Logic Part 1 - Controlling a Power Sequencer

Will Fraser

Logic Part 1 - Controlling a Power Sequencer

In this series we will explore some basic logic circuits and how they can solve some common problems encountered when designing a system.

In this guide, we will start with a simple request from the customer and evolve the design to meet the changing functional requirements of the application, venue and hardware.

We start with a customer having a request for the ability to power cycle his sound system from a control device located at the mix position. A latching toggle switch is tied to the Control Input port of a Soundweb London device. In this most basic logic circuit, we are going to use the Control Input port to drive the Logic Output that is connected to the Power Sequencer.

In HiQnet London Architect, a Logic Source is associated to a Control Input of a Soundweb London device in the Design Tree. The output of the Logic Source processing object feeds the input of a Logic End processing object. This Logic End is associated with a Logic Output of a Soundweb London device in the Design Tree.

When the switch is in the closed position or ‘high’, it will turn on the Logic Output, setting the Power Sequencer to the On state. When the switch is in the open position or ‘low’, it will turn the Logic Output off setting the Power Sequencer to the Off state.

In other guides we showed how to use control ports within London Architect, so we will not go into detail here.

Now we will add our first change. We discovered that the Power Sequencer control is not as we thought. This particular Power Sequencer has a separate control port for Power Up / Power Down and a system status output for driving an LED. We also need to use a momentary switch at the mix position so that the Power Sequencer can be controlled from multiple locations (i.e. the mix position and the rack location). The first step is to replace our latching switch with a momentary switch that has a lamp indicator built in. We need the lamp indicator to tell the Operator the status of the system. Our next challenge is to make this single momentary switch toggle between two Logic Outputs. We will use a Counter Shifter processing object to do this.

Like many processing objects, this object is scalable. The number of outputs can be changed in the Properties Window.

Every time the input to the Counter/Shifter turns on, it will count on its output. Through properties you can configure this object to count in Binary or simply shift the output down. When the count reaches the last position, the Counter/Shifter will start counting over from the beginning. For this application we want this Counter/Shifter to have two outputs and shift down as its counting method. This object will now toggle between two outputs every time the input changes from ‘low’ to ‘high’. We configure these settings in the Properties Window for this object. The two outputs now alternate back and forth each time the momentary button is pressed.

We need these output signals to be momentary pulses not maintained. To accomplish this we add a Single Pulse Trigger to both outputs of the Counter Shifter.

The Single Pulse Trigger pulses its output each time its input changes to the ‘high’ state. This is how we convert the latching toggle functionality of the Counter/Shifter to a pulse signal the Power Sequencer requires.

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