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Solderless, Ultra Simple Flyback driver

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LAN_403

Dragon64

Sat Apr 12 2008, 04:11AM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

Almost an year ago, I was staring at a electrical mouse killing trap. I bought one home and inserted the battery and turned it on. I reached inside and poked around until a painful zap that I felt made me jump up in the air. I went back to the mouse trap and noticed a 2.7 KV output with a very few mAh. I opened up the curcit and found a driver curcit for an odd type of bar transformer. I disconnected the wires from the bar transformer and hooked it on to my flyback. It worked great. I will post pictures.

quicksilver

Sat Apr 12 2008, 01:40PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

I am familiar with this circuit. It is rather complex (IMO) and uses quite a bit of not so simple (to my eyes at least) design. I pulled one from a trap that was out of service as I really thought this worth of study. If you can't come up with the picture; say so and I'll post mine. I wish I had it written out as well. Quite a few transistors and a bar coil with seemingly two layers separated by paper. Circuitry was quite small (SMD) and the input was 4 AA batteries.

Dragon64

Sat Apr 12 2008, 04:05PM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

Here, I got the pictures. Sorry for the delay, slow Internet connection.
I agree that the curcitry inside is complicated by it is pre-done for you so that there's no hassel for you to take out your solder.

My Pictures came out sort of blurry mod edit: not to mention far above the 400 pixel width limit :P

northern_lightning

Sat Apr 12 2008, 04:55PM

Registered Member #1348 Joined: Sun Feb 24 2008, 01:48AM
Location: Michigan's Upper Peninsula
Posts: 22

i had no idea such a trap existed. if you're gonna kill a mouse what's wrong with the old-fashioned spring and lever contraption? howabout a catch-and-release style mouse trap that uses tetanizing laser induced plasma channels?

EDIT:

Dr. Shark

Sun Apr 13 2008, 02:00PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Looking at those puny sparks, I really suggest trying a solid state 12V halogen lamp transformer instead as a "solderless flyback driver". They put out AC at about 40kHz, which is just right for a TV flyback.

Oh, and you might want to resize those pictures, since they really f*** up the board format.

quicksilver

Sun Apr 13 2008, 04:00PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Dr. Shark wrote ...

Looking at those puny sparks, I really suggest trying a solid state 12V halogen lamp transformer

I did a search on this as it really piqued an interest and came up with a confusing array of items....could you elaborate on it a bit and point me in a direction in the USA if possible? (Purchase...I checked local places like Home Dept, etc..) You're saying 40KHz @ what? 12 vdc?

One item that appeared fantastic was a toroidal transformer that seemed to be a monster! But I imagine the cost was too high.

Thanks

~The "mouse trap" appeared to be an over complication as to it's circuitry. I really couldn't understand why the inventors just didn't go with "simpler is better". As I re-iterated, I have one, torn down and when I looked at it: it appeared to drive the voltage up then pull it done again just to drive it up one final time to achieve a wee bit more current at a higher frequency. A very round-a-bout way of getting what could be done with a larger initial supply. What's more the design is very interesting but it was meant to be used under conditions that could present a challenge. Dust, moisture and dirt would make for a fast short within the traces, which are almost on par with 1980's small stuff (it's pretty small!) and uses components that really were not meant to be field mouse trap material. <grin>

I'm keeping mine specifically as a learning tool as the design is pretty interesting. Sections of it are worth extrapolating and posting on the board. I only wish there was a way to obtain the schematic.

jpsmith123

Sun Apr 13 2008, 06:16PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Does anyone know if these "electronic transformers" (ETs) are generally potted? Also, I wonder if they are generally set up for soft switching? Supposedly the ir2161 has that feature, so units based on that IC might be, but I don't know what percentage of commercially available ETs use this chip or what alternate control circuits are being used.

quicksilver

Tue May 06 2008, 02:50AM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

I've been looking closer at the example of this "mouse trap" and lit it up to examine the arc.

Some models are stronger than others. The complication of the thing's design made it more and more interesting. What they have designed is a HV high frequency device that is switchable upon a short. Thus when the thing is armed the rodent trips the device (by shorting it with its body) and the thing delivers a powerful shock which continues for a set period of time; then switches off to protect the circuit; re-setting itself.

The purpose here appears two-fold. First to allow for multiple methods of entrapment. Second, for it to protect the circuit from a continually "on" discharge. The use of the IC's for this timing-arming technique is clever for this application.
Several makers have implemented the concept. One uses a rod-core coil & a higher level of miniaturization than the unit pictured.

RE: Electronic transformers being potted......I saw several but they were sold in Europe that were NOT potted (so it appeared from the pictures). I imagine many designs exist but those sold from a European parts place are obviously open to investigation. There's a link within the Forum but what I remember is that a gentleman from the Czech Republic is the guy who uses that parts place & provided the link thereof.

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