All I needed I found in the datasheet of LM The LM can be feed with AC signal without any rectification, but I wanted to implement a precision full wave rectification. I chose the schematic on page 13, fig. The schematic needs bipolar power supply to work correctly, but the negative rail can be as low as -5V or even
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Unfortunately LM chip has been discontinued. In this instructable we will be creating an alternative circuit to imitate a LM chip to drive a 10 LED bar graph. Did you use this instructable in your classroom? Add a Teacher Note to share how you incorporated it into your lesson.
We started by looking at the LM schematic to see how it functioned. From this Schematic we were able to analyze it and start creating circuits that would imitate the function. 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. From the circuit we designed on LTspice we were able to start creating the circuit on a bread board.
Now we can start by correctly hooking up the the op amps. 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.
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. 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 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. Your circuit emulates a LM chip which uses a linear resistor ladder where all resistor values are 1K ohms.
The LM chip uses a logarithmic resistor ladder where the values are 1K, 0. The LM chip uses a VU scale and the resistor ladder values are , , , , , , , , and ohms. By mimikamp Follow. About: I'm actually a horse trapped in a woman's body. Add Teacher Note. We used the program LTspice to design and test this circuit to make sure it ran correctly.
Finally you want to connect all of the outputs of the op amp to the positive side of the LEDs. Hope this tutorial helped! Did you make this project? Share it with us! I Made It! Electronic Affirmation Mirror by bekathwia in Arduino. Reply Upvote.
LM3916 Driver. Datasheet pdf. Equivalent
January General Description. The LM is a monolithic integrated circuit that senses. One pin changes the display from a bar.
LM3916 LED Chip Alternative