How to connect 0.1uF to implicit VCC and GND pins (not shown) in certain parts from Eagle distributed libraries?

AL[1

wrote on Sun, 30 May 2010 18:20]Hi,

 

I am using the 74HC154 device, that is, 74154DW (74*154) device from

library 74xx-us, of package SO24W, which is SOIC-24pin format.

 

I put this device in the schematic and notice that VCC and GND pins are

 

not shown.  How would I have a 0.1uF cap connected to the device's VCC

 

and GND, since they are not shown?

 

Thanks.

This is a feature of Eagle. You need to use the "invoke" command, then

select the gate, power, etc. you want to add to the schematic. It is in the

tool bar on the side. It looks like 4 small gates and it right above the

"T", text, button.

When you create a part in Eagle which has multiple gates, and other pins,

like power pins, you can tell Eagle whether or not these extra gates should

be automaticaly added or not. I forget all the options, but on virtually

all IC's with power, the power pins are made to be "Request". That is, they

are only added to the schematic if you request them using the invoke

command.

The danger is that not all IC part creators use the same naming convention

for the power pins. One might be VCC, another VEE, so when you are doing

your power nets, you might connect some IC's and not others. An ECC check

should catch this, but you need to be aware of implied power pins.

Read the sections on part creation in teh manual and it will give you much

more detail than I can here.

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On 5/30/2010 8:14 PM, David Ingebretsen wrote:

AL[1

wrote on Sun, 30 May 2010 18:20]Hi,

 

I am using the 74HC154 device, that is, 74154DW (74*154) device from

library 74xx-us, of package SO24W, which is SOIC-24pin format.

 

I put this device in the schematic and notice that VCC and GND pins are

 

not shown. How would I have a 0.1uF cap connected to the device's VCC

 

and GND, since they are not shown?

 

Thanks.

 

This is a feature of Eagle. You need to use the "invoke" command, then

select the gate, power, etc. you want to add to the schematic. It is in the

tool bar on the side. It looks like 4 small gates and it right above the

"T", text, button.

 

Thanks.  That works!  I actually saw the power pins of all the ICs

connected by generating a *.brd.  But wasn't sure how to add the 0.1uF

until I saw your response.

Thanks again!

When you create a part in Eagle which has multiple gates, and other pins,

like power pins, you can tell Eagle whether or not these extra gates should

be automaticaly added or not. I forget all the options, but on virtually

all IC's with power, the power pins are made to be "Request". That is, they

are only added to the schematic if you request them using the invoke

command.

The danger is that not all IC part creators use the same naming convention

for the power pins. One might be VCC, another VEE, so when you are doing

your power nets, you might connect some IC's and not others. An ECC check

should catch this, but you need to be aware of implied power pins.

 

Read the sections on part creation in teh manual and it will give you much

more detail than I can here.

On 5/30/2010 5:20 PM, AL wrote:

Hi,

 

I am using the 74HC154 device, that is, 74154DW (74*154) device from

library 74xx-us, of package SO24W, which is SOIC-24pin format.

 

I put this device in the schematic and notice that VCC and GND pins are

not shown. How would I have a 0.1uF cap connected to the device's VCC

and GND, since they are not shown?

 

Thanks.

You could also just connect the cap to the VCC and GND nets by drawing

nets from the pins and NAMEing the nets to VCC and GND. But I would

always INVOKE, I do not trust the implicit power connections at all!