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Author Topic: Arduino LCD Voltmeter and Ammeter  (Read 301 times)

KB3ONA

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Arduino LCD Voltmeter and Ammeter
« on: May 03, 2020, 10:32:44 PM »

I'm in the process of building an adjustable power supply and I want to use digital meters for the voltage output and current instead of analog. I started playing around with an Arduino Uno and would like to use two 5v LCD meters I got from Sparkfun a little while ago (https://www.sparkfun.com/products/255). I've read several articles in various places where people made similar LCD meters and it looked like they mounted the meters along with the Uno board with a shield on top of it in the enclosures they were using. I view the Uno as a prototyping board and I'd prefer to use one board for several projects so I'd prefer not to do that. I'd rather include the necessary connections for the meter on the PCB I'll make (for 5v input, ground, etc.) and only mount the meter. I'm new with Arduino so I was wondering if there's any reason why I couldn't just do that instead of mounting the whole shebang (Uno board and everything) like people have done in some of the articles I've seen. Why would you have to mount the Uno? Or is it not necessary? Any info would be greatly appreciated.

Thanks, Gene (KB3ONA)
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W9IQ

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Re: Arduino LCD Voltmeter and Ammeter
« Reply #1 on: May 04, 2020, 04:36:38 AM »

The LCD panel (not meter) is simply the display portion. It gets its data via digital signals from the Uno uP.

The reason to locate the Uno close to the power supply and to shield it is to prevent interference with the relatively high impedance of the A/D (analog to digital) converters. Without short leads and proper shielding, the A/D will pick up noise which will cause the readings displayed on the LCD to "jump around" even when the actual voltage and current is constant. This can be very frustrating.

The shielding may also help with keeping the digital noise from the Uno out of your power supply.

There is no harm in experimenting with different configurations. It may work well for your application. But if you experience problems, then work on shorter leads and better shielding. It's all part of the homebrewing  fun and learning.

- Glenn W9IQ
« Last Edit: May 04, 2020, 04:41:29 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

N7EKU

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Re: Arduino LCD Voltmeter and Ammeter
« Reply #2 on: May 04, 2020, 10:17:55 PM »

Hi,

Seems like a pretty complicated way to make a volt or ampere meter!  Do you want to eventually make an energy meter or something?  Small LED digital meters are available for a couple bucks each.

73.
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Mark -- N7EKU/VE3

KX4OM

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Re: Arduino LCD Voltmeter and Ammeter
« Reply #3 on: May 06, 2020, 03:20:40 PM »

Harbor Freight DVMs are available free from time to time. I've repurposed a few and still have some in original packaging. Connect one as "Ammeter" and one as "Voltmeter." Kinda large for a small power supply, though. There was a section in the ARRL handbooks for a few years that showed a commercial DVM stuck to the panel. That was more involved than putting 2 cheap ones in. I have one that I carry to hamfests without leads, just to check transformers and chokes.

Ted, KX4OM
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