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.

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.

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.

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 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

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.

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 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.

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

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

Hi

Please can you confirm that I haven't made any mistakes?

I made some changes, added to new column that flags the changes.

For the 5v version, you mentioned I need a smaller inductor, can you recommend any that would be good for the job? Or will either of the ones I all ready have do the trick which seem to be 100uh and 330uh?

I left the inductors at 100u you can probably go smaller as well, probably down to around 10u. So many variables to choose these. 100 will be fine if you have them but say 33u might be better, but only marginally.

You also said I need a different TVS diode, what would you recommend for this? PS I am probably going to order from Mouser in the UK.

Look for operating voltage of 5v, but since you are providing a regulated low noise supply off board, the only thing this will do is protect against reverse polarity.
Also bear in mind that you need to provide the regulated low noise supply off board because this is what the 12->5v part of the supply was doing.

I guess the current sense will change in value right? Do you have the equation for 700ma from a 5v input?

No the sense resistor is about right, it will be ridiculously efficient but may be prone to noise.
You may want to try 200mOhms. I tried to layout my board inputs as "kelvin" inputs. Unless you do this well your current sense inputs will be prone to noise.
Any prototypes you may want to use up to 500mOhms.

Calcs: 100mOhms at around 700mA the current sense should read .7 x .1 = 0.07 volts at full load.
We are not getting all that 700ma through the sense resistor so say we get 500mA. ( Some goes through the Shottky). = 0.05v
then we multiply by 32 in the internal gain stage = 1.6 volts. our full scale may be 3.3 volts so we get a reading of 500/1024 at full current.

Finally the parts for the dimmer channels, are these already on the BOM and do the values still stand for 5v?

Your pwm outputs should feed straight in to these as long as they are 5v full scale. Dont connect the 5v but connect the rest.

Have you recieved your boards yet and got one soldered up?

Apparently they are in transit.
I have the parts from Digikey. The murata inductors look a mess, they must've been made by the apprentice. The last ones looked great.
I have also got some really fine prismatic diffusing glass on order, it breaks up the leds nicely. The plastic ones are good too but they look shit when they are turned off.

Good luck

Hi

Thanks for pointing out the missing caps from my BOM, it was also missing R1.
All the caps are just decoupling or filtering caps of 100n 0805 and the Resistor was just a 10k 1206.
I cant believe I made this mistake, It just goes to show how easy it is. I am definitely not a computer.

I haven't gone exhaustively through your list as it seems your not quite decided the best way to go anyway.

As far as boards go I would go the modular approach, so if a board fails you can have spares, x channels per board.
Maybe 3, maybe 8, maybe 16. Design decision.

Also that way you could have some boards at 12 volts some at 5.

Actually on the subject of design decisions, the way just about every project I have worked on has been is that you never design it right first time anyway.
So there is no point trying to perfect the initial design. The moment the first working version comes out, somebody sees things that they hadn't noticed before.

So I think,

• Get something out there,
• Get something out there that isn't impossible to change or fix.
• Keep changing it till you think it's right.

If you go the small number of channels per board approach, you can chop it and change it. fix it without turning the whole thing off.

I am writing as I think so the conclusion of what I think you should do is 3 channel boards (wait till I confirm that the design works) start with 5 or 12 volts, (your decision) and see how things go.

As far as 5 or 12 volts for 1 led.
5 volts can be slightly more efficient but, will it always be one led, because you can't easily change it.
If you go 5 volts you may have a noisy supply to the micro, this may or may not be a problem for the Current sensing on the Attiny.

If you go 5 volts you don't need the step up bc847 and it's two resistors. But you do need a different, logic level FET, just like AHellene's circuit.
5v you can use a smaller inductor.
I would use 12 volts but there could be a case for 5v and event a case for 7 volts.

If you want to use my circuit with 12v
just use a different TVS (12v operating voltage).
and remove everything including C3 to L2 reading left to right on the schematic.
Jumper the 24 volt rail to the 12volt rail.

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
It gets a bit harder as you may need a clean supply for the micro. I don't know.
Personally I wouldn't bother. It probably would be ok, but I think 12v will give you what you need.

Do you think this side of the circuit can be powered practically off the netduino

No the netduino can only source less than 1 amp.
I would power the netduino from my 12v supply. Maybe via a resistor to just take away a bit of the heat.

Also one of the resistors is marked as a bit wide, is this the foot print or the value and does it matter?

That is a mistake, it was left there from some other current sense resistor that I had considered, please disregard.

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.

Perhaps even provide a jumper option, where by you can select 5v or 12v and swap out the power supply accordingly?

You will loose very little running 1 led at 12v vs 1 led at 5. Only really in the higher series resistance of the inductor because you need a bigger inductor.
Just run at 12v.

How many ma are your running your Crees at in this circuit?

Steff shield is currently running 3 channels of 7 leds at 24 volts and at about 500mA. (XTE warm white) No heating problems on the shield and very little heat sink on the leds.
I will do 7 leds as well with my 24 volt prototype.
I want to move to 24 - 48. but will probably have to settle on a 24-36v version and 36-48v version, the black regulator doesn't have a wide input range. I just need to change a resistor value to switch between the two variations.

One thing that will work for you is the input circuitry on the Dimmer channels, you should be able to put your square wave straight in.
The input filters use 10k and 0.1uF which gives 166 Hz. If you can give it a pwm above 15KHz then your filtering is done.

BOM is corrected, thanks for finding the errors.

Here is the final schematic for the first spin and the BOM. The 0805 resistors I didn't bother getting the part numbers for. Same with some of the others which I already have. BOM was wrong, it has been corrected.

I know I am jumping in a little late here, but I just looked at the picture with the inductors. Aren't the ones on the left actually 33mH instead of 33uH?

I looked at this link coilcraft series

I must admit I don't know.

The bit in the bottom right corner is the black regulator right?

that's right.

ps. I changed the logo, it will come out on the silkscreen.

I almost mounted the torroid footprints upside down, that would've been a disaster.
I just sent the gerbers off to seeed studio last night.
If you want I can send you some, I will test them first though.

Hi I have all but finished the board for the Steff2, attiny version. I also have a BOM, I will post soon, I am at work now. I will probably send off to seeed studio or similar this week. The board picture is attached, the inductors haven't got a 3d model, they are vertically mounted torroids. Either 100uH or 220uH, probably I will try both.

Hi I have all but finished the board for the Steff2, attiny version. I also have a BOM, I will post soon, I am at work now. I will probably send off to seeed studio or similar this week.

All my parts will be surface mount where possible. If you want to go dip you will have to find similar.

But the Attiny will be Dip, just so I am sure that I can program it, I have never done an ISP header before and a cock up here would be catastrophic, the big inductors will be dip, and the connectors and fuse holder.

I think the program will be very small, probably the tiny261 will be fine.

I have an avr ISP mk2 will that do the trick?

I assume so but I really don't know.

Those connectors look good (your favourite).

I think I want the screw in onthe flying lead and the L shaped black header pins, probably I will go for 5mm.
I will draw the pcb at 5mm.

Yes you could change it to 5 volts maximum. I have changed my input protection, to at TVS diode and a fuse. and got rid of the mosfet. You can do the same. If you wanted to make it a sort of 5-12 volt combo that probably would be best. It would give you the option to have more than one led per channel if you want it. I don't think the efficiency loss would be too bad. Just get rid of the 24-12 stuff, then you have virtually the same circuit as me. It may save a bit of testing. Alternatively you can move the fet down to 5 volts. you would need a logic level fet. and you could get rid of the bc547s and associated resistors. Just like AHellenes diagram. If you did this there would be no point in using a linear regulator to get the 5v for the mosfet drain, it would just be a waste of power, but the regulator for the 5volts to the micro would be still necessary. If I was you I think I would go the 5-12 volt combo. I am currently selecting Parts from Digikey for the boards, for the first time I will be able to give you a real BOM and even Digikey part numbers as well as Manufacturers part numbers. Do you have anyway of programming the Attinyx61? I am not sure whether to go with the Dip20 or the Soic20, (Actually I will go Dip) I think I am going with Murata 4 pin torroids for the inductors @ about $1.80 each. The only problem is their height which is about 15mm at a guess. And which connectors for the led sting, I used green phoenix connectors on the Steff shield. Have you got any good 2 way connectors say 3 amp max. Less than 15mm height. You can probably use my boards if you want, with a couple of hand modifications if you go 5-12, I will make sure that you don't have to cut tracks if you want. I will put in a jumper before the black regulator and you can wire that straight to 12 volts.

I will reply on yiour Aquarium thread.

It is going ok.
I have posted a schematic, and now I am choosing parts footprints.

steff2

I am wondering whether to use the super torroids or to go with lower profile.
Also I am wondering what connectors to use.

But I have decided on the transistors and fets.

AHellene gave me some good tips for the Attiny.

Hi Frankie
I'm really glad you managed to find some use for the code, hope you make something really good with your project.
I know how hard it is to use somebody elses code, so that fact that you can use code from an unfinished, poorly documented project, mean that at least my attempt to write reusable code must be partially working.

Here is my liability waiver, It was a work in progress that got stalled because I couldn't get it right, then ran out of program memory.
I didn't mean to put it out to general view until I had fixed the bugs, done the binary upload and rearranged it neatly.

4.2 RC5 should give that extra space. But I was a bit disappointed that I still have a memory leak, so maybe it is my code.

My logger is still actually running but I have to cycle power as it crashes every 10 days or so due to the memory leak. I am fairly sure it is to do with being on the Internet because it used to run for over a month before I opened my gateway for it.

I still cant finish the Webserver/Logger due to my limited amount of time, but if you want to mention any bug fixes you see in the code then go ahead.

Biggest challenge so far was getting the multithreaded hardware calls synchonised to the hardware implementations, making sure the same relays doesnt get triggered by 2 requests at the same time.

Just use a lock for Thread synchronisation. I view any hardware as a resource and therefore because you can have multiple callers on different threads one has to wait for the other to complete.
I do love the challenges of multithreaded apps, fun to debug.

For handeling the webrequest that have no mimetype and are skipped by the webservice ive created a factory(mapper) that has all the availeble implementation for the hardware in the form of handlers stored in an hashtable.
All i have now are a relay handler and a logginghandler loaded in the hashtable.
I use a switch statement to find the correct handler based on the url fragments and then invoke doWork on the handler. I provide the doWork method with a string array of urlfragments. So all the implementation logic like calls to the hardware resides in the handlers. Ive created an interface for the handlers and a baseclass for the general work.

You seem to be making a real webserver.
I know I should use JSON in projects but I tend to use XML due to my familiarity.

psps: fixing the n+ crash when using too much requests is easy by upgrading the firmware.. theres a bug crashing the n+ with an outofmemory exception in the 4.1 firware when theres plenty of memory left

I don't quite follow, I haven't really tried 4.1. I have tried 4.2 RC3,4 and 5 no joy for me here.

I love the language C# I just wish one day in the future we could have a Jit compiler on the Netduino.

Dont get distracted by paying work, spend more time on your hobby projects. When is the full system coming out?

Hanzibal, Yes yes I got the boards back and posted a photo on the 6th of May. It has been working happily every since, well except when I turn the lights off at bedtime. As I mentioned before the dimming wasn't working properly probably because of some sort of emi. It runs cool and efficiently though. I had to make about 4 ugly soldering hacks due to my mistakes. Right now I am workng on an Attiny solution, without the Netduino smarts. The links are in this thread on about the 30th of May.

I am drawing a schematic to lay out a board, but it will be for 24-48 volts input. You don't need the black regulator it is only to drop the voltage down from 24v to 12. My understanding is you will be using 12v input. I have actually made up a 3 transistor black regulator on a bread board and it did work as expected. I will be using a 2 transistor regulator to drive the 12volt rail with no current limiting. I only need a small amount of power at 12v. Then from 12volts I use a regulator to bring it to 5 volts. Obviously this step loses 7/12 of the power. As far as the bom goes just look on the schematics. I am wondering if down the track I should use the attiny25 (8 pin) and just do one channel per micro, this may suit you better, but for this version I am using the attinyX61a 20 pin. Maybe what you should do is a block diagram of your entire system. Maybe you have. This can really help you see things once its gets complicated. Then add a couple vero board prototypes to a couple of channels and see what works best. I will post a schematic with micro attached soon, I want to send it to the manufacturers soon. Hopefully 1 week.

I have decided on a rough schematic, I am using the negative input as common again.
The details are on my domestic lights project . It is based on the Attiny but with some improvements.
I hope this helps.<br>