Hardwiring multiple switches to common inputs - Electronic Circuits Projects Diagrams Free

Franknstein · 24th April 2007, 08:45 PM

Hi all

Just a general question here, please help me try understand whats best to do in a situation like this:

I am using a 4511 IC to control digits 1-6. My inputs are six individual sing pole switches. Obviously the 4511 IC has 4 inputs, truth table can be found here:

Here is a diagram of how I wanted to wire the circuit up...

Problem I can see here is that the inputs are all bridged, so when one switch is closed it will set inputs A,B,C to '1'.... which is not what I want obviously. How do I isolate each switches inputs? Diodes? Resistors?

Help please.

Thanks

Brevor · 24th April 2007, 11:50 PM

Diodes are usually used for this, you will also need to add a pulldown resistor directly to each input pin including the D input.

Franknstein · 25th April 2007, 06:41 AM

like this?

Oh ya, and what do i connect terminal 'D' to if not in use.... just to ground? Or to V+??? (with the resistor of course)

ericgibbs · 25th April 2007, 07:25 AM

hi ryan,
Pin 'D' on the 4511, will go to 0V gnd.
Dont forget the /EL, /BI and /LT pins, do you need help on how to connect these?

/EL to 0V.
/BT and /LT are +V

EDIT: The contacts on the 6 switches, which are shown on your drawing, as not connected, will have to go directly to the +V rail.
The +Vrail is the supply to the 4511.

Franknstein · 25th April 2007, 07:30 AM

Are the diodes in the correct place?
Its cool, I have a nice diagram for the 4511 which shows all the connections, and I've already wired up the 4511 to the diagram I have, and it works perfectly, I just need help integrating these 6 seperate switches to that circuit... Thanks!

ericgibbs · 25th April 2007, 08:25 AM

hi,

> Are the diodes in the correct place?

The diodes look OK. Dont forget the pulldown resistors.

If you draw a truth table it will show the logic.

AllVol · 25th April 2007, 09:45 AM

Quote:

Originally Posted by ericgibbs

The diodes look OK. Dont forget the pulldown resistors.

The attachment will show the usual arrangement for switch and resistor. The diode is optional.

ericgibbs · 25th April 2007, 12:02 PM

hi allvol,
On his project he is using the diodes as a 'gate' function, so the resistor will have to on the other side of the diode.

He his encoding 6 push buttons into a 4511

Regards

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24th April 2007, 08:45 PM	(permalink)
Franknstein	Hardwiring multiple switches to common inputs Hi all Just a general question here, please help me try understand whats best to do in a situation like this: I am using a 4511 IC to control digits 1-6. My inputs are six individual sing pole switches. Obviously the 4511 IC has 4 inputs, truth table can be found here: Here is a diagram of how I wanted to wire the circuit up... Problem I can see here is that the inputs are all bridged, so when one switch is closed it will set inputs A,B,C to '1'.... which is not what I want obviously. How do I isolate each switches inputs? Diodes? Resistors? Help please. Thanks

24th April 2007, 11:50 PM	(permalink)
Brevor	Diodes are usually used for this, you will also need to add a pulldown resistor directly to each input pin including the D input.

25th April 2007, 06:41 AM	(permalink)
Franknstein	like this? Oh ya, and what do i connect terminal 'D' to if not in use.... just to ground? Or to V+??? (with the resistor of course)

25th April 2007, 07:25 AM	(permalink)
ericgibbs	hi ryan, Pin 'D' on the 4511, will go to 0V gnd. Dont forget the /EL, /BI and /LT pins, do you need help on how to connect these? /EL to 0V. /BT and /LT are +V EDIT: The contacts on the 6 switches, which are shown on your drawing, as not connected, will have to go directly to the +V rail. The +Vrail is the supply to the 4511. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 25th April 2007 at 07:35 AM.

25th April 2007, 07:30 AM	(permalink)
Franknstein	Are the diodes in the correct place? Its cool, I have a nice diagram for the 4511 which shows all the connections, and I've already wired up the 4511 to the diagram I have, and it works perfectly, I just need help integrating these 6 seperate switches to that circuit... Thanks!

25th April 2007, 08:25 AM	(permalink)
ericgibbs	hi, > Are the diodes in the correct place? The diodes look OK. Dont forget the pulldown resistors. If you draw a truth table it will show the logic. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

25th April 2007, 12:02 PM	(permalink)
ericgibbs	hi allvol, On his project he is using the diodes as a 'gate' function, so the resistor will have to on the other side of the diode. He his encoding 6 push buttons into a 4511 Regards __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/