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Inverter unit:

September 1985

I rcccntly built and operated a 12/230V 3(X)VA inverter as dcscribed in your September 1985 issue. This in-verter fulfilled its basie function and proved to be a fundamentally sound design. It appears to be an update with extra features of an earlier design pub-lished by yourselves in February 1979.

During operation a number of minor design idiosyncracies were noted. These were annoying in that they limited the usefulness of the unit. Minor changes only were needed to eliminate these problems. You may wish to pass the de-tails on to other readers, as some of them may have encountered similar problems.

Auto starting: This Circuit functions as intended, provided that a Iow voltage drop DC path exists in the 230V appli-ancc. Equipment containing triac or SCR speed controllers, or the inereas-ingly popular mains level switch-mode power supplies will usually fail to trigger . the inverter into action. The result is total frustration. The simplest fix is to connect a 22k resistor in series with a slider switch between the -ł-12V raił and

011    base-D12 cathode junction. Open-ing the slider gives autostart operation, closing it gives ćontinuous running of the inverter. Space exists on the front panel for mounting the switch and label.

Voltage rcgulation at start up: At start up, a transient of maximum output voltage maximum duty cycle occurs for about 1/2 sccond. Output then disap-pcars for about 1 second, followed by a slow risc from zero to the correct finał value. This form of start up is not al-ways desirable. Also, high dissipation can occur in the 2N377Fs from trans-. former saturation during start up at fully duty cycle. These problems are due to the initial abscncc of charge on the 0.47/zF capacitor connectcd to IC7a pin 3. The cure is connection of a second capacitor of 0.68/iF between IC7a pin 3 and the +9 volt raił. The output now ramps up smoothly without the start-stop-start bchaviour previously ap-parent.

Control Circuit filtering: Bypassing the

12    volt linę to the control circuitry with 4,7(X)/xF in lieu of the lOOjtF uscd, and feeding this portion of the Circuit via a smali germanium power transistor con-nected as a “super diodę” to limit diodę drop, improves regulation and protec-tion on noisy, poorly regulated battery circuits. This becomcs important if di-

Continued on page 122

Editorial

iwpoint

A sad day for Australian electronics manufacturing

I*ve just finished one of the saddest stories Fve ever had to write. It’s our exclusive story in this issue on the demise of Appfence Control Systems, and the sale of its hi-tech manufacturing plant to Singapore.

Fm hopping mad about what happened to ACS. I believe it’s a tragedy, not only for ACS and its employees, but for Australian electronics manufacturing. I also believe it’s an incredible indietment of our financial community, its current practices and attitudes towards manufacturing.

What infuriates me morę about this story is that it probably wouldn’t have happened if manufacturers like ACS could get genuine long-term finance to build their businesses in a solid way. Not the kind of pseudo help that’s cur-rently all the ragę: “Here*s a few hundred grand — but we want 22% inter-est, or a big slice of the company. And if we buy in, we expcct to get our money back in six months.^M

No doubt if Laurie Larscn had wanted to borrow $1(X) million for a few weeks to make a quick killing, the banks would have fallen over themselves to lend him morę money. The problem was that he only wanted a much smaller figurę, to do something constructive like building a good solid manufacturing and export business.

Frankly, I doubt whether we’re ever going to get a dccent manufacturing industry in Australia while our finance industry continues to be ruled by this fast-buck mentality. If a rcally innovative, efficient and internationally com-pctitive little company like ACS can comc to grief like this, what hopc do we * have? We might as well sit back and watch while countries like Singapore, Korea and Hong Kong leave us far behind. Not cvcn counting those like Japan and Taiwan, that alrcady have . . .

The frustrating thing about all this is that with good long term planning and financing, Australia could so easily build up a solid, world class and internationally viable manufacturing industry. We have the innovators, the knowl-edge and the skills — they’re not the problem.

I don*t think the answer is morę Govcrnmcnt agencies set up to “help our manufacturing industry”, either. We’vc probably got morę of those already than the countries that rcally are nurturing their manufacturing industry. In our case, all they secm to do is create an ever-growing army of bureaucratic paper-shufflers. Very little rcal assistance ever seems to filter through to the actual manufacturers who necd it and could put it to efficient use. -

We dcsperately need a genuine, no-bulldust commitment to manufacturing, or Australia the banana republię is almost inevitable. By the way, guess whose electorate ACS was in — why Paul Keating’s, of course. Ironie, that.

ELECTRONICS Australia. September 1987

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