Looking for some help in defining the specifications of SMPS required to power an embedded project around (rather surprisingly, may be), Intel Atom motherboard. The plan is to run the system fan-less (or try to do so, if possible), with minimal peripheral count, in a closed-box fashion, i.e. without exposing capability to add additional peripherals, yet run on least amount of grid power. All of the following would be housed inside a custom-made (non-standard, i.e. nothing like mini-ITX etc.) cabinet.
Considering the power requirements specified by following blocks --
- Dual-core Atom 1.8GHz, Mobo+CPU combo - ~ 15W ( some articles talk about ~13W )
- 2GB DDR-III 1333MHz RAM module (single) - ~ 1W ( not sure, just guessing )
- 16GB USB thumb-drive - ~ 1W ( not sure, just guessing )
- Teensy+ USB connected (bus powered) - ~ 3W ( assuming 500mA @ 5V from USB)
- 315MHz ISM Rx/Tx module w/ Teensy - (included in Teensy's power requirement)
- USB Bluetooth dongle - ~ 1W
USB WiFi dongle - ~ 2W
Sum of operational power = ~ 25W
So the questions -
- Does the above calculation and assumed power values seem reasonable ?
- Can I really add up the power values as I've done to arrive at the required SMPS rating ?
- Can I target a 30W SMPS, or say a 50W SMPS (to take the cold-start current draw into account) ?
- Most standard desktop SMPS's available today seem to be rated for at least 400W, and very rare few at 250W (which BTW seem quite expensive). Is there something significantly different between such SMPS's and some of the other SMPS's found on electronics distributor sites which seem to supply a single DC rail (usually I've seen 12V) ? I believe standard PC mobo requires 3.3V, 5V and 12V (both +ve & -ve rails), but are all of those required by Mobo, or for the peripherals ? Does typical Mobo have onboard voltage regulators to convert 12V to 3.3V / 5V if required by say the processor / memory ?