4-20mA CONVERTER

Today we will make a 4-20 mA current converter through 3 or 5VDC very easy

GERBER PCB:

https://mega.nz/file/ncYwUaYL#aMh3h1Lf413_znTVPFgFPiD2wb6x34Ir9-EEAg7aJVQ

SIMULACION:

https://mega.nz/file/HdpFgDyR#8u5RrZ8EkKezBPhSyEADaqFJ2a6scTB2dzWqjNyZhHg

Here we will see the schematic diagram made in the easyeda software with all the electronic components and their respective values.

Our star component for this project will be the Lm358 operational amplifier. This first comparator will serve as a voltage preamplifier, then we place the second comparator, the latter is the one that will be in charge of providing us with a 4-20mA signal, additionally this same output also has to give me a signal from 0 to 10 volts. Well, for the calculations to be exact, we are going to take only the upper values ​​of 20mA and 10V. Before we get to the calculations we need to understand the concept of closed-loop configuration in op amps. We refer to closed loop when the negative pin of the comparator is connected to the output. With this configuration we manage to have the same amount of voltage at the output with respect to the positive input of the comparator. As we can see, as I increase the voltage at the input, I also manage to have the same amount of voltage at the output. Now, in the real circuit we are going to have 5 volts at the input, and when I have this 5v signal I need to have 10v at the output. To achieve this we add a resistor between pin 6 and 7 and another resistor connected from pin 6 to GND.

Now, how do we calculate the values ​​of these resistors? Very easy, remember that we already have the voltage and current data, so we say R is equal to 10V over 20mA, the result of which gives us 500.

And since we have 2 resistors, we are going to assign 250 ohms to each one. Well, for the voltage pre-amplification part we will also do the same with the resistors, first we place a 1k fixed resistor connected from pin 2 to GND, and another resistor from pin 2 to pin 1. However, I still don't know the value of this last Stand. To find this value we need to remember the concept of closed loop, aaa you already remembered, we had mentioned that the output will have the same amount of input voltage, huh, consequently, if we have 3.3v at the input, here in the pin 2 will also be 3.3v, so this 1k resistor has a voltage drop of 3.3V. Well, and since I want 5 volts at the output, the voltage drop across this resistor will be 5-3.3V, which result is 1.7V, so far we are still not able to determine the value of this resistor, but since these two resistors are in series, the same amount of current will flow. So first I'll take the current in the 1k resistor. Applying ohm's law it would be Intensity equals 3.3v over 1k and this gives us 3.3mA as a result. Now if we are able to find the value of this resistance, then we say R = 1.7v over 3.3mA, and this gives us 515 ohms, now we only have to simulate, for this we first add a 12v supply to the operational amplifier, then we put a potentiometer to regulate the input voltage of 3.3v, then we put a voltmeter in this part, next we put another voltmeter in the output of comparator A, we continue adding voltmeters in the output part and finally the most important thing we integrate an ammeter right at the exit. Great, now we click on simulate and we can appreciate the behavior of the circuit. We can still improve this circuit by placing 100nf filters on the comparator inputs and outputs, we can also add pull down resistors. I challenge you to implement this circuit at home and you will see that it will work correctly.

• 1 CI LM358
• 2 CAPACITORS 104
• 2 RESISTORS 10K 1/4W
• 4 RESISTORS 220 ohm 1/4W
• 1 RESISTOR 515 ohm 1/4W
• 1 RESISTOR 1K 1/4W
• 1 DIODE 1N4007
• 1 ESPADIN 2 PINS 90°
• 1 CONECTOR BLUE TERMINAL 3 PINS
• 1 CONECTOR BLUE TERMINAL 4 PINS
• 1 PCB

• Supply voltage 12VDC
• Voltage inputs (0-3.3V) / (0-5V)
• Current Outputs (0-20mA)
• Current Outputs (0-10V)

PCBWAY has 10 years in the electronics industry manufacturing professional PCBs, assembling PCBs managing to satisfy the demands of all parts of the world, in addition to meeting the highest quality and delivery time standards. PCBWAY allows the manufacture of your PCBs from 5 units.

This project was carried out thanks to PCBWAY, a company dedicated to the manufacture of prototypes and professional PCBs, in addition to offering you a ready assembly service with all the components in your PCBS, complying with the established quality and delivery time standards.

We thank PCBWAY, a leading company for manufacturing and assembling professional PCBs with the highest quality, PCBWAY has fair reasonable prices, punctual shipping time and 24-hour customer service, it also offers you the option of quoting all its services in his web page. Do not think twice and start manufacturing your professional PCBs from 5 units safely.

10pcbs at $5 order them here www.pcbway.com

We thank PCBWAY for the professional pcb they provide us for this project.

GERBER PCB:

https://mega.nz/file/ncYwUaYL#aMh3h1Lf413_znTVPFgFPiD2wb6x34Ir9-EEAg7aJVQ