This application note is in order to introduce the USB charging current acquisition system, the system included one Arduino UNO R3 board, one DS-REFF-431,one DS-CS-4173, external five volt supply, one ATFT LCD screen(We have the LCD-2000-7775 and the LCD-2000-9225, you can choose one to use).The main content of this article is to present the current data display。The measured temperature range is 0~800 mA .
(1We can use the DuPont to connect the several module.
(2)The first we can connect the reference source module to UNO R3 board.
Because of the development board internal reference source is not accurate enough, so in order to get a accurate value we need an external reference source. In this experiment ,we used the reference source module is designed an production by ourselves, which will provide a stable precision reference voltage. In this test , it will provide an accuratevoltage of 4.096V. If you want to know more about the DS-REF-431, you can scan our website to download the datasheet.
In this experiment, we use a high-side current sensing module to collecting the current where we want to know. In this experiment we use a high-side current sensing method, it is able to detect any subsequent loop faults and to take appropriate protective measures, particularly suitable for control applications. Our high-side current sensing module is alow cost, high precision module. The device work from a single 2.7V to 28V power supply and consumes only 30 μA. It is a feature of only one voltage output that eliminates the need for gain-setting.
For the module, Derivation of calculation function is:
Vout = Vsense * 50, I = Vsense/Rsense, so the end result is I = Vout/(50*Rsense) = Vout/5, the unit is A
(3)LCD-2000-7775(LCD-2000-9225) is a thin transistor liquid crystal display，each pixel can be drove by the thin film transistor which is behind the TFT. By this way, it is not only improves the response speed of the display, and you can precisely control display levels. Then the color of TFT LCD will be more realistic. For the TFT LCD module, we can display numbers, English characters, pictures color and the like.
(4)Finally we can see the USB charging current data from the LCD-2000-7775.If you use this systerm to connect your phone or tablet PC, you can see the charging current.