LM3916 LED Chip Alternative

About: I'm actually a horse trapped in a woman's body.

Unfortunately LM3916 chip has been discontinued. The LM3916 was an integrated circuit that senses analog voltage level and it was able to drive ten LEDs, LCDs or vacuum florescent displays.

In this instructable we will be creating an alternative circuit to imitate a LM3916 chip to drive a 10 LED bar graph.

Step 1: LM3916 Schematic

We started by looking at the LM3916 schematic to see how it functioned. From this Schematic we were able to analyze it and start creating circuits that would imitate the function.

Step 2: LT Spice Testing

We used the program LTspice to design and test this circuit to make sure it ran correctly.

In order to simplify our version of the chip, we have the op amps run through the LED when the non inverted input is a larger voltage than the inverted input. In the original chip schematic (in this instructable), the LED ran into the op-amp and then to ground.

Step 3: Step 1

From the circuit we designed on LTspice we were able to start creating the circuit on a bread board. But before we start we have to make sure we know how to properly know the schematic of lm358 op amp which can be found at https://www.digikey.com/product-detail/en/texas-in...

Now we can start by correctly hooking up the the op amps. What we need to do is shown above, we connected all of the V+ together and let 5 volts flow between them. We also connected all of the V- to ground. Lastly we connected the two positive inputs in each op amp together for all 5 op amps.

Step 4: Step 3

Next we have to created the resistance ladder. To do this we connected 10 resistors together. At the bottom of the ladder you want to ground it and at the top of the ladder you want to connect it to 5 volts. After this is all set up you want to make sure it is working okay by taking the voltage at each resistance. If it is working properly you should be able to see that the voltage is going from a very low volts at the bottom to 5 volts at the top.

Once you confirm that your ladder is working correctly you can connect each point of the ladder to the negative inputs of each op amp. Note that each negative input should be connected to their own resistor. Also to make it easier you should connect the bottom two resistors to the last op amp and the go up from there.

Step 5: Step 4: LED Bar Graph Set Up

As shown above you want to set the bar graph so that the each of the 10 LEDs negative side is connect to ground.

(Notice that the top left has a notch... that indicates which side of the bar has the input/high voltage pins.)

Step 6: Step 5

Finally you want to connect all of the outputs of the op amp to the positive side of the LEDs.

Step 7: Final Notes...

In the end, you should be able to increase the number of LEDs on your bar by increasing the voltage being provided to your op amp inputs. In order to be used with other circuits, you will likely have to add a way to control the voltage levels.

In our project, we added about 5k Ohms of resistance to our input in order lower how many volts our knob supplied to the op amps. You may need to add other things, like buffers, in order to get the LED behavior you want.

Hope this tutorial helped! Thanks!

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    2 Discussions

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    kiwigrinder

    6 weeks ago

    Your circuit emulates a LM3914 chip which uses a linear resistor ladder where all resistor values are 1K ohms .
    The LM3915 chip uses a logarithmic resistor ladder where the values are 1K, 0.41K, 0.59K, 0.83K, 1.17K, 1.66K, 2.34K, 3.31K, 4.69K, 6.63K ohms.
    The LM3916 chip uses a VU scale and the resistor ladder values are 708, 1531, 923, 819, 1031, 1298, 769, 864, 970 and 1087 ohms.