Today we will be learning some of the Sequential led controllers, which include:
1) Solid State Sequential Controller
2) Micro Controller Based Bag Filter Timer
3) Continuous cleaning
4) On Demand Cleaning

1) Solid State Sequential Controller: Sequential Timer is the major part of Dust Collector system for continuous cleaning of the system. The pilot operated pulse valves used on dust collector system can be operated using Sequential Timer Control. Light emitting diodes (LEDs) are used to provide visual indication through which pilot valve is being charged as well as it gives "Power On" indication on the display. The series of sequenced steps is customizable from 2 through 10.To adjust the length of time between valves being de-energized (Off time / Pulse Frequency) and the length of time that the valve is energized ( On time / Pulse Duration) controls are provided. All logic functions and timings are controlled by Silicon semiconductor components.
To Start and stop the Controller Two independent strategies are provided. They are as follows:
1) The first strategy will consequently stop the sequence and reset the Controller to the initial valve position whenever A. C. power is detached and then again reconnected.
2) The second strategy is by a remote control contact associated with the terminals provided. At the point when the remote contact is opened, the execution stops. When the remote contact is released, the execution proceeds from the previous.

Solid State Sequential Controller/Sequential timer Operation:
The Sequential Controller gives continuous sequential energization of associated loads. The "Power On" light emitting diode (LED) gives visual indication and the Pulse Valve number 1 is immediately charged, when power is applied to the sequential led controller. LED provides visual indication of this event as "Output 1".
For the particular length of time which is indicated by the setting of the “On time/ Pulse Duration” control, the pilot valve will remain energized. Note that the aligned dials are for estimated settings only and they must be measured, if exact times are required.
Pulse valve number 2 will consequently be charged at some time span after pilot valve number 1 has been discharged. This time span will be as shown by the setting of the "Pulse Frequency / off time" control. "Output 2” LED will give appropriate visual indication that this function is occurring. The Controller will continue to sequentially energize the pilot valves until the power is detached.
2) Micro Controller Based Bag Filter Timer:
The Dust Collector Controllers of various sequences can be programmed to suit customer’s actual necessities which are micro controller based units. This requirement can be fulfilled by using Sequential Timers.
The two basic modes of operation are: a) Program Mode b) Manual Mode
a) Program mode: The unit can be programmed to follow desired set of instructions as specified by client. This mode acts as automated dust collector systems
b) Manual Mode: We can process output (Pilot Valves) serially. This controller has been intended to operate the pulse solenoid valves used on dust collector systems.
The controller has been given with SEEPROM to hold programmed values of various criterions in case when there is power failure. The current data gets automatically stored in SEEPROM. This SEEPROM will store up to 1million read/write functions and the stored/existing data will be saved up to many years.
Operation of Micro Controller Based Bag Filter Timer:
The Micro Controller Based Bag Filter Timer provides timed sequential energization of connected loads. The Pilot valve will remain energized for the length of time as indicated by the setting of the “ON “control, when power is applied to the controller.
When we keep MENU key pressed on keyboard for approx 3sec, we can select “PROGRAM MODE” for modification in data of various specifications.
3) Continuous Cleaning:
Sequential timer boards are used for continuous cleaning. This means that the timer board is continuously pulsing to purify the filters while the system is in working condition. Only limited applications require this type of sequential timers; and most of all do not. In this type of system, there is no notification status to the sequential timer control from a pressure device which continuously observes the filter status. Rather than this, the system only uses a sequential timers, like the DCT500A Series timer board, which makes use of the on-board potentiometers to set the on and off time intervals for the continuous pulsing. Regardless of the reason why the system was developed that way, continuous cleaning could actually result in more damage than good. By continuously cleaning the filters, system could result in cleaning the filters even before they have had a chance to develop a dust matter, which is the main task for filtering purposes and protecting the filters. This can cause damage to the filters, which would end up in an added maintenance cost. In addition to this, during continuous cleaning, you are continuously using the precious compressed air, which is very costly. Therefore, in order to cope up with these issues and to optimize efficiency, manufacturers have implemented next version i.e. on-demand cleaning for mostly all applications.

Sequential Controller, Dust Collector

4) On-Demand Cleaning
In on-demand cleaning system, the sequential timer control does not start pulsing to clean the filter, until they seems to be dirty. This method not only helps to increase the filter efficiency and their life span, but also limits the amount of pulsing that helps to save the compressed air.
This helps the customer to run differential pressure lines from across the filters right into the timer board. This not only combines all the parts into one board, but also provides a digital readout versus the dial. With the pressure module, you will also have a linear 4-20mA output which can be used to remotely monitor the pressure, if desired. Furthermore, the digital display is used in setting parameters such as on and off times versus potentiometers like the other boards.
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