Connecting RCT / Deltang receiver output pads to soundcard trigger inputs
 Probably, the most useful feature of RCT/Deltang receivers is the range of outputs which are provided. For example, the RCT-Rx65b has fifteen outputs in addition to those controlling the motor. By default, they provide outputs to control servos, to operate LEDs and also 0v outputs for triggering the effects on soundcards, such as sounding the horn or whistle. Furthermore, the outputs from the pads can reprogrammed thereby vastly increasing the range and diversity of applications to which the receivers can be put.

The output which is the most straightforward for triggering soundcard effects is from Pad C (numbered 15). This provides 0v when the Bind button is pressed on the RCT-Tx22 or any Deltang transmitter. The Bind button operates Channel 5 by sending it 'low' when pressed and so a conventional DSM2 transmitter could also be used to trigger the output pad via Channel 5. Connecting a wire from Pad C to the horn/whistle trigger input on the soundcard is all that would be needed to operate the soundcard's horn or whistle - provided the receiver and the soundcard share the same battery. If they use separate batteries, the trigger will still operate provided the negative terminals of both batteries are connected together (But don't connect the positive terminals!).

The outputs from Pads A, B and C are buffered on the RCT-Rx65b and so provide some protection for the receiver from excess current. When using any other output pad to trigger soundcard effects, it is advisable to protect the receiver by installing a 1k ohm resistor in the lead from the pad to the soundcard trigger input. This will help to protect the receiver from excess current being passed from the soundcard. Most soundcards operate internally at 5 volts whereas the RCT-Rx65b operates at 3.5 volts internally - hence the need for the precautionary measure.

For more information on using output pads to trigger soundcard inputs see these entries on my Blog: