1
Introduction
The H
ORNET
-III is an engine control unit (ECU) for model jet turbines, originally developed and produced
by ProJET electronic components GmbH, Fuchsmühl, Germany. Its home builder version (still distributed by
ProJET) can be used for engines of a wide range of manufacturers. All H
ORNET
-III variants have the following
features in common:
• ECU settings accessible via Ground Support Unit (GSU).
• Engine can be started using standard fuel or an auxiliary gas.
• Controls an analogue (brushed) fuel pump.
• RPM sensor can be optic or magnetic (Hall).
• Dynamic throttle response depending on the temperature and RPM sensor signals.
• Fail-safe mode in case run time errors (e.g. one or both sensors fail and other errors).
• Support for connecting to a GPS module.
• Support for a smoker valve.
• Communication with XBee modules for saving telemetry data.
After acquiring the BF Turbines product line in 2017, AeroDesignWorks GmbH purchased the H
ORNET
-
III firmware source code together with a license to use, modify and redistribute the firmware in 2018. The goal
was to be able to make modifications for the BF range of engines. AeroDesignWorks and ProJET continue
to work together on the hardware, but starting in 2021, AeroDesignWorks distributes their H
ORNET
-III ECUs
with a new firmware starting at version v3.0.
• All H
ORNET
-III ECUs sold by AeroDesignWorks only work with our own range of model jet engines.
• As they are configured for a fuel start, we no longer provide information on using an auxiliary gas.
• The firmware version v3.0 brought some changes that affect the end user and hence a long overdue update
to the manual.
ProJET developed a H
ORNET
-III capable of powering and controlling brushless fuel pumps called H
ORNET
-
III-BLC (Brushless Controller), which uses different hardware and cannot be used with analogue fuel pumps.
There are some notable differences, which will be mentioned in the manual where appropriate.
1.1
Hardware information
The H
ORNET
-III is powered by an Atmel Atmega2560 processor, which has 256 KB of program memory and
4 KB of EEPROM to persistently store settings. The EEPROM has an unlimited amount of read cycles and a
limited but large (100,000+) amount of write cycles per byte.
• The maximum supported battery voltage is 12
.
8
V
for continuous operation.
• The receiver input supports 5 cells with a maximum voltage of 7
.
5
V
and a minimum pulse amplitude of
2
.
7
V
.
• The fuel pump can be supplied with a current of 10
A
for continuous operation, with peaks of 20
A
for up
to 0
.
2
s
.
• The starter can be supplied with a current of 10
A
for continuous operation, with peaks of 20
A
for up to
0
.
2
s
.
• The glow plug can be supplied with a current of 10
A
for continuous operation, with peaks of 20
A
for up
to 0
.
2
ms
.
• The fuel valves can be supplied with a current of 0
.
25
A
for continuous operation, with peaks of 0
.
5
A
for
up to 1
s
.
2