Powerful Aquarium Lighting
#161
Posted 16 November 2012 - 12:23 AM
#162
Posted 16 November 2012 - 02:02 AM
#163
Posted 19 November 2012 - 10:21 PM
Attached Files
#164
Posted 19 November 2012 - 10:40 PM
Edited by Magpie, 20 November 2012 - 12:15 PM.
#165
Posted 20 November 2012 - 08:27 PM
#166
Posted 20 November 2012 - 10:39 PM
8mm ? 8mil big difference. Very confusing, if only the world would go metric.
I choose 6mil because it didn't cost any more. but I don't think you have anything will a very small pin pitch so it wont matter.
I just used a chip that was a DFN (QDFN) package. Then it starts to matter. 50mil between pins. unlike the dip which has 254 mil.
the fuse holders I used are from futurlec
futurlec fuses
the picture at the top with two separate holders. I cant remember if we used m205 (5mm) or 3AG(6.3mm) but obviously you need to get the ones that fit the footprints. Check the length of the mechanical outline, it will say what fuse size we used.
update: I checked my steff2 boards and they have m205 ( 20mm x 5mm) so I think you have the same.
I used no lense yet, it is actually what I am having the most trouble with. the leds can be very dazzling and they need some diffuser. The board doesn't need heatsinking but the leds probably do. I just riveted them onto aluminium. I didn't even use heat compound as it is too messy. I tend to run everything fairly cool (<500mA) so they almost get away with just the mcpcb.
Yes the pots will be good.
remember for testing you need a current limited supply.
You can make a current limiter with a pot on vero board. and maybe just use a wall wart.
something like this.
My link
Or maybe start with some very low fuses and if you see a bit of light on the leds then move in bigger fuses.
You will also need some code , which I must have posted before, that you need to adjust and upload. You will need AVR Studio 6 which integrates somehow with Visual Studio.
And a programmer board. to program the chips. I have an AVR dragon but I think a Bus Pirate would do the job, it also might be useful for your SPI, I2C stuff.
You can probably also use a netduino if your very clever. I don't recommend this path.
The coding part of it is harder than C# and VS. But you should be able to almost straight copy my code. Its in C.
Edited by Magpie, 21 November 2012 - 07:43 AM.
#167
Posted 21 November 2012 - 12:39 AM
What fuses would you recommend?
Also I am wondering if I am as well ordering a few smaller resistors for the current sense e.g. to get 500ma for test rather than start at 700ma which I have calculated for. what resistors would you recommend for 3.15v @ 500ma?
On my digikey BOM my aluminium 47uf resistors are available but aren't going to be re-ordered in the future, would you swap them and if so can you recommend any? I caught up in ripple current and impedance. These are the ones I have currently.
Finally these say:
32209 IN STOCK/NO DELIVERY DATE AVAILABLE
Hopefully the above being ok and my boards coming out well (fingers crossed) I should have everything I need, oh in terms of soldering the SMD stuff do I need solder paste and any thing else?
Thanks,
Andy
PS had a thought for Steff 3..... Coasters! You could give them someone as a Christmas present.
Let me know how Steff 4 comes along, I have a feeling Steff 4 will be a winner!
#168
Posted 21 November 2012 - 01:07 AM
Edited by Magpie, 21 November 2012 - 01:29 AM.
#169
Posted 22 November 2012 - 12:13 AM
Just going through my bom vs the foot prints and 3d view...
C16-C18 which is the 4.7uf cap on each channel, on my BOM I have some radial ceramics, but on my board they are 0805 footprint, is this OK?
If so I was thinking of these to replace these?
I've managed to save on some resistors already, I had some that were like £9+ for 30 and I have them down to £1.42 same spec.
Solder paste is cheaper on ebay so I will get that from there.
This means my caps and resistors are all pretty reasonable now, just the fets to check out now.
Cheers,
Andy
#170
Posted 22 November 2012 - 01:49 AM
#171
Posted 22 November 2012 - 08:09 AM
What did you get your price for parts per 3 channel board down to, mine £9.10 currently?
These are the bits I think are still pricey but they are mainly fets so...
410 PCE3819CT-ND CAP ALUM 100UF 63V 20% SMD C3 10 Immediate 00.71 000 £7.10
530 MBRA140T3GOSCT-ND DIODE SCHOTTKY 40V 1A SMA D5,D6,D7 30 Immediate 00.19 040 £5.71
830 NTD4963NT4GOSCT-ND MOSFET N-CH 30V 8.1A DPAK Q13,Q14,Q15 30 Immediate 00.27 160 £8.15
930 ZXTN2040FCT-ND TRANSISTOR NPN 40V 1A SOT23-3 Q7,Q9,Q11 30 Immediate 00.19 840 £5.95
1030 ZXTP2041FCT-ND TRANSISTOR PNP 40V 1A SOT23-3 Q8,Q10,Q12 30 Immediate 00.19 840 £5.95
1730 445-5980-1-ND CAP CER 4.7UF 50V 10% X5R 0805 C16-C18 30 Immediate 00.46 100 £13.83
Those last caps are just expensive and they are cheaper than the previous ones!
#172
Posted 22 November 2012 - 12:10 PM
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.
#173
Posted 25 November 2012 - 01:36 PM
Attached Files
#174
Posted 25 November 2012 - 10:45 PM
Lets face it was your diligence not mine. I normally just buy the first thing.Thanks those caps got me down to about £70!
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..
Copper braid.Can you think of anything else that will be useful?
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.
? 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.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?
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.
Edited by Magpie, 26 November 2012 - 12:11 AM.
#175
Posted 26 November 2012 - 10:52 PM
Thanks that was very helpful, I think I understand power a lot clearer now, I suppose the only question I have left is how do you deal with situations where power requirements are less than the supply?
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?
I found this power supply for all 30 channels, if I think of it in terms of powering all 10 boards would I be best getting the 5v 11A allowing me scope up to 500ma per channel, or would I be better getting say a 5v 20A supply allowing me to go up to say 1A per channel if I wanted?
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?
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.
I just need to get my no clean flux, tweezers, solder paste and I already have copper braid.
Thanks,
Andy
Solicitors tomorrow for the first wave of fees before buying my house, I definitely need to curb my spending
#176
Posted 27 November 2012 - 01:34 AM
This is actually fundamental to the workings of electricity, I didn't realise that you didn't know this stuff.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?
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.
This is true.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?
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.
Sounds like a bargain.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.
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.
#177
Posted 28 November 2012 - 10:56 PM
#178
Posted 29 November 2012 - 12:53 PM
Second thoughts I think they are a bit low to be useful. Dont worry about them but do wire up a current limited wall wart or something.I will get some low blow fuses like you recommended 100ma or so.
Something like that , turn on with the current limit set to say 40mA and the lights dim. then wind it up checking for too much warmth in the various components.I'm going to test with the 1A 5v I have and will probably run the boards at a lower output for testing, maybe 200ma or so?
I meant power resistors to initially sub in place of the leds. Just a few 2, 5 or 10W wired up to be one or two ohms. Until you get the control circuitry and firmware correct and tested you don't want to blow the leds.This being said I will need to add a few extra resistors for testing, I guess you would recommend creating some form of regulator then for the boards especially whilst using the wall wart.
I would wait until you are happy with the boards. I still dont like the 5v and also I think I have made a layout mistake with the 5 volt tracks. I don't know how critical it will be but it isn't optimal. We should really have two separate rails for the 5v. So the noise from the leds switching doesn't upset the micro or the analogue. The analogue 5v is already separate from the micro 5v but the micro is sharing a supply with the fets and therefore will be subject to unnecessary noise. Sorry about that, It only recently occurred to me. Ideally we would supply the micro with an output from a linear regulator which is nice and clean. Have you got a cro? Anyway we will see when the boards come back.I think I am going to get a 5v 20amp switching supply eventually with build in protection as listed above, so it will give me some scope for expansion or if I really wanted to push the leds. Plus I guess the fact its switching should make it a little more efficient when running at lower output right?
This seems good enough. But you may need to beef up the transistor and lessen the resistance to give say 500mA.http://www.zen22142.zen.co.uk/Circuits/Power/add-on.html
But you will loose a volt with this the current limiting, so just for testing start with 8-12v, put the current limiter, then put a standard LM7805 (or 317 + 2 resistors) and then you project.
the current limit should be selectable so maybe switch in/out a resistor. Make on setting 30mA to limit damage on board faults. and the other one 500mA, so you can actually test you channels and firmware, without burning anything.
Edited by Magpie, 29 November 2012 - 01:23 PM.
#179
Posted 30 November 2012 - 08:16 AM
#180
Posted 30 November 2012 - 09:12 AM
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