Current Source

[Hlias]

Hello!

I want to build a circuit where I have a load of 10 - 15K and a DC source of 12-20V max.
I want to have a minimum current of 8-10 mA through the load.

Is this at all possible or not?? (I know that supposedly I would need a min voltage of about 80V, but I was wondering if it were possible through any other way..)

Thanks in advance.

 

[Pommie]

No, it's called ohms law because it's a law and if you break it you go to jail. Well, actually you wont go to jail, but your circuit just won't work.

Why don't you tell us what you are trying to do.

Mike.

 

[Hlias]

I am trying to make a small circuit to be able to induce a small electric shock through an open electrode when one's finger is placed on it. From what I found out a typical resistance value for a finger (not dry) is about 15k(max) and the necessary current that needs to be applied to perceive the small shock is 5.2 mA min (for males).
Furthermore I would like this device to be portable.

Any suggestions?

 

[Pommie]

This question gets asked regularly and so the webmaster kindly put together this.

Mike.

 

[Hlias]

Thanks man.

 

[Hero999]

From what I found out a typical resistance value for a finger (not dry) is about 15k(max) and the necessary current that needs to be applied to perceive the small shock is 5.2 mA min (for males).

Where did you get this from?

I've read all sorts of things on the Internet but the lowest reading I've had from my finger is 200k and that's after I licked it!

Without licking my finger, measurements of over 1M were more typical.

From this you could assume that you could apply 200VDC to my finger and I'd hardly feel it, but you'd be wrong because the resistance drops at higher voltages. In practise I start to feel a shock at around 50VDC if my skin is damp or much higher if I have dry skin - I've touched >75VDC live parts before without being shocked.

Use a much higher voltage and limit the current to just below 5mA which is the maximum current that is considered harmless.

 

[walshlg]

as an illustration take a 9 volt battery and put your finger across the elctrodes = nothing! So go ahead and lick it, it'll nip but won't really bite.

 

[audioguru]

as an illustration take a 9 volt battery and put your finger across the elctrodes = nothing! So go ahead and lick it, it'll nip but won't really bite.

Don't try it!
If your tounge is really salty then the current from a brand new 9V alkaline battery will burn your tounge off.

 

[Hero999]

Don't be silly audioguru, I've done it many times before, even with a new 9V battery my tongue didn't burn off.

 

[audioguru]

Eat some salty potato chips or a salty pickle then lick a new 9V alkaline battery. The current will be about 5A and the resulting 25W will burn your tounge badly.

 

[gramo]

Eat some salty potato chips or a salty pickle then lick a new 9V alkaline battery. The current will be about 5A and the resulting 25W will burn your tounge badly.

Im taking your word on that