Re: New Godzilla Design--done! AUTOSWITCHER CKT

[Guest guest]

Linear Technology LT 1490 CN8 is a dual operational amplifier that

combined draws 5.4 mA with no pads connected. When connected it can

support up to 15 square inches of pad area. They are available in CS8

[surface mount devices; strongly recommend you NOT order them, requires

professional soldering skills beyond most users]. The CN8 is an 8 pin

dual inline chip that can use all batteries recommended, has built in

reverse voltage protection [can't fry it by backwards connection] and

if you include special low current indicator LED's - can indicate

connection quality and automatic trouble shooting - PROVIDED YOU USE AT

LEAST 4.5 V batteries for the LED's to work. When the second op amp is

wired as an integrating inverter - polarity reversal spikes DO NOT

HAPPEN; can vary the time for switching completion. My personal

recommendation is the pads below about 15 sq. inches need no further

suppression. This is unlike the LM324 series - only drops 0.08 V due

to transistor losses from the battery terminals - 40 mV each. Cost is

about $3 for the chip in unit quantity.

I have an obsolete schematic, artwork for growing your own circuit

boards, can be slightly updated & fits your description of need. Board

size is about 1 " x 3 " . When in use - current needed will be 7.4 mA or

less. I've run all mine with no case. Production versions won't have

any either - potted.

The idea of adjusting your wire strip length allows there to be no

current limiting on the board needed. Then you can make up multiple

pads of several sizes and let the insulation length serve as limits for

current.

If you decide to grow your own - expect to get 10 boards from a 6 x 6 "

single sided copper clad board. Power on switch is a connector plug /

socket that will cost for 100 connectors about $20 which will be enough

for 50 assemblies with 50 spare power connectors - 3 position [idiot

resistant], 2 pad connectors with 2 pins so you can run 2 pad pairs at

once - different sizes. Board etching materials will run about $15 for

enough to do about 50 boards. Resistors, etc., about $15 per board.

Tools:

60 / 40 solder, rosen core, 1/16 " .

water soluble flux - tin the bare etch.

25 Watt adjustable temp needle tip iron [Radio Shack].

hack saw blade [cut etched boards to size].

flat iron, steam OK - transfer image from mylar to your card blank.

access to a laser printer - uses the printer toner to make the image,

when ironed onto the card blank - it fuses and hides the wanted image

from the etchant.

double boiler, [any old pot big enough, wide bottom coffee cup to soak

the card in the etchant]; directions supplied w the treated mylar.

Email if serious.

Joe.

> BG for your approval n refinement, if only we could find a cheap

> > small chip or device to intermitently change polarity that would be

a

> > dream come true godzila even james bond would envy

> >

>