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Powerful Aquarium Lighting


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#121 mcinnes01

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Posted 01 August 2012 - 01:32 PM

Sounds like your getting there! I will have a look tonight and hopefully by the end of the week I should have a pcb design ready to send off for printing (I may need your help in this as I have NEVER sent a pcb off for print). Andy

#122 Magpie

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Posted 02 August 2012 - 01:51 AM

Hi Andrew Good news I have fixed the init problem by setting the brown out fuse to 4.3 volts. I have three channels current sensing. Controlled by the dimmer. the differential sensing works and so I can just touch the slider and the output will correspondingly change, the output is quite stable. I will do more accurate tests later. All channels are behaving the same way. I have almost no flickering, maybe the tiniest bit at very low light settings. I have tons of scope to tighten the feedback loop, this will be the major factor of any flickering. I have written it in C. But have been told that assembler is better for this job. I am using Amtel Studio 6, which should be familiar if you us a netduino. I will give you the project now but I will probably change things before you are ready to program. the only thing not planned is I am using the 2.56 vref for the dimmer as well as the current sense. there is a good chance it will work with 5v as planned. Also I don't think we need Attiny461a as the code and ram requirements are very small, you can probably save your cents and get the 261a instead. I can give you help in the layout. not that I am an expert I've only done 3 boards but no abject failures yet. Apart from the silkscreen layers. Have you sorted out your tlc5940 stuff yet? NB I haven't tested the 3 channels independently yet, I am worried the current sense may be subject to cross talk, hence the strange track layout.

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#123 Magpie

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Posted 04 August 2012 - 12:15 PM

I just checked the channel independence and all is good. No visible effects of one channel effecting another. I did an efficiency check 3 channels at 20.5 volts input and 1.23 amps input gives 25.2 watts. V1 20.27v I1 430mA p1 8.72W (not actually switching, because it is turned fully on) V2 20.3v I2 350mA P2 7.11W (barely switching) V3 17.56v I3 440mA P3 7,73W (only 6 leds in series not 7 that is why it is different) Pout 23.56W efficiency 93.5 % Obviously this figure has some error, but very hard to say what it is, but I think 93.5 % is in the ball park, nothing is dissipating heat bar the leds. Theoretically when the channel is fully on I will get losses in the inductor 40mOhm and the sense resistor 100mOhm and Rds 40mOhm. At 440mA this should give me a voltage drop of 0.0792 volts coming from 24 volts which is 99% - minus the gate drivers. Still I wanted over 90% and I am sure I have that. the light seems very solid now it's been running for hours, cant fault it at the moment.
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#124 mcinnes01

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Posted 04 August 2012 - 02:15 PM

Fantastic news! How the feedback loop coming along, have you got any further with the low end flicker? I have been really busy the last weeks so not got much further with the pcb design yet. I was playing around with foot prints, performing the module mapping stage, one thing I was struggling with was editing the foot prints. For example with the C21 cap that is 47uF, if you look at the data sheet it seem about 6.6mm x 6.6mm with the pins taking it to 7.2mm x 6.6mm. There are foot prints for this type of cap but none that are exact so I wanted to edit the component to make one for my cap, but couldn't workout how to do this in the editor. The lines didn't seem selectable and the couple of pdfs I read didn't seem to help much either? Am I right in saying all the resistors should 1206 and all the other caps should be 0805? Still got to match and find foot prints for the other parts yet. In terms of my TLC's I am currently soldering up a test module that is seperate from the all in one aquarium control board I had made. I was finding issues with the shift registers and as these were controlling the TLC's consequently it created some rather random behaviour also. I'm hoping to have my TLC's finished off in the next week or so, time permitting and in the mean time get this pcb sketched up. Andy

#125 Magpie

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Posted 04 August 2012 - 11:58 PM

Hi

There are foot prints for this type of cap but none that are exact so I wanted to edit the component to make one for my cap, but couldn't workout how to do this in the editor. The lines didn't seem selectable and the couple of pdfs I read didn't seem to help much either?

Firstly, put your Kicad stuff including libs and mods into source control, if you are going to work effectively this is a must, being a programmer you probably already use source control, it is so easy to make a mistake by clicking the wrong button, that rollback will save you and give you clues into how it all works and tell you what has been changed.

Just to start by giving everything standard footprints. Doesn't matter if the footprints are wrong as long as the pins are the same.
Then in pcb editor right click and edit module on the components that need changing. Then on each pin you can edit by right clicking. The pads are normally simple shapes, so you can edit the them by just changing the sizes and offsets in the text boxes.
If you need a complicated pad shape you can make it as two or more separate pins but give them the same pin number. This is a strange but necessary work around and it does work fine.
Work out how to save these modified mods into your own mod library and then associate them.
Did you see a youtube video on Kicad, I found one in particular it quite useful.

the footprints for the caps don't need to be exact, if it roughly good enough it should solder ok, you are better off using a standard footprint because you might change caps anyway.
Also there is a difference on components between the actual footprint and the solder pad needed. the solder pad is normally a bit bigger around the edges of the component so you can stick the point of the soldering iron onto the pad itself.

Am I right in saying all the resistors should 1206 and all the other caps should be 0805?

that's what I did, the caps need to be close to the processor and the resistors are not so critical. I would go with that unless you have a specific reason. The bigger components are easier to work with.

ps. the reason I chose 4.7uF through hole is because I had 100 of them already.
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#126 mcinnes01

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Posted 04 September 2012 - 06:30 PM

Hi Magpie, Sorry I've been a little quiet recently, had a lot on at work the last month (and this coming month :( ) but I am still slooooooowly chipping away at it... I am just trying to get my head around the PCB layout do you have any tips? I followed your advice in terms of the footprints, copying many of your choices off your example and so far have dispersed the components on the pcb designer. However I am a little unsure what the best method would be for arranging them? Also I'm unsure what/how to do ground plates? And when I get to it track widths, I notice your higher power traces are much wider than others. I want to try to make the board as small as possible with out making assembly for my novice hands difficult. As my LEDs will be spread across the top of my aquarium in rows of 3 I was thinking perhaps long thin boards to which there will be 10 in total. With this in mind ideally all power connections and control signal connections will be orientated at one end for the connectors and perhaps at the side of the 3 channels that will be in a row. I also want to get as many of these per board as possible. I am unsure to board sizes at the print houses but perhaps if I could get 5 or even 10 per board that would be great? Or even 20 if I have to pay for a whole board to be printed? Any advice will be much appreciated! :) Andy PS I have attached my attempt so far...

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#127 Magpie

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Posted 04 September 2012 - 11:18 PM

Hi I've been a bit preoccuppied too. Also I'm actually having trouble with the mechanical and light aspects of my light fittings. I would keep the little drivers as functional blocks and close together. ie. inductor, diode, fet, connector, sense resistor, and then the bjts and other resistors. Once you have perfected this as a block. I would copy it and manually assign the part id to each of the new parts. Once you do this the little node lines should dissappear to show that it matches your schematic. this should give you a perfect copy of part of your circuit but with different part ids. Do you use source control? I really consider it a must. If you do you can to the diff between your original file and your new file. For doing this sort of copying work, It might actually be easier to edit the pcb as a text file than in the pcb editor. Look into it. It will give you real insights into what the pcb editor does. You are probably having trouble changing track widths because you have DRC on and so all tracks will go to the default track width. In DRC I think you need set track widths for each node. create 3 types of track/node. I use thin, normal and thick. Set each of them to the thickness you want. The assign all nodes to the appropriate type of track. When you go to place a track it will select the correct thickness. The only trouble is making the super thick nodes go into a small pin. Here you temporarily change the thickness of the track type. -> lay the track -> reset back to the normal thickness. Flooding areas was a bit weird, I only recently worked it out, I cant remember off the top of my head though. You can leave it to last anyway. When I get the chance I will have a look. I would use Seeed Studio because they are sooo cheap but the turn around is a bit longer. Just keep each channel as a small perfected block and you should be able to move them around quite easily. I am going long and thin and black for the next spin of my board. I want to make it look a bit Steam Punk, so I can expose part of the board.
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#128 mcinnes01

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Posted 06 September 2012 - 09:59 PM

I've done a little more to my board attempt, I think I have got the ground plane, but I'm not sure if I got the cap that is directly behind the ATTiny on the right layer? Also I don't know if my routing is right, and the various track widths baffles me? I have managed to get the layout a little more compact, but I'm not sure if my footprints are correct any way for my components. How can I makes sure what I am doing is going to be correct? Have you got any tips for going though the BOM and making sure the footprints match and if not how do I edit them to fit? Thanks again for all the help, Andy EDIT: New file attached

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#129 Magpie

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Posted 15 September 2012 - 01:12 PM

Hi You have managed a lot of the hard stuff, ie working with PCB layout is hard. Did you use autoroute? Looks a bit that way. The most obvious problem is the track widths. on the high current paths. Also C1 pin 2 is not connected. I think you could virtually copy my layout, apart from the step up transistors of course. Apparently component placement is the key to pcb design. In your Design rules you have only small track widths even for the power tracks. Also the kelvin connections aren't done. You are just sharing the ground plane. These are hard to explain, Technically the Gnd side of the sense resistors are shorted to earth. But the trick is that no short is a complete 0 milliohm. So for each sense resistor short the ground pin to the ground plane but as well run a pair of tracks to the attiny filter input circuit( 10k and 100nF) , Right next to each other one from each side of the sense resistors. These tracks only go to the filter they do not touch ground except at the sense resistor. Have a look at my layout it might be clearer. the idea is that only current that is required to measure the voltage travels along these tracks, and the loop area of the pair of tracks is minimised. I can try and explain again if you need but look up Kelvin connections if you have any doubt. You will make mistakes in the design but often they can be fixed with a cut and a join. My Fets had the wrong foot print, I incorrectly chose a smaller one but it wasn't a show stopper. The rest of my foot prints were right.
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#130 mcinnes01

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Posted 21 September 2012 - 05:44 PM

Hi

You have managed a lot of the hard stuff, ie working with PCB layout is hard.

Did you use autoroute? Looks a bit that way.

The most obvious problem is the track widths. on the high current paths.
Also C1 pin 2 is not connected.

I think you could virtually copy my layout, apart from the step up transistors of course.
Apparently component placement is the key to pcb design.

In your Design rules you have only small track widths even for the power tracks.

Also the kelvin connections aren't done. You are just sharing the ground plane.

These are hard to explain,
Technically the Gnd side of the sense resistors are shorted to earth. But the trick is that no short is a complete 0 milliohm.

So for each sense resistor short the ground pin to the ground plane but as well run a pair of tracks to the attiny filter input circuit( 10k and 100nF) , Right next to each other one from each side of the sense resistors. These tracks only go to the filter they do not touch ground except at the sense resistor. Have a look at my layout it might be clearer.
the idea is that only current that is required to measure the voltage travels along these tracks, and the loop area of the pair of tracks is minimised.

I can try and explain again if you need but look up Kelvin connections if you have any doubt.

You will make mistakes in the design but often they can be fixed with a cut and a join. My Fets had the wrong foot print, I incorrectly chose a smaller one but it wasn't a show stopper.
The rest of my foot prints were right.


Hi Magpie,

Yes I used the auto route :unsure:

I couldn't figure the track widths and how to amend them, what kind of trace do you think I should be looking at? Would or can you use the auto route then edit the trace for various bits or can the trace widths be defined then the auto route used or do you recommend another way?

PS I saved a "Vanilla" version with no traces and one with no gnd plane.

I read up on kelvin connections as recommended, are we using single or double?

Also in terms of physically applying this to the board what do I need to do? Is it that these connection can't be ground to the plane they need there own traces and if so which bits does this relate to so I can compare yours and mine?

Which bit is the attiny input filter circuit?

Thanks,

Andy

#131 Magpie

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Posted 25 September 2012 - 02:16 AM

I've been playing around trying to do the track widths, do you place all the tracks yourself

I have done, I found it quicker now that I know what I am trying to acheive. If you had a lot of obvious connections then I think that the autoroute can do those fairly easily.

and if so how do you make sure you are connecting up correctly/ deal with vias?

The ratsnest will dissappear as each node is fully connected. If you are using vias for higher current paths then you can use multiple.

What widths do you think I should be aiming for, for my thin, medium and thick traces and what clearances would I need?

Default for thin, 8mm for thick and say 3mm if it is carrying some current. But reduce these widths just for segments where it is necessary.
Do your placement first obviously.

In terms of my layout, which is similar(ish) to yours can you see anything that will/may cause me a glaring issue?

I haven't looked have you changed anything since last time I looked?

Sorry Andrew, I was actually Sailing all weekend, it was fantastic.

Did you sort out how to change track widths, I know it is very cumbersome.

You probably found this out already but

assign a track to a track type in the digital rules.

When you lay it out it will take the track width of the track type.

If you want to temporarily make some tracks a different width such as for the ground plane, Where the Kelvin connections carry a tiny current and the power ground has high current you can just change the track width for the track type(eg. High Current) while you lay that track. Then set it back to normal.
Also sometime you want to run the track thin into the pins but run it fat for most of the length.
First run it thin, then change the track thickness for the track type and right click and adjust the track thickness on the segments that you want thicker.

for the thicknesses

Connections into the processor only need to be thin. Power tracks make thick. Tracks on the ouput stage make thick as you can but thin them down as they feed into the component legs. It basically comes down to the current through the track. 8mm wouldn't be amiss joining the inductor to the Fet and the diode, if you can fit that much.
I quite liked my posistioning of the components, to minimise track lengths for the high current tracks. But maybe you want the connectors to be organised differently.

As for the Kelvin connections run them as pairs or threes lik it did. The only place the ground of the kelvin connection touches ground is at the sense resistor.
the point is we want to measure the voltage of the ground at the sense resistor compared to ground at the micro, but using only the minimum current we can to do it. (Conceptually tricky). Also we want the minimum induced noise so we run the differential inputs right next to each other, for as long as posible.

Hope this helps
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#132 mcinnes01

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Posted 26 September 2012 - 08:43 PM

Hi Magpie, Sailing cool! The weathers that bad here the moment I'll be able to sail to work soon, we're supposed to be getting a few inches of rain over the last few days! Thanks for your reply, it seems like what I was trying to avoid (manually routing) seems the only real logical answer taking in to account kelvin triples, keeping output stage close until the last minute and track widths for power. I had a little play around on the setup and added one more at the moment, I will add a 3mm too, firstly is this millimetres or mils? One thing I did notice is that once I did this and tried an auto route, it did the widths but also on some pins I didn't expect thicker traces on? I assigned the thick track to nodes by check your board and mine and selecting the high power nodes ids on my board. I haven't tried doing the tracks by hand yet so will have a play and see how I get on. I noticed some key design features on your board the more I look at, such as separating the ground plane on the output side from the rest of the board, and also I was planning to have my connectors for the leds facing out but I noticed your power line has a nice straight run through the caps, connectors and diodes with the connectors sideways. Have you got any tips on where to start tracing and anything to leave to the end? Also I'm sorry about keep asking about this but I am not too sure which traces on your board are the kelvin connections, are they 3 three tracks that go under the attiny to the caps and resistors on the output side of the attiny and join together to go in to pin 6 of the attiny? Thanks as ever for your patience, pcb design is a steep learning curve for the noob! How are your lights coming on? Have you fashioned at suitable enclosure with diffuser and installed a low power circuit throughout your house? Andy

#133 Magpie

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Posted 26 September 2012 - 11:11 PM

No worries about helping, I know many many projects die a death and I don't want your project to die because of me pulling out, and advising you what to do is easier than doing anything myself. Sailing to work are you serious? I really thought you could almost copy my layout of the output stage. Assuming your connector requirements aren't too different. So layout the power stage first for one channel, including 2 x bjt and the sense resistors. With the best track widths, try to keep on one side if possible but use the 2nd layer for short runs if you need it.. Get this section laid out perfectly. Keep all the components close as is comfortable. If you want I can check at this stage, before you go further. I have a notification on this thread. Delete the components for the other two channels from the pcb editor. Then cut and paste the perfect layout to make 3 copies. then edit the component identifiers to connect the copied channels to the ratsnest. This should give the three channels fully connected to everything else in the same channel. After this layout the attiny and the caps and resistors, you could almost copy my layout. The only change I would make is the smd inductor I would put it on the top layer with the IC socket( use a socket). It should fit in mechanically, within the socket. Once you have these sorted and close to the attiny. give me another look. Lastly you need to route the pwm outputs and the current sense inputs. The Kelvin connections from the sense resistors are the thin 2/3 tracks together. Dont use vias on the Kelvin connections. Use Vias only where you really need to(which you will) firstly on the power and then the second preference is the the pwm. The kelvin connections only have less than 100mV max, and we are trying to detect changes in the micro volts. They are run together so that any noise present will effect each track similarly.
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#134 mcinnes01

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Posted 17 October 2012 - 09:09 PM

Hi Magpie,

I am sloooooowly getting there, please see that attached when you have a few moments.

Where I am up to now....

Following your suggestions I have more or less copied your layout, there is some clever stuff going on in some place, some of which I have eventually figured out why and I guess some I haven't even noticed yet, so following your design seems a good move.

I've got the hang of the track widths now and the placement, vias seem quite easy to place also and I am following your circuit with much more understanding. I also have the layout ok, what do you think any glaring errors in terms of layout?

I have most of the attiny connections in place I may even have the kelvin connections placed?

You said this:

After this layout the attiny and the caps and resistors, you could almost copy my layout. The only change I would make is the smd inductor I would put it on the top layer with the IC socket( use a socket). It should fit in mechanically, within the socket. Once you have these sorted and close to the attiny.
give me another look.


Is this the component under the atting and if so where would you recommend placing it in terms of my layout? How would the socket work?

In terms of space, pads and footprints can you see anything I need to think about, I remember my inductor footprints were slightly smaller than the inductors I was going to use as an example? Also do you think I have left enough space between components? Perhaps around the attiny? I was going to use a socket for the attiny to make things a little easier.

I haven't connected much to the output stage and there are some connections missing on the output stage e.g. I have 1 pwm connected to the output stage but already I'm not sure if this is correct. I think I am having difficulties where components were removed in relation to your example. The areas I could do with advice are around the output stage (the 3 channels) and the power input where you had your black invertor?

The other issue I noticed, when trying to place the ground plane now it doesn't fill only does the outline, this may be because I haven't connected the output stage up? Should this be the last thing I do and what should I do in terms of the vias to the ground plane as per your design? Also I notice there are some cut out areas and a separated ground plane on the output stage, especially around the capacitor. Does the capacitor decouple the or filter the ground between input and output stage?

Thanks,

Andy

PS the sailing to work was a joke but not far from the truth we had 2 months of rain in a couple of days (and we get A LOT).

No worries about helping, I know many many projects die a death and I don't want your project to die because of me pulling out, and advising you what to do is easier than doing anything myself.
Sailing to work are you serious?


I really thought you could almost copy my layout of the output stage. Assuming your connector requirements aren't too different.

So layout the power stage first for one channel, including 2 x bjt and the sense resistors. With the best track widths, try to keep on one side if possible but use the 2nd layer for short runs if you need it.. Get this section laid out perfectly. Keep all the components close as is comfortable.
If you want I can check at this stage, before you go further. I have a notification on this thread.

Delete the components for the other two channels from the pcb editor.

Then cut and paste the perfect layout to make 3 copies.

then edit the component identifiers to connect the copied channels to the ratsnest.

This should give the three channels fully connected to everything else in the same channel.

After this layout the attiny and the caps and resistors, you could almost copy my layout. The only change I would make is the smd inductor I would put it on the top layer with the IC socket( use a socket). It should fit in mechanically, within the socket. Once you have these sorted and close to the attiny.
give me another look.

Lastly you need to route the pwm outputs and the current sense inputs. The Kelvin connections from the sense resistors are the thin 2/3 tracks together. Dont use vias on the Kelvin connections. Use Vias only where you really need to(which you will) firstly on the power and then the second preference is the the pwm.
The kelvin connections only have less than 100mV max, and we are trying to detect changes in the micro volts. They are run together so that any noise present will effect each track similarly.

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#135 Magpie

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Posted 18 October 2012 - 08:13 AM

Hi I laid it out for you, but bear in mind I didn't do any checking, so please check all, I take no responsibility. there is always a stuff up or 7. though it passed DRC. I didn't knowingly change the schematic. Or the models used. I am getting better at Kicad even the fill areas are getting easier, but as you know there are quite a few strange things in Kicad. I thought rather than explaining again I would just do it. If you want to change things around, please do. I may have put things too close, please check, I kept the same size board as you, but the connectors are in different spots. I removed the zip I fixed it up a bit.
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#136 Magpie

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Posted 18 October 2012 - 10:03 PM

I just remembered, I didn't put in any drill holes for mounting. And I made a mistake with the 5v rail. I will redo the 5v, it should fork at the bulk capacitor with one trace going to the attiny and the other trace going everywhere else. This should give better noise immunity. I think I prefer the 12volt version though. Noise may be a problem with the 5v version, it is hard to say. Although I think you are using the internally regulated reference for the ADC so it might be ok. The 12v version gets 5 volts by using a linear regulator, this give it a very clean 5v. Whereas the 5v rail in your circuit has noise from the switching of the Fets straight onto it.
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#137 Magpie

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Posted 19 October 2012 - 08:48 AM

Fixed 5 volts as best I could, still needs mount holes.

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#138 mcinnes01

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Posted 19 October 2012 - 09:17 AM

Hi, Thanks, this will save me a lot of time and I've still learnt a lot from what I have done. I also found a cool setting when doing the zones if you set the outline slope to H,V and 45 degree only it makes it much easier for making straight lines on zones. You probably already know this but when I was playing doing the zones I struggled at first then found that option and it was great. I noticed when I ran the DRC I got a few errors I think on the 5v between the output zone and something else, not entirely sure why I tried redoing the zones and this solved a couple of issues but I created more perhaps because I didn't place the zones quite correctly? Any way thanks for this I really appreciate your help, I will get my parts ordered and check my foot prints so if there is any lead time I can hit the ground running, I guess the boards will take a few weeks to get printed right? Do I need to do anything in terms of getting multiple boards printed, e.g. do I have to supply a full sheet layout for multiple boards or will the print house do it? I will probably use the company you used, I had a look at their site and they seemed ok for what I am doing. Cheers, Andy

#139 Magpie

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Posted 21 October 2012 - 11:09 PM

Last time I used Seeed Studio but they do boards in certain sizes which may not fit your board. They do boards in multiples of 5cm dimensions. See what fits! They are a truly minimilist service. The advantage of these guys is they are super cheap. 10 boards for $50 or something. itead is the other very cheap one. I also used Olimex? Bulgaria. They were good and but a bit more expensive, but based in Europe so may be faster. (Actually they have suspended their service because they are at full capacity.) So much for the Euro zone economic calamity. You could try Fritzing and just get one board done and see if it works. Take some time to get the silkscreen right, it makes soldering much easier. Also dont expect zero mistakes first board, aim for no critical mistakes. I haven't really done much layout so I am learning too. But trying to explain the Kelvin connections to someone is hard, so I thought I would just do them.
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#140 mcinnes01

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Posted 30 October 2012 - 12:15 AM

Hi Magpie,

Just doing some final checking before I order some components and send the board off for a test run...

I noticed on my digikey bom I had C1 missing, does this cut the bill: http://www.digikey.c...284-1-ND/416060

Can you recommend digikey parts for the fuse and all connectors?

To confirm all caps bar the 47uf (C21) are SM0805

All resistors are SM1206.

The C21 47uf cap, I used a footprint 6.3 x 7.7 but in fact the part is 6.6 x 6.6, but this should be fine right as the solder pads will be larger than needed?

Are there any other things you can think of I need to check design wise and in terms of silk screen what things am I looking for?

Finally what files do I need to send to seeed that kicad produces and are the drill holes on I can't tell?

Many thanks,

Andy




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