SparkSwitch Pro RPM for DA/Valach(Fiala)/OS/Zenoah/ZDZ/Moki/3W ignition modules without tacho output, temperature sensor device

  • Combustion gas engines ignition modules without additional pulse signal with RPM output are unable to pass directly RPM information into SparkSwitch Pro (SPW) device. It was the reason, why developed a special accessory device for SPW.

    The first version of the accessory was a simple circuit, able to read mainly hall sensor signals, and after amplifying of the signal, passing this signal into the SPW device. But this accessory was unable to read some special signals, mainly from a magnetic coil, used in DA ignition modules. The same case for Valach ignition modules, there was also a problem with dual controlling of the ignition module. Valach ignition modules required connection to receiver for switching on, therefore two control signals needed, for switching on/off of ignition module.

    The current version of the RPM accessory is designed for usage with all types of ignition modules. It is a microprocessor-controlled device, which is able to read any input signal from any type of engine sensor. A side effect of the design is fact, that all cables from the ignition module are connected to this special accessory, and only one lead is connected to the SPW device. It is a big advantage also for Valach ignition modules, because the module is connected only to the accessory device, and is not needed to connect the ignition module to the receiver, the functionality of the ignition module is controlled only by switching SPW on/off. The accessory device controls the ignition module and read signals from the sensor.

    RPM accessory is a small device of dimensions 14x32mm, with five JR male connectors in one row, on the left side. All cables from the ignition module are connected directly into that device.

    RPM accessory device is configurable for different types of ignition modules, but the main process of analysis of input signal from engine sensor is done by special firmware, analyzing the signal with fast analog to digital converter. For controlling of all functionalities of accessory was used micro-controller SAMD21 Cortex M0. The accessory device is designed for two independent circuits, separated by optocoupler, to eliminate possible interference's from ignition modules. The accessory power supply circuit is specially designed for the elimination of possible noises. The signal from the engine sensor is separated using an instrumental operational amplifier, to be sure not disturbing ignition module input circuits for the right operation of spark timing and distribution.


    The same dimension, components only on the top side, new regulator, HV PWM output, new version of firmware.

    Generally, we have three types of ignition modules:

    1. Basic type, engine sensor of Hall type, connected to the ignition module, and ignition module powered by second cable, battery connected directly to ignition module (using a switch).

    2. The ignition module controlled by the receiver means switching on the module using the receiver channel. Battery connected directly to the ignition module (using a switch).

    3. Ignition module with a magnetic coil engine sensor. Signal generated by the magnetic coil is hard to read and pass into SPW, therefore functionalities of RPM accessory are needed for analyzing the signal. Battery connected directly to the ignition module (using a switch).

    Ad 1)

    Connection setup: (OS Max, Zenoah, ZDZ, EME, DA 35, Moki)

    P1 – connected to engine sensor using patch lead male/male (*) (For Moki ignition module is needed a special adapter when you will order RPM device for Moki, please add comment 'Moki')

    P2 – connected to ignition module sensor cable directly, or using patch lead male/female. (For Zenoah or Saito ignition modules, with one cell power supply battery, is connected into this port small 'Pump' device, and output from this device to the igniter.)

    P3 – empty, not connected

    P4 – connected to ignition module power supply cable, using patch lead male/male (For Moki special adapter with MPX connectors and Pump device)

    P5 – connected to SPW using patch lead male/male

    Jumpers: inserted J2 and J3 (**)

    Patch leads detail:

    Special patch leads and adapter for Moki setup:

    Ad 2)

    Connection setup: (Valach all ignition modules for all Valach engines)

    P1 – connected to ignition module power supply cable, using patch lead male/male

    P2 and P4 – connected together, using short patch lead male/male

    P3 – connected to ignition module output (usually connected to the receiver in setup without RPM accessory device)

    P5 – connected to SPW using patch lead male/male

    Jumpers: J1 and J3 (**)

    Patch leads detail:

    Ad 3)

    Connection setup: (Desert Aircraft all ignition modules excepting DA 35, see 1)

    P1 – connected to engine sensor using patch lead male/male, wires 1 (signal) and 3 (ground), please use patch lead without wire 2 (+V) (***)

    P2 – connected to ignition module sensor cable directly, using patch lead male/female, wires 1 (signal) and 3 (ground), please use patch lead without wire 2 (+V) (***)

    P3 and P4 – connected to power supply output from the ignition module, using Y-harm patch lead male/male+male, please use patch lead with only power supply wires 2 (+V) and 3 (ground) (***)

    P5 – connected to SPW using patch lead male/male

    Jumpers: none, empty jumper block (**)

    Patch leads details:

    (*) – patch leads with JR connectors for all ignition modules excepting OS Max. Futaba connector has a guide, which is not possible plug into JR connectors used in most of the ignition modules.

    (**) – 5 position jumper area, please do not connect jumpers into the first two positions! Those pins are used for programming of device


    In all cases is an ignition module controlled by SPW, not needed an additional switch, additional channel. It is better to use the accessory device as a junction box for all ignition module leads, and a single lead connected to SPW. Better organization of cables, better resistance to noise, interferences.

    Accessory device firmware is providing small hysteresis for rpm pulses, which means the visualization is more stable, not ‘jumping’ rpm values. Hysteresis is small, not affecting fast rpm changes, but helping out to have stable information about rpm.

    Measuring the temperature of multi-cylinder engines.

    For multi-cylinder engines we developed the special small device, able to sense temperature from up to 5 cylinders, and sending to SparkSwitch Pro maximal or minimal value of temperature. The device is connected to the SparkSwitch Pro temperature port, or S.BUS2 port, or both ports. You can connect analog output from Temperature device to SparkSwitch Pro and to visualize maximum/minimum of temperatures on telemetry screen, and you can define also warning events for that temperatures, and simultaneously you can have connected S.BUS2 port to S.BUS2, and to have visualization of all temperatures on separate telemetry screen.

    On picture below you can see device with all 5 temperature sensors and patch leads:


    In new version of the device was removed jumper area, added micro-USB port for configuration. Also new firmware.

    Short description of device functionality.

    The device is controlled by a SAMD21 microcontroller with 256kB of flash memory and 8kB of RAM. Temperature sensors (original PowerBox sensors) are connected to connectors T1 - T5. Does not matter what number of sensors will be connected, the minimum is 1 :-) Device register all connected sensors automatically, provide calibration for initial temperature and then is measuring each one temperature in the loop.

    The device has two outputs, first, analog, is resistance output, the same behavior as a single PowerBox temperature sensor. Resistance is set up as a linear function, based on the temperature, the device set up the resistance of output to the same, as in the case of a single temperature sensor.

    The output resistance is set based on the configuration, maximum or minimum value of the temperature of all connected sensors. Usually, almost all pilots are using maximal temperature output, to be able to know the maximum temperature of each one from connected cylinders. Of course in the run-in process is important also the minimum value, but for normal flying is used maximum value.

    The second output is the S.BUS2 output. In that case, the device send all temperatures from T1 to T5 to telemetry using the S.BUS2 protocol. We are working on Jeti/Core and Futaba telemetry firmware to be able visualization of all temperatures on the telemetry screen. So far, we implemented only Futaba telemetry, but approaching the target soon :-)

    Mainly is the device used to connect more than one temperature sensor to SparkSwitch Pro, as described above.

    Warning - in new version we don't have jumpers area, configuration is done using micro-USB port and configuration software.

    Connection setup: (Connected to temp port of SparkSwitch Pro - Old version)

    T1 - T5: Connect temperature sensors

    P2: Output to temp port of SparkSwitch Pro

    P1: Connect to ignition output of SparkSwitch Pro, use Y-splitter cable

    Jumpers setting:

    J1 - calculating the maximal temperature from all attached sensors

    J2 - calculating the minimum temperature from all attached sensors

    J3 - not used (S.BUS2)

    Connection setup: (S.BUS2 - Old version)

    T1 - T5: Connect temperature sensors

    P2: Not used

    P1: Connect to SparkSwitch Pro Data port, use Y-splitter cable

    Jumpers setting:

    J3 - switching to S.BUS2 mode

    J2 - is inserted, the device will send minimum temperature to telemetry slot 1

    J1 - is inserted, the device will send maximum temperature to telemetry slot 1

    J1 + J2 - special setup for boxer engines, the temperature of the 1st cylinder will be sent to telemetry slot 1, 2nd cylinder to telemetry slot 6

    In case when is inserted only J3, the device will send all 5 temperatures (from active sensors the real value, not active sensors will be shown on telemetry screen as -------) to telemetry, using frame 3, 5 slots.

    For further details, orders please contact me directly.

  • Hello All,

    The latest version of the RPM device is working properly with all Ignition systems without tacho output. This device is flying with OS/Moki/DA/Saito/3W/Valach engines without issues, stable measurement, able to operate with HV, PWM output for digital/analog servos.

    Development and improvements/updates were completed.

    For DA users the device is assembled also with patch leads, mainly the lead for power supply with Anderson PowerPole connectors and double JR connector. For Moki engine users is a device assembled also with Moki ignition ribbon/JR cable, for 3W users also with special power supply cable with double JR.

    Who interested in it, can drop an email to, I assembled more than 50 devices for you:-)

  • Hello all DA, 3W and other users :-)

    let me inform you, that I ordered PCB's and components for the last 50 pieces of the RPM device. I will not plan for the future with further production, therefore all who are interested in this device, please send me an email. At the end of the week I will assemble all 50 devices, the last series, and from Monday - next week - I will be able to send the device.

    contact me directly on email




  • Hi...It is hard to get an overview of what is actually possible to do in CORE radio at present (other then what can be read in preview User manual). It seems it is quite some work in software that remain to be finished, at least as I have understood it.

    And this is possibly one weak spot with the CORE radio, PowerBox Systems is rather small company so the resources to implement all features wanted in software may take some time.

    pcb assembly