What are some good rules of thumb for making clean schematics.

[Gyro]

I didn't get nearly as much agreement as I expected about avoiding 4 way (cross) junctions. I'm surprised.

Maybe I should modify my advice to 'minimise'. For example, the +15V supply to V2. This could sensibly be moved left to that it forms a T junction above R4.

With regard to removing cross connections on the diodes creating "more mess". Simply move the bottom row of diodes to the right slightly and hey presto, all T junctions.

Maybe it's because I grew up in an era of 2nd or 3rd generation photocopies (and dyeline) but it's something that I religiously avoid.

[vealmike]

Gyro,
I completely agree. I didn't mention this as I thought it had been well covered.

Never ever make a connection at the intersection of four wires. It is too hard to spot the difference between this and a crossing without a connection.

When the wires meet at a T there is no room for confusion.

[dsharp02]

Bson, thanks for the example.  I'm filing this away for future reference.

The op amp only needs power once, not in every unit.

I connected them all in an attempt to work around an apparent bug in EasyEDA's PCB module.  For some reason connecting just one op-amp to power and ground resulted in the ground pin of the LM324 not being connected to any net.

Dave

[andyturk]

[...]

The SN754410 got a custom component that better suits the schematic.

[...]

Bingo. How often do folks make their own schematic components?

[ataradov]

Bingo. How often do folks make their own schematic components?

I do make mine, but once, not for each schematic. I prefer to think and figure out what will work for most use cases.

[ataradov]

I didn't get nearly as much agreement as I expected about avoiding 4 way (cross) junctions. I'm surprised.

I would agree that in some cases it may cause confusion, but not everywhere. Here you have an example of a circuit that will make no sense if all diodes are attached, and depicted circuit is very typical.

I really see no need to complicate things here.

[tggzzz]

[...]

The SN754410 got a custom component that better suits the schematic.

[...]

Bingo. How often do folks make their own schematic components?

As often as is beneficial. The proportion depends on the type of component: 100% for FPGAs/CPLDs, 0% for standard logic and standard opamps/comparators/R/L/C, very variable for "special purpose" ICs such as motor controllers.

[vealmike]

I didn't get nearly as much agreement as I expected about avoiding 4 way (cross) junctions. I'm surprised.

I would agree that in some cases it may cause confusion, but not everywhere. Here you have an example of a circuit that will make no sense if all diodes are attached, and depicted circuit is very typical.

I really see no need to complicate things here.

Surprise, surprise we disagree again!
There's no confusion in this case, but there is still room for mistake. One missing junction dot and you're looking at a board spin.
Please don't do it OP, it is widely considered to be bad practice.

[Gyro]

I completely agree (  ).

I can't think of a single case where I've needed to connect on a cross, there is simply no need to do it.

Referring to bson's recent schematic, having +15V going through a cross connection to U2 Pin 16 (VCC1) is an instant fail, too open to errors. As I said previously on motor output clamp diode, moving the upper row left or the lower row right would eliminate cross connections with zero loss of clarity and lower risk of schematic error.

Sorry but it's a cardinal rule with me (and I think most people), both composing and reviewing.

[schmitt trigger]

Surprise, surprise we disagree again!
There's no confusion in this case, but there is still room for mistake. One missing junction dot and you're looking at a board spin.
Please don't do it OP, it is widely considered to be bad practice.

I am also in agreement with you.
There is another reason (although lately is less important): making copies. Small dots may be obliterated, and dirt could be also confused as a connection.
A T-connection is the best practice.... And since this topic is about best practices, I think this advice should be heeded.

[dsharp02]

Ok one more try.  Sorry to , but I think I've taken everyone's suggestions to heart.  I created a custom footprint for the SN754410.  I moved the power connector and the decoupling capacitors into a separate block.  Sensors are on the far left, so signals travel left-to-right.  Motor outputs are on the far right and I've only connected VCC and GND to the op-amp once.  I've tied the loose end of the pot to the wiper to reduce noise.

Let me know what you think.

Thanks,
Dave

[ataradov]

I don't understand why you try to avoid power supply symbols. Why do you need those 4 parallel lines on the bottom? Why all those lines going to the diodes?

[vealmike]

I've fixed D2/D3 for you. Do you see what we mean about not making a connection at a 4 way intersection?