[[!meta title="EasyMotor"]]
# EasyMotor
This board is designed for in-flight characterization of research rocket
motors. It records chamber pressure and acceleration to an on-board flash
memory chip, the contents of which can be downloaded after flight over USB.
## Features ##
### User View ###
* Data logger storing motor chamber pressure and acceleration
* supports inexpensive 5V analog output pressure sensors
* 3-axis 200-g accelerometer
* On-board non-volatile memory for flight data storage
* USB for configuration, and data recovery
* Designed for use with a battery from 9-12V
* 1.5 x 0.8 inch board
## Example Installations ##
There are lots of ways to mount an EasyMotor board, but since we've been
asked, here are a few photos from snap-ring case forward closures
machined by Bdale for
test flights of EasyMotor. The sensor bodies are 316 stainless with a 1/8 NPT
male boss, so the approach chosen is to drill a 1/8 inch touch hole all the
way through the closure, then drill and tap 1/8 NPT female threads part way
through the closure thickness. The hole gets filled with grease and the
sensor screwed in.
The first example is a 98mm snap-ring closure, with the
sensor and electronics mounted off-center so a 3/8" all-thread could be used
in the center for motor retention in a minimum-diameter-ish airframe. This
motor had a small gap between the last propellant grain and the forward
closure, so having the pressure sampling port off-center wasn't a
problem. The mounting bracket for the electronics was bent from a bit of
1/16" aluminum sheet and screwed to the forward closure with two short 4-40
screws into tapped and drilled mounting holes. Note the use of an A23 12v
alkaline battery in a holder on the bracket with the
EasyMotor prototype. These batteries are fine for a flight or two, and both
they and the little holders for them are cheap on Amazon and make installations
like this fairly easy to put together:
This second example is on a 75mm snap-ring closure, and was Bdale's first attempt
using 16-gauge steel to bend a mounting bracket that could also be used for recovery
harness attachment. Another A23 and holder are taped on the other side of the
sensor not visible in this photo:
This example is a refinement of the 16-gauge steel strap used to form a mounting
bracket and harness retention point, this time for a 54mm snap-ring closure.
Bdale has flown this setup several times now, and the only down-side is that
it obvious takes up a few extra inches of airframe length. Note also the quik-link
wrapped in electrical tape to make sure it doesn't flop down and short against
any of the electronics in flight. Note also a long piece of shooter wire that
gets fed through a vent hole in the airframe as a twist-n-tape power switch.
## Artifacts ##
The firmware for this product is part of the [AltOS](../AltOS) suite.
This board was designed using lepton-eda and pcb-rnd.
The hardware design files are available from
[git.gag.com](http://git.gag.com) in the project
[hw/easymotor](http://git.gag.com/?p=hw/easymotor;a=summary).
## Availability ##
Prototypes of v2 were built and successfully flown. The initial production
run is back from our surface-mount assembler, and testing is underway. We
hope to have these available for sale by February 2021.