doc: update EasyMotor behavior description for firmware 1.9.13 and later

[fw/altos] / doc / motortest-installation.inc

diff --git a/doc/motortest-installation.inc b/doc/motortest-installation.inc
index 290c7b8fa7d3542511944278321f2ae77c012bb6..3914bc709b1ffbc0d136211601454f9b54547390 100644 (file)
--- a/doc/motortest-installation.inc
+++ b/doc/motortest-installation.inc
@@ -1,22 +1,36 @@
 == Installation
 
-       EasyMotor needs to be rigidly attached in the airframe, and the
-       long axis of the circuit board needs to be aligned with the axis
-       of flight. By default, the round beeper on the board should be
-       “up” towards the nose cone, and the screw terminal strips should
-       be “down” towards the fins and motor nozzle end of the rocket.
+       [WARNING]
+       Firmware versions prior to 1.9.13 used acceleration to detect
+       launch.  Starting with 1.9.13, the firmware switched to using
+       pressure to trigger recording. Altus Metrum strongly recommends 
+       upgrading all EasyMotor boards to current firmware, the
+       behavior of which is described here.
+
+       EasyMotor needs to be rigidly attached in the airframe, in any
+       convenient orientation.
+
+       === Trigger to Start Recording
+
+       Starting with firmware version 1.9.13, a pressure sensor must
+       be attached, and pressure change is used to initiate and conclude
+       data recording.  Pressure and 3 axes of acceleration are recorded
+       for later analysis.
+
+       EasyMotor looks for a 50 psi rise in pressure from ambient to
+       start recording.  Recording stops when the pressure drops 
+       below 50 psi and shows variation of less than 30 psi for at 
+       least 10 seconds. These conditions are intended to capture all
+       actual burn data including anomalies such as "chuffs".
 
        === Power Switch and Battery
 
                In addition to the circuit board itself, EasyMotor needs
-               a power switch and battery to operate. Unlike most other
-               Altus Metrum products, EasyMotor does not work with
-               single-cell LiPo batteries. That's because commonly
-               available inexpensive pressure sensors need 5V, which is
-               more than a single-cell LiPo provides. Any battery that
-               provides from 6.5 to about 15 volts should work. Good
-               choices are the common 9V alkaline battery, or the very
-               small and light A23 12V alkaline batteries.
+               a power switch and battery to operate.  Like many Altus 
+               Metrum products, EasyMotor requires a single-cell LiPo 
+               battery, and has an on-board charging circuit.  The 5V
+               needed for inexpensive pressure sensors is generated 
+               onboard using a switching regulator to boost the voltage.
 
                Because he often mounts EasyMotor to the motor's forward
                bulkhead instead of to the airframe itself, Bdale often
@@ -40,7 +54,8 @@
                by the sensor. Very inexpensive sensors that have a
                “1/8 NPT” threaded input, a “Buick-style” 3-pin connector,
                and typically ship with a short cable and mating
-               connector, are readily available on eBay and AliExpress.
+               connector, are readily available through various vendors
+               including Amazon, eBay, and AliExpress.
 
                To log in-flight chamber pressure, a typical approach
                might be to drill a 1/8" sampling hole all the way
@@ -49,3 +64,8 @@
                NPT” pipe tap. Fill the touch hole with grease, screw in
                the pressure sensor, and attach the sensor leads to
                EasyMotor.
+
+               If you aren't up for machining closures yourself, 
+               link:http://lokiresearch.com[Loki Research] sells 
+               54mm and 75mm "experimental bulkheads" with threaded
+               sensor ports that can be used with snap ring cases.