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Topic: Internal Pullups Not Enough? (Read 681 times) previous topic - next topic

roowilliams

Hello,

I am trying to make a steady hand game (the kind with a loop and a wiggly path to follow). The path is connected to a pin configured as INPUT with INPUT_PULLUP set to enable its internal pullup resistor, the loop is GND. Touching the loop against the path triggers a serial FAIL message. I also have a start and a finish section which are also INPUT pins with pullups enabled. I am controlling a 12v car horn which is triggered on fail via a transistor but since connecting my 12v power supply the noise levels seem to have gone up and the FAIL and COMPLETE pins get triggered arbitrarily as if they were floating.

Could it be that the internal pullups are now not enough? The copper path is actually copper pipe, over 4 meters of it, so it is one big ol' conductor.

Appreciate any input on this.

Thanks
- Roo

larryd

Quote
Could it be that the internal pullups are now not enough?

It's easy enough to use external ones.
Try them.
I would spend time on adding decoupling and rearranging the grounds to stop the electrical noise.
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

fungus


Could it be that the internal pullups are now not enough? The copper path is actually copper pipe, over 4 meters of it, so it is one big ol' conductor.


It will only take a few seconds to add a 1K pullup to it and find out...

(or whatever other resistor you have handy....so long as it's over 150 Ohms and less than 30,000)

Advanced Arduino

roowilliams

Hi fungus,

I agree, the reason why I asked is because the whole thing is soldered onto one of those proto strip boards and they're horrible to work with; shorts etc.

I just wondered if it might be a potential case before I go meddling.

Thanks

- Roo

groundFungus

Just a thought, but is the ring insulted where the person is touching it?  It may help to isolate the person (big ol' antenna) from the ring.

roowilliams

It is! It has a plastic handle (with a vibration motor inside to simulate electric shock  ]:D)

Grumpy_Mike


I just wondered if it might be a potential case before I go meddling.

Yes there is a case. The internal pull ups are quite weak and only offer a modicum of noise protection.

fungus


Just a thought, but is the ring insulted where the person is touching it?  It may help to isolate the person (big ol' antenna) from the ring.


The way I read it, the thing the person is holding is connected to GND.

(Which is a good thing...)
Advanced Arduino

fungus


I agree, the reason why I asked is because the whole thing is soldered onto one of those proto strip boards and they're horrible to work with; shorts etc.


So? The resistor can go on the end of a wire which is connected to +5V. No need to modify the PCB, just wrap one leg around your "path" and try it.

Advanced Arduino

MarkT

Add 10nF ceramic cap to ground too, that will kill any RF pickup from mobile
phones / WiFi.
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