The Smartisant 8-Channel Output Board OP3 is an 8-channel, high power output board to allow control of low-voltage devices such as lighting, pumps, etc. This board uses 'high side' switching, i.e. it switches the positive connection to the load instead of the more usual method of pulling the negative side of the load to ground.
The board uses our standard 10-way shrouded header connector and features opto-couplers to provide isolation from the switched power and loads. Eight FQP27P06 P-channel MOSFETs enable voltages of 12V dc to 60V dc to be switched and high current support. Without heatsinks, these MOSFETs can easily switch up to 5A loads. With suitable heatsinks, they can be used to switch higher currents.
An advantage of a board like this is that only the components required for each application need to be installed. So for example, if only 3 channels are required, just one opto-coupler and three MOSFETs ned to be installed. This can significantly reduce implementation costs and the board can be populated/expanded later when more channels are required.
Construct the board by installing the resistors first, then the IC sockets. Then add the connectors, including a jumper for the grounds if required. Then add the MOSFETs and finally insert the CNY-74 opto-couplers, ensuring that they have the correct orientation.
High side switching enables the use of a common ground, which can be very useful in the smart home. It also makes it easy to use individual fuses per channel and we typically use an automotive 8-way spade fuse holder like this.
