Question on PCB and routing

Question on PCB and routing , well more .. will it work I guess ? Anyway I have hammered the tutorials and finally got to where I think I can start to mill the board. Only thing is is a question on power voltage etc. as you can see I have highlighted my concern in a red box , this is two molex 2 male pin plugs , I want to draw power from both as they go to different parts of the hardware .. will this work ? Will this affect the voltage ?

Attachment 8907

and blew a close up :)

Attachment 8908

any help as normal appreciated :) only had four beers so far .. record lol BTW the board is tiny only only 60mm x 40mm .

As long as your within the limit of what the regulator can supply AND the traces are wide enough for the current desired, it should work.

Depending on current, it may mean a slightly higher voltage drop at X7, however provided that whatever you're powering from the connectors aren't going to be affected by noise/voltage spikes from each other, and you're not going to overload the tracks, it'll be fine.

Quote:

---

Originally Posted by C_Bubba

As long as your within the limit of what the regulator can supply AND the traces are wide enough for the current desired, it should work.

---

I've made the traces as wide as possible, I think it should be able to handle the current , suppose I wont know until I try it Bubba lol , again thanks for the reply mate :)

Attachment 8909

Quote:

---

Originally Posted by m_c

Depending on current, it may mean a slightly higher voltage drop at X7, however provided that whatever you're powering from the connectors aren't going to be affected by noise/voltage spikes from each other, and you're not going to overload the tracks, it'll be fine.

---

Hi MC , nah the last on the rail powers two 5v servos the first powers a raspberry pi , i'll have to rethink if it drains or spikes to much, but they are 7 quid a pop I would expect then to have some umthh ! lol
Beer 5 ..now poured !

Quote:

---

Originally Posted by Fivetide

Hi MC , nah the last on the rail powers two 5v servos the first powers a raspberry pi , i'll have to rethink if it drains or spikes to much, but they are 7 quid a pop I would expect then to have some umthh ! lol
Beer 5 ..now poured !

---

Use this: The PCB Track Width Calculator to calculate track width...

Incidentally, 3-pin regulators should have 10 - 100nF ceramic capacitors on input and output else things can get noisy. See their datasheets.

Quote:

---

Originally Posted by irving2008

Use this: The PCB Track Width Calculator to calculate track width...

Incidentally, 3-pin regulators should have 10 - 100nF ceramic capacitors on input and output else things can get noisy. See their datasheets.

---

Hi Irving hope your feeling ok , they are used for pure power no signal its just a drop down box.

Quote:

---

Originally Posted by Fivetide

Hi Irving hope your feeling ok , they are used for pure power no signal its just a drop down box.

---

read the datasheets... HF noise on power lines can cause all sorts of issues.. trust me, been designing electronics for 40 years!

Quote:

---

Originally Posted by irving2008

read the datasheets... HF noise on power lines can cause all sorts of issues.. trust me, been designing electronics for 40 years!

---

So you think I should add 10k's at the voltage out ? I'm going off the guys schematic , he didnt include them only on the data line.

PI Tank power

I normally include an electrolytic cap on the output of linear regulators, then add a ceramic near the input of anything that may be affected by noise.

Although things may work without caps on the linear regs, it's not good practise. Lots of linear regulators specify minimum capacitence on the output lines in their datasheets.

Quote:

---

Originally Posted by m_c

I normally include an electrolytic cap on the output of linear regulators, then add a ceramic near the input of anything that may be affected by noise.

Although things may work without caps on the linear regs, it's not good practise. Lots of linear regulators specify minimum capacitence on the output lines in their datasheets.

---

Hi MC , I'm more than happy to take your advice on this, what should I include and where .. Remember I'm a total Noob and I'm just following someone schematic. I have some CFR50 carbon film resistor,10K 0.5W will these do ?

moresettingchanges=lessposting

Quote:

---

Originally Posted by m_c

Capacitors aren't resistors ;)

I usually go for 220uF electrolytics of a suitable volatge for throughole linear regulators, but that's probably overkill.
I'll check some datasheets later to see what you can get away with.

---

Thanks MC very much appreciated, I’d like to think of this project as evolving so adding things to make it better is exactly right

I have some 220 uF 25v Low ESR 8mm dia x 15 mm high 3.5 mm LS ( UPW1E221MPD) from a project also some Panasonic small-form but not sure what stats

Quote:

---

Originally Posted by Fivetide

Thanks MC very much appreciated, I’d like to think of this project as evolving so adding things to make it better is exactly right

I have some 220 uF 25v Low ESR 8mm dia x 15 mm high 3.5 mm LS ( UPW1E221MPD) from a project also some Panasonic small-form but not sure what stats

---

They would be fine - you don't need anything special like low ESR, but no problem using them. Still need ceramic capacitors on the input.

What voltage are you supplying to the 5V regulators and at what current?

Quote:

---

Originally Posted by Jonathan

They would be fine - you don't need anything special like low ESR, but no problem using them. Still need ceramic capacitors on the input.

What voltage are you supplying to the 5V regulators and at what current?

---

The idea is to drop 7.2 v to a 5 v 1 amp and the other is 7.2 to 5 v 1.5 amp...the first feeds the raspberry pi the 2nd a USB hub

Ok, so you have (7.2-5)*1.5=3.3W dissipated by the regulator... you'll need a heatsink on that. The datasheet for your regulator (link?) should specify the junction to case thermal resistance which you can use to find the required size of heatsink, which may well require making more room on the circuit board.

What Ian said is that the regulator has a low thermal output , I don’t know Reg one

justanothefpissedoffuser

Oh so they're switching, not linear, regulators - disregard what I said about the power dissipation then as that's irrelevant. I'd still use some small capacitors though.

You're pushing your luck asking for 1.5A from a regulator rated for 1.0A.

Quote:

---

Originally Posted by Jonathan

Oh so they're switching, not linear, regulators - disregard what I said about the power dissipation then as that's irrelevant. I'd still use some small capacitors though.

You're pushing your luck asking for 1.5A from a regulator rated for 1.0A.

---

Hi Jonathan, yes there are 2 regulators R-785 0-1.0 and R-78B5.0-1.5 the 1 amp is for the Raspi and the 1.5 is for the USB the 1.0 amp has 2 output 2 pin Molex’s, one powers the Pi itself and the other powers Independantly RC-servo controller board for Raspberry PI Version 3

Attachment 8910

Quote:

---

Originally Posted by Fivetide

Hi Jonathan, yes there are 2 regulators R-785 0-1.0 and R-78B5.0-1.5

---

Fair enough. They're both labelled as -1.0 on the PCB which was a bit misleading...

Do you really need the high efficiency from these switching regulators? As m_c hinted, you could save a lot of money by using linear regulators and adding heatinks.