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Current Meter LED Bar Graph

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Hey Everyone.

I want to make a simple Current Meter that measures up to 1A and I want to display this on 10 LED Bar Graph Array. (10 LED's in a line in the 1 package)
So, 0-99mA will light 1 LED. 100-199mA will light 2 LED's and so on.

I was thinking of using the LM3914 to drive the LED's, but this means I need to convert the Current to a Voltage.

So, I was thinking of using this part; ASC712 Hall Effect Current Sensor
I think you can put it in series with the circuit and the IC picks up the magnetic field and outputs a voltage.
185mV per Amp for the 5A version.

So becasue I want to measure up to 1A in increments of 100mA, I need the LM3914 to measure a Range of only 0V - 185mV (18.5mV increments)

I cant understand the LM3914 datasheet on how to adjust its range.

Can anyone help?
Or is there a better way to do want i want to do?
 

bountyhunter

Well-Known Member
I cant understand the LM3914 datasheet on how to adjust its range.
You do it by changing the voltage at the top and bottom of the resistor string inside the LM3914. Use the internal reference voltage with external dividers to create any voltage you need.

Or is there a better way to do want i want to do?
I'd use an analog meter because LEDs throw away so much resolution and therefore, reading accuracy. The LED is either lit or it isn't, you basically have a 10% (of full scale) reading error built in.
 
Last edited:

bountyhunter

Well-Known Member
LEDs themselves give a very good indication of percentage, They are NOT simply on or off.
If you think that's true in this case, you don't understand how the LM3914 works or why they put positive hyteresis on comparators. When an LED is driven from a comparator, it's either ON or OFF, there is no analog representation.
 
Last edited:

k7elp60

Active Member
Hey Everyone.

I want to make a simple Current Meter that measures up to 1A and I want to display this on 10 LED Bar Graph Array. (10 LED's in a line in the 1 package)
So, 0-99mA will light 1 LED. 100-199mA will light 2 LED's and so on.

I was thinking of using the LM3914 to drive the LED's, but this means I need to convert the Current to a Voltage.

So, I was thinking of using this part; ASC712 Hall Effect Current Sensor
I think you can put it in series with the circuit and the IC picks up the magnetic field and outputs a voltage.
185mV per Amp for the 5A version.

So becasue I want to measure up to 1A in increments of 100mA, I need the LM3914 to measure a Range of only 0V - 185mV (18.5mV increments)

I cant understand the LM3914 datasheet on how to adjust its range.

Can anyone help?
Or is there a better way to do want i want to do?
One way to do it with the LM3914 is us the bargraph mode, then use a current sense resistor, an opamp to amplify the voltage across the current sense resistor to feed the LM3914. What is the DC voltage of the current you want to measure?
 
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