Nuts & Volts - September 2005

Project

Parts List

Figure 6. After you remove the belt clip, there are two “stabilizing” alignment holes that can be used for routing all of the circuit’s wiring inside the radio.

Figure 7. Never throw anything away. This salvaged helmet from a Robosapien can be used for hiding and protecting the external “Instant Replay” circuit. I used Teflon® washers for connecting the visor to the helmet. Therefore, the “slippery” washers enabled the visor to be moved up and down for accessing the radio’s battery compartment.

The Hack — Add a ChipCorder message center to an FM Radio.

What You Will Need:A ChipCorder IC (e.g., ISD1212), (2) 4. 7 mF capacitors, ( 4) .1 mF capacitors, (2) 1K resistors (brown-black-red), (2) 4.7K resistors ( yellow-violet-yellow), 80K resistor (gray-black-orange), LED, ( 3) micro SPST NO momentary pushbuttons, and one FM radio ($2.99; Walgreens) (see Schematic 1).

Approximate Cost: $12.65.

Time Needed: 16 hours.

include a separate power switch.

You can either mount your pushbuttons externally or internally. Duh? The mounting decision will be based on the amount of space that you have inside the radio. My selected radio had no space for internally mounting the pushbuttons, so I had to come up with a method for “tastefully” integrating three micro SPST buttons along with my entire ChipCorder circuit onto the radio’s exterior case (see

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Figure 5). Just such a spot was found on the radio’s underside. I had to eliminate the supplied “belt clip,” however. This omission was more a blessing than a loss — the belt clip wouldn’t stay “clipped” to anything, including my belt. And, as shown in Figure 6, the two mounting holes for this belt clip were ideal for running the speaker and power supply wiring inside the radio.

In order to protect my external “Instant Replay” circuit, I glued a “spare” Robosapien helmet to the underside of the radio. This helmet had been removed from a Robosapien for a video camera hack that was included in my book The Official Robosapien Hacker’s Guide (TAB Electronics, 2005). By using some 4-40 hardware (two bolts, four washers, and two nuts), I was able to secure the old Robosapien visor to the helmet as a movable cover (see Figure 7). This cover did a good job of hiding the ChipCorder circuit, as well as protecting it from accidents. Then, as needed, raising the cover enabled the batteries to be changed (see Figure 8).

Step 4. Speaker in the House. Wire the SP+ and SP-speaker output from the ChipCorder circuit into the external headphone port of the radio. You will then hear your recorder through your radio’s headphones (or, ear buds).

Step 5. MIC Check. A small discrete electret microphone

ChipCorder Family Members

Each of these ChipCorder series consist of a complete “system on a chip” set of components. Only a speaker, microphone, several passive components, and a pushbutton interface are needed to make a digital recording/playback system. More advanced members of the ChipCorder family are better suited to microcontroller and/or computer control.