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.
+This is what a production v3 board looks like:
+
+<a href="v3/top.jpg"> <img src="v3/top-thumb.jpg"></a>
+<a href="v3/bottom.jpg"> <img src="v3/bottom-thumb.jpg"></a>
+
## 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
+* works with inexpensive 5V analog output pressure sensors
+* USB for configuration, data recovery, and battery charging
+* Designed for use with a single-cell LiPo battery
* 1.5 x 0.8 inch board
+### Developer View ###
+
+* Hardware Features
+ * [NXP LPC11U14](http://www.nxp.com/products/microcontrollers/cortex_m0_m0/LPC11U14FHI33.html) System-on-Chip
+ * ARM Cortex-M0 MCU
+ * 32k Flash
+ * 6k RAM
+ * USB 2.0
+ * 8 12-bit analog inputs
+ * I2C, SPI, async serial
+ * digital I/O
+ * Analog Devices [ADXL375](https://www.analog.com/en/products/adxl375.html) 3-Axis Digital MEMS Accelerometer
+ * +- 200g full-scale
+ * on-chip digitizer
+ * on-board USB-based charger for single-cell LiPo battery
+ * low noise 5V switching regulator to power pressure sensor
+ * precision divider with 0.1% resistors to scale pressure sensor
+ analog output to match SOC analog input voltage range
+* Software Features
+ * Written mostly in C with some ARM assembler
+ * Runs from on-chip flash, uses on-chip RAM, stores flight data to serial flash
+ * USB serial emulation for "console" interface
+* Tools Used
+ * [lepton-eda](https://github.com/lepton-eda/lepton-eda) for schematic capture
+ * [pcb-rnd](http://repo.hu/projects/pcb-rnd/) for PCB layout
+* Licenses
+ * The hardware is licensed under the [TAPR](http://www.tapr.org) [Open Hardware License](http://www.tapr.org/ohl.html)
+ * The software is licensed [GPL version 2](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
+
## 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
+machined by Bdale for test flights of EasyMotor. For launch detection to
+work, the board must be mounted so the board's long axis is aligned with the
+axis of flight, and by default the "beeper end" must be towards the nose.
+Note that these examples all feature earlier versions of EasyMotor that used
+a different power supply and battery strategy. Don't be confused by that! The
+production version of EasyMotor uses our standard Altus Metrum LiPo batteries.
+
+The body of the pressure sensors used are 316 stainless with a 1/8 NPT
+male boss, so Bdale's usual approach is to drill a 1/8 inch "touch hole" or
+sampling port all the way through the forward closure, then drill and tap
+1/8 NPT female threads part way through the closure thickness. The hole
+gets filled with grease, and then the sensor screwed in. Since Bdale usually
+builds airframes that assume the recovery harness can attach to the motor
+case, several prototype installations depended on the stainless steel sensor
+body to act as a bolt to attach a bracket that supported both circuit board
+mounting and recovery harness attachment.
+
+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
+motor had a small gap between the forward 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:
+screws into tapped and drilled mounting holes. Note that this early version
+of EasyMotor used an A23 12v alkaline battery in a holder on the bracket. Those
+batteries were fine for a flight or two, but dealing with them was a hassle,
+which is one of the reasons the production was designed to use a LiPo.
<a href="photos/IMG_20200905_112722.jpg"> <img src="photos/IMG_20200905_112722-thumb.jpg"></a>
-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 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:
<a href="photos/IMG_20200907_101910.jpg"> <img src="photos/IMG_20200907_101910-thumb.jpg"></a>
-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
+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 flew this setup several times, and the only down-side is that
+it obvious takes up a few extra inches of airframe length. Note 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.
+Motor characterization products from Altus Metrum are documented in a manual
+available in [html](../AltOS/doc/motortest.html) and
+[pdf](../AltOS/doc/motortest.pdf) formats.
-This board was designed using lepton-eda and pcb-rnd.
+The firmware for this product is part of the [AltOS](../AltOS) suite. Test
+data can be downloaded, plotted, and exported in CVS form using the altosui
+ground station executable.
-The hardware design files are available from
+The current 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).
+For easy reference, pdf snapshots of the files used for production version 3
+are available here:
+
+* [schematic](v3/easymotor-sch.pdf)
+* [pcb artwork](v3/easymotor-pcb.pdf)
+* [bill of materials](v3/partslist.csv)
+
## 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.
+Version 3 is in production and available for sale.
+
projects / web / altusmetrum / blobdiff