Go Down

Topic: Arduino AC Triac power shield (Read 19 times) previous topic - next topic

MrAlvin

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 (<100*C) 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.

MrAlvin

#1
Jun 20, 2010, 02:11 am Last Edit: Jun 20, 2010, 05:55 am by MrAlvin Reason: 1

retrolefty

#2
Jun 20, 2010, 02:41 am Last Edit: Jun 20, 2010, 02:42 am by retrolefty Reason: 1
Quote
What do you think about this design?


Looks like a nice design and of course very useful. However I've never been a fan of mixing high voltage AC and digital logic physically onto the same circuit board, especially when it's a standard Arduino shield type and keeping in mind the broad variation in experience that the Arduino population includes.

I would rather the high voltage section be mounted separately with proper safety coverings, etc. The use of optical couplers does cover the electrical safety aspects but not the physical separation requirements.

In the refinery I worked on we were required to use separate field conduits and junction boxes for control wiring and components (24v and under) and power voltages (120vac and higher). Just too many chances for worst problems when human error enters the picture as it always will from time to time.

Lefty

MrAlvin

Quote
I would rather the high voltage section be mounted separately with proper safety coverings

I actually agree. So I have also made a separate AC board design, see http://www.flickr.com/photos/44817533@N00/4715784199/

It has the following advantages:
* its smaller than a shield
* it has fewer parts, and is thus less expensive
* its easier to add cooling to the Triac
* the control connector follows the same scheme as servos. I'll make a shield so its easy to control many units using this kind of connector. Sort of like RoboDuino. I am thinking of stuff like temp sensors, relays, buttons and maybe more.

bosscock

could you use this shield to drive nixie tubes?  (usually around 120-150v)?

Go Up