I'm making a little LED display with a 28X2 chip that will be on all the time.
18 separate outputs from the 28X2 will turn on an N-channel MOSFET which will supply power to each of the 18 LEDs in a sequence, and a pot to adjust the pause time between switching to the next output. The current through the MOSFETs will be about 400mA, and the sequence will switch at about 1hz.
I have a UL listed 5V "wall wart" to supply power to the Picaxe, and another UL listed 12V supply that will power the LEDs through the MOSFETs.
Since this is something that will be plugged into mains and always on, what considerations need to be made to ensure everything will work properly and safely?
I will be putting a fuse on each of the 18 outputs, as well as the 5V input and 12V input.
Should I use opto-isolators between the Picaxe outputs and the MOSFETs, so that I don't have to connect the 0V side of both the 5V and 12V transformer together, or is that not necessary?
Is there anything else to consider? Is it possible for the Picaxe to freeze or crash when on for such a long time? Maybe an external 555 timer to reset the Picaxe every 24 hours or so?
I'm going to get working on the schematic and post it here when I'm done, but am curious of a few things before I start.
18 separate outputs from the 28X2 will turn on an N-channel MOSFET which will supply power to each of the 18 LEDs in a sequence, and a pot to adjust the pause time between switching to the next output. The current through the MOSFETs will be about 400mA, and the sequence will switch at about 1hz.
I have a UL listed 5V "wall wart" to supply power to the Picaxe, and another UL listed 12V supply that will power the LEDs through the MOSFETs.
Since this is something that will be plugged into mains and always on, what considerations need to be made to ensure everything will work properly and safely?
I will be putting a fuse on each of the 18 outputs, as well as the 5V input and 12V input.
Should I use opto-isolators between the Picaxe outputs and the MOSFETs, so that I don't have to connect the 0V side of both the 5V and 12V transformer together, or is that not necessary?
Is there anything else to consider? Is it possible for the Picaxe to freeze or crash when on for such a long time? Maybe an external 555 timer to reset the Picaxe every 24 hours or so?
I'm going to get working on the schematic and post it here when I'm done, but am curious of a few things before I start.