On Wed, Nov 6, 2013 at 4:30 PM, skypuppy <[email protected]> wrote: > Why in the world would anyone set analog in voltages as 1.8V??? > Everything I have and know about uses 0-5V. > ...
> Allow me to add an example: AD594 and AD595 thermocouple chips output the > temps in a 0-5V range. > The operating voltage is determined by the semicondurctor technology used to make the CPU chip. The latest high performance chips use high-density processes that can make lots of very tiny transistors, but the down side is that the features (gates) of those transistors are very thin and can't take large supply voltage, which determines all other operating voltages used by this chip. Since the power consumption turns out to depend on the squae of the supply voltage, lowering the chip operating voltage is inevitable, and 5V hasn't been seen on such chips in a long time. You can reduce the voltages from the outside of your system down to what BBB can take by a variety of active or passive voltage dividers; the simplest one would just consist of two resistors, say 2.2kOhm and 4.7kOhm in series connected between the ground and your analog voltage. You then connect the top of the 2.2kOhm resistor to the analog input of the BBB. 5V should get divided down to 1.6V, which should be safe for BBB (this assumes that your analog has low impedance, and BBB input impedance is high enough) Having said that, you should brush up on electronics if you want to do such analog interfacing. It's not rocket science, but if you don't know the basics there's a gazillion ways in which you can damage your BBB. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
