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#38645 Powerful Aquarium Lighting

Posted by Magpie on 06 November 2012 - 10:23 PM in General Discussion

Hi

I think you should build something soon, but I have a different idea for you for control.

the netduino can talk SPI and the attiny can talk SPI. so you could drop the tlc5940s completely.

Just have the netduino set the dimming level direct to the attiny via SPI. The only trouble with this is you would loose one channel of PWM, giving you two outputs per attiny.
Although if you can handle a small blink while the communication is done you could have 3 channels.

Also I have never written any SPI code in AVR so you would be on your own there.

L1 will be ok, it just needs to fit mechanically and I think it will fit but it will be tight.
If it doesn't fit you can easily make it fit by soldering L1 just off centre or filing a small notch into the ic socket.
You understand you need to use a socket dont you? I am not sure if I made this clear.

I tried editing the pad offset, but every time I pressed OK, and went back in to the settings, it had gone back to zero?

Right click on the footprint and Open the footprint in the module editor. Set the working library to say 'Andrew' and put all your mods as you do them in here. Create a new part from what is in the editor and save it into your footprint library. At this point you can save it as you make changes. Once it is done then delete the old footprints and place the new footprints into your pcb. The tracks may be no longer connected, so reconnect them using your knowledge of grids and snap to.

One day when I get something looking good made I will post about my latest version, hopefully soon.

Let me know how you get on with your new boards, out of interest I know you have dropped a channel, but how small do you think I could realistically drop these boards to? I don't know if I definitely will, especially if these boards work, but I may lay it all out on one big board eventually with the TLC board built in and the power distribution for the 30 channels will be much more elegant and a lot of the connectors could be dropped. I could essentially get away with a GO! bus connector and a power plug, but this really is dreaming ahead!

Yes I think before the final board is built you could optimise, but it is so hard to get the perfect design from scratch. It is iterative and I think 2 iterations will be your minimum.
If you get this first board made in small quanties, turn it on then I think you will find unexpected things, good and bad, especially in regards to the lighting aspect of it.

#38664 Powerful Aquarium Lighting

Posted by Magpie on 07 November 2012 - 09:54 AM in General Discussion

here is a list of pcb manufacturers in ol' blighty

pcb manufacturers

Or probably go with seeed.

Try editing the yellow pcb outline layer, I just looked at your board there is loads of room, but you may just have to reduce the copper pour a fraction.
Just fit (edit) the pcb edges to be 50mm apart. and move the copper pour to be at least say 1mm away. Move the fiducials too or you can just delete them.

Or when you are completely done with the other stuff I can do this step for you. I gave it a quick test it took just a few minutes.

the price from seeed is going to be $US 35.00 and if you waste $15 on something you dont want then you get free postage. The have a resistor book 805, but at $60 it is very expensive.

when you order from seeed you are not paying for service so do everything they say and it will be ok. I forgot my order number on one board but it didn't matter it still came. This time I put it under a big inductor so no-one could see it.

#38545 Powerful Aquarium Lighting

Posted by Magpie on 05 November 2012 - 09:56 AM in General Discussion

Hi edit: sorry I probably wrecked the kelvin connections I did fix it up. I emailed you the brd and the gerbers. to save on my upload space. The problem was a few unconnected tracks that were actually connected but the DRC isn't smart enough to realise. there was only 3 but the the DRC thought there was heaps. The problems (gotchas would be more accurate) were caused by the grid settings, nets wont be connected unless they snap to the grid. if you change grid settings some of your pads will no longer snap. Also Kicad doesn't seem to remember your grid settings so you have to change it whenever you open up. Try to use the same one or two all the time. I had to go down to the very lowest to get one track to snap. The other problem is not actually a problem with the board but with Kicad. the DRC doesn't understand the copper areas and that everything inside is connected. So work around this I just join the unconnected ground pins on the underside of the board with thin tracks until the DRC says no errors. The actual copper pattern ends up being the same. Its like programming, get rid of the warnings so you can see important ones when they eventuate. Also a put vias into a lot of the ground pads, which I have only just learned how to do. Apparently my steff3, 2 channel, 36 volt, Black boards are finished manufacture and are returning to me.

#37401 Powerful Aquarium Lighting

Posted by Magpie on 18 October 2012 - 10:03 PM in General Discussion

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.

#37372 Powerful Aquarium Lighting

Posted by Magpie on 18 October 2012 - 08:13 AM in General Discussion

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.

#39942 Powerful Aquarium Lighting

Posted by Magpie on 22 November 2012 - 12:10 PM in General Discussion

Sorry those caps were overspecced.

Try these.
445-1369-1-ND

on the caps you can go down to 16v which still leaves a comfortable safety factor. None of the caps need accurate tolerances or temp coefficients.

the fets should be at least 20v.
same with the bjts.

I probably waste a bit of my money but then again we aren't just about to buy a house.

#40199 Powerful Aquarium Lighting

Posted by Magpie on 25 November 2012 - 10:45 PM in General Discussion

Thanks those caps got me down to about £70!

Lets face it was your diligence not mine. I normally just buy the first thing.
I wouldn't change the BJTS they are good quality and not so expensive and have been used in Steff2.

I think Atten 858D , (Dave does a video too, #167) do a budget heat gun (dont get ZHIAOXIN 858D and YiHUA 858D, and check earthing before using), but If you want to save money a small wedge shaped soldering tip would probably be good enough for the whole job..

Can you think of anything else that will be useful?

Copper braid.

I have had my own mcpcbs manufactured. mcpcb I think it was $30 for 600 peices + $170 for tooling postage and TT payment. <sigh>
You can mount them on FR4 but need thermal vias. Each led doesn't need a huge amount of Al and it depends on a few factors but you can definitely get away with 50mm x 50mm for each XTE or XPG led. Probably even less. Heat sink at the back mean you can place them closer together, but they make a lot of light.
I am using Steff2 in my workshop and it gives enough light, maybe a little more than a single fluoro. 21 leds @ maybe 300mA. I don't think heat will be a big problem.

my calc was 3 x 500mA x 3.15 volts = 4.725W
+ attiny and gate drivers 5v x 100ma = .5W
+ inefficiency = .5W

Total power for 3 channels on one board = 5.725W @ 5v = 1.1 amps.

I'll go to really plain terms now, so in terms of voltage drop in series this would be 3.15v per LED so you would need say 12v, but we get away with 5v as the channels run in parallel right?

? each led has its own channel, in this case there is no series or parrallel. In the 12v 24v, and 36v designs you have the led strings in series. You cant really parrallel the leds without individual power resistors to share the currents equally, this is wasteful so not considered.

Current i.e. the 1 or 1.5 amps we will supply can be larger than the required 700ma plus any other losses, as the circuit will only take what it needs right? Would this increase if say we needed 5 LEDs in a row to say 4A or does current not drop like voltages does in series hence it would still be 1 - 1.5A?

So here's where I get confused, where do Watts come in to the equation?

For example will my 5v 1A wall wart be able to power all 10 of my boards and I guess I would need to distribute the power in a parallel design between the 10 boards right?

If you run 10 boards or 30 channels of 1 led then you will need 1 x 11 amp 5 volt supply. Or you can use 5 x 2.2 amp supplies or 10 x 1.1amp supplies. Dont parrallel the supplies just join the negatives as common. Keep the the positives of the supplies separate to each other.

Try not to overload a supply, you can probably use standard 1amp wall warts but maybe turn the power down a smidge. you can do this in the attiny firmware so that the Netduino firmware cannot cause failure. Check the warmth of the Wall wart while at full load. You don't really need to use wall warts there are other more efficient supplies.

Also I would put a smoke detector in your lab especially while still in development.

#43131 Powerful Aquarium Lighting

Posted by Magpie on 10 January 2013 - 09:22 PM in General Discussion

For some reason we don't pay our VAT (10%) on items below $1000. And buying overseas is the norm for any serious purchases.

House negotiations are not going my way, out of the �11k devaluation the bank imposed, I'm currently fitting 8 of the 11

Sorry I dont understand, but then I don't know much about buying houses. I would take care as it is such a huge purchase.

Get some reflow practice on the hardier components first,

If you want a challenge try DFN with a thermal pad and no solder mask between the pads. That's what I did for the Solar charger. Each one took about 5 goes. Once you get the hang of it, it gets easier.

I must admit I found 2 soldering irons easiest for the big inductors.

#43102 Powerful Aquarium Lighting

Posted by Magpie on 10 January 2013 - 12:57 PM in General Discussion

Heres the project files for steff4.

You need Atmel studio 6 to compile it.

A few things to do to modify it to your purposes.

The main file is Steff4.c

the others are mainly defines and historical. they dont need changing.

Set the fuses on the Attiny to what is at the top of Steff4.c in the comments.

Careful with the fuses you can actually brick it if you are careless, I did this once.

steff4 is only two channel and you have to change the code to 3 channel. 0, 1 and 2

So create a few more defines eg. //#define PWM_OCR_REGISTER_2

also create another section in main for channel 3 that uses the channel 3 defines.

You have to set the all the defines 0, 1 and 2 to be correct for your hardware, so you need the attinyX61 data sheet, your hardware should be very similar to mine.

ReadPWMRegister and WritePWMRegister need to be set whether you are using the positive part of the pulse as on or the negative. If you get it wrong it will turn fully on. This is where the current limiter will save you. Your led wont like 5 volts.

When you get that working and only then, uncomment the dimmer section for each channel in main(), also check any defines used here are correct.

Todo:

I have to fix the function

U16 GetLoadCurrent(S16 sensorCurrent, U16 currentPWMSetting)

to more accurately get the load current from its parameters, as I mentioned before we only measure the fet current.

Lastly I could optimise and or use interrupts, or I could neglect them, it seems to work fine without them.

No doubt you will have many queries about my code, hopefully you can understand it.

I am sure most embedded C people would have a nightmare about the lack of efficiency if they saw it.

You can also run stuff in the simulator, although you have to break and then change variable values to get into some of the code sections.

Attached Files

Steff4.zip 15.97KB 2 downloads

#42694 Powerful Aquarium Lighting

Posted by Magpie on 04 January 2013 - 11:41 AM in General Discussion

Hi Andy We are just having the hottest day in Hobart for around 40 years, 41.6C. I am sitting with a wet cloth on my head trying to cool down. Did you buy the house? If you did I hope you have a dedicated Aquarium room. the voltage across RL should be 5volts (+/- say 5%) at low currents ( high load resistance) and up till the current limiter kicks in. The Attiny is happy with 3.3v up to 5.5 volts and 5.04 volts sounds just right. You need two current settings very low and normal. Use say 30mA to test for shorts and then say 100mA to see if the led works and then you can probably discard the current limiter for that board.

Cant get some of the links for digikey. the 0.1uf are ok.

goto go sorry back in a few days.

#40278 Powerful Aquarium Lighting

Posted by Magpie on 27 November 2012 - 01:34 AM in General Discussion

For example we have quoted for 500ma per channel, what if either in the firmware or in the netduino code I set the output to 50%? Does the circuit just take what it needs, does the additional power create issues or is this wasted in the form of heat output from the power supply?

This is actually fundamental to the workings of electricity, I didn't realise that you didn't know this stuff.
The way mankind uses electricity is normally at a constant specified voltage, it could have been current but we like voltage.
Loads are often characterised as an impedance or resistance. Sometimes it is constant like a resistor often it is varying like an oven turning on and off or a monitor changing brightness.

When you connect a load to a nominal voltage they work together to find an operating point which is a voltage and also a current (and therefore a power and a resistance too). As long as the load doesnt draw more current than the source can supply then the source or power supply should sit at near its nominal voltage, the load at this operating point will only draw whatever current it needs.
So for a 5v supply.
A resistor 1 ohm will draw 5 amps.
A buck converter led power supply will draw roughly 250mA if it is supplying the led at 3.15V and 300mA.
the same buck converter at pwm of 0% will draw roughly 40mA (due to overhead of the chip and the gate drive) and put out zero amps.
If the buck converter is completely disconnected from the supply then the output voltage will still be 5v but no current will flow.
If there is a short on the board then a large current will flow, and the supply wont be able to provide the full 5 volts, fortunately your fuse will soon blow and completely disconnect the supply.

Also if say 15 channels were at 0ma with the 5v 11A supply, would this mean I could take the other 15 channels up to 1A per channel?

This is true.
Just remember there is a difference between the power supply current and the output LED current. This is because you have a buck converter.
If you used a linear regulator instead of a buck converter, then input and output currents would be the same.
You have a power supply (wall wart) supplying another power supply (led driver) therefore there will be two operating points both dependant on what current the leds want to draw which is dependant on what pwm you set.

I have bought an Atten 858D+ as per Dave's web blog, although I bought before I watched his review and that made me feel like I got a good deal at £30 including postage.

Sounds like a bargain.

Don't start with the big supply use your wall warts first, and start with smalller fuses test the boards individually. Put on a dimmer pot for initial testing.

George Best said.

I spent a lot of money on Women, Booze and Electronics. the rest I just squandered.

possibly misheard.

#36036 Powerful Aquarium Lighting

Posted by Magpie on 26 September 2012 - 11:11 PM in General Discussion

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.

#32917 Powerful Aquarium Lighting

Posted by Magpie on 30 July 2012 - 11:17 PM in General Discussion

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.

#29736 Powerful Aquarium Lighting

Posted by Magpie on 25 May 2012 - 01:50 AM in General Discussion

Hope your boards work out fine, you will have to let me know how they go.

Finally I have my lights working.

I haven't used or really looked at the Go architecture yet, but I think it may suit your project.

#30795 Powerful Aquarium Lighting

Posted by Magpie on 17 June 2012 - 01:44 AM in General Discussion

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.

#27976 Powerful Aquarium Lighting

Posted by Magpie on 23 April 2012 - 11:28 PM in General Discussion

Hi

Glad it is going well.

The good news for me is my NCL30160 boards finally arrived, so I may as well power them up.
I am going to do it at 24 volts and put Transient suppressor diodes on the inputs for a bit of protection.
I will let you know how it goes.

OnSemi assured me they tested the chips and said it was probably overheating.
If you look at the photo I posted on the SteffShield thread you will have to agree with them.

But as it is decision time for you, I will give you some thoughts becasue as you know proscrastination is the enemy of success.

I would go 12 volts per channel and use a mains down to 12v supply. This means you can add extra power to any channel if you need it, but you will need the single inductor per channel.

I like the meanwell supplies and I would get one that is highly efficient, this doesn't mean super expensive. ie. higher than 90% at rated current. Try a recent model of the meanwell ones.
The one in you picture looks ok but you really cant tell from a picture.

What other parts do I need and what adjustments need to be made in terms of the power supply?

As far as Amps go .
Work in watts and then at the last minute divide it into amps.

Add other power requirements and led requirements.

the leds will be say 30 x 3 watts = 90 watts

other stuff say 50 watts???

= 140 watts
add some spare capacity and you have say 250-350 watts.
divide by volts and you have say 25 amps.
so that is a fairly hefty supply.

ps. I know this sounds like a computer psu but they aren't very efficient.

you can probably add extra amps later if you really need to.

So do you think this is powerful enough for the 30 channels if we base on 30 Cree xp-e 3watts leds? Or would you suggest a high voltage perhaps 12v? I'm just mindful about you saying the NCLs operate better with lower voltages and that I will just be wasting power with high voltages as my leds only need upto about 3.5v max.

the NCLs with the inductors in the standard circuit will limit the current and the voltage to appropiate levels.

Finally what additional parts will I need to take in to account the PWM from the open drain of the TLCs?

just a pullup resistor. the tlcs need to put out a square wave <= 20khz, I assume they can do this. you better check.

Also do I need any current limiting circuits and if so what parts would I need?

Just need the standard NCL circuit, running at 12v and definately use a nearby TVS diode with an nominal operating voltage of 12-24v and a let through voltage of 27-32 volts. like this SMA6J24A-TR
Also you need anti static wriststrap connected to earth to use the NCLs and dont take them out of the silver bag until you have your wrist strap on.

I tried a value of 33uH for the inductor, use surface mount for the diodes and caps so you can put them really close to the pins.
In order of component closeness to the chip
1. caps ceramic (smd, if possible)
2 diode
3 inductor
4 resistors
5 caps electrolytics if any

the other thing I have found is that I am using the new Cree XTE leds now, at around 2 bucks each without the aluminium backing.
Last night I sent off a design for my own mcpcb, to mount them, this should cut costs a lot.
They are rated to be very similar in performance to the XPG but 1/3 the cost. so I bought a 100 of them.

No worries about helping, good luck, I just hope you have better luck with the chips than I did. (Luck? It may have been incompetance)

#26779 Powerful Aquarium Lighting

Posted by Magpie on 09 April 2012 - 02:15 PM in General Discussion

I am thinking for your purposes, you can get away without current sensing.
You just need over current protection.
This will give you
less losses
very simple circuit
excellent linearity, good for colour.
but at a cost of

fair bit of software fiddling if you change the leds per circuit, or supply voltage, if this is the case you will have to reset the max pwm
you will need fuses too, to protect your leds. make sure the fuses blow before the leds.

Have you worked out how many channels of how many leds?
Is it 32 channels of 1 led?
For the single led channels I don't think I would bother getting an inductor either.

just something like.

tlc -> PMD3001D -> nfet gate.(logic level fet, or maybe STN3NF06L) 

and VCC - fuse - leds - nfet drain and nfet source to ground.


or VCC - fuse - leds - inductor - nfet drain and nfet source to ground.
              |              	|
              |--- diode --------|

Obviously prototype first.

For my purposes ( domestic lighting 10 leds in series) I am going to rejig the Attiny461a, finish, improve the code, and choose the best transistors, and fet.
Maybe even go synchronous.

#26773 Powerful Aquarium Lighting

Posted by Magpie on 09 April 2012 - 12:54 PM in General Discussion

I take back anything I ever said about the NCL30160s

They are Junk!

I had my last one running this afternoon, and for one hour it was fine.
I went away and came back in another hour, my workshop was smokey and chip number 5 had gone short circuit. It was only running at 130mA and the chip was running cool. It did actually run very cool for the work it did. I once had it up to 800mA.

I initially had 29 volts, 130mA running into the chip but now I had 450mA running into it (I didn't read the voltage but It would have dropped to about 3-6 volts at a guess).
My current limiting supply had gone into limit mode and I had 450mA running through a breadboard to my chip. The heat in the chip was making the smoke and now it is stuck to the breadboard, I will send a photo, soonish. My smoke alarm didn't go off, it only goes off for normal cooking smells. sigh.

The only excuse I could find for this chip is that the circuit was breadboarded, and you shouldn't do this at High frequencies, but I dont actually believe the breadboarding of this circuit was a problem.

In short the NCL30160 is junk. Dont use it for your own safety.

If you look at the block diagram the short seems to be in the built in voltage regulator.

A timely reminder to take precautions when doing power electronics,

smoke alarm
current limited supply
fuses
watch closely

#31639 Powerful Aquarium Lighting

Posted by Magpie on 05 July 2012 - 11:00 PM in General Discussion

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.

#31648 Powerful Aquarium Lighting

Posted by Magpie on 06 July 2012 - 10:30 AM in General Discussion

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.

Attached Thumbnails

#32886 Powerful Aquarium Lighting

Posted by Magpie on 30 July 2012 - 01:07 AM in General Discussion

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.

#32873 Powerful Aquarium Lighting

Posted by Magpie on 29 July 2012 - 01:50 PM in General Discussion

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.

#32016 Powerful Aquarium Lighting

Posted by Magpie on 14 July 2012 - 01:03 PM in General Discussion

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

Attached Files

Steff2 BOM revised for 5v.zip 4.88KB 1 downloads

#31702 Powerful Aquarium Lighting

Posted by Magpie on 07 July 2012 - 01:54 PM in General Discussion

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.

Attached Files

Steff2 BOM.zip 4.01KB 2 downloads

#26758 Powerful Aquarium Lighting

Posted by Magpie on 09 April 2012 - 12:03 AM in General Discussion

Hi Andrew How is the aquarium going? I have some of the NCL30160's but I have blown 4/5 of them. They are static sensitive. But seem to work as specified. I used the circuit straight out of the datasheet. I may soon try and rejig my attiny version for my domestic lighting project. I have a book on PID control and and some better surface mount fets. But I would recommend you continue with something like the NCL30160, to keep the part count low and to interface nicely to your tlc5940s.

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