SECU-3

SECU-3 project logos
SECU-3T revCU6 USB with MAP
SECU-3L with MAP and ignition coil drivers
SECU-3 Micro ignition controller unit
SECU-3i engine management system unit
SECU-3 system structural diagram (SECU-3T version)

SECU-3[1] is an internal combustion engine control unit. Open source project (drawings, schematic diagrams, source code etc. are open). Anyone can take part in the project and can access all information without registration.

Device controls the ignition, fuel injection and various other actuators of the internal combustion engine (ICE) and vehicle. In particular, it is capable of controlling the carburetor's choke using a stepper motor (auto choke), thus controlling RPM when engine is warming up. Manages AFR on the carburetor (like AXTEC AFR systems), idle cut off and power valve on carburetor, electric fuel pump, stepper gas valve with oxygen sensor loopback etc. Unique opportunities for reassigning the I/O functions. Smooth speed control of the cooling fan motor. The ability to edit the main settings and maps in real time (when engine is running) and switching between 2 or 4 sets of maps. And other features and functions (see below).

Currently, there are five modifications of the unit:

  1. SECU-3. The first version of the unit developed in 2007, controls ignition, cooling fan and some other functions. In the latest software releases, support for this unit has stopped. History of the SECU-3 versions with photos is here
  2. SECU-3T.[2] It can control the ignition and fuel injection. It does not contain built-in power drivers for ignition coils, fuel injectors and idling air control (IAC) valve. It is necessary to use external drivers.
  3. SECU-3L.[3] It designed for ignition control only and it can be viewed as a lightweight version of the SECU-3T unit. It contains built-in drivers for ignition coils and manifold absolute pressure (MAP) sensor. It is fully software compatible with SECU-3T unit.
  4. SECU-3 Micro.[4] Very simple and budgetary ignition controller unit in small plastic enclosure. Has only few inputs and outputs and doesn't contain built-in power drivers for ignition coils. It is the simplest SECU-3 unit.
  5. SECU-3i.[5] Full-featured, complete engine management system in metallic enclosure with integrated power drivers (for ignition coils, injectors, IAC actuator etc.), extended number of I/O and Bluetooth. The latest author's development. This unit has two boards design.

Device performed on the 8-bit AVR microcontroller ATMega644, with 64kB memory (ROM), 4kB random access memory (RAM), and operates at a clock frequency of 20 MHz. It includes analog and digital inputs, chip for preprocessing signal from the knock sensor (KS) (except SECU-3 Lite and Micro units), a signal conditioner for reference VR sensor (except SECU-3 Micro unit), a signal conditioner for the crankshaft position (CKP) sensor, interface with a computer and outputs for actuators control.

Structural diagram of the system with SECU-3T unit:

SECU-3 system structural diagram (SECU-3T version)
SECU-3 system structural diagram (Lite version)
SECU-3 system structural diagram (Micro version)
Example of wiring diagram of the SECU-3T unit for controlling of fuel injection
SECU-3T revD U6 assembled board without MAP
SECU-3 Lite assembled board without MAP
Assembled PCB for the SECU-3 Micro unit
Bottom board of the SECU-3i EMS
Top board of the SECU-3i EMS
SECU-3 Manager v3.4 - first tab

Structural diagram of the system with SECU-3L unit is shown on the following picture:

SECU-3 system structural diagram (Lite version)

Structural diagram of the system with SECU-3 Micro unit:

SECU-3 system structural diagram (SECU-3 Micro version)

Example of wiring diagram of the SECU-3T unit for controlling of simultaneous or semi-sequential fuel injection on the 4-cylinder engine is shown on the picture below. Hi-z injectors and stepper IAC valve are used. On the right side of picture we can see external connector functions which should be remapped to specified values. It is done in the SECU-3 Manager software.

Example of wiring diagram of the SECU-3T unit for controlling of simultaneous or semi-sequential fuel injection. Hi-z injectors, stepper IAC

History

The first version of SECU-3 was launched in October 2007 and successfully works on the author's (A.Shabelnikov) vehicle for now. Since then, the project has received a lot of new features and synchronization methods. First discussing of the project was started in 2007 in one topic on the iXBT conference.[6] Since Dec. 2010 discussion moved to the forum on diyefi.org.[7] In 2013 own project's forum had been opened.[8] The system has evolved from the ignition control to the engine management system (ECU). The project is supported by author all the time.

Current status

Continue to develop and extend fuel injection features and algorithms (inter alia, full-sequential injection support). Also, author works on software for the SECU-3i unit.

Features of the current firmware related to fuel injection:

License

GPL, TAPR OHL with one addition: developments can not be used in commercial purposes without written approval of author (according to information from the official site).

Features

Additional features:

Version differences

SECU-3 SECU-3T SECU-3T revC and later SECU-3L (Lite) SECU-3 Micro SECU-3i
Date 2007 2012 2014 2015 2016 2016
MCU ATmega16, ATMega32 ATMega32 ATMega644 ATMega644 ATMega644 ATMega644
Features Wasted spark, synchronization from CKP sensor full-sequential ignition,

synchronization from Hall sensor, CKP sensor, CKP + reference sensor, automatic control of carburetor's choke, immobilizer with iButton key, optional embedded bluetooth

 same, plus fuel injection control,

AFR control on carburetor, stepper gas valve control, programmable outputs

 Lite version, intended for ignition control and two additional outputs.

Simplified installation and wiring. Ignition coil drivers integrated to the unit.

 Maximum simplified version, intended only for ignition control. Has only two ignition outputs and several inputs.

Simplified installation and wiring.

 The most functional version among SECU-3 units, a full EMS. All the necessary devices are built into the unit (drivers for injectors, ignition, IAC, stepper motor, PWM etc.).

The unit consists of two boards, has optional embedded Bluetooth.

Main connector DB-25 MiniFit 24 pin MiniFit 14+12 pin MiniFit 14 pin MiniFit 12 pin MiniFit 24+6+14+12 pin
Interface RS-232 with optical insulation RS-232 with optical insulation or USB USB Insulated USB USB Insulated USB

References

  1. ↑ http://SECU-3.org
  2. ↑ Shabelnikov, A.A. (2015). "Electronic control unit for internal combustion engine SECU-3". Visnik Nacional'nogo tehnichnogo universitetu «HPI». Kharkiv Polytechnic Institute. 156 (22): 90–95.
  3. ↑ Shabelnikov, A.A. (2015). "Ignition control system for internal combustion engines SECU-3L (Lite)". BULLETIN OF THE NATIONAL TECHNICAL UNIVERSITY “KHARKIV POLYTECHNIC INSTITUTE” Series: "New solutions in modern technologies". Kharkiv Polytechnic Institute. 155 (46 (1155) 2015): 115–121.
  4. ↑ Alexey Shabelnikov (2016). "MICROPROCESSOR CONTROLLED IGNITION SYSTEM SECU-3 MICRO". MATERIAŁY XII MIĘDZYNARODOWEJ NAUKOWI - PRAKTYCZNEJ KONFERENCJI AKTUALNE PROBLEMY NOWOCZESNYCH NAUK - 2016. Sp. z o.o. «Nauka i studia». 111: 55–61.
  5. ↑ Shabelnikov, A.A. (2016). "SECU-3i PROGRAMMABLE ENGINE MANAGEMENT SYSTEM". Technology, energy, agriculture transport AIC. Vinnytsia National Agrarian University. 112 (2(94)): 67–73.
  6. ↑ http://forum.ixbt.com/topic.cgi?id=48:5576
  7. ↑ http://forum.diyefi.org/viewforum.php?f=47
  8. ↑ http://SECU-3.org/forum
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