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| jarrin > Interests > Electronics > Embrace the Light | |
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Microcontroller and Relay Strip 2/16/2007 7:00 PM
The PIC sits in the middle of the breadboard. 5vdc from a power transformer gets fed through a 78L05 voltage regulator to power it. A 4-position switch (off, low, med, high) salvaged from an old box fan provides a little bit of user interface (I was able to program three test patterns alongside the one main production display routine). Each of twelve output pins controls a 3903 transistor which in turn provides 5vdc (@~72ma) to the 250vac relays. Each relay is connected to a bus terminal
Because I am thorough I attached an ECC port to provide power to the lights and I even installed a 10a fuse (because if a short did occur I wanted it to only effect my light display and not, say, the much more important primary sound system for the event). I only had one significant problem in developing the control system. My first version wouldn't light open more than two or three relays at a time (even if no lights were connected to them). It took me an entire day to eventually realized that the 78L05 voltage regulator I was using could only source 200ma; I would have needed 864ma for the relays alone. It then occurred to me that I didn't need regulated voltage for the relays: just for the PIC. The solution was simple and I experienced no further problems. |
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