Am I a resistor?

So I was working on a project to move a servo using a motor shield.

I wrote some code and uploaded it to an Arduino Uno.

The thing i noticed is that the program would run, but only when I applied a force with a screw driver on the power port of the shield and when my hand was placed on the board. :0 :0

So I was wondering why that is so, and what I should do to fix it.

Thanks everybody~~!!

Yes, you are most definitely a resistor. You are also a capacitor.

But this might also be a bad connection on the board or in the power port. We need more information.

Perhaps you have a floating input (internal pullup not activated, no external pullup resistor)?

So here is the set up, I’m not too sure about the floating input :roll_eyes: , but I haven’t grounded the solenoid.

I'm not too sure about the floating input

Read http://www.thebox.myzen.co.uk/Tutorial/Inputs.html

What you are doing is a fault finding technique known as "the laying on of hands", if this fixes things it points you in the direction of what is wrong. As polymorph said this could be a floating input, or adding a bit of decoupling or damping of a signal, or physically making a loose contact. Try and minimise what you are doing to narrow down the ared of circuit you are affecting.

Grumpy_Mike:

I'm not too sure about the floating input

Read http://www.thebox.myzen.co.uk/Tutorial/Inputs.html

What you are doing is a fault finding technique known as "the laying on of hands", if this fixes things it points you in the direction of what is wrong. As polymorph said this could be a floating input, or adding a bit of decoupling or damping of a signal, or physically making a loose contact. Try and minimise what you are doing to narrow down the ared of circuit you are affecting.

... and if "the laying on of hands" technique stops working try the "application of the lunar boot". It might not make it work but it's great for the relief of aggression!

Poking things with a screwdriver is a common debugging technique. And when you find the spot that makes it work solder the screwdriver in place.


Rob

sexybeast: So I was working on a project to move a servo using a motor shield.

I wrote some code and uploaded it to an Arduino Uno.

The thing i noticed is that the program would run, but only when I applied a force with a screw driver on the power port of the shield and when my hand was placed on the board. :0 :0

So I was wondering why that is so, and what I should do to fix it.

Thanks everybody~~!!

It might some loose connection Also check whether arduino power and Sheild power/ gnd under same potentials

Graynomad: Poking things with a screwdriver is a common debugging technique. And when you find the spot that makes it work solder the screwdriver in place.


Rob

If you hit a really good spot, the screwdriver will weld itself in place, no soldering required!

Poking things with a screwdriver is a common debugging technique. And when you find the spot that makes it work solder the screwdriver in place.

I suggest a piece of wood like a whittled down popsicle stick instead to reduce the chances of the welding in place mentioned in another post.

okay, well i soldered on the screwdriver and it doesn't seem to be helping:( it's still only working while i touch it. Am i truly a resistor? :p

Perhaps you are irresistable.

To an extent, most things are a resistor once the voltage overcomes a threshold for that material.

Glass , rubber and plastic are the best non conductors.

cjdelphi: To an extent, most things are a resistor once the voltage overcomes a threshold for that material.

That is simply not true there is no threshold to overcome. On non linear things like LEDs there are voltage points where the resistance changes but there are no thresholds as such.

sexybeast: okay, well i soldered on the screwdriver and it doesn't seem to be helping:( it's still only working while i touch it. Am i truly a resistor? :p

Yes you are but you are also a capacitor and an antenna.

Grumpy_Mike:

cjdelphi: To an extent, most things are a resistor once the voltage overcomes a threshold for that material.

That is simply not true there is no threshold to overcome. On non linear things like LEDs there are voltage points where the resistance changes but there are no thresholds as such.

i was not talking about semi conductors, electronic components, i was refering to every day materials, wood for example, skin, cotton, they can all conduct if you appy a high enough voltage.

There is still no voltage threshold for material like this. It is just that the ammount of current they conduct is negliable at lower voltages.

Grumpy_Mike: There is still no voltage threshold for material like this. It is just that the ammount of current they conduct is negliable at lower voltages.

Look, when I said that I had a distributor cap in mind, when the contacts fail you can see the path left behind in the plastic... but that's never going to happen with a few volts...

As far as humans go... what you're saying is if you touch both terminals of a battery (be a 1.5v or 12v) a very low amount of current will flow ... I get it, but to me a threshold value is something were substantial current can flow... but fine your point is made even though most multimeters would not be able to measure how much current flows through your body or maybe they do...

I'll start with 1.5v and see how much current will flow through me (1.5v/500k)..

Put multmeter on 10 or 20Mohm range, grip probes tightly, you'll see a value.

Being sweaty or having damp fingers and it'll be a low lower resistance.

Apply 250V(*) and there's a breakdown and the value is far lower and high currents will flow along your blood vessels and stop your heart (blood is salty and v. good conductor compared to dry skin).

(*) DONT DO THIS!!!

To a low impedance circuit such as a 12V motor driver you are effectively an insulator, to a high-impedance circuit such as a CMOS input your are a good conductor.

I was talking about actual current readings… the resolution might not be good enough to measure how much current flows with just a couple of volts…

Yes you are but you are also a capacitor and an antenna.

Oh, great, now he's going to be full of himself! :P