Author Topic: Domestic Led Lighting project.  (Read 20032 times)

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Offline HackedFridgeMagnet

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Domestic Led Lighting project.
« on: May 26, 2012, 02:24:59 pm »
I want to change all the wiring of the lights in my house to DC, using leds.
At least half the mains wiring in my house is for lighting, a lot is old and running a separate earth, sometimes no earth.
Ps. I am a sparky and allowed to do this stuff.

I want to start with 24 volts but possibly move later to 36 or 48 volts.
I am also thinking of putting in a few DC wall sockets. At one of those nomimal voltages.
As part of this I want to choose an inline plug and socket to use as the standard for the house.
Also I would like a wall mount GPO equivalent.
Specs Max voltage: 48 v dc
max current: Say 2-5 amp DC.

I also need a nice looking standard light switch dimmer control, which just has a pot and a switch instead of a thyristor or triac or whatever they use these days. Each light switch itself is not switching/ dimming current of any real power.

One further thought is if there is any defacto standard that exists or that looks like catching on, then I might want to go with them.

So I need to find:
  • Wall Socket and matching plug. similar to a 10A gpo in use but with different power requirements and obviously different shape. Hopefully with a switch.
  • Inline plug and socket. for general purpose DC connections it would be good if it was the functional equivalent of an extension lead.
  • Light Switch with dimmer.
  • DC low current circuit breaker. I think Jaycar has some but don't know if they are any good.

Has anybody got any ideas on what would be most common and most suitable.
I do have some ideas but I have never found anything satisfactory.
ps. It has got to look better than my usual home made stuff.
Obviously I am from Aus but happy to purchase anywhere where the goods and the price is right.

As far as the led lighting goes I have purchased about 100 cree XTEs warm white, and my own mcpcbs, 660 of them, The leds should at least do part of the house. I also have two types of home made constant current led drivers. I haven't decided which type to use yet. One is based on an Attiny461 and the other on NCL30160.
I will post more about these later.
 

Offline T4P

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Re: Domestic Led Lighting project.
« Reply #1 on: May 26, 2012, 03:03:13 pm »
Look for a constant current buck driver that has pwm inputs for dimming << that works best or you can find them premade
 

Offline SeanB

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Re: Domestic Led Lighting project.
« Reply #2 on: May 26, 2012, 03:20:08 pm »
Why not order Shucko sockets, as they will fit in the AUS boxes, and are available with a switch. Otherwise a double switch plate and mount an IEC female socket there in place of the one switch, and use IEC male leads on the DC power lines. All you need is to use a power system that is not used in AUS, so choose any from around the world, and order them from China.
 

Online IanB

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Re: Domestic Led Lighting project.
« Reply #3 on: May 26, 2012, 04:16:24 pm »
Low voltage halogen modular lighting systems come to mind. Do they have a standard design of plug and socket you could reuse? Though it may be designed for 12 V and so not so suitable for higher voltages.
I'm not an EE--what am I doing here?
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #4 on: May 27, 2012, 02:07:06 am »
Quote
Why not order Shucko sockets, as they will fit in the AUS boxes, and are available with a switch. Otherwise a double switch plate and mount an IEC female socket there in place of the one switch, and use IEC male leads on the DC power lines. All you need is to use a power system that is not used in AUS, so choose any from around the world, and order them from China.
Thanks for the idea, it hadn't even crossed my mind to use non Aus power sockets, it seems like a good idea I may go with the Shuckos unless something better comes up, I am fairly sure it would be legal too, the only trouble is it may be confusing to overseas visitors. Not that we have many of those.

I will keep looking though.
 

Offline codeboy2k

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Re: Domestic Led Lighting project.
« Reply #5 on: May 27, 2012, 07:02:06 am »
I was starting to think along the same lines as you a few years back, but I never did anything.  I am not a licensed electrician, so technically I can't wire my house, even though I know what I am doing.  I didn't have the time to get started.

But I was thinking that with everything moving to LED lighting, and more and more handheld, electronic, low voltage devices, battery powered equipment and battery chargers in our lives now, that all these AC-DC-DC convertors at point of load are not so efficient in a modern home. It would be more efficient to eliminate the first stage AC-to-DC conversion (the PFC stage) at every  point of use, and just do that once at the demarcation point, and supply a DC bus inside the house.  I was thinking 24 or 48 V too.

I hope there is some new low-voltage DC standard bus for homes, and that future homes have AC outlets and AC appliances as now, but there is also a single, high efficiency AC-DC convertor at the breaker box, and DC fed lighting, and DC outlets for powering electronics and portable stuff.  I am sure electricians won't
approve it, as they would then have to run 2 separate services through the home.

 

Online IanB

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Re: Domestic Led Lighting project.
« Reply #6 on: May 27, 2012, 07:17:53 am »
It would be interesting to figure out the typical power load of a low voltage DC system and see how that maps to current load and wiring requirements at different voltages.

For instance with LED lighting alone, suppose you need 100 W per large room and 50 W per small room on average, then you could easily have 300 W typical load in a house. At 12 V that would be 25 A, at 24 V 13 A, at 48 V 7 A. That's not allowing for other devices like LCD TV's, computers and so on. It's not hard to see the need for quite heavy gauge wiring with a central power distribution point. It may be better to have localized low voltage systems per room, rather than a centralized system?
I'm not an EE--what am I doing here?
 

Offline SeanB

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Re: Domestic Led Lighting project.
« Reply #7 on: May 27, 2012, 09:09:27 am »
48V would be good for lighting, as there are many converters available that are meant for telecoms use which is 48V based. High enough voltage to keep current low, but only needs cheap 100v capacitors on the input side, and smallish inductors, plus the power devices are cheap as the voltage stress is low along with the current.
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #8 on: May 27, 2012, 10:59:32 am »
Thanks for the input, ideas, I appreciate it.
I am actually going with the high efficiency AC-DC convertor idea but near the middle of the house. I have an 24V 7amp (from memory) Meanwell switch mode psu. If I need more I will get  another similar. The I find my current to each light is only going to be about  1.5 amps at 24 volts but I think I will need 2 lights per room. I am trying to use everything to make the system as energy efficient as possible and dont worry so much about the up front cost.
As you say at low voltage you are going to need a lot of amps for any high power but I am really not wanting to replace all the mains in my house, just the lights and fire alarms and maybe a few small things.

I will probably end up settling on 48 volts as these give a nice long led string and great efficiency, maybe 14 x hbleds.
The only advantage of 36v is there seems to be a lot of 40V chips that I might be able to use, including the NCL's.
I am going to start with 24v only because that is my Meanwell psu.

I have my first home made light running at 3 x 7 xte led strings with a Netduino controlling the dimming(dont ask) and 3 x Ncl30160s as the current drivers. 24 volts in and about 1.2 amps in. My lack of heatsinking on the leds means they are running a little warm. But not excessively.

All in all it is a beautiful light.
The NCL's dont seem to dim well at the low end. I will probably go back to the Attiny drivers.
 


 

Offline T4P

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Re: Domestic Led Lighting project.
« Reply #9 on: May 27, 2012, 03:04:12 pm »
Eh wait ... 7 LED's in series ? NO  >:(
That's dangerous
 

Offline SeanB

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Re: Domestic Led Lighting project.
« Reply #10 on: May 27, 2012, 03:10:46 pm »
No, 60 LED's in parallell on a OHLJ torch is dangerous. Especially as they do current limiting by using the resistance of the thin traces, the wiring and the 4V SLA battery internal resistance. I added a 1R2 series resistor, to make it a little more sane. Wonder where I will get 4V cells when these die, they are not a common size I have seen in shops. Cyclons are very expensive.
 

Offline Zero999

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Re: Domestic Led Lighting project.
« Reply #11 on: May 27, 2012, 09:54:35 pm »
48V would be good for lighting, as there are many converters available that are meant for telecoms use which is 48V based. High enough voltage to keep current low, but only needs cheap 100v capacitors on the input side, and smallish inductors, plus the power devices are cheap as the voltage stress is low along with the current.
Another advantage is safety.
No, 60 LED's in parallell on a OHLJ torch is dangerous. Especially as they do current limiting by using the resistance of the thin traces, the wiring and the 4V SLA battery internal resistance. I added a 1R2 series resistor, to make it a little more sane. Wonder where I will get 4V cells when these die, they are not a common size I have seen in shops. Cyclons are very expensive.
RS and Farnell both sell 2 and 4V  lead acid batteries, albeit in a limited range.
 

Offline johnwa

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Re: Domestic Led Lighting project.
« Reply #12 on: May 29, 2012, 09:50:06 am »

So I need to find:
  • Wall Socket and matching plug. similar to a 10A gpo in use but with different power requirements and obviously different shape. Hopefully with a switch.
  • Inline plug and socket. for general purpose DC connections it would be good if it was the functional equivalent of an extension lead.

Hi,

I have got a similar setup going using a 24V battery backed system. There are a few options for connectors that I am considering. The Clipsal 402/32 sockets are standard for this application, see e.g: http://www.12volt.com.au/General%20Htmls/webcat2003/plugs2.html#plugs. However, these are rather expensive.

One other possibility is the IEC C19/C20 connector: http://au.mouser.com/ProductDetail/Qualtek/743W-00-02/?qs=4zF2lffhceFneFZOI9verGYnNrLlYXgx. Though nominally a 240V connector, use for this seems to be fairly rare, at least here in Australia. Good for 16A, and available in all combinations of line/panel plug/socket. You could make quite a neat job of a wall outlet using a panel socket and a standard GPO blanking plate.

I have also got a quasi-standard power over ethernet system running from my 24V supply. With suitable fusing, an RJ45 plug should be enough to run a few LEDs.



DC low current circuit breaker. I think Jaycar has some but don't know if they are any good.

These would be an option, though I am a little dubious of these thermal breakers in higher energy applications. I think you can get proper DIN rail mount magnetic breakers in low current ratings if you look hard enough.

Regarding the choice of voltage, I think 24V is a good choice for a small system like this. 12V is too low for anything larger than a vehicle. You are already four times better off with wiring losses compared to 12V. While there is a lot of 12V equipment available for the automotive market, there is still quite a bit of stuff made for 24V. This figure is used in trucks, industrial automation, printers and photocopiers, vending machines, etc, so there are plenty of things on the market to suit it. With some things, such as LED light strips, you can just run two 12V units in series as well.
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #13 on: May 29, 2012, 10:35:01 am »
Thanks johnwa.

I had seen those clipsal ones and was considering them, but as you say the price is expensive.
I like the IEC C19/C20 connectors, I think I may try them first. The shucko ones look great but obviously they could cause confusion, even in Australia.

The reason I want to go with higher voltage is I get efficiency gains in my system. I can get 14 leds running at 500mA from one channel of driver with barely a heatsink and generating a useful amount of light.
In Australia we can go to 50Vdc before the wiring needs to be done by a sparky. So I want to keep under this.
 

Offline johnwa

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Re: Domestic Led Lighting project.
« Reply #14 on: May 29, 2012, 11:11:39 am »
Yes, I think I have convinced myself to use the C19s as well. Unfortunately the plugs are a bit dearer, but I managed to snag some on eek-bay for $5 each including postage, which isn't too much more than you would pay for a normal 240V plug. Mouser also have right angle style plugs, around $8 each I think.

Fair enough on the higher voltage, if you are only running lights you probably don't need to be as flexible. I have just been running pairs of 12V LED light strips from dealextreme, without the need for any driver: http://www.dealextreme.com/p/3528-5w-75-led-380-lumen-plastic-shell-white-led-light-bulb-12v-50cm-33059?item=2.

I seem to remember reading someone managed to get a usable amount of light from 120V CFLs running from a fully charged 48VDC battery bank, though I am not sure what the life expectancy would be like running this way.

Are you planning on including a battery in your system HackedFridgeMagnet?

 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #15 on: June 02, 2012, 02:24:30 pm »
No batteries for the time being, not unless somebody donates them.

Next in line as part of this is my dimmable led driver circuit.
As far as goals for this board:
efficiency,
no flicker,
3 output channels if possible from 1 IC,
input voltage 24-48 volts.
capable of 1 amp but I am only going to run it at about 500-700 mA per channel.
dimmable by a 1 or maybe 3 pots,
low/no power when off,
temperature shutdown if possible.
no problematic em noise.
cost per unit I am not so worried about, but obviously lets not waste money.

I really want to do this as a pwm micro with discrete components.
Feel free to point out the disadvantages of this method. But I have searched without success for chips that will give what I want and haven't found them.
I will rely on a fuse for overcurrent protection if micro control fails.

Attached is the simulation of the driver part of this.  A micro will watch the current and dimmer and set the duty cycle. I have tried the Attiny461A before and it performed ok once I ironed out the oscillations.
The fets, bjts components and inductor size are not firm.
The ones in the LTSpice model are not my choices, just similar.
the actual components are
NPN: PBSS4560
PNP: PBSS5560 ( I could change to two types if there is a reason)
FET: FDMC86324

For a small explanation:
The micro sits with its Vcc on the 24volt rail and its ground on 19V (using a 7905 or similiar)
It works out the PWM(possibly a bit of PFM too)  output based on the dimmer level and the sense current.
Q4 changes level from 24-19 volts to 0-12 volts.
Q1 and Q2 totem pole output to give fast charge/discharge of the Fet's Gate.  still roughly 0-12 volts.
M1 main drive fet, drain voltage =  0-24 volts when in continuous mode.
L1 will be discontinuous at low-medium duty cycle, I can't do much about this due to the low speed.
Switching speed as fast as I can get out of an Attiny or some other micro, hopefully at least 128khz. at 8 bit pwm resolution.

I guess the first thing I want to get nailed down is what speed can I get out of an inexpensive micro, I am not sure I really need to run fast due to the nature of the leds as a load.
Then attiny or msp430. (I haven't done any PIC).
Then what Fet to use at this speed and what size inductor.
Next would be suitable drive transistors for this fet.

Another thing I have been thinking of is reducing the Sense resistance and using a rail to rail input opamp to amplify the voltage so I have some sense current resolution but with lower losses.

ps. My first version of this circuit uses the attiny at about 64kHz with L = 100uH, some cheap to220 Fet, 2n2907 and 2N2222, it does work fine, but I want to improve it where I can.
 
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #16 on: June 03, 2012, 02:11:27 am »
Does anyone know if I can run an ATTiny461A at a pwm of say 256kHertz with a resolution of at least 256 steps?
According to my calcs in fast pwm mode I should be able to get 256kz. But I have never got more than 64khz.
From memory I must've been in 10 bit mode with the main counter.

Is it possible to increase this if I use the Sigma Delta technique as implemented by Amspire and AHellene in the
https://www.eevblog.com/forum/projects-designs-and-technical-stuff/general-purpose-power-supply-design-7488/ thread?
If it is possible, which I suspect it is then I can design around this chip and this switching speed.
If it isn't then I might have to change chips or strategies.

Slightly revised driver stage with model attached.


 

Offline Kremmen

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Re: Domestic Led Lighting project.
« Reply #17 on: June 03, 2012, 02:43:34 pm »
Does anyone know if I can run an ATTiny461A at a pwm of say 256kHertz with a resolution of at least 256 steps?
According to my calcs in fast pwm mode I should be able to get 256kz. But I have never got more than 64khz.
From memory I must've been in 10 bit mode with the main counter.

Is it possible to increase this if I use the Sigma Delta technique as implemented by Amspire and AHellene in the
https://www.eevblog.com/forum/projects-designs-and-technical-stuff/general-purpose-power-supply-design-7488/ thread?
If it is possible, which I suspect it is then I can design around this chip and this switching speed.
If it isn't then I might have to change chips or strategies.

Slightly revised driver stage with model attached.
Just for your information, some time ago i implemented some led drivers for my sister's solar powered summer house. I had good luck using the Supertex HV9910 led driver that is available from DK under $2 in single quantities. Dead simple to apply and it has dimming both by analog pot or external pwm signal (a few kHz), making it easy to control by a microcontroller. Note that the external pwm is not the one driving the leds; that is defined by an RC constant in the driver (typically 100 kHz). The HV9910 is capable of off line topologies so input voltage will not become an issue. Also it can operate in constant off time mode avoiding stability issues.
Nothing sings like a kilovolt.
Dr W. Bishop
 

Offline A Hellene

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Re: Domestic Led Lighting project.
« Reply #18 on: June 03, 2012, 04:49:43 pm »
The t261/t461/t861(A) have a high speed timer-counter (TC1), which is 10-bit wide. Using TC1 in Fast PWM Mode as an 8-bit counter (by setting the TOP count (OCR1C) equal to 0xFF), the PWM cycle speed will become equal to: 64MHz/0xFF = 250KHz. But, I can see no reason why not to increase the PWM resolution and run the inductor at lower frequencies.

A problem might be the current loop, which is digitally implemented by reading the voltage drop on the LED shunt resistor (which will additionally need a typical low pass filter because the ADC might sample a zero LED current point during the transition of the inductor cycle states). The ADC can accurately run up to 15Ksps at full resolution (that is 10-bit wide) or up to five times faster at lower resolutions (8-bit accuracy, typically). Care should be taken when changing the differential or amplified ADC channels; please, read the data sheets.

A typical current loop implementation would be reading the ADC (in free-running mode) and decide either to increase or to reduce the target PWM output value by one unit, within the ADC ISR. Since this can be done fast enough, there will be no actual need for any additional PID or even PI control loops.

Now, what I would do to improve the design is to redesign the application to be ground-referenced. This will help the ADC to produce more accurate results and, thus, a more stable output.


-George
Hi! This is George; and I am three and a half years old!
(This was one of my latest realisations, now in my early fifties!...)
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #19 on: June 04, 2012, 01:18:12 pm »
Thanks Kremmen
That does look like a useful chip, 8-450volts is pretty amazing. I will bear it in mind and maybe get a few as they look like they would suit many jobs.
I do doubt that I can do better than the Supertex HV9910 but part of this is a learning experience, so I am going to continue to implement my own driver and gradually in other projects move up into higher power things.

Thanks also A Hellene
I realise there are tradeoffs everywhere designing converters, and I am in no position to make the correct decisions without a bit of testing anyway.
I was hoping that I could run at high speed an so run in continuous mode to reduce em noise, although I must say my version 1 ran fine at 64kHz. As long as I know I can get 256khz if I want it I will lay the board out assuming I may run at that speed, I can always run slower, on the same board. I will oversize my inductor just in case.

Yes a low pass filter, I don't know why I neglected it, I should know better. I actually did it in code which was stupid. This is why I am throwing my ideas out for review.
I will flip the circuit around to be ground referenced and use single sided adc. Because I know my load I am not worried about having the low side sense resistor.
Or probably I will put a rail to rail op amp in to increase my current resolution.

I am assuming A Hellene that you think the t261/t461/t861(A) are the suitable for the job, can you confirm this.
I was thinking of trying the MSP430s. I have limited AVR experience but quite a bit of experience in C++ on the Netburner modules. It takes me some time to even read assembler, I normally use C or C++ on embedded.



 If you can be bothered and are not heartily sick of the whole saga.
You should start a thread and tell us what is going on in Greece, I assume you live there, I would be interested to hear what the word on the street is.
My view from a distance is that the Greece would be better off to default and start anew. But really dont know, I only know what I hear on news.
 

Offline A Hellene

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Re: Domestic Led Lighting project.
« Reply #20 on: June 04, 2012, 03:55:13 pm »
Yes, the tinyX61 is more than enough for the job. TC1 actually is a stripped-down 3-channel Fast 10-bit Power Stage Controller with fault protection unit, dead time generator, etc. The ADC is adequately fast to monitor and regulate all the three output channels --even for an RGB LED solution, maybe.

You can also do the job by using the 8-pin t25/t45/t85 chip, whose TC1 is a single channel Fast 8-bit counter/timer, and its ADC also has a software selectable gain stage.

Using the internal 8 MHz internal RC oscillator clock (that will run slightly faster at 5.0V, since it is factory calibrated for use with Vcc=3.0V --but this can be easily corrected if needed) the AVR ADC can be running at (8MHz/32)/13.5 = 18.5 Ksps without any noticeable accuracy loss. The selectable ADC gain of 1x/8x/20x/32x can help reduce the LED current sensing shunt resistor value to a few tens of milliohms, making it possible to directly use a logic level MOSFET driven by a complementary emitter-follower stage gate driver (i.e. the 1.0A BC639/BC640 matched pair), and reading the FET source current by inserting the shunt resistor between the FET source and the ground.

You can also use both the buck or the buck-boost topologies. For the timing and the component calculations you can read the data sheets and application notes of HV9910, Kremmen suggested above.

The only problem I can see is the bloating, the use of high level programming languages (C++ or even C) will introduce, especially when CPU cycles counting becomes critical...
__________



Now, Greece should have never entered the Eurozone in the first place; just like Britain did or, more accurately, just like [The Corporation of ]The City[ of London] did with the help of the scumbag called George Soros, whose actions justified Britain's (The City's, actually) refusal to enter the Eurozone. That the Euro is a hard currency does not make it suitable to be the currency for any nation. For example, the Greek Drachma used to be one of the hardest currencies in the world until 1975, when the bankers begun shutting down sector by sector the Greek industry, and flooding steadily the country in debt since 1980:



Please note that during the ministry of Simitis, the debt did NOT decrease, as it seems it did at the chart above: This was the outcome of the "creative accounting" trick PM Simitis pulled with the help of Goldman Sachs, in order to make Greece deceptively meet the requirements to join Eurozone.

What needs to be done (or, needed to have already been done) is Greece to renounce that Goldman Sachs loan as Odious Debt; but to do that we need politicians of integrity and not the bankers' clowns our Parliament is infested with...


-George
« Last Edit: June 04, 2012, 04:43:02 pm by A Hellene »
Hi! This is George; and I am three and a half years old!
(This was one of my latest realisations, now in my early fifties!...)
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #21 on: June 04, 2012, 10:55:34 pm »
Quote
need politicians of integrity and not the bankers' clowns our Parliament is infested with...]need politicians of integrity and not the bankers' clowns our Parliament is infested with...
Yes, I think we have some of the same politicians, only ours are doing more hours for the mining industry than the bankers at the moment.
« Last Edit: June 05, 2012, 12:30:14 am by HackedFridgeMagnet »
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #22 on: June 04, 2012, 11:26:00 pm »
Thanks for the input
Ok a couple more descision made,
No external op-amp to amplify the current sense, I will investigate the software selectable gain stage.
I will brush up on the Avr assembler,
Now I need to choose between either the tinyX61 (3 channels) or the t25/t45/t85 chip (1 channel)
then I can layout a prototype.
 

Offline A Hellene

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Re: Domestic Led Lighting project.
« Reply #23 on: June 05, 2012, 12:21:38 am »
You are welcome!

Since breadboarding can save you lots of time, almost any stage of this project can be breadboarded; with the exception of the high current paths.

Additionally, do not be afraid of making mistakes because mistakes are the best teachers any designer can have.


-George
Hi! This is George; and I am three and a half years old!
(This was one of my latest realisations, now in my early fifties!...)
 

Offline HackedFridgeMagnet

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Re: Domestic Led Lighting project.
« Reply #24 on: June 05, 2012, 12:56:50 am »
No, I'm not afraid of making mistakes, sometimes that's my problem.
 


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