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Low Power Inverter

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Electrix

Member
Hi,
I am trying to find a low power inverter design that provides 230V 50Hz from 12V dc. I came across the following circuit, but can't figure out the transformer connections. The 12V positive line is connected to the centre tap of the transformer-what does this connection mean ??

Please see the attachment (ckt diag)- --

Awaiting your views.
Thanks.
 

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2PAC Mafia

Member
Hello,

as you see on the circuit the 4047 IC creates an oscillation outputs which makes the "push-pull" on the 12Vdc using the ULN2004, then there is the oscillation signal on the 9-0-9v side of the transformer to make the inductivity and to get the 230Vac on the other side.
 

eblc1388

Active Member
Hi Electrix,

If you built the circuit and it does not work, try connecting the Pin 4 of CD4047 to 0V(GND) instead.
 

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audioguru

Well-Known Member
Most Helpful Member
The oscillator won't run if pin 4 is grounded. It is the same oscillator circuit from this 500W inverter that works fine:
 

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eblc1388

Active Member
audioguru said:
The oscillator won't run if pin 4 is grounded. It is the same oscillator circuit from this 500W inverter that works fine:

The oscillator will definitely runs if pin4 is grounded. Both pins are telling the chip to be an astable.

In fact I would connect up the pins this way because I think its is the correct way. I am not sure if the chip works with one pin telling it to be an astable and the other pin telling it not.

That's why in my previous post I stated "If it doesn't work..."
 

audioguru

Well-Known Member
Most Helpful Member
Hi L. Chung,
As long as one of the astable pins is correct, the oscillator will run:
 

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eblc1388

Active Member
:D :D :D :D :D

Nice one. I was not sure that it will run so I left myself some steps to fall back to but why are you so sure that it would not run if Pin4 is grounded?

It turns out that both of us are not wrong.
 

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audioguru

Well-Known Member
Most Helpful Member
Hi L. Chung,
I had a quick look at the cruddy photocopy TI took from Harris Semi like you posted and didn't bother reading it. The other oscillator works with pin 4 high so I wrongly assumed it wouldn't work if it is low. :oops:
Thanks for pointing it out. :lol:
 

eblc1388

Active Member
:D

We are victims of the datasheet.

Normally in these cases the manufacturer would put in a logic table in the datasheet listing all possible combinations of these two lines and the resultant modes. Sure would save us a lot of troubles figuring them out.
 

audioguru

Well-Known Member
Most Helpful Member
Hey Electrix,
What are you going to use a 4W square-wave inverter for? :roll:
 

Styx

Active Member
audioguru said:
Hey Electrix,
What are you going to use a 4W square-wave inverter for? :roll:

That is what has been confusing me...
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Styx said:
audioguru said:
Hey Electrix,
What are you going to use a 4W square-wave inverter for? :roll:

That is what has been confusing me...

How about for feeding a 60Hz electric clock?, I used to have a 2m transceiver base station years ago, it included a mechanical digital clock - which was 60Hz. They were modified for the UK market by fitting a similar crude little inverter - it kept really bad time though :lol:
 

audioguru

Well-Known Member
Most Helpful Member
It would power a few NE-2 neon bulb night-lights pretty well.
Just think how poor its output voltage regulation would be, more than 300VAC without a load with a 12V regulated input and about 353V with a fully-charged car battery for a power source. :)
 

Electrix

Member
Hi audioguru and all you guys..
Thanks for your interest. Well, the circuit that I have presented is only a "basic inverter working principle circuit" that I picked up from a local book. Nevertheless this particular circuit is meant to power very light loads like window chargers and night lamps, or simply give shocks to keep the intruders away !

Cheers !
 

jtzanis

New Member
Another inverter

Can someone help me with an inverter with the below specs.
I've seen the previous msgs but im not to familiar with electronics, and i dont know how easy it would be to go from one set of spec to another.

I know that there are a number of products off the shelf that can come close to what im looking for but i would rather have a design that takes up as little area as possible while not costing that much as i intend to make quite a few.

This is powering an electroluminesent lamp.
Again, I would prefer that it be as small and cheap to make as possible.

Input voltage: 12V D.C.
Drive Voltage: 65 ±5 volts A.C.
Amperage: less than 20 mA
Power: approximately 0.3 watt
Frequency: 50/60Hz sine or square
A maximum frequency of 200Hz if it would make any difference.

Thanks in advance!
John
 

audioguru

Well-Known Member
Most Helpful Member
Hi John,
The TL494 is a 16-pin IC for power supplies. It costs only $.52US at Digikey and has an oscillator and two push-pull output transistors. It could drive a small 115V:40VCT power transformer in reverse and make a 63V square-wave output.

The only small 115V:40VCT transformer I found is one that Digikey doesn't stock, is 12 times too powerful and costs about $5.00US. A smaller, cheaper transformer might be found instead.

If your 12VDC is from a car and varies up to 14.4V, then a small zener diode could be added to the TL494 to limit the voltage to 12V. :D
 
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