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amountdollElectronics - Devices

Nov 2, 2013 (3 years and 7 months ago)

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Cheap 12V to 220V Inverter




Even though today’s electrical appliances are increasingly often self
-
powered, especiall
y the portable
ones you carry around when camping or holidaying in summer, you do still sometimes need a source of
230 V AC
-

and while we’re about it, why not at a frequency close to that of the mains? As long as the
power required from such a source rema
ins relatively low
-

here we’ve chosen 30 VA
-

it’s very easy to
build an inverter with simple, cheap components that many electronics hobbyists may even already have.



Though it is possible to build a more powerful circuit, the complexity caused by the v
ery heavy currents
to be handled on the low
-
voltage side leads to circuits that would be out of place in this summer issue.
Let’s not forget, for example, that just to get a meager 1 amp at 230 VAC, the battery primary side would
have to handle more than 2
0 ADC!. The circuit diagram of our project is easy to follow. A classic 555
timer chip, identified as IC1, is configured as an astable multivibrator at a frequency close to 100 Hz,
which can be adjusted accurately by means of potentiometer P1.



Circuit di
agram:












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Cheap 12V to 220V Inverter Circuit Diagram


As the mark/space ratio (duty factor) of the 555 output is a long way from being 1:1 (
50%), it is used to
drive a D
-
type flip
-
flop produced using a CMOS type 4013 IC. This produces perfect complementary
square
-
wave signals (i.e. in antiphase) on its Q and Q outputs suitable for driving the output power
transistors. As the output current ava
ilable from the CMOS 4013 is very small, Darlington power
transistors are used to arrive at the necessary output current. We have chosen MJ3001s from the now
defunct Motorola (only as a semi
-
conductor manufacturer, of course!) which are cheap and readily
a
vailable, but any equivalent power Darlington could be used.



These drive a 230 V to 2 × 9 V center
-
tapped transformer used ‘backwards’ to produce the 230 V output.
The presence of the 230 VAC voltage is indicated by a neon light, while a VDR (voltage dep
endent
resistor) type S10K250 or S07K250 clips off the spikes and surges that may appear at the transistor
switching points. The output signal this circuit produces is approximately a square wave; only
approximately, since it is somewhat distorted by passi
ng through the transformer. Fortunately, it is
suitable for the majority of electrical devices it is capable of supplying, whether they be light bulbs, small
motors, or power supplies for electronic devices.



PCB layout:


PCB Layout For Cheap 12V to 220V Inverter Circuit Diagram


COMPONENTS LIST

Resistors

R1 = 18k?

R2 = 3k3







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R3 = 1k

R4,R5 = 1k?5

R6 = VDR S10K250 (or S07K250)

P1 = 100 k potentiometer

Capacito
rs

C1 = 330nF

C2 = 1000 µF 25V

Semiconductor

T1,T2 = MJ3001

IC1 = 555

IC2 = 4013

Miscellaneous

LA1 = neon light 230 V

F1 = fuse, 5A

TR1 = mains transformer, 2x9V 40VA (see text)

4 solder pins




Note that, even though the circuit is intended and designed f
or powering by a car battery, i.e. from 12 V,
the transformer is specified with a 9 V primary. But at full power you need to allow for a voltage drop of
around 3 V between the collector and emitter of the power transistors. This relatively high saturation
voltage is in fact a ‘shortcoming’ common to all devices in Darlington configuration, which actually
consists of two transistors in one case. We’re suggesting a PCB design to make it easy to construct
this project; as the component overlay shows, the PCB o
nly carries the low
-
power, low
-
voltage
components.


The Darlington transistors should be fitted onto a finned anodized aluminum heat
-
sink using the standard
insulating accessories of mica washers and shouldered washers, as their collectors are connected to

the

metal cans and would otherwise be short
-
circuited. An output power of 30 VA implies a current
consumption of the order of 3 A from the 12 V battery at the ‘primary side’. So the wires connecting the
collectors of the MJ3001s [1] T1 and T2 to the trans
former primary, the emitters of T1 and T2 to the
battery negative terminal, and the battery positive terminal to the transformer primary will need to have a
minimum cross
-
sectional area of 2 mm2 so as to minimize voltage drop.


The transformer can be any 2
30 V to 2 × 9 V type, with an E/I iron core or toroidal, rated at around 40
VA. Properly constructed on the board shown here, the circuit should work at once, the only adjustment
being to set the output to a frequency of 50 Hz with P1. You should keep in m
inds that the frequency
stability of the 555 is fairly poor by today’s standards, so you shouldn’t rely on it to drive your radio
-
alarm
correctly


but is such a device very useful or indeed desirable to have on holiday anyway? Watch out
too for the fact t
hat the output voltage of this inverter is just as dangerous as the mains from your
domestic power sockets.



So you need to apply just the same safety rules! Also, the project should be enclosed in a sturdy ABS
or diecast so no parts can be touched while
in operation. The circuit should not be too difficult to adapt to

other mains voltages or frequencies, for example 110 V, 115 V or 127 V, 60 Hz. The AC voltage requires
a transformer with a different primary voltage (which here becomes the secondary), and
the frequency,
some adjusting of P1 and possibly minor changes to the values of timing components R1 and C1 on the
555.











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BIC1422 DC
-
AC converter circuit




BIC1422 DC
-
AC converter circuit is shown as picture








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inverter circuit 11


(View)



The inverter circuit 10







The inverter circuit 13










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(View)


The inverter circuit 12














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Electronic transformer


The circuit is as shown. The operating principle is the same as the switching power supply, the diodes
VD1

VD4 forms the rectifier bridge and this rectifier bridge changes the city electricity into the DC, the
high frequency oscillation circuit is copmosed of the oscillation transformer T1, the transistors VT1 and
VT2, and this high frequency oscillation circu
it changes the pulse DC into the high
-
frequency current,
then the high
-
frequency high
-
voltage pulse is reduced by the ferrite output transformer T2 to get the
voltage and power. R1 is the current limiting resistor. The start trigger circuit is composed of
the
resistance R2, the capacitance C1 and the two
-
way trigger diode VD5. The transistors VT1 and VT2 use
the S13005, the B is 15

20 times. Also you can use the BUceo>=35OV high power transistor such as
the C3093.



Starting Principle: Before the power switch is pushed, PS
-
ON signal is pulled high by 5VSB voltage and
will remain high level. PS
-
ON signal is P4 POWER's working contro
l signal and when it is high level, P4
POWER doesn't work. When the switch is pushed, there will be a PWRBT# signal which will be sent to
south bridge. The SLP
-
S3# signal output by south bridge is high level, which will control the triode Q33 to

be connect
ed. Then PS
-
ON signal of high level will be pulled low. PS
-
ON signal of low level will control
POWER to output other working voltages 12V,
-
12V,
-
5V, VCC, VCC3.