I2C DAC Controlled Electronic Load – Battery Performance Tester

  • Rajkumar Sharma
  • 49 Views
  • medium
  • Tested
  • SKU: EL143803
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The project presented here is an I2C electronic load, intended for testing power supplies, solar panels, batteries, and supercapacitors. The board consists of an I2C interface DAC MCP4725, OPAMP U2 acts as V to I (Voltage to Current), OPAMP U3 measures the load current across the shunt resistor and provides 0 to 4.9V Voltage with a current range of 0 to 1A. Users may control the battery discharge current using the MCP4725 DAC in the range 0 to 1A. The circuit also provides load current feedback and voltage feedback. This way it can help users to measure the battery’s performance. Suppose the user desires to measure the battery’s performance as it is being discharged at constant power. In that case, a current measuring circuit can be used in the feedback loop to enforce the constant power constraint. This enables you to discharge a battery at a controlled way. The project can handle 1A @ 24V, thus a total of 24W with the use of a large-size heatsink and fan. The circuit works with 5V DC voltage input. The project can be used with Arduino, ESP32, or other microcontroller.

Voltage Feedback

It is important to use the right voltage divider resistor for voltage feedback of the load. For example, for 24V load R1=100K and R2=20K will output 4V. For a 3.7V battery, R1=10K Ohms and R2=47K Ohms will provide approx. 3V Output.

Current Feedback

U3 OPAMP OPA992IDBVR is used as I to V converter. The amplifier measures the current across the shunt resistor R14 and provides 0 to 4.9V for current 0 to 1A.

Arduino Example Code

Download the Arduino code to test the board. We have conducted an easy test with the code. The DAC increases output every 2 seconds in 6 steps, it starts with 0.18A and goes to 1.08A.

Arduino connection to Electronic Load

  • 5V = CN2 Pin 1 VCC (5V Power to Electronic Load)
  • VF Connect It Any Arduino Analog Pin A0 to A3, Voltage Feedback (CN2 Pin 2)
  • CS Connect It Any Arduino Analog Pin A0 to A3, Current Feedback (CN2 Pin 3)
  • SDA Arduino A4 (CN2 Pin 4)
  • SCL Arduino A5 (CN2 Pin 5)
  • GND = Arduino GND (CN2 Pin 6)

Features

  • Supply 5V DC
  • Maximum Load 24W with Large Heatsink and Fan
  • Maximum Load Voltage 24V
  • On Board Amplifier for Current Feedback I to V Converter
  • On Board Divider Resistor for Voltage Feedback
  • V to I Controlled Using I2C DAC
  • Easy Micro-Controller Interface
  • Screw Terminal for Load Connection
  • On Board Power LED
  • Header Connector for easy connections to Arduino
  • 4 x 3 mm Mounting Holes
  • PCB Dimensions 33.81 x 28.73 mm

Schematic

Parts List

NO.QNTY.REF.DESC.MANUFACTURERSUPPLIERSUPPLIER PART NO
11CN12 PIN SCREW TERMINAL PITCH 5.08MMPHOENIXDIGIKEY277-1247-ND
21CN26 PIN MALE HEADER PITCH 2.54MMWURTHDIGIKEY732-5319-ND
33C1,C5,C71nF/50V CERAMIC SMD SIZE 0805MURATA/YAGEODIGIKEY
41C2100nF/50V CERAMIC SMD SIZE 0805MURATA/YAGEODIGIKEY
51C310uF/35V CERAMIC SMD SIZE 0805MURATA/YAGEODIGIKEY
61C41uF/35V CERAMIC SMD SIZE 0805MURATA/YAGEODIGIKEY
71C622nF/50V CERAMIC SMD SIZE 0805MURATA/YAGEODIGIKEY
82C8,R15DNP
91D1LED RED SMD SIZE 0805OSRAMDIGIKEY475-1278-1-ND
101J1SOLDER JUMPER-PCB
111Q1IRF1404 TO220 MOSFETINFINIONDIGIKEYIRF1404PBF-ND
121R1100K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
132R2,R820K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
143R3,R4,R54.7K 5% SMD SIZE 0805MURATA/YAGEODIGIKEY
152R6,R111K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
161R7150E 5% SMD SIZE 0805MURATA/YAGEODIGIKEY
171R93.6K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
181R102.2K 5% SMD SIZE 0805MURATA/YAGEODIGIKEY
191R12270E 5% SMD SIZE 0805MURATA/YAGEODIGIKEY
201R13120E 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
211R140.1E 2W 1% SMD SIZE 2512MURATA/YAGEODIGIKEY
221R165.76K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
231U1MCP4725 SOT23-5MICROCHIPDIGIKEYMCP4725A2T-E/CHCT-ND
241U2MCP6071T SOT23-5MICROCHIPDIGIKEYMCP6071T-E/OTCT-ND
251U3OPA992IDBVR SOT23-5TIDIGIKEY296-OPA992IDBVRCT-ND

Connections

Arduino Connection

Gerber View

Photos

Video



MCP4725 Datasheet

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