Construction is relatively simple. I suggest installing the parts onto the circuit board working from the middle outward and starting first with the components that lay flat, then ending with the upright components. One construction hint, before you begin populating the board with components, mark where the 3 power leads need to exit the plastic box by passing a heated nail or pin through the 3 wire lead holes and into the plastic.
The picture below on the left shows where all the components are located. The picture on the right shows an assembled board. Note that some of the components are optional depending on what functions you want to implement:
- The LED and R12 (which drives the LED) are optional if you don’t need any indicator functionality. This option is not present in the photo on the right.
- R14 and R15 are for two-wire mode USI interface, but may not be necessary, Fair warning, I haven’t tried this functionality yet. This option is also not present in the photo on the right.
- If you are using the sample software, and you are not using the reed-relay input, you must jumper the reed relay pins together. The jumper is included in top right corner of the board photo.
Note that there is no in-circuit programming capability on this board. For obvious reasons you don’t want to mix 120VAC and your AVR programmer. Please remove the ATtiny26L and re-program it outside of the 120VAC environment.
The wires to connect your AVR Switch to your 120VAC circuit are not included in the kit. Make sure you select wires long enough and appropriately rated for your particular installation. The wire pad under N-Fuse is for the Neutral wire and should probably be a White wire. The wire pad under the H-Fuse is for the incoming Hot wire. I suggest using Black for this and the wire pad to the right of H-Fuse and beneath the TRIAC is for the switched Hot. I suggest using Red for this wire, but follow your own local codes and regulations for wire color coding.
Once you have the 120VAC wires connected and the rest of your circuit assembled, double check all your connections, look for shorts and any other construction errors that may have occurred. Then with the ATtiny26L chip removed, power up your board by connecting the neutral (white) and hot (black) wires to your isolation transformer. At this point if things are seriously wrong, you’ll pop one or both of the fuses.
Once you’ve successfully passed the smoke test, carefully measure the voltages between the various pins in the 20 pin socket. (remember the isolation transformer!) The highest pin to pin voltage you should find in 5Vdc. You also shouldn’t read anything less than -5Vdc. If you read something larger, go back and re-check your circuit. Now, disconnect the power, give it some time to discharge the capacitors, then insert the ATtiny26L chip. Reconnect the power. If you’re using the sample code, then with the reed relay pins shorted, the LED should be ‘on’. Unshorted, the LED should be ‘off’. If that all passes, you should be ready to try out your AVR Switch.
Note that if you need to ask why you need the isolation transformer for the above steps, then you probably aught not be building this circuit!
One final note. The kit does NOT include a heat-sink for the TRIAC. I have run a 100W bulb with no heat sink with a 5-10 minute maximum ‘on’ time limit. I have also run 480 watts of lights for 60 minutes, but that does require a heat-sink and I used the metal top of the plastic box. However, if you need a heat sink, how large it needs to be and how it needs to be constructed depends entirely on the size of the load you intend to drive as well as the maximum ‘on’ time you’ve programmed. You’ll probably need to get creative if you start experimenting in this space.