a 5kV megger is very effective.

I had a dog steal our cat food usually at night.

One day put the cat food outside, and kept our cats inside.

Put the plastic cattray on an aluminium plate on top of a rubber mat.
made surrounding concrete floor damp.

Connected 5kV megger (AVO BM 25) and monitored from the window.

Dog arrived, connected HV lead with HV gloves while megger was on.

Lots of noise, Dog ran away like a torpedo.

Never came back to steal our catfood.

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There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

Can't wait to try this one!!

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"Stick around" - Arnold Schwarzenegger in The Predator after impaling a soldier to a wood post

9vDC Guitar Pedal PSU

PIC16F84a Game Module

 

Careful now, you could end up killing someone with that if it's not sufficiently current limited.

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Seems like if 'someone' has been eating the pet food, they have bigger worries... That big recall few weeks ago was really Shocking. You'd think there would be some minimal for of quality control. A biological contaminate could easily be transfered to pet owners, not mention I still believe the urban legend about senior citizens... Fixed incomes and high priced prescriptions, old people are always popping pills, can't all be vitamins.

 

Some Megger s are current limited to such an extent that they can't shock you at all.

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Screen name: Aloone_Jonez

 

I was looking at the "stun gun" design and came across this website.

http://www.uoguelph.ca/~antoon/circ/hv/dazer/dazer.htm

This person is using 1200:8 ohm transformer. Does this mean that in order to get the transformer "working" you need 1.125 amps on the primary (9 volts/8 ohms).

1) Can a 9 volt supply 1.125 amps?
2) Power= VI, 9*1.125= 10 watts

Using (Z1/Z2)^(1/2)=N1/N2=I2/I1

(8/1200)^(1/2)=0.0816

I2=0.0816*1.125=0.091 amps

Therefore on the secondary you get 0.091 amps.

 

Only if the 9V supply is regulated and only if the transformer has a 1200 ohms load. It has a high load resistance so the 8 ohms winding has a low current and the output also has a low current.

Only for a moment but the voltage will be much less than 9V.

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Uncle $crooge

 

rather then just building it, I’m trying to understand how people have calculated the values for various components for the stun gun picture attached.

Looking at this person website for some help (and also using my brain):
http://www.kpsec.freeuk.com/trancirc.htm

To calculate the base resistance for the transistor (tip 31) you need voltage and current:

First, using basic ohms law.

- The difference between the emitter and base should be about 0.6 V
i know the output voltage from the 555 timer is about 1.7 v less then Vcc. so if you have 9 volt supply then 7.3 Volt would on pin 3.

so therefore the voltage difference across the base resistance would be 7.3-0.6 = 6.7 Volts. ok

Now for the current.

(Using the above website and the attached datasheet for tip31)

The load current is 9 volts/8 ohms =1.125 amps

Using the datasheet attached, looking at the graph of Ic vs Hfe, 1000 mA, hfe is about 100.

Therefore Ib current is about 1.125/100=0.01125 amps.

Therefore the resistance would be about 6.7/0.01125=600 ohms
if you use the method as described by the website, you would get about 130 ohms.

i can see 600ohms is close to 1000ohms, but if you used 1000 ohms, would you not get about 0.67 amps passing through the transformer. Or is my understanding flawed.

At the moment I am having difficulty trying to get this circuit to work. I can get the 555 timer to work, but when it comes to getting a voltage across the transformer I get nothing.

I can get current flowing through the base of the transistor, but it is a lot lower then I have calculated even with a fresh battery.

Can someone correct me if I’m wrong about the above.

Attached Images

stun_gun.gif (14.6 KB, 51 views)

Attached Files

TIP31.pdf (37.7 KB, 41 views)

 

It depends on the size of your 9V battery, one of those large 9V batteries (the kind used in transistor radios) will, a small 9V battery (the kind used in a smoke alarm) won't. The maximum current available will depend on the impedance of your battery, the kind of 9V battery here probab;y has an impedance of about 30hm: and therefore won't supply more than 300mA even when short circuited.

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Hfe is used to design a linear amplifier, not a switch. If the collector current is 1.125A and the base current is only 1125mA/100= 11.25mA then it would not saturate. Its collector voltage would be about 4V for most of them.
The datasheet spec's a low saturation voltage of 1.2V max if its collector current is 3A and its base current is 375mA. The graph of typical saturation voltages has the base current at 1/10th of the collector current.

Look at the picture of the TIP31's pins on its datasheet. Maybe you have them connected backwards.

The base current is in fast pulses. You need an oscilloscope to measure them.

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Uncle $crooge

 

well, if over 300mA is needed on the base of the transistor, and if i remember correctly the 555 timer can only deliver a max of 200mA. How can this circuit work?

 

The circuit with the TIP31 transistor uses a dinky little transformer that has a high resistance and a low power. The transformer is not 8 ohms, it is half of a 1k winding which is 250 ohms if it is loaded which it is not. So the transistor's current is low and it can be driven with a 1k series base resistor from the 555.

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Uncle $crooge

 

Ok,

The reason why i was using 8 ohm, was somebody told me to use 8 ohm because i got confused on impedance, so i asked somebody. Looks like they need some lessons as well.

OK, so i understand.

However as a side issue, half of 1K is 500 isn't. as 1/4 of 1000 is 250.

OK, well just to bug you for another question.

Going back to
http://www.uoguelph.ca/~antoon/circ/hv/dazer/dazer.htm

I now understand, it is not the impedance i should be using as resistance. (it has the same units, which is probably what the other person thought, same units same thing).

Ok, looking at the datasheet for the mouser transformer (attached)
The primary has 75-ohm resistance, so therefore the current required is (volts/75 ohm) 0.12Amps or 120 mA. Which a 9 V battery can provide for a short amount of time.

Therefore 120 mA is the load current if you like, therefore you need 0.0012Amps on the base if you assume Hfe is 100.

Am i getting there?

Attached Files

mouser.pdf (199.8 KB, 58 views)

 

Your transformer is connected backwards. The transistor must drive the low impedance winding (8 ohm AC impedance when loaded) then if the current is high enough the transformer will step-up the voltage. The impedance is much higher than 8 ohms because the transformer is not loaded. The resistance is used for DC calculations of current but here there is AC.

A transistor switches well if its base current is 1/10th of its collector current. Hfe is used to calculate the base current for a linear amplifier, not a switch.

This circuit uses a PNP output transistor. Before you said your TIP31 NPN transistor didn't work. They are completely different transistors in completely different circuits.

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Uncle $crooge

 

Sorry, the tip31 transistor is used in the "stun gun" design which has the 555 timer, which i was referring to on the 30th march.