Basic Electronics Question

Refering to this project ...

http://arduino.cc/en/Tutorial/Debounce

In my project, when the switch is pressed, I want it to provide 5v to 2 inputs, so in the debounce project I'd also connect a wire from the right side of the resistor to, for example, pin 3. Do I need to add any components?

Thanks, Paul.

Why would you connect the lead to the resistor? If you want 1 button to register on 2 pins then connect another wire where the first one is at.

But what bothers me is why you would need to have 2 pins connected to a single button to start with? It seams to me whatever you need to achieve with this kind of setup could be better dealt with in the code rather then hardware. Just seams like you adding more hardware then needed. Sure its only 1 wire but it could also add more to the code then what needs to be there.

Why would you connect the lead to the resistor?

I did say in my post "Referring to this project" and "In my project". That means the example is just a functional example to show what I'm trying to achieve electronically.

I don't particularly want to connect the lead to the resistor, I was just trying to show whereabouts it goes logically without having to download the drawing, alter it, then upload it on here. Instead of saying "from the right side of the resistor" I could equally have said "from the left hand side of the switch to, for example, pin 2".

Moving away from this example, functionally what I want to achieve is to press a momentary button and for that to feed 5 volts to 2 separate IC inputs - they're both likely to be 555 timer inputs but may end up being other cmos type ICs.

Well one button on 1 pin is all that is needed. That one button, when detected, can tell the Arduino to digitalWrite(HIGH) to the 2 desired pins that will feed the possible 555 timers mentioned. Depending on the kind of load the end device has you may be able to get away with a single output pin feeding both timers. Just keep in mind the 20mA limit per pin.

Moving away from this example, functionally what I want to achieve is to press a momentary button and for that to feed 5 volts to 2 separate IC inputs - they're both likely to be 555 timer inputs but may end up being other cmos type ICs.

Google "driving digital inputs".

Or see...

http://www.arunet.co.uk/tkboyd/ele1bd.htm

Thanks for the links. Unfortunately neither of those really helped :frowning:

There’s a more specific example here …

Forget the left hand side, my question has to do with the right hand side of this partial schematic.

Considering the output from the Schmitt trigger IC1A, is this electrically valid with no other components such as resistors capacitors etc? If this is valid, how many inputs could this output drive? Are there standard ways of doing this?

I’ve also posed this question in another place as part of a wider rotary encoder discussion …

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267140146/17#17

Paul.

It's called "fanout" in the datasheets and there is nothing odd about it. (It's done all the time)

the CMOS schmitt trigger has a "fanout" of 10 Low power Schottky TTL loads. IE; You can connect (1) output to (10) 74LSxx family inputs.

Seems you have some wiggle room...

Excellent news! Wiggle room is good. Thanks for your help.

Just keep in mind the 20mA limit per pin

@ digimike - what limit would that be?

what limit would that be?

The derating limit that results in ultra safe arduino loading.

I've dumped the 555 timer idea for the moment. Still, it was lovely to revisit it. I'd forgotten how uniquitous they are - every text book I look in seems to use them for just about every example. Even after 20 years in the hobbyist desert I recognized it on the page straight away.