We do not recommend powering third-party devices from the i/o board. Use a separate external power supply when wiring additional exit devices. Powering multiple controller devices from a single source is not recommended because whether it's from an external power supply or an on-board source, neither option generally has sufficient amperage to power multiple controllers.
The required amperage for multiple connected devices must be carefully measured and calculated to ensure that the power supply can sufficiently handle the amperage that is required. Limited amperage is available from just a single power supply.