Programmable 8-character LCD module and digital voltmeter




Signal and power from the same voltage source

Most hobby electronics store carry cheap and ready to use digital voltmeter modules (DVM) the problem with those is that they do usually require an independent power source to power the DVM-module. Many circuits are made such that you have one power supply and you would like to power your circuit and the voltmeter module from this one single power supply.

This is exactly how you can use our 8-character LCD module and it saves you a lot of headaches on the power supply side. The module can either be powered with exactly 5V DC (without the voltage regulator installed) or it can be powered with a DC voltage of 6.5V or more.

Programmable 8-character LCD module and digital voltmeter

A display that works in the dark and in full sun light

We have used an LCD display that has back lighting but is at the same time able to take advantage of any surrounding light sources. In other words you get a module that works well in the dark and in full sun light. The readability is very good.

Space for your own sensor and components

This module is not just a display. It has as well a dot-matrix area where your can add your own components.

How can I program this 8 character display module?

The system has an atmega328p (or atmega328) chip and you can basically program it in any way you like and make it do anything that a microcontroller can do: Time events, read digital or analog signals, output digital signals, interact with the users.

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The display is 8 characters long and fully alphanumeric. You can display letters, punctuation and numbers.

The possibilities are almost endless you just need to write the software for it. We provide some basic examples in the download section at the end of this article. You can take that code and use it to build your own application.

A configurable DVM module: flexible with no need to write any software

You can write your own software for this module but it is optional. It comes with software loaded and this default software covers a wide range of applications
We have noticed that a lot of user want to measure analog signals, run them through some linear formula and then display the result. All our “8 digit LCD modules” come now with software per-loaded that allows you to do such things without writing code. You just set a jumper wire and you enter a setup mode where you can enter the parameters for a linear equation.

The equation you can configure is:
Display_value = Analog_to_digital_converter_output * M / D + A

M, D and A are configurable constants (M=multiply, D=divide, A=add or subtract). All math is done with integers and from left to right in the above equation. You can as well configure a parameter P which is the amount of digits behind the decimal point. In other words you can e.g set P=2 which will then display 10 as 0.10 and 100 as 1.00 etc… The “Analog_to_digital_converter_output” is an integer number that the analog to digital converter (ADC) provides and in this case it is a number between zero and 4092 (12 bit with oversampling).

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It is as well possible to optionally configure a short two character string that will be shown behind the numbers in the display. This can be used to display a measurement unit such as “mA” or “‘C”.

A configurable DVM module: Dual voltmeter

As of firmware version 1.1 this configurable digital voltmeter supports the measurement of two voltages. Thus you can measure two different signals: One analog signal on ADC0 and another one on pin ADC1.

This display can then be switched between the two channels:

  • pin PD0 on CONN4 open: show readings from analog input ADC0
  • pin PD0 on CONN4 connected to GND: show readings from analog input ADC1

Note that both analog channels (ADC0 and ADC1) have one common ground pin.

 

For more detail: Programmable 8-character LCD module and digital voltmeter




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