Automation skills provide home lift
After a career in electronics, instrumentation and automation, combined with a lifelong affinity for all things mechanical, I can’t help but keep an eye out for any equipment or system I can improve, no matter how small. Recently, I completed a project to re-automate a commercial-grade garage door opener using an industrial-grade Programmable Logic Controller (PLC), Human-Machine Interface (HMI), and hardware. a variable speed drive (VFD). The result met my specific needs and is much better than the original equipment, and is an example of how users can perform many similar types of projects at home or at work.
When Stock Isn’t Good Enough
Although I am now retired, I am fortunate to have a 60×100 ft garage on my property where I can store various “toys” such as RV’s, a tractor and even a dump truck . Access to the garage is through a 16 foot wide by 14 foot high roll up door operated by a commercial grade electric door opener.
This popular brand of door opener looks much like what you find on any typical residential garage door, but with a heavy-duty motor and chain drive reduction system. The stock drive uses a 120 VAC 0.5 hp motor, with sprockets and chains to reduce the motor’s rated speed from 1800 RPM to something much less to drive the gate at a appropriate speed and with torque multiplication.
The basic mechanical operation of the door was adequate, but the opener used what I call “bang-bang” control. Each time the user pressed the wall button or the remote control, the opener opened completely at full speed or closed completely at full speed. Besides the jarring sound this produced and some level of mechanical impact on the door, the real problem was that the various drive chains would be slammed so hard they would stretch. And once the chains stretched, the jerking action worsened and the resulting looseness in the mechanism could lead to over- or under-actuation of the door.
When new, the various chains were correctly tensioned on their respective sprockets. However, no provision has been made to compensate for the normal type of stretching of roller chains as they age. The controls simply revved the engine to maximum rpm, exacerbating the chain stretch as the engine attempted to instantly accelerate the rather massive gate from a standstill to top speed. After a few thousand cycles, the start of the door movement became noticeably violent due to the excessive “slope” of the speed reduction mechanism. The opener was bound to mechanical failure if corrective action was not taken.
If there was a problem with the opener, there was little diagnostic information for troubleshooting. For example, once the motor was operating erratically and after considerable troubleshooting, it was finally determined that a spider had built a web in front of an optical sensor, which triggered a false operation.
In addition to wanting to address these drive issues, I also had a few special needs for my purposes. Sometimes I just wanted to open the door enough for a small car to enter. Other times I needed the door to accommodate a much taller dump truck or open fully to its 14 foot height. These multiple positions prevent wear and tear on the door mechanism, but the real goal is to keep as much heat in the winter and cool air in the summer inside the building by only opening the door as much as necessary. Other times I’d like the door to open about 6 inches off the floor so my barn cats can get in and out, while still maintaining some degree of access security.
Based on these needs, I decided to use my experience in industrial automation and some off-the-shelf devices to upgrade the door to work as I wanted and to add functionality.
Having worked with different makes and models of PLCs, HMIs, VFDs and other automation components, I was already familiar with many of the options available from AutomationDirect. I researched what was needed for the project, keeping in mind that it was a personal budget, and selected the following devices, which were easily installed in a control panel:
- CLICK series stackable micro-brick PLC: numerous logic capabilities, numerous I/O options, communication ports and free programming software.
- C-more Micro touch screen: 6 inch. color touchscreen, with five user-definable buttons and free programming software.
- GS2 Series AC Drive: Capable of accepting 120/240V 1P/3P input power and generating 240V 3P output with communications.
- IronHorse 0.5 HP 3P motor: inverter and suitable for pre-mounting on the door opener.
- Various sensors, wiring accessories such as pre-wired ZIPLink connection cables and other items.
Since switching from old to new controls needed to be done quickly, to keep the door usable, it was essential to pre-test the system as much as possible. A carefully detailed architectural drawing of the control system has been created to show the connections, pinouts and settings of each device.
The project took advantage of serial communications between the PLC and the VFD, providing the PLC with the maximum data and control functionality possible from the engine controls. The correct cable was selected, but during initial testing, operational delays and communication errors were noted. This problem was eventually solved by better protecting the cable, which is a good practice whenever communication cables pass close to three-phase power or UPS outlets. Another factor is that the panel is powered by a rural electricity network, which can experience momentary blackouts and brownouts.
Programming new features
There are traditional limit switches on the door to indicate different travel positions. For the upgrade, a proximity switch and pinion were added to act as a simple encoder and provide pulse counts to the PLC, so that door travel distance can be tracked with repeatability effective position greater than ± 0.25 in. The pulse count is reset each time the door closes completely.
Control buttons and a touch screen are available to the user. With all these elements, it was possible to create much more advanced features including:
- Automatic, manual and jog up/down functionalities.
- Normal closing function.
- Open to predetermined heights of approximately 6″ (for ventilation), 8′ (for standard person and vehicle access), and fully open (for large equipment access).
- Jog function up or down.
- Accelerate from the start and decelerate until the end, for each movement to minimize mechanical wear. This also helps to ensure that the gate reaches the target position more accurately as it moves slower. This feature alone has greatly extended the mechanical life of the door drive mechanism as it may never need repair, but rather routine maintenance.
- Provisions for the system to determine the location of the door when restarting after a power failure.
- Extensive diagnostics via the HMI which in most cases do not require any other troubleshooting tools.
The PLC and HMI development software was easy to use with a simple feature set, and AutomationDirect provided helpful phone and web support to resolve some minor hardware and software issues. For programming the PLC, a single level of nested subroutines was used to make the program organized and modular.
There are a few more advanced features that would have been useful if more advanced functionality was needed in the PLC software, such as nesting multiple levels of subroutines, finding subroutine calls by name, and applying from a visibility animation to grouped objects instead of individual objects on the HMI. But overall, the freeware is extremely capable and easy to learn and use.
Do things your way
Consumer goods are often quite advanced today as manufacturers strive to meet consumer needs. But there are still cases, like the standard garage door opener, where the results fall short. For this situation, I was able to use components to create a control system that operated the equipment more efficiently and economically with less wear, while adding many functional and diagnostic capabilities.
Using devices like these that support standard communication protocols makes it easy to add future functionality. The system currently uses a traditional garage door opener remote button, but I could easily add web-accessible capability for monitoring and control. As with any new design, there were a few issues, mostly in the programming, but with all system data made visible through the HMI, troubleshooting was relatively easy. Careful design and documentation will make it easy for anyone to work on the system.
This project is a good example of how end users can approach an automation project, whether at home or at work, and make it their own.
Mike Thiel is a retired engineer whose career began as a US Navy specialist working on firearms fire control computers, radars and electronic counter-countermeasures. He then held positions as an electronics technician and electrical engineer working in materials handling, robotics, and combustion hardware and software design. Electronics has always been a hobby for him and he is always on the lookout for interesting projects to work on. Thiel also operates a garlic farm and can be contacted for agricultural or technical questions at email@example.com.