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Fivetide
10-05-2013, 12:08 AM
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 ?

8907

and blew a close up :)

8908

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

C_Bubba
10-05-2013, 12:24 AM
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.

m_c
10-05-2013, 12:25 AM
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.

Fivetide
10-05-2013, 12:28 AM
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 :)

8909

Fivetide
10-05-2013, 12:31 AM
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 !

irving2008
10-05-2013, 03:34 PM
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 (http://www.pcbco.com.au/tracecalc.html) 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.

Fivetide
10-05-2013, 04:11 PM
Use this: The PCB Track Width Calculator (http://www.pcbco.com.au/tracecalc.html) 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.

irving2008
11-05-2013, 09:33 PM
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!

Fivetide
11-05-2013, 09:51 PM
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 (http://raspberrytank.ianrenton.com/day-9-power-to-the-pi/)

m_c
11-05-2013, 10:24 PM
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.

Fivetide
11-05-2013, 10:52 PM
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 ?

m_c
11-05-2013, 11:09 PM
moresettingchanges=lessposting

Fivetide
11-05-2013, 11:20 PM
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

Jonathan
11-05-2013, 11:35 PM
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?

Fivetide
11-05-2013, 11:49 PM
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

Jonathan
11-05-2013, 11:59 PM
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.

Fivetide
12-05-2013, 12:09 AM
What Ian said is that the regulator has a low thermal output , I donít know Reg one (http://uk.rs-online.com/web/p/dc-dc-converters/6727124/?searchTerm=672-7124&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6 265724D504E266C753D656E266D6D3D6D61746368616C6C267 06D3D5E5C647B337D5B5C732D2F255C2E5D5C647B332C347D2 426706F3D313426736E3D592673743D52535F53544F434B5F4 E554D424552267573743D3637322D373132342677633D4E4F4 E4526)

m_c
12-05-2013, 12:38 AM
justanothefpissedoffuser

Jonathan
12-05-2013, 12:41 AM
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.

Fivetide
12-05-2013, 07:30 PM
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 (http://www.ebay.co.uk/itm/261201504780?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

8910

Jonathan
12-05-2013, 07:35 PM
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.