![]() Q1 is used as simple BJT switch used to drive current through relay's inductor. C1 has value of 10uF, it is sufficient for the waveform even of low frequencies to pass through capacitor without being distorted, only affected by DC removal. C1 capacitor is connected in series to the amplitude selection stage, and can be silenced via driving current on the relay inductor, thus making output signal traced straight to the output stage. Since there is only single power supply on device (5V), there is need to attach coupling select circuit to the output cascade. ![]() This sub-circuit provides appropriate output waveform, defined by AD9833 module (U1). Make sure that bypass capacitors of several values are present on the circuit, since there is a DC-DC boost converter switching noise on ground and 5V potentials of the whole circuit. As it can be seen from the schematics, when external power supply is connected via micro-USB connector of the Arduino Nano module, battery is being charged through TP4056 module. SW1 is a SPST toggle switch that controls power flow on the whole circuit. ![]() Power supply circuit is based upon powering the whole device via Li-ion battery 3.7V converted to a 5V. Notice that battery voltage line VBAT is attached to the analog input pin A7, because we need to get its value in order to determine low battery state of Li-ion battery voltage. Analog pins A6 and A7 are dedicated analog input pins and only can be used as an ADC inputs, because of Arduino Nano microcontroller ATMEGA328P TQFP package, as it was defined in the datasheet. There is an option for using dedicated analog pins (A0.A5) as general purpose I/O, so some of the pins are used as digital output, communicating with LCD and AC/DC coupling select of the device's output. Because of that, J1 - the mini-USB connector is detached from schematic symbol of Arduino Nano (U4). Since this module has its own mini-USB input connector, it will be used both as a power supply input and programming interface input. It controls all the peripheral modules on device, in both digital and analog operating modes. In order to make it easier to understand the schematic diagram, description is divided in sub-circuits while every sub-circuit has responsibility for each design block:Īrduino Nano module acts as a "Main Brain" for our device. 1 x 12.5cm x 8cm x 3.2cm Plastic enclosure.EC11 - Rotary Encoder with SPST switch.X9C104P - 8-bit 100KOhm digital potentiometer.DC-DC Step-Up coverter module: 1.5V-3V to 5V converter.TP4056 - Li-ion battery charger module.CJMCU - AD9833 Function generator module.1602A - Generic liquid crystal display. ![]() In order to reduce energy consumption, there is an option to adjust LCD backlight via PWM signal from the Arduino pre-defined "analog" pin.Īfter this brief introduction, we can proceed to the building process. Since AD9833 has no capability to change output signal amplitude, I've used a digital 8-bit potentiometer as a voltage divider at the device output endpoint (Will be described in further steps).ĭisplay: is the basic 16x2 LCD, which is probably the most popular liquid-crystal display among Arduino users. the circuited designed in a way that when the 5V DC source is connected, Li-ion battery is being charged by TP4056 charger module that is attached to the power supply circuitry (Topic will be expanded further in the following steps).ĪD9833: integrated function generator circuit is a central part of the design, controlled via SPI interface with ability to generate square/sine/triangle wave with frequency modulation option. Powering the board: Device has a single mini-USB connector that receives 5V from the external power supply, that may be either PC or external USB charger. Thus, this project is easy to build, completely modular, with relatively simple schematic diagram. It is known that Arduino Nano board requires 5V as a power supply, so electronic design contains DC-DC boost converter that converts 3.7V battery voltage to 5V required for powering up the Arduino. This project in based on Arduino ( Arduino Nano in this case), with 3.7V a Lithium-Ion battery as a power source thus making the device portable. There are a lot of circuits that require some testing equipment in order to get information about circuit's response to a certain waveform.
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