Low-Cost 6-Bit DAC Circuit Diagram

For controlling the load of appliances such as cooling fans, low-wattage heaters, thermostats, low-wattage light sources, small electrical toys and test benches for loudspeakers, we need a power source whose voltage can be controlled in small steps and is capable of providing current of more than 1A. For that, we require low-resolution digital-to-analogue converters (DACs) with three to seven bits.

Here is the circuit capable of setting output voltage between 1.25V and 15V in 64 steps. The circuit can be adapted for a lot of applications.

 Low-Cost 6-Bit DAC Circuit Diagram

Circuit and working

The circuit of the low-cost 6-bit DAC is shown in Fig. 1. The DAC is built around IC 7406, hex inverter (IC3). We may also use IC 7407 with six followers without changing the PCB. Steps are generated with the help of 6-bit digital input code D0 (LSB) through D5 (MSB) at CON2. Consequently, 64 combinations are possible starting from 000000 to 111111. At each combination, you will have a pre-determined output voltage between 1.25V and the possible maximum 15V.

Inputs D0 through D5 are TTL and CMOS compatible. These can be generated by microcontrollers, parallel-interface adapters such as PPI8255A, PIA6820/1 and Z80-PIO. In the simplest case, inputs can be driven with switches connecting inputs D0 through D5 to ground 0V or to 5V.

The size of the steps is programmable with trimmer potentiometers VR1 through VR6. Consequently, we can produce regular or irregular steps according to the need, depending on the characteristics of the load being controlled.

You can set any output voltage with any potentiometer between 1.25V and the maximum. For example, if you have a transformer for 18V AC, you can set outputs between 1.25V and around 15V with any potentiometer.

For adjustment in the simplest case, apply a set of seven test codes, as listed below, on CON2; output on CON3 will be as under.

Test code with 7406 (invert with 7407):

000000 Vout=Vmax (unadjustable)

000001 Vout=1.25V (VR1)

000010 Vout=3V (VR2)

000100 Vout=5V (VR3)

001000 Vout=7.5V (VR4)

010000 Vout=9V (VR5)

100000 Vout=12V (VR6)

The maximum output voltage on CON3 and CON4 is with code 111111 on the outputs of IC3 and depends on the input voltage of IC2. Please note that, if you use 7407, the codes will be non-inverted, and if you use 7406, the codes will be inverted.

The 6-bit input digital code D0 through D5 is buffered with 7406 or similar (IC3). With an open collector, the IC works as a translator/buffer between standard TTL levels to higher voltages needed for LM317.

Fig. 2: An actual-size PCB layout of the low-cost 6-bit DAC

Fig. 3: Component layout of the PCB

If the requirement of current is more than 1A, then select adjustable regulator IC2 from series LM317T (1.5A), LM350 (3A) or any compatible adjustable-linear regulator.

This makes the DAC adaptable to a lot of applications. In many cases, there is no need to start the output voltage from 0V. This makes the solution even simpler.

Input digital code D0 through D5 is buffered with IC3, which should be obligatory with open connector. The preferred device is 7406 or better, with outputs that can work with up to 30V.

Power requirements are from a common configuration built around step-down transformer X1 (secondary voltage 18V to 20V with current 1A or above), bridge rectifier BR1 and voltage regulator IC 7805 (IC1). The mains power is applied on connector CON1. 5V is available at connector CON5.

The selection of mains transformer X1, bridge rectifier and heat sinks for IC1 and IC2 depends on the required maximum output current from the DAC. IC1 and IC2 can be mounted on a common heat-sink after proper mounting is done.

The load is connected to connector CON3. A DC voltmeter with 50V range is connected at CON4 for measuring the output voltage. The DAC can be tested with 12V/5W/0.4A light bulb, 12V/0.3A fan, heating element for thermostat with nominal current up to 0.3A and maximum current below 1A and similar loads.

Construction and testing

An actual-size, single-side PCB layout for the low-cost 6-bit DAC is shown in Fig. 2 and its component layout in Fig. 3.

Sourced By: EFY Author:  Petre TZV Petrov

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Flexible Electronic Circuits Based on silicon ink

In an effort to develop the next generation of microelectronic transistors, scientists have long been trying to find a new solution. To solve this problem, recent studies in the field of flexible electronics is completely focused on a variety of organic and metal-oxide ink to print, which often do not have all the positive electronic properties of silicon. But recently, a team of researchers from Delft University of Technology in the Netherlands has proposed a method that allows you to apply directly to the substrate is silicon, using liquid silicone ink and single laser pulses.

The ability to print on a substrate of silicon ink has been known for some time, but previously required step of thermal annealing at 350 ° C, which is too high a temperature for many flexible substrates. The new method proposed by researchers completely bypasses this step, converting the liquid silicon in the polysilicon used in the schemes.

The researchers applied the liquid polysilane directly to the paper in an oxygen-free environment. Then they were annealed layer via excimer laser [conventional tools used for displays of smartphones]. The laser burst lasts a few tens of nanoseconds, leaving the paper completely untouched. Test TFTs obtained in this manner was successful.

The greatest use of this technology can be found for wearable electronics, because it allows high-speed, low-power, flexible transistors with a surprisingly low cost. The technology also can be used for biomedical sensors and solar cells

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Compressor Circuit with 570/571 Compandor IC

Compressor Circuit with 570/571 Compandor IC circuit provide high gain for low amplitude input and provide low gain for high amplitude input. This action, in effect, produce a nearly constant amplitude even though the input has very high dynamic range (very high amplitude variation from time to time). The action of compression like this is needed in some situation, such as in maximizing modulation depth in broadcasting, or sustaining electric guitar signal which has very high variation between the plucking time and fading out.  The following circuit has complementary input/output characteristic and unity gain at 0.775 VRMS input. Voltage gain through compressor is square root of 0.7/Vin. Vin is average input voltage. This circuit  uses Signetics dual channel compandor IC.  570 has lower inherent distortion and higher supply voltage range (6-24 V) than 571 (6-18 V).

Compressor Circuit with 570/571 

Source :circuitsdiagram-lab

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50 watt 12 VDC to 220 VAC Power Inverter

This is the Simple 50 watt 12 VDC to 220 VAC Power Inverter. Power inverter (UPS Uninterruptible power supply) is a very useful device which can convert Low voltage from a DC source to high voltage AC. The most common power inverter is 12V to 240V inverter. Perhaps that is because 12V batteries are common. This type of power inverter usually draws current from a DC battery. This battery should be able to provide a high flow of electric current.

Normally lead acid batteries can server this purpose well. This current is then converted to 240V square wave alternative current so that we may empower those electric appliances which work on 240V instead of 12V. Inverter falls in the category of expensive devices so many people don’t buy them even they need them. What if I tell you how to build an inverter (UPS Uninterruptible power supply) yourself?

 Iverter circuit diagram 

Parts.

Transformer 12+12/220 (50W) ( you can make your own inverter transformer visit Make your own homemade (DIY) Electric Transformer)

2, metter copper wire (for winding)

2 Transistors 1047

2 Heat sinks to fit power transistors

Some wiring wire (for connections)

A wiro-board (To build circuit on)

A 12V battery of 12V power supply for testing purposes

1 Resisters 1 k

Method:

First of all you have to make some changes in transformer. If u are using 500 V transformer then take 18 to 22 gauge copper wire and on the one side of transformer’s core make five turn and put a point on it, and turn this point, and again turn the wire five times on the same direction. In this way u get three terminals. If u r connect the transformer to 220 V power supply then it gives 1.5 V on both terminals. Now put transformer D1047 on the palm of your hand and turn it such a way that number appears your way. Now you will see three points. The point on your left side is known as (B) Base, middle one is E and the right one is collector(C). (These are the information only for D1047)

connect the E of both sides of transistors with the outer terminal of secondary coil, after that connect the both outer terminals of the third coil with the base of the both heat sinks of transistor. then connect the collectors of both side by wires n then connect the 500 ohm resistor on emitter and resistor on either side. Now connect the middle terminal of primary coil by one to two ft long wire and clip (crocodile) it and attach this terminal always by the positive terminal, and with the negative terminal of battery connect the both collectors of transistor.

After that the central point of the third coil and a wire attach it with emitter to connect using a heavy ampere switch between both terminals of the Inverter primary coil to apply a capacitor which will prevent the current from the sparking. inverter will switch on as soon as starting to work.

Working:

With both the terminals of battery connect the positive and negative wires to its terminals positive to positive and negative to negative and then open the switch, slightly vibration starts in the inverter as switch is open. Now you can run it into 1 to 500 watt load.

This inverter also can charge the batteries, you just need to( on and off) the switch.

Charging:

You will need to switch off for battery charging and connect the primary coil indirectly with 220 V of power supply, after that battery will start charging. To converts it into UPS you needs only one relay. These relays are AC 220 V and 4.4 terminals.

For online help visitPak Science and technology Forum

Inverter circuit diagram for battery charging :

Inverter circuit diagram for Inverter operation :

 Sourced By: circuitsdiagram-lab.blogspot.com

Power Inverter Wattage Chart

inverters	Transformer voltages (Input)	Transformer Amps	Transformer watt	No of Transistors D1047
50 watt inverter	12 V	4 A	50 W	2
100 watt inverter	12 V	10 A	100 W	4 to 6
300 watt inverter	12 V	25 A	300 W	6 to 8
500 watt inverter	12 V	40 A	500 W	8 to 10
1000 watt inverter	24 V	45 A	1000 W	20 to 26
3000 watt inverter	24 V	125 A	3000 W	40 to 50
5000 watt inverter	48 V	105 A	5000 W	60 to 70
Note. table shows that requirement of D1047 transistors for different power inverter wattage

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Simple Low-Power Audio Amplifier

The small-signal amplifier is generally referred to as a voltage amplifier because it usually converts a small input voltage into a much larger output voltage. The audio power amplifier works on the basic principle of converting low-power audio signal to a suitable level to be delivered to the load.

This low-power amplifier circuit is useful for the amplification of sound from small-signal devices such as mobile phones, laptops or desktops.

Circuit and working
As shown in Fig. 1, this circuit is built around a step-down transformer (X1), bridge rectifier BR1, regulators 7809 (IC1) and 7909 (IC2), dual op-amp TL072 (IC3), low-power amplifier LM386 (IC4) and some other components.

The circuit can be divided into two sections—dual power supply section and amplifier section. The dual power supply section is built around step-down transformer X1 (230V ac primary to 12V-0-12V, 1A secondary) and two voltage regulators 7809 and 7909. IC 7809 is a positive voltage regulator, while 7909 is a negative voltage regulator. Diodes D1 and D2 are used to protect IC1 and IC2 against reverse voltages from capacitors connected to the regulators. These regulators provide ±9V regulated output for the operation of the circuit.

Use suitable heat sinks with the regulator ICs because they get hot during operation. In case of overheating, there is provision for a thermal shutdown.

The amplifier section is built around TL072 (IC3) and a low-power amplifier LM386. The op-amp A1 of IC3 operates as a low-noise preamplifier. Capacitor C8 is used in order to pass low frequency. The op-amp A2 of IC3 operates as a low-pass filter. For changing the cut-off frequency, you have to change the values of capacitors C11 and C12.

 Simple Low-Power Audio Amplifier circuit Diagram

LM386 is a low-power amplifier IC with built-in biasing and inputs that are referred to the ground. It has a gain of 20 and can drive a speaker of 8-ohm impedance.

The circuit is simple to use. You have to simply feed the output from a mobile phone, or any other low-volume device, into RCA1 socket on the PCB. The amplified sound can be listened-to through the speaker (LS1). Potentiometer VR1 is used for volume control.
 
Construction and testing
An actual-size, single-side PCB for the simple low-power amplifier is shown in Fig. 2. Its component layout is shown in Fig. 3. After assembling the circuit on the PCB, enclose it in a suitable plastic box.

Fix RCA1 socket on the front side of the box for an audio-in signal. Fix a three-pin connector on the PCB for connecting secondary terminals (12V-0-12V) of transformer X1 and to two-pin connector on the rear side for mains 230V AC, 50Hz. Fix the transformer firmly on the cabinet with screws or nuts and bolts. Connect the speaker affixed on top of the box or placed at a distance. Use a shielded cable for connecting to the RCA socket.


Before inserting IC3 and IC4 into their respective IC bases, verify that all the connections have been made properly.

Sourced By : EFY  Author :  S.C. Dwivedi

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