3 HMI Failures Disguised as Hardware Failures
A frequent and frustratingly common failure in industrial equipment is HMI (Human-Machine Interface) failure. Since it is the piece of the equipment that gets interacted with the most, it stands to logic that HMIs would suffer higher rates of failures. Equipment that has a lot of use can be prone to abuse – as the saying goes. But sometimes what is thought as a hardware failure can be misdiagnosed and really something that can be remedied with some simple troubleshooting. Here are a few examples of this we see often when helping customers with their HMI issues.
The Display is Very Dark but Can Still Be Read
Anyone familiar with LCD screens has seen one or more go dark but where you can barely see the image. Often this means that the LCD screen’s backlight has burnt out. You see, LCD’s (or Liquid Crystal Displays) must make use of a back light as the colored liquid crystals within do not emit light on their own. So brightness must be achieved by another source. Many who see one of their screens go dark in this way automatically think that the screen must be repaired or replaced due to a backlight issue. One thing they don’t always check is to see if the brightness or contrast settings have changed on the device. Sometime these settings set incorrectly can fool one into thinking it’s a hardware issue.
Screen Only Comes on When I Press Down On Something
If you have ever seen the old show Happy Days, you’ll remember this bit that “the Fonz” would perform whenever he would enter the restaurant. He would saunter up to the malfunctioning juke box and give it a thwack with his fist. Seemingly this fixed it by magic. As far fetched as it seemed to the viewer, this act did have some basis in reality. Many times, in the service center we get reports that sound a little like “it only works if I press the back of it just so…” or “We have to keep this piece or tape on the board here or the power goes off.” The types of hardware failures that can cause these conditions are many. Sometimes it will be due to a cold solder joint on a PCB that makes a connection only when in just the right position. Other times it will be an IC chip or relay loose that is only connected intermittently and will eventually become disconnected by vibration or by other machine movements. But for every hardware issue we lead a customer to, we also find plenty of user error as well. The simplest of which is a connector not being plugged all the way. Always check cabling and connections first before moving on to assuming something has failed.
Button Stays Depressed or Only Works Intermittently
Keyboards and keypads head up the list as components that get the most abuse. From frequent use, frustrated operators or even lack of cleaning, anything with buttons will need to be replaced eventually. One thing we hear a lot about is buttons getting stuck or staying depressed even when released. Before assuming that the button has failed ask yourself, when was the last time this was cleaned? A lot of you will answer never. Always clean before anything else, you’ll find that many failures in electronics can be resolved with a little bit of TLC rather than needing to be replaced.
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