Description The EP-321/323 converts a tristate (on/stop/on) 24VAC/VDC signal to a stepped pneumatic output. The increase or decrease signal is resolved into multiple steps/pulses of pressure change. Each step/pulse width is field programmable. Similarly, the time interval between steps is also field programmable. In this way, a 24VAC/VDC signal can be used to step a pneumatic actuator from a fully closed to fully open position over a given time by individually controlling the pulse width and the pulse interval of the output pressure change. The EP-321/323 is an inexpensive alternative to proportionally control a pneumatic signal without using expensive analog output or complex software. Model EP-321/323 incorporates a revolutionary new concept of accepting a tristate signal to step a pneumatic actuator from a closed to an open position. When the increase input is energized by providing a 24VAC or 24VDC signal, the increase solenoid starts pulsing and as a result, the branch line pressure increases in steps. The pulse width of the percent of branch line pressure change can be easily field programmed by adjusting a multi-turn trimmer. Also, the interval (time) between the two pulses/steps can be easily field programmed by adjusting a second trimmer. When the increase input is de-energized, the unit will discontinue increasing the pressure. Similarly, when the decrease input is energized, the decrease solenoid pulse/step width and interval can also be individually programmed to decrease the pressure in the branch line over a given time with a certain percent change per step. In this way, a steady 24VAC/24VDC signal can be used to proportionally change the pressure to an actuator over a given time in controlled steps. The pressure change can be as little as 0.1 PSIG per step or as great as 10 PSIG based on actuator volume and main pressure flow rate. The interval between two pulses or steps can be as fast as 0.30 seconds or as slow as 25 seconds. The stroke of any pneumatic actuator can be proportionally controlled over a given time without an analog signal or complex software routine. The EP-323 has an additional feature. The unit accepts a 24VAC/24VDC hi/lo limit input. If the unit is increasing pressure and the increase input is on, and if the variable crosses the hi/lo limit by energizing a third input, the EP-323 will circumvent the pulse width and plus pulse interval time programming and jump to full pressure. Similarly, if the decrease input is on the hi/lo limit is energized, the unit will dump pressure. The hi/lo limit can be used to override the stroke of the actuator an quicken the control if the variable exceeds the hi/lo limit. The EP-321/323 accepts a universal 24VAC or 24VDC power and input signal. By using high-performance integrated circuits, the units exhibits excellent repeatability and stability over time. A unique electropneumatic converter assembly is incorporated to eliminate pressure regulators and filters. The complete assembly can be field replaced if need be. The unit is immune to mounting orientation and fabrication. After a significant R&D effort, the size of the EP-321/323 has been reduced to occupy the least amount of panel space. In fact, the EP-321/323 is the smallest and highest performance electropneumatic transducer in the industry.