Help needing smallest 240v to 9v transformer

[Gabriel Knight]

Hi I am interested in making my own 240v double adapter spy bug like the one
found here:

http://www.ozspy.com.au/products/7-listening-devices/116-double-adaptor-vhf-bug/

but the price is too much for me to afford, so I would like to make my own.
Would the power it needs have some sort of transformer in it?

I have a small bug I made from talking electronics that uses a 9v battery I
might be able to squeeze it into an adapter most likely I'll have to
customize it.

Does anyone here have any ideas how I would go about making one or any
schematics they could offer to make one as this sort of thing is new to me.

Thanks all

GK

 

[Phil Allison]

"Gabriel Knight"

Hi I am interested in making my own 240v double adapter spy bug like the
one found here:

http://www.ozspy.com.au/products/7-listening-devices/116-double-adaptor-vhf-bug/

but the price is too much for me to afford, so I would like to make my
own. Would the power it needs have some sort of transformer in it?

** The unit described almost certainly use tiny SMD components so it fits in
the space available. The circuit is very likely powered directly from the
AC supply - which make it electrically dangerous.

But MOST IMPORTANTLY - using such a device to secretly listen to
conversations is a breach of the criminal law anywhere in Australia or most
places.

Eg:

http://corrigan.austlii.edu.au/au/legis/nsw/consol_act/sda2007210/s7.html


..... Phil

 

[Jasen Betts]

Hi I am interested in making my own 240v double adapter spy bug like the one
found here:

http://www.ozspy.com.au/products/7-listening-devices/116-double-adaptor-vhf-bug/

but the price is too much for me to afford,

I have a small bug I made from talking electronics that uses a 9v battery I
might be able to squeeze it into an adapter most likely I'll have to
customize it.

Ok take the for example the voyager MKII and sort out a capacitor derived supply

it will have essentially constant current requirements so should suit the
capacitor supply, you're going to need a Y2 rated capacitor else you're building
a fire bomb... (I've not read Phil's reply yet, but take his warnings
seriously too)

take current measurements from your bug on different supply voltages,
eg: 10.5 and 7.5 if the current consumption varies like a resistor
it should work fine with an unregulated capacitor supply s long as the
capacitor supply is within range, else it's going to need a zener.

Does anyone here have any ideas how I would go about making one or any
schematics they could offer to make one as this sort of thing is new to me.

http://electroschematics.com/5678/capacitor-power-supply/
this one uses an X2 capacitor and a fuse, Y2 is better as they don't
fail short-circuit, so if it does fail the bug circuit won't get cooked.

C1 will have to be sized to supply the correct current for your bug

everything right of the zener diode can be replaced with the bug.
use a 10V zener. R2 seems larger than is needed it need only be
about 10 times ESR of C2

See how it goes, you might get a lot of hum on the transmission. if you
do better supply filtering will be needed, perhaps adding a
capacitance multiplier stage will be enough.

For experimenting with circuits like this one you really need a mains isolating
transformer, here's a cheap way to make a small one.
http://www.electronicspoint.com/very-low-power-line-isolation-transformer-t13401.html