the project box.
Carefully route all 8 wires to the project box and secure them with wire ties so that they do not get close to the heating element.
Step 6: Assemble and mount the power supply board.
Mount the miniture transformer, 4 - 1N4007 diodes, and the 1000 mf electrolytic capacitor to one of the perf boards per the schematic.
Mount the power supply board inside of the project box.
Solder the two wires that you spliced onto the power cord with wire nuts in the previous step to the primary (120 vac) terminals of the transformer.
Step 7: Mount components to the project box.
Drill holes and mount the door bell chime to one of the long sides of the project box and feed the wires inside the box.
Mount the remote control receiver to the other long side of the project box and drill a hole to run wires from it to the inside of the project box.
Drill a hole on one of the short sides of the project to run wires into the base of the coffee maker.
Step 8: Mount the project box to the coffee maker
CAUTION - The top rear of the coffee maker is also the wall of the water tank. If you drill into it, the coffee maker will leak water and be ruined. Do not drill any holes in the coffee maker above the seam between the bottom of the water tank and the top of the base. Since there is very little pressure or weight on the project box, two holes drilled into the base will be be more than enough to secure the project box.
Step 11: Finishing up and testing
Use electrical tape to insulate the power relay and perf boards.
Install the cover on the project box and radio receiver.
Plug in the coffee maker and look for smoke or fire.
If you don't see any then press the button on the radio transmitter.
You should see the LED come on and hear the chime ring twice.
Press the NC pushbutton to make sure the LED turns off.
Get ready to become a hero.
Step 12: Operating the coffee maker.
For manual operation just turn the original switch on. The green light in the switch lets you know the coffee maker is on. Turn the switch off and the light goes off indicating the coffee maker is off.
For remote control operation you will need to set the coffee maker up the night before with water, a filter and coffee. In the morning you simply press the button on the transmitter. The chime will sound and the LED on the front panel of the coffee maker will turn on to indicate the coffee maker has turned on. When you are finished with the coffee press the push button you added to the front panel of the coffee maker and the LED and coffee maker turn off.
The LED does not turn on when the coffee maker is turned on manually and the green light in the switch does not turn on when the coffee maker is turned on using the remote control. This allows you to quickly tell whether the coffee maker was started using the manual switch (the green light is on) or it was started using the remote control (the LED in on). This is necessary in order to know how to turn off the coffee maker.
Step 13: Listen to her brag.
Many thanks to my lovely wife, Semone, for all her ideas, help and encouragement. I love ya girl!