In which cases do I need to buy 4 channels instead of 2?
2 channels control the forward and reverse direction of a single movement. When a second independent movement is required you move up to 4 channels: on a twin-motor platform CH1-CH2 drives the first motor and CH3-CH4 the second. Crane hoisting plus boom movement, a gate plus a barrier, and actuator control on the X and Y axes are typical 4-channel scenarios.
A channel does not mean a movement, it means a relay output. Every movement that changes direction uses two channels; a one-way on/off action can be done with a single channel.
Typical applications where 4 channels are needed:
- Twin-motor platform: CH1-CH2 for the forward/reverse of the first motor, CH3-CH4 for the forward/reverse of the second.
- Crane + boom: hoisting-lowering on one channel pair, boom movement on a second pair.
- Gate + barrier: managing two independent mechanisms from a single remote control.
- X/Y actuator: positioning on two axes.
When planning your channel budget, write down every movement on paper and note next to it how many relay contacts it needs. If there is a movement likely to be added later, moving up to the next channel option from the start is more economical than replacing the receiver afterwards.
ST100 is offered with 2 and 4 channel options, and ST200 with 2, 4 and 6 channel options. The relay current rating of the 4-channel receivers is not stated in the product data; make your load calculation with the value in the manual, and drive large motors through a contactor.
The full topic: Wireless Crane Remote Control Selection Guide