5.1. Pinout

Pinout of the Pololu RC Switch with Isolated Solid State Relay/Switch, SPST.

Pololu RC Switch with Isolated Solid State Relay/Switch, SPST, bottom view with dimensions.

The Pololu RC Switch with Isolated Solid State Relay/Switch has five pins spaced 0.1″ apart that give access to its logic interface.

RC interface

The GND, VRC, and RC IN pins make up the switch’s RC interface and can be connected directly to an RC receiver or servo controller:

• The GND pin is the ground or reference voltage.
• The VRC pin is the power input.
• The RC IN pin is the RC signal input. The switch measures the width of pulses on this line and uses that to decide whether to activate or not.

Power

The VRC pin powers the basic functions of the board and needs to be connected to a power source between 2.7 V to 16 V. This allows the board to be powered from a 4- or 5-cell NiMH or NiCD battery pack through an RC receiver or separately. The board’s control circuit will typically draw up to 15 mA from VRC when the switch is enabled and up to 5 mA when the switch is closed.

The logic is powered by an on-board regulator that outputs 5V when VRC is above 5 V. When VRC is below 5 V, the board’s logic level is approximately equal to VRC.

Load interface

The two slots on the opposite side of the board from the logic interface provide access to the switch. The switching is performed by a pair of MOSFETs controlled by an optically isolated driver that galvanically isolates the load from the control inputs. The MOSFETs are arranged back-to-back to make the two outputs symmetric and equivalent, allowing bidirectional current control with the switch in any orientation relative to the load (for example, this board can be used for high-side or low-side switching). Benefits over modules with mechanical relays with comparable current ratings include silent operation, a smaller form factor, and immunity to problems like contact wear and arcing that limit the service life of mechanical relays.

Versions of this switch are available with different voltage and current capabilities, and each of those is available with connectors soldered or without connectors:

Max load voltage	Max load current	Connectors	Item #
60 V	6 A	soldered	#5422
		not included	#5423
30 V	10 A	soldered	#5424
		not included	#5425

Real-world power dissipation considerations

In our tests, we found that the 30 V version of the relay/switch could conduct about 10 A continuously, and the 60 V version could conduct about 6 A continuously, without reaching the thermal limit for the MOSFETs. Our tests were conducted at approximately 25°C ambient temperature with no forced air flow.

The actual current you can pass through the board will depend on how well you can keep it cool. The printed circuit board is designed to help with this by drawing heat out of the MOSFETs. Solid connections to the output pins (such as with thick soldered wires) can also help reduce heat build-up in the MOSFETs and board.

Warning: Exceeding temperature or current limits can cause permanent damage to the MOSFETs. If you are switching an average continuous current greater than about 2/3 of the specified maximum, we strongly recommend that you monitor the MOSFETs’ temperature and look into additional cooling if necessary.

This product can get hot enough to burn you long before the chip overheats. Take care when handling this product and other components connected to it.

Creepage and high voltage isolation considerations

This product is designed to be compact, without consideration for extra creepage that is often associated with solid state relays and electrically isolated systems. As such, this product is not suitable for isolating regions at significantly different voltages. For an alternative that can provide the same functionality with significantly higher isolation voltage ratings, consider using our RC Switch with Digital Output with our Isolated Solid State Relays.

Outputs and indicator LED

The RC switch provides feedback about what state it is in via a yellow indicator LED. The LED behavior is described in Section 9. Status information is also provided by two additional outputs:

• The GOOD pin indicates the presence of a valid RC signal (10–330 Hz pulse rate, 0.5–2.5 ms pulse width).
• The OUT pin indicates whether the relay is activated (i.e. the relay coil is energized).

When high, the GOOD and OUT outputs will output a voltage approximately equal to 5 V or VRC, whichever is lower. When low, these outputs will be at 0 V (ground). These outputs do not have resistors in series with them. Each output can source or sink up to 25 mA.

Configuration interface

The learning mode jumper can be used to get the device into learning mode and configure it. The configuration procedure is described in Section 10.

Assembly options

The Pololu RC Switch with Isolated Solid State Relay versions are available with connectors soldered or without connectors

• Connectors soldered versions ship as shown in the left picture below, with 1×3 0.1″ male headers soldered to the RC control inputs, and these headers are compatible with standard servo cables that can be used to connect it directly to an RC receiver or servo controller. The two load connection points are accessible via a soldered 2-pin, 3.5mm-pitch terminal block.
• Versions without included connectors give you the flexibility to choose different connections. The control pins work with 0.1″-pitch male headers and female headers and are compatible with standard solderless breadboards. The load side of the board has two 0.045″×0.095″ slots that can accommodate 3.5mm-pitch and 5mm-pitch terminal blocks, a 1×2 0.2″-pitch header, or a 1×3 0.1″-pitch male header with the middle pin removed. Wires can also be soldered directly to the slots for high-current applications.