PCTx Royal Transmitter Hack

Submitted by Grzegorg Cielniak

 

The following info was submitted by a PCTx user wishing to use the PCTx with an incompatible radio. Greg wanted to use a Royal transmitter with the PCTx and after an unsuccessful firmware update Greg discovered the following:

"I managed to discover what the problem was and successfully connect the PCTx to my Multiplex radio. The output signal from the PCTx was too low, so the right solution requires an additional amplifier/buffer. The simplest version of this device can be found here: http://www.designsoft.com.au/ahome/rc/EVOtraining/
The solution is provided for Royal Evo radios but might be valid for other radios with compatibility issues. By the way, the RoyalEvo radios work with both positive and negative PPM signals. Thought this information might be useful in future."

Greg explains his hack in detail:

"The output from the PCTx is connected to the transistor's base through 4k7 resistor, the emitter is connected to both the ground from the PCTx and radio's ground pin (actually the ground is connected to the pin 3 instead of the connector's shield). The collector is connected directly to radio's PPM input (pin 4 in Multiplex radios). Normally the transistor would need an extra resistor that provides the power to the collector but it is omitted in this design. I suspect that this is somehow resolved inside the radio and that the transistor is powered from radio's internal battery. I can only testify that this design works like that and that the whole thing can fit inside the connector if properly squeezed. :)"

Based on Greg's discovery we have created the following schematic. Parts for this hack can be obtained from our sister site, Endurance Robotics: www.endurance-robotics.com Thanks Greg!

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