A popular purchase from the usual stockists of imported electronic modules is a digital panel meter. A very small amount of money secures a module with a seven-segment display that you can stick on the front of your power supply or project for an easy readout. Even before the advent of these ultra-cheap Chinese products there have been readily available digital meters, in a line stretching back to the 1970s with chips such as the Intersil 7106.
[Marcus Taciuc] is eschewing the off-the-shelf parts, and creating his own digital panel meter. He’s using an MSP430 microprocessor as the brain of his device, and a Hitachi HD44780 compatible LCD display at the front end. The appropriate combinations of resistors and op-amps feeding the MSP’s ADC inputs allow his meter to be used to measure up to 40 VDV, and up to 10A.
He’s put up a video which we’ve included below the break, showing the use to which this meter has been put: replacing the moving-coil meter in what looks like a classic piece of Heathkit equipment. A 3D printed bracket allows the new meter to fit the circular hole of the original meter, with the LCD on the front. You might still order a prefab meter module, but you can’t deny this looks good.
Not all LCD panel meter builds are so polished. A few years ago we brought you one using a dollar store pedometer.
A nice build, but a shame that a nice old Heathkit SWR bridge had to give its life up to make it happen.
But the swr bridge didn’t give its life just had its life enhanced
I feel like this post kind of undersells the project here. He just didn’t whack a digital volt meter onto his adjustable power supply, he developed the hardware/software for his own multimeter. Open source as well, by the looks of the page on IO. This is not a light undertaking, and now that he can run his own code right in the power supply, who knows what kind of future features or enhancements are possible.
Though for all that work, I would have put in a backlight LCD personally…
there are 2×16 fluorescent hitachi style displays. FAST and bright! but beware of burn-in, you must run a screen saver. (I used one to control an arduino espresso machine mod I did and after 2 years of it being always-on (in clock mode) I saw definite burn-in). they also make expensive oled style hd44780 displays but the ones I tried were buggy and would not always init properly. they were also very fast for i/o speed and their contrast was the best I have seen (thin panels, too).
The 3D printed bezel for the LCD really makes that look very good! Turn on the LED or EL back light (if equiped) and it will look even better. No doubt, the purists will insist on keeping the moving needle meter (I am in this class), but if it’s for equipment that is used for active service, then a digital display usually (not always) works better. In the case of an SWR meter, I would think you would prefer a moving needle since it sort of “averages” the value. Same goes for current meters. But Marcus’s work here is definitely top notch and there are many more ways it can be applied to other equipment.