Connect 'Source' signal name to 'GND'

On 10/04/2018 12:25 a.m., dave hofer wrote:

 

Hello,

I need to attach the 'Source' on the this diode to GND without changing its name but Eagle will not allow me to do so.  I've found older threads that mention creating a 'short' type part to do this.

But, I am wondering if this is made easier with newer version of Eagle?  I'm a maker who has managed to create 2 PCB with Eagle that actually work, but still consider myself an extreme newbie.

Any guidance would be greatly appreciated.

 

Dave

 

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Hi Paul

A few observations.

If you wish to emulate the layout of the Electronics Hub circuit, then

you have not achieved that.

(1)  You do not have a common point where the motor, diode and battery

are connected together as there is in the Electronics Hub circuit.

(2) Your image showing a motor and BAT1 3.7v has a problem. The diode is

forward biased all the time so even if you remove the MOSFET, current

will flow in the motor.

(3) If you review the data sheet of the MOSFET you will see it has an

internal diode that is in parallel with your discrete diode and oriented

the same way so it would be doing a similar job. You could remove your

discrete diode and still have the same circuit.

As per the Electronics Hub circuit the diode needs to be across the

motor and only the motor.

So to keep the same board layout you would have to do the following.

(a) remove the diode from the board as it is across the FET and it

should be across the motor

(b) Swap the wires going to J1 so the negative of the motor supply is on

the round pad on the right and the motor negative is on the left square pad.

(c) Mount the diode directly across the motor terminals with the anode

to the negative terminal

Also you need to achieve the equivalent of your white ground wire.

What you need to do is common the negative of the motor supply with the

ground of your arduino circuit.

Assuming you have a schematic, change the name of the net attached to J1

pin 2 to GND. That will make the connection. This assumes your pull down

resistor is connecting to a ground polygon in the area  and that polygon

encloses the pads currently connecting to the 'source' net which you

have just renamed GND.

HTH

Warren

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Warren,

Thank you very much for the in depth explanation.  I will adjust my design based on your feedback.

I had no idea how much needed to change.  Believe it or not, this does work, but it sounds like it probably should not.

Since my designs are sort of basic and I'm completely new to Eagle, I have not changed any Net definitions.  Instead, I just change the names at the schematic level.  I need to spend more time understanding how to use nets to my benefit.

Regards,

Dave Hofer

Warren,

Thank you very much for the in depth explanation.  I will adjust my design based on your feedback.

I had no idea how much needed to change.  Believe it or not, this does work, but it sounds like it probably should not.

Since my designs are sort of basic and I'm completely new to Eagle, I have not changed any Net definitions.  Instead, I just change the names at the schematic level.  I need to spend more time understanding how to use nets to my benefit.

Regards,

Dave Hofer