X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=doc%2Fmotortest-installation.inc;h=3914bc709b1ffbc0d136211601454f9b54547390;hb=debian;hp=290c7b8fa7d3542511944278321f2ae77c012bb6;hpb=b115522c41228b26133f322ea68ddb187c0b68cc;p=fw%2Faltos diff --git a/doc/motortest-installation.inc b/doc/motortest-installation.inc index 290c7b8f..778a914f 100644 --- 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 +54,18 @@ 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. + + These pressure sensors have three wires and sometimes a + shield around those wires. The colors of the wires can vary, + but typically are red for power, black for ground, and green + for the analog output. Hook red to '+5', green to 'PRES', and + black to one of the two 'GND' screws on the board. The other + 'GND' screw is available for connecting the shield if one is + present. This is mostly relevant if you're using the product + for static testing on the ground with a longer than usual + cable. To log in-flight chamber pressure, a typical approach might be to drill a 1/8" sampling hole all the way @@ -49,3 +74,9 @@ 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, + and other related mechanical bits and pieces.