Tuesday, July 5, 2016

101: My New Raspi Model B 3 -- and a Gotcha!
-- revised again --

Back at post 2 of this blog I told about running pi.py -- my little Python program that computes Pi to 10,000 places. My first April, 2013 model B took 4 seconds. The new one: 1.4. That timing is for the 2nd execution (with the Python app already loaded in memory). Same deal on my new-ish iMac (quad 3.1ghz, i5): 0.17 seconds.

Nice. However, I've been bitten by the increased power requirement of this (release 3) model. I fired it up with a 2.1 Amp power source, 32GB micro SD and with the following attached: HDMI cable to 7" monitor, USB wifi dongle and USB keyboard. In this configuration the red light comes on but the SD is never accessed (green LED stays dark). It boots OK with any of the plug-ins removed. After initial power-up the removed device can be added. I failed to read about the need for a 2.5 Amp source.

Later: I got the 2.5amp converter. Better. It not only boots up with everything connected, it stays up, too (accessing the new Raspi via ssh always failed after an hour or so with the 2.1 amp supply -- I didn't get why).

Later: just got a new power strip that besides "surge protection" has 4 USB power outlets rated at 2.4 amps each. Guess what? My new Pi appears to not quite require 2.5 amps.