#### tezza1

##### New Member
Hi all: I'm trying to make an electric rat trap with a car ignition coil but don't really know how to make the coil produce the spark?. just wondering if anyone would draw up a diagram for me to help me along a little!. Also would a 12v DC to 220v AC inverter wired to 2 metal plates do the trick?. any help would be more then appriciated. Thank's guy's. Tezza1.

#### SABorn

##### New Member
Do you want to Kill em, Cook em, or Scare em?

As for the coil all you need is something like a 555 generating a squarewave going to the base of a large transistor so it switches the coil on and off repeatedly.

Rats are a tricky animal and leave sence for other rats so they learn fast.

Pete.

#### ericgibbs

##### Well-Known Member
Hi all: I'm trying to make an electric rat trap with a car ignition coil but don't really know how to make the coil produce the spark?. just wondering if anyone would draw up a diagram for me to help me along a little!. Also would a 12v DC to 220v AC inverter wired to 2 metal plates do the trick?. any help would be more then appriciated. Thank's guy's. Tezza1.
hi,
This circuit gives approx 10KV at a 1 second rate.
The circuit must be connected to EARTH to close the fence loop.

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#### DerStrom8

##### Super Moderator
Do you plan to have it on continuously?
I have often used this circuit--it plugs directly into mains and uses a capacitor to limit the current. The larger the capacitor, the more current flows, and the more dangerous the arc becomes:

I would not recommend going over 20-30uF because that might heat up the coil too much. Also, be sure to use AC (or at least non-polarized) capacitors. If you used an electrolytic cap, for example, it could explode (literally).
I must insist, as you will be dealing with high voltage, that you take all necessary precautions to protect yourself and others. THIS COULD BE LETHAL, so be extremely careful.
Good luck!
Der Strom

#### crutschow

##### Well-Known Member
Such a circuit is unlikely to kill the rats, but it may scare them off.

#### tezza1

##### New Member
Thank's for sharing your time on this for me guy's: I now have a bit more direction of where i'm going with this, although ericgibbs's plan is far to technical for me LOL but thank's.

#### SABorn

##### New Member
I though Erics circuit was very basic, so if you have trouble understanding that then perhaps a Cat or a big hammer is more practical to you.

#### tezza1

##### New Member
Well i'm really sorry i dont meet your great expectations SABorn! i have only been learning about electronics for the last 6 months since i was 17 & a half & was actually hoping to learn a little from you guy's with the knowledge not get sarcasm. They say sarcasm is the lowest form of wit so maybe you were trying to be funny ?.

#### ericgibbs

##### Well-Known Member
Thank's for sharing your time on this for me guy's: I now have a bit more direction of where i'm going with this, although ericgibbs's plan is far to technical for me LOL but thank's.
hi,
Two of the version I posted have being working on a farm in South Africa for about 5 years, keeping stock animals confined.
I chose a relay drive, because of the very strong and frequent electrical storms in that area, a long fence post makes a great lightning conductor and the MOSFET drivers used to 'pop'.!

#### Boncuk

##### New Member
Hi tezza1,

if you have problems creating a PCB from Eric's design you might want to use my design.

It uses a car ignition coil designed for electronic ignition.

The power generated depends on the slide switch position and varies between 250 and 450mJ. The pulse repetition frequency might be increased by shorting out R5.

I recommend using the circuit battery buffered (30Ah car battery).

Boncuk

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#### ericgibbs

##### Well-Known Member
hi Hans,
Check this part of your circuit, the LED current.??

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#### SABorn

##### New Member
Code:
They say sarcasm is the lowest form of wit so maybe you were trying to be funny ?.
It was not intended as sarcasm, just honest advice.

You come to a electronic forum asking for advice and give no indication of ability, and get given a very practical simple circuit and then quote it is beyond your ability.

If you are unable to understand a simple circuit than a cat might be a better bet to solve your problem.........no sarcasm intended.

how can we help you understand a circuit when you quote its beyond you, and its a simple well proven circuit that is presented very well.

What is it you want ....... as all circuits will require some degree of ability to be able to construct them, and unless you spell out your full ability than a cat might be a safer bet.

You are asking for advice to play with a high energy discharge circuit here, that has the potential ability to kill or maim a creature including yourself or other humans and you lack the skill to construct or even understand the workings of such a device, that alone is a recipe for trouble and needs to be considered if this information should be given to a person who sees constructive advice as sarcasm.

I recommend you get a prospective of what you are asking and what your actual abilities are before you attack advice given.

Pete.

#### Boncuk

##### New Member
hi Hans,
Check this part of your circuit, the LED current.??

Hi Eric,

that part of the circuit is OK. The LED current should be 2mA for a low current LED. Using a battery charger (13.8V) the resistance value should be increased to 680Ω at which a low current LED 2.4V/2mA with draw 2.15mA. Using 820Ω for current limiting the LED will stay dark.

The LED to be used is contained in the circuit description.

Regards

Hans

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#### SABorn

##### New Member
I think the thing Eric missed (and so did i on the first schematic) is the fact the diode is a zener and is reversed bias,
I thought Eric was drawing a polite refference to the fact of a reversed diode and asked you to check the circuit because of this.

although your resistor value looks wrong for around 3 volts.

Pete.

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#### Boncuk

##### New Member
I think the thing Eric missed (and so did i on the first schematic) is the fact the diode is a zener and is reversed bias,
I thought Eric was drawing a polite refference to the fact of a reversed diode and asked you to check the circuit because of this.

although your resistor value looks wrong for around 3 volts.

Pete.
Hi Pete,

I don't know where you took 3V off. The LED is labeled 2.4V/2mA.

Here's a simulated circuit showing the voltages across each part.

Boncuk

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#### ericgibbs

##### Well-Known Member
Hi Pete,

I don't know where you took 3V off. The LED is labeled 2.4V/2mA.

Here's a simulated circuit showing the voltages across each part.

Boncuk
hi Hans,
At 13.8V I agree with your results.

Pete, The 10Vz zener is not reversed.
My query was that
with a 12V supply as posted, the LED has only a 0.4mA current.!

#### DerStrom8

##### Super Moderator
Code:
They say sarcasm is the lowest form of wit so maybe you were trying to be funny ?.
It was not intended as sarcasm, just honest advice.

You come to a electronic forum asking for advice and give no indication of ability, and get given a very practical simple circuit and then quote it is beyond your ability.

If you are unable to understand a simple circuit than a cat might be a better bet to solve your problem.........no sarcasm intended.

how can we help you understand a circuit when you quote its beyond you, and its a simple well proven circuit that is presented very well.

What is it you want ....... as all circuits will require some degree of ability to be able to construct them, and unless you spell out your full ability than a cat might be a safer bet.

You are asking for advice to play with a high energy discharge circuit here, that has the potential ability to kill or maim a creature including yourself or other humans and you lack the skill to construct or even understand the workings of such a device, that alone is a recipe for trouble and needs to be considered if this information should be given to a person who sees constructive advice as sarcasm.

I recommend you get a prospective of what you are asking and what your actual abilities are before you attack advice given.

Pete.
Pete, we all had to start somewhere. I see nothing wrong with this thread or the OP--He's just trying to learn. Remember when you were there? I remember how I usually just jumped into a project, and I'd learn whatever I had to along the way. Yes, the OP should know that this is dangerous, and understand how to take precautions, but if he is unable to read a schematic, then it is our job to teach him. We are all here to help. We are not here to criticize anyone's amount of knowledge or level of expertise.
With all due respect,
Der Strom

#### SABorn

##### New Member
Der Strom,

Mate i could not agree with your point more.

As like yourself and many others i spend a lot of time helping people learn electronics and develop projects.

There is also several things to consider here as well, we are responsable for the information given should it harm someone,(or a moral duty) maybe not all countrys fit this rule but many do, and for example if we post how to make fire crackers and some kid blows his arm off, then we can be held resonsable for supplying the information.

I dont intend on stomping on anyones knowledge or learning ability, but we all have a duty to access a persons ability to use the infomation we give.

If the person wants to learn electronics then flashing some leds is a good place to start, compaired to playing with high voltage discharge circuits.

So hence my comment ......if you cant understand a basic schematic then but a cat.

Pete.

#### SABorn

##### New Member
Hi Pete,

I don't know where you took 3V off. The LED is labeled 2.4V/2mA.

Here's a simulated circuit showing the voltages across each part.

Boncuk
I thought the zener was labeled 10 volt, meaning 3.8 volt would go to the led.

The eyesight might not be so good and i read the rating wrong.

Pete.

#### Boncuk

##### New Member
hi Hans,
At 13.8V I agree with your results.

Pete, The 10Vz zener is not reversed.
My query was that
with a 12V supply as posted, the LED has only a 0.4mA current.!
At 12V supply voltage it's advisable to use an 8.2V zener diode.

Anyway, I don't suggest to run the circuit off battery power. The ignition coil draws approximately 19.7A at 13.8V supply voltage.

At a pulse repetition frequency of 1Hz (normally 0.667Hz) and a pulse width of max 31.5ms (minimum pulse width is 16.5ms) the battery would be depleted pretty fast.

So I suggested using battery buffered operation - with the battery being charged on demand.

Just to add: The dual 3-position slide switch is put in for proper function under all circumstances. If the timer circuit fails due to bad contacts of a single pole switch the timer output might go to steady high output burning off the transistor and/or the ignition coil. So a 5A fused supply for the ignition coil eliminates the need for new parts every once in a while.

Boncuk

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