infinityis 16 Posted February 20, 2012 Share Posted February 20, 2012 NOTE: this BoosterPack uses high voltage (120V) AC power which is dangerous and can be fatal if not handled/packaged properlyI created my first BoosterPack for the MSP430: an AC-powered AC relay. This BoosterPack takes in 120V AC and uses a transformerless power supply to cheaply/compactly create low DC voltage, which is then used to power the MSP430 Launchpad and drive a 7A relay. There is enough overhead in the currently design to power at least 3 relays, but it only has one designed in at the moment to make for the smallest/cheapest proof of concept. The board provides approximately 30mA at 3.3VDC and 30mA at 24VDC (note: the 3.3V VCC is wired directly to the 24V GND).A video of it operating is , pictures and schematic are here.There are some minor changes/fixes in the works for the next version but I thought I'd go ahead and open it up for comments/feedback.-The board was set up to accommodate either a 7A or a 15A relay, but the overlapping drill hits required for the relay didn't come out right so this one only works with the 7A relay. Also, if the 7A relay is unpopulated, you can still use the coil's thru-holes as a controllable 24V source (on/off).-One of the AC connector terminals was bigger than the datasheet stated so it currently leans to the side a bit.-The plan was to have a 6V+ output which passed through a LDO that provided a steady 3.3VDC. However, the LDO doesn't regulate very well without a minimum load, and MSP430 itself doesn't draw enough power by itself to meet that minimum requirement; it only works right when the top portion of the Launchpad is powered by it as well. I'll probably be changing the LDO in the future to one which does not require as much load current. fixed: it was a just board layout issue-I am currently drawing 24V and 3.3V separately (without common ground); I have considered with the idea of just drawing the 24V and regulating it down to 3.3V levels to get even more current at 3.3V. This would also allow the same board to be used in both AC-powered and non-AC-powered applications (where all you want is an AC relay board).-I placed the DC caps on the back of the board; unfortunately right where the crystal oscillator is. They'll be moved the next time around.-Would something like this work better as its own board (with the MSP430 on the board itself, not as a BoosterPack)?-There is a tradeoff regarding more current vs. being referenced to neutral; this board uses a bridge rectifier to get extra current. A neutral-referenced version would be needed to work with SCRs/TRIACs instead of relays.-Is the general preference for 3.3V or 1.8V operation of the MSP430? Are there pins that are recommended or discouraged for use in driving the relays?-Several "tall" components are used on the board; would it be best to move them out of the Launchpad area entirely to allow other BoosterPacks to be stacked, or is something like this more acceptable to always have as the top of the stack?If there is any interest in this type of BoosterPack (or a customized variant), please let me know what you'd like to see. I should mention that in general, if/when sold in small quantities, it would be as a kit with the AC line cap and/or relay(s) not installed to minimize liability. bluehash, xpg and larsie 3 Quote Link to post Share on other sites
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