Embedded Dreams

I’ll be writing a few articles on easy and fun things you can do with a linear LED bargraph such as our Linear bargraph LED scale module, and this 1st one is meant to show you how to make the basic adjustments. Keep on reading and stay tunned!

The module

Although I’ll be using our linear LED bargraph module which was developed to be easy to use, you can use any similar (linear) module. This bargraph contains 12 LEDs, an input connector and 2 adjustable limits for the graph. The graph displays the voltage value at the input connector by lighting a number of LEDs proportional to that voltage. The higher the input voltage, the higher the number of LEDs lit. Just like a sound system VU, but linear; the graphs used for sound are usually logarithmic, in order to match our ear’s perception of sound volume.

Depending on the graph mode (bar or dot), the 1st LED will turn ON when the input voltage reaches or is below the voltage set by the BOTTOM adjustment control. The last (12th) LED turns ON if the input voltage reaches the voltage set by the TOP adjustment control. In between the BOTTOM and TOP set voltages, the other LEDs turn ON proportionally.

How to adjust the input range limits

In practice, it’s very very easy to make the adjustment of BOTTOM and TOP controls. In most of the projects in future articles, 2 voltages are involved: the input minimum and maximum voltages. Start by connecting the module to a power source. Then set the multi-meter to the 10V or 20V scale and put the negative (black) probe on a 0V point (like the regulator’s package) and the positive (red) one in the BOTTOM point:

Next adjust the BOTTOM control until your multi-meter reads the desired BOTTOM voltage. You may need some form of holding the negative probe, like an alligator clip, while adjusting the variable resistor with a screwdriver. The BOTTOM is now adjusted.

Then move the positive probe to the TOP point:

Adjust the TOP control until your multi-meter reads the desired TOP voltage. And that’s it! You’re now ready for the projects to come.

Check the Free Articles page for the articles in this LED bargraph series and other articles.