Multi-purpose dual power supply regulator board AMS1117

All embedded systems require electric power to operate. Most of the electronic components inside them, including the processors, can operate at a wide range of supply voltage. For example, the operating voltage range for the PIC16F1847 microcontroller is 2 to 5.5 V. But there are certain applications where you need a regulated constant voltage to avoid malfunctioning of the circuit or getting erroneous results. For instance, any application that involves analog-to-digital conversion (ADC) requires a fixed reference voltage to provide accurate digital count for input analog signal. If the reference voltage is not stable, the ADC output is meaningless. Here is my latest dual power supply regulator board that provides constant 3.3V and 5.0V outputs from an unregulated DC input (6.5-10V). It is small in size and can be easily enclosed inside the project box along with a project circuit board. It can also be used to power test circuits on breadboard. The board uses two AMS1117 series fixed voltage regulators and receives input power through a DC wall wart or an external 9V battery.

he regulator circuit uses two AMS1117 series fixed voltage regulators, AMS117 5.0 and AMS1117 3.3, to derive constant 5.0V and 3.3V outputs from an unregulated DC input voltage. The circuit diagram of the board is shown below.

Note that both AMS1117-3.3 and AMS1117-5.0 derive input power directly from the unregulated supply voltage, which means each of them can deliver up to 0.8A of current. However, for this particular board it is recommended to limit the output current up to 500 mA maximum. For the safety of the AMS1117-3.3 regulator IC, the unregulated input voltage is also recommended to be within 6.5 to 10.0 V. This board is best to use in a project that is designed tobe powered with a 9V DC from either a PP3 battery or a wall adapter. The PCB is only 1.9″ x 1.4″, and occupies a small area inside the project box.

 

The board doesn’t have any ON/OFF switch, because it may not be useful if this board is enclosed inside the project box. But through-hole pads are provided on the board if you want to add one externally. There are two surface mount pads which are shorted together by default with solder to close the circuit permanently. These must be disconnected if an external ON/OFF switch has to be added.

The regulated output voltages (5V and 3.3V) are accessed through screw terminal blocks. This power supply board can also be used to power breadboard circuits (see the picture below).

 

MAX232 product image MAX232 DUAL ELA-232 DRIVERS/RECEIVERS

The physical communication standard defines the signal voltage of -10V for logic '1', and +10V for logic '0'. However in practise, the voltage can be ranging from +/-3V to +/-25V. Not to worry if the measured voltage is not +/-10V. Typical receiver is able detect the incoming signal with voltage as low as +/-3V.
A microcontroller like PIC16F877a uses USART (5V system). The PC (personal computer) that we have in the office/home uses the standard RS232. To enable a microcontroller to communicate with the computer, a RS232 to TTL converter is required.

 

IC chip maker has come up with the integrated circuit for interfacing RS232 with TTL logic (5V for logic 1, 0V for logic 0), making the interfacing work very simple. MAX232 is one of the many IC in the market which helps to convert between RS232 -/+10V and TTL +/- 5V. It is a simple voltage level converter in short. The charge pump design allows the circuit to generate +/-10V from a 5V supply, with the help from the four capacitor. With charge pump to double up the supply voltage for RS232 transmitter, there is no need to design a power supply for +/-10V.
The diagram on the left shows the schematic of the MAX232 IC circuit. It consist of only 4x 1uF 16V electrolytic capacitor, and the MAX232 IC itself. It is that simple. I have include a layout which I always use for PC to PIC16F877a microcontroller, RS232 interface.

Diagram Block IC TDA7377

The TDA7377 is a new technology class AB car radio amplifier able to work either in DUAL BRIDGE or QUAD SINGLE ENDED configuration.



The exclusive fully complementary structure of the output stage and the internally fixed gain guarantees the highest possible power performances with extremely reduced component count. The on-board clip detector simplifies gain compression operation. The fault diagnostics makes it possible to detect mistakes during car radio set assembly and wiring in the car.

The stand-by can be easily activated by means of a CMOS level applied to pin 7 through a RC filter. Under stand-by condition the device is turned off completely (supply current = 1µA typ.; output attenuation= 80dB min.). Every ON/OFF operation is virtually pop free. Furthemore, at turn-on the device stays in muting condition for a time determined by the value assigned to the SVR capacitor.

While in muting the device outputs becomes insensitive to any kinds of signal that may be present at the input terminals. In other words every transient coming from previous stages produces no unplesantacoustic effect to the speakers.