B3F-4055 switch bounce

[Demon]

Received my $2 scope and tested one of my switches.

Does this result seem possible?




I expected some flutter, but this switch has no bounce. Either the switch performs much better than I anticipated, or this scope device is garbage.

[Ioannis]

I suppose you have only a switch and a resistor, right?

Either you got a perfect switch or the scope is slow enough with low memory depth.

I will do a similar test. Maybe you have to use 5ms/div or lower?

Ioannis

[richard]

i would not expect to see any "bouncing" at 50mS per div , @ 0.5mS/div you are more likely to see something

[Demon]

i would not expect to see any "bouncing" at 50mS per div , @ 0.5mS/div you are more likely to see something

I went back and redid the tests. Here's the falling edge of a SR-25 rotary switch on a BK Precision 1560 at 1ms:



(Let me know if there's a better setting for the scope. I just went with trial and error.)


And the rising and falling edges on the DSO-TC3 at 1ms:





It's not even remotely close to similar. I should have started testing with the BK; its buttons aren't making the screen jump around.

The Tektronix 466 was giving mismatched readings; giving a jagged trace, then curves, then just dropping on/off. It would need a serious cleaning, which I can't afford. And that wouldn't repair worn switches and pots, they'd need to be replaced. Let alone if there's fried circuits in there. I figure the old owner got rid of it for a reason.


Here's a pic of the SR25 switch. That wiper seems to bounce a lot as it moves out of one position and into another.

[Ioannis]

Well we expected the BK screenshot response. That is what a good switch bounce should be!

The Fnirsi I guess is either for the recycle bin or has some settings to smooth out the ripple so much that looks like a perfect rect wave.

The SR25 switch, depending on their oxidation state, since the contacts are very much exposed, is normal to have such a behaviour.

Ioannis

[Demon]

...The Fnirsi I guess is either for the recycle bin or has some settings to smooth out the ripple so much that looks like a perfect rect wave....

It's a toy to help teach electronics, nothing more. I'm starting my first return to AliExpress, along with those 3 DMMs that I tried out. I'll see how that goes.

EDIT: I was wrong about this device (next post).

...The SR25 switch, depending on their oxidation state, since the contacts are very much exposed, is normal to have such a behaviour.

Ioannis

This one is brand new though; straight from the manufacturer 2 months ago.

Turns out this was caused by me touching the metal shaft. As soon as I installed a knob, that erratic bounce has mostly gone away. There's still a slight bounce, but nothing so drastic.

It did show to me though that the chinesium scope is useless to analyse signals adequately.

[Demon]

Only the switch, says Omron underneath. Zero resistors or capacitors.

I wanted to do a baseline so I had something to compare any debounce circuitry.

I'm gonna test some other switch types and omron clones.

[Ioannis]

I suppose you have to add the whole circuit. Omron is a good company but in any case, mechanical switch always have a small time of bouncing.

Ioannis