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        General >> Give/Need advice to/from others >> A little gadget!
        
(Message started by: harry.m1byt on Oct 28^th, 2006, 2:03pm)

Title: A little gadget!
Post by harry.m1byt on Oct 28^th, 2006, 2:03pm

Here is a little gadget I designed many years ago which makes electrical fault finding on cars that bit quicker. All it does is indicate whether the probe point is connected to a negative or positive - assuming you connect the red and black wires the right way round.

You take two tiny 12v metal capped bulbs and solder the metal caps togther and to a long sharp needle to form the probe. To the centre contact of each lamp you solder a black wire to one and red wire to the other.

To the other end of the red and black wires you fit either a pair of crocodile clip or a cigarette lighter plug. On connecting it to power, both lamps glow dimly. Touch the probe tip to ground and one lamp glows bright and the other goes out. The other one lights if you connect to a +12v. So mark the bulbs up as +12v and ground.
A fuse in the red lead might be prudent.

Now put it in a suitable case - an hypodermic syringe works well as a case, with the probe where the needle usually fits, the wires out the back and the rubber syringe piston pushed back (less the plunger) in to help hold the wires.

Great for checking the Scorps fuses -
Simply turn on the circuit you are having trouble with then stick the probe tip into the still in place fuse - most have a contact along the side which faces you whilst still inserted. Check both ends of the fuse, if polarity is different between the two ends the fuse must have blown.

The needle point probe also allows you to poke it through wire insulation. This device should never be used on any wires involved with the electronics in the cars, but is fine for checking straight forward 12v and ground feeds.

Title: Re: A little gadget!
Post by Spannerdemon on Oct 28^th, 2006, 6:30pm

Sounds good. Any chance of a picture? ;)

Title: Re: A little gadget!
Post by taliban on Oct 28^th, 2006, 7:06pm

harry, you seem to be a bit of an auto electrician, i think you should pop over to my place and suss out my non working scorp

Title: Re: A little gadget!
Post by Paul B on Oct 28^th, 2006, 7:33pm

on 10/28/06 at 18:30:45, Spannerdemon wrote:

Sounds good. Any chance of a picture? ;)

Exactly what I was wondering. :)

Title: Re: A little gadget!
Post by harry.m1byt on Oct 28^th, 2006, 10:02pm

on 10/28/06 at 18:30:45, Spannerdemon wrote:

Sounds good. Any chance of a picture? ;)

It's it not very picturesque, it looks just like a syringe with wires poking out of the end ;D

Perhaps a diagram might be more useful....
____
probe tip L1> ____ o------------------black to ground
_____________I
I____
L2> ____ o-------------------red to 12v

Connect to a supply and both lamps light up dimly because they are in series, which confirm the thing is working.

Connect tip to a ground - L2 lights up bright and L1 goes out.

Connect the probe tip to a 12v positive supply - L1 lights up bright and L2 goes out. Simple![/font][font=Verdana][/font][font=Verdana][/font][font=Verdana]

Title: Re: A little gadget!
Post by harry.m1byt on Oct 28^th, 2006, 10:14pm

on 10/28/06 at 19:06:47, taliban wrote:

harry, you seem to be a bit of an auto electrician, i think you should pop over to my place and suss out my non working scorp

Got enough Scorp troubles of my own to deal with at the moment :(

I'm an electrical/electronics engineer, even a spell as a communications engineer. I just dabble with cars when I have to - which seems to be everytime I get a new to me car :-0