help please
imagine a piece of metal where is a hole of 4 mm. Through that hole may appear a little bar of metal that will rise about 10 to 15 millimeters ...
so .... I need to know as much as possible about that bar rising throught the hole. Is there ? how high is ? what is the highest point that will reach ??
exist some sensor I can use for that ?
How does it move/mount? Can you attach anything to it? Is it conductive? You could mount a coil like a metal detector. There are lots of point switches as well as linear and rotary position sensors.
A mech sketch would be helpful. Also, is the moving piece ferrous?
What kind of accuracy are you looking for?
very good question
1/10 of millimeter will be good enough
if I glue a magnet at the top of the stick and set one of those 'hall effect" sensor at 20 millimeters above the hole will that works ?
will I get that level of accuracy ??
regards
En lunes, 29 de agosto de 2022, 22:29:10 GMT-4, dougp via Arduino Forum notifications@arduino.discoursemail.com escribió:
| dougp Faraday
August 30 |
- | - |
sivi1234:
a little bar of metal that will rise about 10 to 15 millimeters ...
What kind of accuracy are you looking for?
I don't believe a hall sensor is that precise. I'd look at something optical. I think it's unrealistic to expect to do this with hobby components. But, I could be wrong.
You could also look at :Adafruit VL6180X Time of Flight Distance Ranging Sensor (VL6180) [STEMMA QT] : ID 3316 : $13.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Hi,
What is the application?
If we knew the overall picture, we may be able to make more suitable suggestions.
What drives the pin?
Thanks... Tom... 
You also neglected to tell if the stick repeats the motion and if so, how often. How much time is taken in each direction and how much time is spent retracted and how much extended.
well there is the explanation for everyone of what is the idea and what is the problem I want to solve with that.
I hope you guys knows about mechanics. I try to make a 'top dead center' finder .... that would be a good name 
most motorcycles and modern motorcycles has marks on the fly weel for that but not vintage british motorcycles. It is sold a very stupid device that goes in the spark plug hole ... it is just a stick that is pushed up by the piston when it goes up but that is all.
The idea is to add some inteligence to that. I mean a device can know the highest point the stick will reach and of course tell me... your are close .... closer .... there your are. It is not useful if that tell me here it is .... that will be too late.
That is a very hard work to do when you work alone. I have to ask for help usually for that. I slowly turns the rear weel and someone else has to watch and measure the stick going up.
The piston goes up twice for every cycle. So if I could also recognize if I am in the compresion stroke that would be ideal.
Hi,
Thanks for the application.
I saw many eons ago, a setup that had a rotary gauge connected to the feeler rod, the mechanic would turn the crankshaft and find TDC, zero the gauge.
Then use its live reading to see how far way he/she was from the scaled zero setting as they rotated the crankshaft.
So I assume you want an electronic version so you don't need to be in viewing range of the gauge or end of the feeler.
You need something like a Digital Caliper, using the other end to measure depth, spring loaded so it will follow up and down motion of the piston. Most have a "zero" button.
Sparkplug hole diameter would possibly be a controlling factor.
As you would know, finding if it is on compression or exhaust is another problem.
Tom...
For a start, trying to apply electronic indicators to such a simple process is a bit crazy to say the least.
If, for instance you are trying to find TDC by turning the rear wheel, there is one of the several problems you bring on yourself due to the gearing/lash in gearbox, chain,etc etc. Whether or not the engine is on compression stroke, simple, both valves are closed.
As far as accuracy for TDC, if it is for just the piston, easy as pie with a "stick/screwdriver, whatever".
If you need to know the absolute correct crank angle at TDC, you need to open the engine and mark the crank and crankcase. For most adjustments, the stick approach will suffice.
As the piston traverses TDC, (or BDC for that matter) the crank will move a couple of degrees either way without any piston movement. It's knowing the "feel" of the "stick/screwdriver" and interpreting the movement into an average both ways. What can I say, arcs are a bugger...????