Designing a Time Delayed Relay

[KrisBlueNZ]

I wasn't meaning to imply that I think you're lazy. Far from it!

I guess drill distance means drill travel, which is the total distance that each size of drill bit needs to travel, in order to drill all the holes of that size on the board. Minimising drill travel will make the drilling process slightly quicker, but it's not

One other thing though.

I would reroute the VCC track to pin 8 of the right hand Allegro chip, starting from pin 1 of the PIC on the underside (instead of the pin on CN4). Run it between pins 5 and 6 of the PIC, under the resistor, up past the transistor, then across to the Allegro chip.

For the track from pin 7 of the Allegro chip, I would take that straight down through a via to the underside, to the left, between the base and emitter of Q2, and up to pin 5 of the PIC.

You might want to move Q2 rightwards a bit first.

Just some suggestions.

 

[chopnhack]

Just messing with you ;-)

I will check out your suggestions later on tonight, I am currently soldering up the Rain Sensor project!

Thanks

 

[chopnhack]

I would reroute the VCC track to pin 8 of the right hand Allegro chip, starting from pin 1 of the PIC on the underside (instead of the pin on CN4). Run it between pins 5 and 6 of the PIC, under the resistor, up past the transistor, then across to the Allegro chip.

For the track from pin 7 of the Allegro chip, I would take that straight down through a via to the underside, to the left, between the base and emitter of Q2, and up to pin 5 of the PIC.

You might want to move Q2 rightwards a bit first.

Just some suggestions.

Its funny you should mention that! I looked at doing that yesterday because its sitting outside of the ground plane, but I couldn't work it out, i thought the clearances were too tight. Awesome suggestions, thanks!

 

[chopnhack]

Thanks again for the suggestions, I couldn't get it the other day, there were so many things connected, I figured it was good enough. The trace from pin 8 is a bit close to the edge, but at least its still within. It's 12 thou so its smaller than the other traces, ok for signal?

I am thinking my next steps would be to get the boards checked again by the board house, if approved - order the parts, when received, do a physical layout to ensure enough space, if good, place order for board. What say you?

 

[KrisBlueNZ]

Yes, that's probably a good idea. Print the board at 1:1 and glue the printout to some expanded polystyrene, and shove all the components through it, or something like that. Good idea.

I think you could keep the VCC track to the right hand Allegro chip further away from the edge. I would probably do this. It's just a suggestion.

 

[chopnhack]

Yes, that's probably a good idea. Print the board at 1:1 and glue the printout to some expanded polystyrene, and shove all the components through it, or something like that. Good idea.

Excellent!! Yes, that would be a really easy method of keeping everything aligned while judging space. Sticky that somewhere for others ;-)

I think you could keep the VCC track to the right hand Allegro chip further away from the edge. I would probably do this. It's just a suggestion.

View attachment 15739

The trace would get pretty skinny, is that ok? The layout looks roomy, but in truth we are dealing in small numbers!

 

[chopnhack]

 

[KrisBlueNZ]

You should be able to get a 15 thou track through those gaps, and that's plenty wide enough. There's a decoupling capacitor right next to the Allegro chip, which gives it a good firm supply rail to work from and negates any problems due to resistance and inductance in the track.

Have you viewed each copper layer independently? Do that after you've poured the groundplanes, and look for thin necks in the groundplane. Sometimes you can avoid those by moving tracks or components. Otherwise, check that there are vias, and groundplane on the other side, bridging the thin part.

What clearance are you using to the groundplane? It looks unnecessarily wide. That's not a problem I suppose.

 

[chopnhack]

You should be able to get a 15 thou track through those gaps, and that's plenty wide enough. There's a decoupling capacitor right next to the Allegro chip, which gives it a good firm supply rail to work from and negates any problems due to resistance and inductance in the track.

Have you viewed each copper layer independently? Do that after you've poured the groundplanes, and look for thin necks in the groundplane. Sometimes you can avoid those by moving tracks or components. Otherwise, check that there are vias, and groundplane on the other side, bridging the thin part.

What clearance are you using to the groundplane? It looks unnecessarily wide. That's not a problem I suppose.

Cool!

Its currently 16 thou.

I have watched each layer after changes and added vias where necessary. The isolation is set at 32 thou, that is what is giving a lot of space between traces and ground plane. I can change it, what would you recommend?

Edit: If I change the isolation to 12 thou I can complete the ground plane by the right allegro chip. I just don't know how much isolation to choose.
Thanks!

 

[KrisBlueNZ]

12 thou is probably OK. The highest voltage across the ground plane clearance will be 48V. Perhaps 15~16 thou would be wise. You can probably move things around slightly to make room for the ground plane around the right Allegro chip. But if you have ground plane on the other side in that area, and vias, that's fine.

 

[chopnhack]

I moved the Allegro slightly down and C10 down and to the left. There is still 0.07" (70 thou) of space between the pads of the chip and the ground plane. Unless you can think of anything else I will submit this to the board house for their check. Thanks!

 

[KrisBlueNZ]

I think that looks great! I'm really impressed.

I think it's definitely ready to go off to the PCB manufacturer for checking.

 

[chopnhack]

I think that looks great! I'm really impressed.

I think it's definitely ready to go off to the PCB manufacturer for checking.

Really?! Well thank you, but I hardly think you can be surprised by the outcome! Novice with expert guidance equals success

Can you assist me with one question on the Rain Sensor build, I had an unexpected outcome despite breadboarding. Perhaps you can aide me in troubleshooting?

Thanks again, I will keep you in the loop on the progress of this build.

 

[chopnhack]

Oh, forgot, before I send it off, I will clean up the names/values layers a bit.

 

[KrisBlueNZ]

Really?! Well thank you, but I hardly think you can be surprised by the outcome! Novice with expert guidance equals success

You have a GREAT attitude! It's a pleasure to help you.

Can you assist me with one question on the Rain Sensor build, I had an unexpected outcome despite breadboarding. Perhaps you can aide me in troubleshooting?

I must have missed that thread completely! Yes I have a lot of thoughts. I'll post there soon.

Oh, forgot, before I send it off, I will clean up the names/values layers a bit.

Yep, good idea. View just the overlay, or just the overlay and the pads. That will cut through the confusion so you can see any problems easily.

 

[chopnhack]

You have a GREAT attitude! It's a pleasure to help you.

You sir, are ACES!!! Truly, you have been such a great source of information and a patient teacher. I treasure you and your help, thank you, thank you, Thank You!
LOL

It's a bit cleaner, I am attempting to print it out and have a gander at it.

 

[KrisBlueNZ]

It's my pleasure

 

[chopnhack]

It's my pleasure

Vinnie Jones, classic Did you ever see him in Snatch? I love that movie. One of the best parts is when he's at the pub and three blokes try to roll him!! LOL

I ordered the parts and somehow, Digi-Key had them here in less than 2 days!! Standard postal service... I was shocked to see the box at the door on a saturday to boot!

First part placed showed me an error in my layout, the K1 relay was drawn upside down from the manufacturer's schematic....

That would have been terribly inconvenient if the board was made up!

 

[KrisBlueNZ]

I think I've seen Snatch but I didn't love it the way I loved Lock Stock. I'll have to watch it again!

That's great you've saved yourself some trouble already!

 

[chopnhack]

I think I've seen Snatch but I didn't love it the way I loved Lock Stock. I'll have to watch it again!

That's great you've saved yourself some trouble already!

Yes!! You must watch it again...LOL

Indeed, I had created the part from a datasheet and only realized when I looked at the model that the datasheet was bottom up schematic!! This is why they prototype!!! I will reprint my pcb and see how the components look when placed. I'll snap a pic when I do.