Digital logic questions...

Hi all..
I have some questions about Digital Logic...

1) on the digital KIT (the large KIT that got the whole ICs of ANDs and ORs.. etc...) there is a push button. What is the (bouncing problem) with this button?

2) I want some infos about the preselector operations.

plz...

1) switch bounce happens because the metal part that moves when you press the switch doesn't stop when ith hits the other contact it bounces off disconnecting the switch for a short time before making contact again. This is a problem if the switch triggers a counter or similar digital logic because each bounce gets counted as a button press.

2) I'm not sure what you are asking. If you give a bit more information we can help more.

bmcculla said:

1) switch bounce happens because the metal part that moves when you press the switch doesn't stop when ith hits the other contact it bounces off disconnecting the switch for a short time before making contact again. This is a problem if the switch triggers a counter or similar digital logic because each bounce gets counted as a button press.

2) I'm not sure what you are asking. If you give a bit more information we can help more.

Click to expand...

1) thanx
2) do u have any more detailed info or graphs i can use?
3) the preselector is a device to change from Decimal to BCD. it looks like the counter that u find on the old tape recorders!!!

sonaiko said:

bmcculla said:

1) switch bounce happens because the metal part that moves when you press the switch doesn't stop when ith hits the other contact it bounces off disconnecting the switch for a short time before making contact again. This is a problem if the switch triggers a counter or similar digital logic because each bounce gets counted as a button press.

2) I'm not sure what you are asking. If you give a bit more information we can help more.

Click to expand...

1) thanx
2) do u have any more detailed info or graphs i can use?
3) the preselector is a device to change from Decimal to BCD. it looks like the counter that u find on the old tape recorders!!!

Click to expand...

Use google for "debounce circuit" and you should get LOTs of examples. Most of them will even illustrate the original problem that it is trying to solve. Try it, you'll like it.

I think you are referring to a decimal to BCD converter. There is an IC that does that.. dont recall the part number..

The situation I "think" you have described involves a circuit that when the button is pressed, it should count up by one and show on maybe a seven segment display. In that circuit there is a BCD converter and a debounce circuit on the switch so that it does not erroneously count more than one when the button is pressed.

Are you talking about a physical switch that you press the buttons and little numbers on the display are mecanicaly changed to indicate a digital switch output. They seem to be called thumbwheel switches.

bmcculla said:

Are you talking about a physical switch that you press the buttons and little numbers on the display are mecanicaly changed to indicate a digital switch output. They seem to be called thumbwheel switches.

Click to expand...

yes im talking about this one!
but they tought me that it is called the BCD preselector!

I'm sure they have a ton of different names.

Digikey.com has a bunch you can choose from under the catagory: Thumbwheel switches. Mouser and other companies should have plenty to choose from too.