Panel Mount Display Solves The Problem Of Drilling Square Holes

[Absolutelyautomation] has a problem with seven-segment displays. Fitting these displays in an enclosure is a pain because you can’t drill perfectly square holes, and you will invariably mess up a few enclosures with overzealous file work. There is a solution to this problem – panel mount meters.

The bezels on these panel mount meters hide the imperfections in the enclosure, and usually don’t require screws. They are, however, dedicated displays, usually for temperature, RPM, or some other measurement.

[Absolutelyautomation] took one of these dedicated panel mount displays and turned it into an all-purpose device. Basically, it’s a panel mount Arduino with three seven-segment displays.

This project is built on perfboard cut down to fit inside the enclosure of a very cheap panel meter found at the usual suppliers. Tucked away underneath this perfboard is an ATmega, a few resistors, and the support parts to make everything go. This panel mount meter can either be a serial slave or as a standalone controller, programmable with the Arduino IDE. It’s cheap, too. You can check out [Absolutelyautomaion]’s video below.

31 thoughts on “Panel Mount Display Solves The Problem Of Drilling Square Holes

      1. Except it doesn’t really leave a clean edge on both sides and requires you to start on an edge.

        But you can actually drill clean square holes. You just need a special bit.

    1. What IS the problem? Have people lost their dexterity?

      Out with masking tape, the plastic square ( as in T), and a hand punch (for impressing corner points). Drill, SLOWLY and carefully, on each dimpled corner mark. Slowly enlarge the holes (a small step drill is great for this) until the linear cutting tool can fit.

      Small files can correct any errors so all the holes are aligned. Then using your metal cutter of choice go from hole to hole. Sometime drilling a central hole allows different techniques. Dremels are great for linear cutting employing lots of patience.

      I often cut small openings in stainless steel. After drilling FIVE holes, I work, with an angle grinder using a small diameter (by wear) disk, from the centre hole into each corner. Practice on scraps of metal – cheaper than damaging cases.

      Then you can fill your new hole with with products from WinMate Mounting Designs, and the many similar offerings from other companies.

  1. Most of these Cheap DVM-Modules come with a STM8 µC as their “brains” and are therefore relatively easy (SDCC supports the architecture, ST-Link flashes the code) to reprogramm.
    I don’t necessarily say, that he should have done it this way instead, but it’s a nice thing to keep in the back of your mind.

      1. I hack a lot of STM8 stuff, but sadly my meters all have a black blob (probably an ICL710x or an obscure mask-ROM 8051 clone with ADC) so no hacking.
        For STM8 hacking I suggest a W1209 thermostat which is still $1.50 and has a 3-digit display, 3 buttons, a relay and an NTC. Replacing it with a voltage divider and rewriting the firmware is all you need to turn those into voltmeters with buttons and a programmable relay.
        They aren’t panel mount, but they are $1.50. Also you’ll need to either move the relay or get a $1 laser-cut box to mount it behind any panel. I usually desolder the relay and use two jumpers to connect the coil pins to the contact pins, which are broken out on screw terminals.

  2. Overzealous, just the typical in a hurry to do sh!t. Approach perfection then land on it. Just like landing on the moon. Never overshoot. If you take half off as much each time you will never overshoot. For layout fine line scratching or fine pen line on masking tape or dull finish clear tape. No pencils.

      1. I’ve sworn off perfection, nothing ever gets finished.

        It’s like that joke, the first 95% of a project takes the first 100% of the time, the final 5% takes the other 100% of the time.

        Yah, there’s such a thing as doing it the right way in the first place, but, if I had stuff with a bezel, I’d just sharpie myself a “good enough” target, chuck up the cutting blade in a dremel and hack a hole out of the thing. A hole was required, a hole has now been installed, mission accomplished.

        I flatter myself that I am a little skilled and smart, hence my 95% is as good as “average Joe’s” 110%, and my 100% if I ever finish is a masterpiece, and my 105% is godly but requires exponential amounts of time.

        So I aim for the get shit done 95% now. Good enough, next thing…

  3. Huh. I was initially going to say that this seemed a lot of trouble when you could just buy a bezel, or that I suspect you can find 3d-printer designs to make bezels for nearly any printer in existence. But I’m not sure either of those is cheaper that the bezel+display+electronics+shipping of those cheap meters!

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