So I have made my first AC power shield design for the Arduino.
These are some of the design notes:
- it can control AC voltages in the range of 12V-600V
- the on/off high voltage circuitry in the middel of the board, with a safety distance of 2-5mm to all the low voltage parts. On the prototype I have covered all the high voltage parts with heat resistant kapton tape, to make it fumble finger safe.
- opto-coupler with mini triac is operating between the high and low voltage section. Optocoupler MOC3041 has zero-detection. Optocoupler MOC3020/21 (no zero-detection) can be used if light show control effects are needed.
- easy selection of which pin on the Arduino controls the on/off function (J4).
- on-board temperature sensor LM335 making it possible to incorporate a temperature safety system/switch when operating higher loads, so an override OFF operation can be made if the chip/board becomes too hot. Without additional cooling of the Triac should probably not control more than max. 3 Amp loads, where as the Triac it self (BT138) is a 12Amp design, and BT139 is a 16Amp design. With higher than 3Amp loads one should however use better cooling. As much as 20W cooling could be needed.
- on-board NTC connector. If used to control a reflow oven, one needs a temp sensor that can go as high as 270 C. By not mounting the 10uF (C2), another LM335 can be used for external low level (<100C) but easy temp sensing.
- the design should be single sided PCB, so its easy to make a copy yourself.
- all drilled holes can be 1mm as its easy to get drills at that size at any hardware store, so its easy to make a copy yourself.
- all wires are at least 1mm thick, so its easy to make a copy yourself.
When I have tested a prototype further, I’ll make the .pdf files available, so its easy to make your own copy on a PCB.
What do you think about this design?
hmm, cant post links or pictures in the first post.