Powerful Aquarium Lighting

Hi Magpie, I added in the capacitor that was a 1u to my BOM (see attached) is this ok? PS I grouped the items as digi-keys bom upload doesn't apply the bulk discounts otherwise. Also the inductors are out of stock Digi-key part: 811-1216-ND just my luck! Not back in till November! Can you suggest a replacement? Any way more importantly I guessing your in the process of soldering something up right? Hows it going? I think I more excited than you are! Sorry for the over infussiasm I just can't wait to get this up and running! Out of interest you wouldn't mind sending me the CAD files so I can hack your design for the 5v version? no worries if not It seems silly to completely re-draw your design. Finally off-topic question... You don't know anything about MVC, Entity Framework and Kendo Grids do you?

I got my boards back last night from Seeed Studio As usual I can see a couple of small things I would change. Especially the Silkscreen. I lost my +- on my connectors, Also the solder mask where the tracks join the pads was a bit uncovered. I don't know why I didn't see them before. Any way the footprints all seem to fit. this is only actually my third board that I have laid out ever. My bosses never gave me Layout jobs, It's normally one guy gets Altium and does all the Layout. I might be able to solder up something tomorrow. Then I have to refactor/ create some code to match it. I should've done it by now. I have used Kicad for the layout, it's a bit of a beast until you get used to it. Then there are the library files. for the foot prints. I can send you them but it might be a big file. If you are not using KIcad, then working off the pdf would be good. Most of the work is in the thinking and the tidying up. The actual track placement, if you know where you are routing is quick. I think in your case you can use any similar inductance inductor. first what inductor do you need. At 5V and one led and say 64 khz you could get away with 33u easy. The inductors job is to limit the instaneous current through the led, if your load were resistors then you wouldn't need the inductor, and you would have a chopper circuit. It also reduces em issues, by reducing ripple through your wire to the led. The only disadvantages of it are the price, space and the series resistance. So for 5v, 1 led, choose 33u and be done with it. Then choose a foot print, I don't think you need the torroids but they are cheap and huge, my ten year old son thinks they look like nuclear reactors, you could go for one of the more conventional SMD packages. Just look for a reasonable low series resistance and good price as it is probably the most expensive component. Yes the digikey bom upload was a bit of a joke. But I got my order in less than 4 days. It got here so fast that I had no idea what it was till I saw the box. the only MVC I know is the Model View Controller user interface design paradigm. Nice idea but I have never seen it implemented well. I saw it in Web Java, Visual Studio and XCode (apple) and maybe in python. Entity Framework : such general terms, seen them near each other many times but I can't place it. (Looked it up, MS's version of hibernate, object to relational DB mapping framework) Kendo: Hitting each other with bamboo sticks then bowing. I would be careful puttng MVC and entity framework together, I had this project in Java given to me once and it was totally out of my control, the MVC(JSF) and the Hibernate would talk to each other, it had a life of it's own, like Frankenstein. Errors were generating call stacks of 70 deep of which only 5 or so of the calls were code that I had access too. I was no longer a programmer I was a configurer. Yuck. Tell me what software you want to do the layout in, I will send the pdfs or the whole kicad directory accordingly. I think get inductors with a ferrite core, not powdered. resonant freq > 1mhz

Edited by Magpie, 24 July 2012 - 10:09 AM.

Hi

You can't use the FDB3502 at all! Not at 5v.

This is a N Channel normal level mosfet. I am driving this at about 11 volts on, 0 volts off.

You need an N Channel logic level mosfet. You will drive this at 5 volts on, and 0 volts off.
Get one in the same package size (DPak, D2Pak)
, with a roughly similar Gate Charge Qg ( 10-30nC) lower is better.
and a low RDS on. I marked it in yellow because it needed changing. Sorry for not making this clearer.

If you used the FDB3502s they would still work, but they wouldn't switch fully on so they would have a higher Rds.
The net result is they would run hot and waste energy.

I added in the capacitor that was a 1u to my BOM

I can't remember what you want the 1u for, it probably wont hurt. Is it C1? For decoupling the power input pins of the attiny. If it is I have used 1u ceramic.
I don't follow your question. Sorry did I leave it out of the BOM I sent you? It definitely needs to be there.

Edit: Confused gate capacitance with Gate Charge

Edited by Magpie, 24 July 2012 - 02:34 PM.

Hi,

I have it down to 5 mosfets, which do you think would be best for the job? I have tried to fit your suggestions above:

MTD3055VLCT-ND
MTD3055VLDKR-ND
497-4335-1-ND
497-4335-6-ND
IRLR014PBF-ND

Finally will these do for the inductors? 811-1222-ND or These?

Many thanks,

Andy

Hi,

I have it down to 5 mosfets, which do you think would be best for the job? I have tried to fit your suggestions above:

MTD3055VLCT-ND
MTD3055VLDKR-ND
497-4335-1-ND
497-4335-6-ND
IRLR014PBF-ND

Finally will these do for the inductors? 811-1222-ND or These?

Many thanks,

Andy

I have assembled the board, I had one big mistake, one of my Black regulator transistors was around the wrong way, And I also put the wrong package on for my mosfets.
Luckily they just squeeze in.
the Black regulator is working.
I need to write the firmware to test the actual dirvers, and especially the current sense part. I should be able to get some results this weekend. Things have been a bit hectic lately.
I'll look at the Fets now.

I did a search, I think these ones are better. For up to 3 leds us the 30Vds for a longer string use the 60Vds. Either will work at Vds of 5v. And your driver will be fine. I still think 12 volts is better, but I didn't want to confuse things too much. So I didn't really talk about the limitations of logic level fets. Fet Characterisitcs: Logic level fets have a lower Vgs turn on or Vthevinen. This is not the absolute max Vgs rating. Vth is not really a voltage but a curve, The curve is Rds vs Vgs They have the curve in the data sheet. Basically by driving the FET further away from Vth you are closer to an ideal switch. When Rds is either 0 or infinity it is not using power. When Rds is in between at say 1 ohm it is using power. At a higher Vth the fet can turn off faster when Vgs is zero and when Vgs is 10v the fet can turn on more fully. You notice when you turn on, you will be supplying around 5 volts to the gate (Vgs) but the measurements for Rds on the digikey search are measured at 10v. You actually want a low rds at 5v which may not be the same thing, although it should be close because it is a curve. Hope this makes sense, it's a complicated business, don't be scared, driving the fets at 5v will still work but driving the fets at 12v will work more efficiently. Your choice. ps. I also forgot to order the 10k resistors so I had to put down 805 instead of 1206 and I didn't have any 3.9nF caps. So for the first board I had to improvise a bit. I did the reflow in my hacked microwave with a fan heaters guts. It worked pretty well for my first board. I circled the Vds max voltage because you need to allow about a 10 volt margin to what you actually want to run.

Hi,

I have found some indutors on ebay that are really reasonable don't know what you think? SMT DS3316P

On the BOM I have made a few comments and corretions based on your advice I think I am almost ready to order now but just want to make sure I have got everything on there. I will also look at connectors as well at some point what did you go for in the end for power, LEDs and control signal?

Finally your last point was about 10K resistors and 39pf caps, I can see some 10Ks on the BOM but do I need to add the caps and if so will these do? CC1206JRNPO9BN390

Thanks for all your help I know this has been a long process so far but I'm glad to hear your latest board is working well.

For the reflow I has seen many techniques but the microwave/heater hack sounds by far the most interesting. I'm thinking of a getting a £20 halogen oven and just keep an eye on the temmperature.

In terms of the cad files I would be keen to use your files, I guess I will need to change the foot prints for the inductors if the ones above are ok and did you mention the footprint of the fets will need adjusting? Software wise I have only really used design spark so far so I can give KiCad a go, I guess there all much of muchness really.

Cheers,

Andy

PS are you making any board or part tweeks based on your last test board?

Hi

I have just been working on it now,

Finally your last point was about 10K resistors and 39pf caps, I can see some 10Ks on the BOM but do I need to add the caps and if so will these do? CC1206JRNPO9BN390

Sorry the cap was 3.9nF. No it is for the black regulator.

I haven't fully tested the boards, only the black regulator.
I have just modified my original code to support the ADC differences, I am using differential inputs on the current sense, and one sided for the dimmers. You will put your TLC5940 square wave into the dimmer inputs, Share the grounds between the chips. the dimmer input must be 0-5v. PWM Square wave is fine, use a frequency just about 20khz or so.

For firmware I am using Amtel Studio 6 and an AVR Dragon, it seems to download ok, if I have any problems I will go back to version 4 which did work.
Last thing I need to do is rescale the current sense, which is just a constant.
Then turn it on and see what happens. I have been really busy but will try to get lights tomorrow.

Have you seen Mikes electric stuff he has a good video on small scale production, there is a link on hanzibals audio project that I posted.

I have found some indutors on ebay that are really reasonable don't know what you think? SMT DS3316P

They are quite good but I personally wouldn't use them as their DC resistance is a bit high at 334mOhms for 330uH. The smaller the package the higher the resistance.
But that may be fine for you as super efficiency is not your main priority. The only way to reduce the resistance for the inductance is to go bigger.
You will have to weigh it up for your situation.

I will also look at connectors as well at some point what did you go for in the end for power, LEDs and control signal?

I just went with cheapie chinese phoenix connectors, for power and leds, but 0.1 inch pitch pcb pins for the dimmer and the ISP header. (both 2x3)

On the BOM I have made a few comments and corrections based on your advice I think I am almost ready to order now but just want to make sure I have got everything on there.

497-5927-2-ND is wrong, use 497-5938-1-ND it is 5v operating voltage tvs.
the little smd inductor is fine use that.
power inductor: see above it is ok but you might want to use bigger.
39pf dont use
the fet is still wrong, see previous post. If you are using 5 volts on the fet gate you need a logic level fet.

Edited by Magpie, 28 July 2012 - 02:57 PM.

Hi

I have made the ammendments as suggested and I also found these inductors that have an RMax of 65mOhms are these better?

I have installed Kicad and have just been playing around a little did you want to email me the cad files or upload them somewhere? That is if you dont mind of course.

Many thanks

Andy

I sent the cad files, you will have to dig up some of the libraries or give me a list of what is missing. I tried to send one more lib directory but it zipped to 87MB. It might be the 3d models that take all the space. In kicad speak libs are the schematic graphics and mods are the pcb footprints. You need to associate these, there is a good video tutorial on Kicad, and also a pdf. the inductors are worth a try. just as long as you can still use the footprint if they are no good. It's almost certain they use a standard footprint.

Hi Andrew Just giving you an update, I am having real trouble with the firmware, not sure why it's been so hard. Good news is I can run the power stage and it runs well, beautiful sharp edges with a .2 u second rise time. This is as fast as we need, and the .2 seconds limitation is probably not actually driver anyway. It might be the 555 timer I was using for testing. I had to go back to Avr Studio 4 before I could even get a square wave out of the Attiny. Not sure why. I am currently running the driver from the Attiny so that side looks good. I haven't tested the current sense arrangements yet. I haven't managed to get the feedback loop going. But the fet driver looks good. Both are pretty standard so It is really only mistakes that make a problem. When I get the current sense going I will let you know.

I found the large part of my problems, good news its an easy fix. Some of y 805 10k resistors that I squeezed onto 1206 pads were not connected. At least 4 of 10 were not actually connected. They actually looked connected. I now have the dimmer inputs going. Still haven't proved the current sense. This may take longer as it is hard to know if it's working until the loop is closed and stable. But I wouldn't wait for me on this as the idea is well founded and it should be ok and also it will take me a while to write this code. Be aware the current sense connections need to be Kelvin connections. This means look at my layout for the current sense. The idea is that these wires go nowhere but to the pin, and therefore carry minimal current and have minimal voltage drop, it might be the same node as another connection but you cant share a track. Also I give the ground it's own input into the adc. It's a bit weird but I am trying to minimise common mode noise. The differential inputs should run together as closely as possible. This stuff is sort of new to me too, but I think I have it right. The dimmer connections are not as difficult.

Edited by Magpie, 29 July 2012 - 01:54 PM.

Nice to see your making progress, I have been playing around with KiCad and your schematic today. Still getting to grips with the software, removing the unnecessary components and reconnecting the wires. This seems easy enough although when I run the ERC I get errors like: ERC report (29/07/2012 15:12:35) ***** Sheet / ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (1.6250 ",5.7950 "): Pin 1 (passive) of component D1 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (1.0500 ",5.1770 "): Pin 1 (input) of component F1 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (1.5500 ",5.1770 "): Pin 2 (input) of component F1 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (0.9970 ",5.6910 "): Pin 1 (passive) of component P1 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (0.9970 ",5.4910 "): Pin 2 (passive) of component P1 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (2.1250 ",5.3700 "): Pin 1 (passive) of component R12 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (2.1250 ",5.8700 "): Pin 2 (passive) of component R12 is unconnected. ErrType(5): Conflict problem between pins. Severity: error @ (1.6750 ",2.0000 "): Pin 16 (power_out) of component IC1 is connected to @ (1.3000 ",2.3000 "): pin 1 (power_out) of component #FLG01 (net 14). ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (1.8500 ",5.7950 "): Pin 2 (passive) of component C21 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (1.8500 ",5.3950 "): Pin 1 (passive) of component C21 is unconnected. ErrType(3): Pin connected to some others pins but no pin to drive it @ (1.6750 ",1.2000 "): Pin 15 (power_in) of component IC1 is not driven (Net 10). ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (1.6250 ",5.3950 "): Pin 2 (passive) of component D1 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (2.4000 ",5.4450 "): Pin 1 (passive) of component C12 is unconnected. ErrType(2): Pin not connected (and no connect symbol found on this pin) @ (2.4000 ",5.8450 "): Pin 2 (passive) of component C12 is unconnected. >> Errors ERC: 0 It seems like the wires I connect on the schematic to the components aren't passing the ERC, obviously some things need changing still like where there a connections to 24v and 12v power rails that have been removed. Hopefully it shouldn't take to me too long to get to grips with the software, then I can finish off the schematic, swapping the relvant components out, and then get on to the pcb. Andy

Yes

Seen plenty of similar errors myself.

the not connected, you just need to zoom in an check it is connected, I think the colour changes in the middle.

If you don't want to connect to a pin, you put a "NO Connect" symbol on blue cross. It's just a message to the DRC.
Also if you label a node, and want to use this node somewhere else you might have mistakenly give a different name.
There are also power markers, that you place like components, these may have the same name as labels but are different.
Eg. you have to label a node as GND if you want to use it in different places, but you also need to attach a power marker to it which will be called Gnd.

ErrType(3): Pin connected to some others pins but no pin to drive it
@ (1.6750 ",1.2000 "): Pin 15 (power_in) of component IC1 is not driven (Net 10).

You have to say where the power is coming from, you can either ignore it or edit a connectors pin, if it is coming off board.
Ignoring it is fine if you are sure what is providing power. I did manage to get my design pass DRC but it was a bit of frigging around.


My mount holes are stupidly big on my board. I think my power vias could be bigger.

Hi,

Thanks figured it out, its quite fussy about exact positioning but I'm getting the hang of it now. Sorted out the voltage regulator part of the schematic, but just wanted to know a few things.

If you want to use my circuit with 5 volts.
just use a different TVS (5v operating voltage).
and remove everything including C3 to U1 reading left to right on the schematic.
Jumper the 24 volt rail to the 12volt and the 5 volt rail.
you don't need the 3 x step up bc847 and short r13 to r15 and open circuit r16 to r18


ps. You probably don't want to populate r28,r29, r30, I just put the footprints in for emergencies. I think 100mOhms if the lowest we could go anyway.
Also you don't need R12, this is also a contingency footprint.

So I have removed and reconnected c3 - u1.

By jumper the 24v to 12v and 12v to 5v, I litterally removed all of these as part of the c3 to u1, so my output is just the 5v, and I changed the global labels for 12v and 24v to 5v. Does this pass as jumpering the rails as you described and will it auto route these correctly?

Also I have removed the bc847s, but I'm a little unsure what you mean by short r13 to r15 and open r16 tor18. Do I just delete these and when I have done what do I need to connect together?

I am a little unsure because where the PWM comes in there was 1 transistor that feeds 2 transistors, but now there are just 2 transistors Q7 -Q12?

I also deleted the extra resistors as you mentioned R28 to R30.

Andy

That's getting there. You must have got the gist of Kicad schematic. I find it not to bad now I know a few of the quirks. Remove r13-r18 but connect the PWM1 tag straight to the base of Q9, similarly for the other channels. Remove r12 Change C21 to a larger electrolytic. maybe 50uF. Get the polarity correct. D5, D6, D7 they are fine as is but they can be a much lower voltage eg. mbra130t or mbra140t. This may give a small cost or Vf advantage. Obviously the fets are a different number. Logic level. You can probably even get rid of R19, R20, R21, replace them by a short or make them 2-5 ohms, these are only to take some heat away from the Fet. Because you are using 5v to drive there will be less power dissapated in the gate anyway. obviously the inductors a smaller value. 33uH? those changes and I think the schematic is done. Dont really bother with the autorouter, and definately don't bother with autoplace. I have tried both, The web service auto router actually works, but I would try to mimic my boards as much as possible. Try to keep to one layer as much as possible and use a ground plane except near the edge use a 5 volt plane where I have my 24v plane. Re. my boards I found on my 24v version that the 1k on r13, r14, r15 was to big, I am changing this to about 200 and maybe reduce r16, r17, r18 to about 800 ohms. You wont be using these anyway. they were slowing things down a bit. I haven't got any sense out of the differential current sense yet, some firmware issue. Not hardware, the current sense lp filter is working fine.

Hi Magpie,

Almost there with the schematic, although I have just been changing the values of the components is this ok?

I have a few questions related to the attached and your last comments...

Are my 3 channel gates looking right in terms of connection? And I guess the rest of the connections?

I also only have 2 errors now which are on pins I have touched which are pins 15 and 16 on the ATTiny where the wire connects.

Conflict problem between pins
Pin 16 (Power Out) of component IC1 is connected to pin 1 (power out) of component FLG01,

Pin connected to some other pins but no pin to drive it
Pin 15 (power in) of component IC1 in not driven.

R12 has been removed.

C21 larger electrolytic capacitor of 50uF, I have been unable to find a suitable part even in stock on digikey, am I missing something or is this a fairly heavty cap? Can you suggest any examples any where?

D5-D7 replaced with mbra140t, the 130t wasn't in stock.

I've changed the FET values accordingly but not used the part picker I guess the footprint is the same right?

On the topic of foot prints is there a standard for all the resistors I remember you mentioning an issue you had 0805 and 1206 I think?

I've reduced R19-R21 to 5Ohms.

The inductors have a different footprint but all I have done is change their values.

I think that should be it, what do you think?

Andy

C21 larger electrolytic capacitor of 50uF, I have been unable to find a suitable part even in stock on digikey, am I missing something or is this a fairly heavty cap? Can you suggest any examples any where?

This is just a bypass capacitor for the whole board. It's size depends on the power used by the board and the length of wire to to power supply and the power of your power supply.
Anything from 10uF to 220uF would be fine, I suggest 50uF but it wont make a difference.
Also its voltage rating doesn't need any high voltage either. 16v is fine but 25v is good too. Remeber it is electrolytic not ceramic. For a computer analogy, the ceramic is like your ram and the electrolytic is like your hard drive. They are often in parrallel. It should be easy to find. The pdf schematic component is wrong is should show a curve on one of the plates and a plus sign. They are unipolar and need to be orientated correctly.

Almost there with the schematic, although I have just been changing the values of the components is this ok?

Yes that is fine.
The diagram looks good otherwise,
dont worry about the DRC on those last things, you can safely ignore it.
If you really want to fix it you can edit the module and then edit the pins to be power in or whatever satisfies DRC.

On the topic of foot prints is there a standard for all the resistors I remember you mentioning an issue you had 0805 and 1206 I think?

Both of those are standard (12 mils x 6 mils) and (8mils x 5mils) dimensions with mils being 1 thousandth of an inch.
Don't go any smaller than 0805 and I would use 1206 out of choice as it will be easier to measure and fix. I used 805 on the caps so I could fit them in nice and close to the ATTiny,
and 1206 on most of the resistors. When buying another thing to watch is the tolerance, but in this case it doesn't matter too much. Though it is easy to get 10% on ceramic caps and 1% on resistors so I wouldn't settle for less, incase you have spare and want to use them on another job.

After that I reckon you are done.

Now assign and/or make footprints and do the pcb layout. I find there is a fair bit of back and forth between metric and imperial while I do and check foot prints.


But I still haven't got the firmware to do the differential ADC inputs, with the 32 x Gain,
I have measured current but only as a one sided input, and because you get no gain I only get a tiny voltage.
I will try again tonight. My feeling is that it should work so it is only a matter of time.

Hi,

Found these they seem relatively cheap and available what do you think?

Will ammend the cap symbol when I get home and then final check should be it.

I am also going to go through my BOM once the schematic is done and have a good check for footprints of what I have part numbers for to make sure they are correct.

In terms of the cap symbol, which library do I need to look in?

Also you mentioned in terms of the library that I may need some files? Do you think this is the case and is this for the PCB design as opposed to the actual schematic?

Many thanks,

Andy

Found these they seem relatively cheap and available what do you think?

they seemed to be $6.00 each or was that a pack of something.
Try PCE3340CT-ND I think you should be able to get something for around 50 cents, you can probably go smaller 33uF on these if you want.

In terms of the cap symbol, which library do I need to look in?

from memory it is in devices and called cp1

Also you mentioned in terms of the library that I may need some files? Do you think this is the case and is this for the PCB design as opposed to the actual schematic?

more so in pcb editor, these is an excellent pdf that is built into the toolbar on pcbeditor. use that to help find footprint names


I have the channels 1 and 2 current sensing and stable.
Now I have init/boot problems and channel 3 I cannot get to current sense.