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511  General Category / General Discussion / parasitic ram explot.. on: March 08, 2014, 09:55:07 am
http://wp.josh.com/2014/03/03/the-mystery-of-the-zombie-ram/

Change the led for a capacitor, avoid eeprom completely?  But is it damaging?
512  Products / Arduino Due / Re: Operating Voltage for components on: March 08, 2014, 09:25:22 am
Gnd/5v (to power the sensor) is fine from the due...

What's not fine is the 5v logic signal, you will need to step it down... zener, voltage divider, regulator before it's fed back to the due.
513  Using Arduino / Project Guidance / Re: calling all experts - need a bit breaduino help... on: March 08, 2014, 09:12:58 am
The two caps on each side of the crystal, you only have 1 correctly seated.

514  Using Arduino / General Electronics / Re: Control 3 LEDs with 2 pins on: March 08, 2014, 06:40:27 am
http://electronicsclub.info/cmos.htm

A 4028 binary to decimal decoder ic will do the job... the other way might be to use logic gates and build your own.
515  Using Arduino / General Electronics / Re: power leds driver on: March 08, 2014, 06:28:23 am
This series has a great explanation of the different ways of driving a power led. There is also a really simple design for an efficient driver.

That driver may be simple, but it's not efficient. It will waste as much power as a resistor.




Replace the fet with an npn ...


What's your complaint with this type of circuit?... inefficient how (for what it does)
516  Using Arduino / General Electronics / Re: input voltage = forward voltage = no resistor required? on: March 06, 2014, 09:54:05 am
http://flashlightwiki.com/Driver#Direct_Drive

Quote
Direct Drive
17mm linear regulator driver with 4 7135 chips and microprocessor
If you apply the correct voltage, you don't need a driver at all. Lithium-ion batteries conveniently provide a decent voltage without any further modification. This is quite efficient since all of the power from the battery is delivered to the LED. However a fresh li-ion battery starts at 4.2 volts fully charged and will be 3.6 volts when it needs to be recharged. As power is applied to the LED, it will draw a certain amount of current from the battery. This current increases with the voltage. When the voltage is higher, the LED will be very bright and draw a great deal of current. As voltage decreases the light will dim and draw less current. If a constant brightness is desired, a driver that offers some kind of regulation is required. Also, many LEDs are being overdriven by 4.2 volts of a fresh li-ion battery.

next you'll be telling me, all flashlights without constant current regulators will kill the LED....

Next you'll be telling me, my flashlight no longer works  because there's no current limiter in place, just a flashlight, LED and the body (ie, the heatsink) and i've used it > 500 hours.

The heatsink prevents it from getting hot enough to self destruct, something this LED string lacks... and i agree, current needs to be limited.

You probably don't agree with that either....  but there's PLENTY of people in the flashlight world who would tell you, you're talking crap when you say you need a constant current driver for ALL LED'S this is simply un freaking true.
517  Using Arduino / General Electronics / Re: input voltage = forward voltage = no resistor required? on: March 06, 2014, 09:48:15 am
And still the rubbish continues!

it's only rubbish if it's untrue.

And are you now going to claim that i never actually did this test and experimented with temperature ? even though i've had a 5mm LED running for days on end monitoring current and voltage? did it blow up after a week? no..

Did i place the LED in an unknown environment where it could get hot and self destruct? no...

Am i claiming it's safe to run it at it's max current to do this?.. no...


So it's not rubbish, it's fact...   do i need to create an Arduino project to monitor the heat in the room and current draw over a range of temperatures and log the data ?


Which part are you failing to agree with?
518  Using Arduino / General Electronics / Re: Solid State Relay, but normally closed on: March 06, 2014, 09:42:04 am
a prebuilt, SSR (ie one you're not making yourself using a TRIAC) should already have an optoisolater for the low voltage DC side to switch the 240/120ac side right?.

so as already suggested, use transistors to keep the SSR normally closed. 
519  Using Arduino / General Electronics / Re: input voltage = forward voltage = no resistor required? on: March 06, 2014, 09:25:01 am
Quote
When adequately heatsinked, the temperature won't rise further increasing the current,
That is just rubbish, please try and refrain from making comments on things you do not know about.

Utter Crap.

Quote
I tried with a 10watt left it for days on end in 40c heat, monitoring it's current draw, I've done it, it works fine I have the proof, I'm using the same method as we speak for an ssc p7 driving it at a constant 3.8v which has been pulling a steady 280ma  for days on end. .

That is not how you make a meaningful test of things. Perhaps living in 40C heat has affected more than you think. Any component dissipating power will get hotter that the heat sink. It has to, this is the law of thermodynamics. This will form a temperature gradient between the component and the heat sink. This happens no matter what the ambient temperature is.

Utter Crap.

Quote
So yes, providing it's heatsinked, driving an led by voltage is safe to do...
No it is not!!! You over simplify things. You can not make sweeping statements like this. Well of course you can make a statement like this but it is very wrong.

Quote
So please don't bring 20ma little leds into the argument.

If you had bothered to read this thread from the start you will have realised that it IS about small LEDs NOT power LEDs. You have got hold of the wrong end of the stick again!

Utter Crap.



This is about the FORWARD voltage of the LED and if it's safe to do so, yes it is.... if you can control the temperature and a heatsink would do it adequately

it's called "Direct Drive" higher powered LED's have a base in which to transfer the heat, Surface Mount also have this ability and this is surface mounted...  if he ran this LED at say 60% of the max current allowing for heat fluctuations, it would be safe.

[edit]

yes, these are surface mount LEDs but not soldered directly to copper pads which i thought they were, but my argument still stands.... run these 30% below the max forward voltage, to account for heat fluctuations, and it will be fine...  but due to their size and lack of heatsink, it is a concern.. i'd probably not attempt it with this string.
520  Using Arduino / Networking, Protocols, and Devices / Re: Unique MAC addresses? Best practice? on: March 06, 2014, 06:09:00 am
Which version of delphi?  Quickest way would be to generate a TstringList and save the list,  turn on the no duplicates property then spit out the mac address to each new unit (generate a random one to begim with to make sure there's no conflict) and store it on eeprom.
521  Using Arduino / General Electronics / Re: input voltage = forward voltage = no resistor required? on: March 06, 2014, 05:35:14 am
Quote
. heatsink the led and it wont,
You seem to know little about heatsink.
Even if you have an infinite heat sink there is a thermal gradient between the device and the ambient. Then how do you stop the ambient changing?

When adequately heatsinked, the temperature won't rise further increasing the current, I tried with a 10watt left it for days on end in 40c heat, monitoring it's current draw, I've done it, it works fine I have the proof, I'm using the same method as we speak for an ssc p7 driving it at a constant 3.8v which has been pulling a steady 280ma  for days on end. .

The only thing I may question is driving it at it's max current using this method.

http://flashlightwiki.com/Driver#Direct_Drive

So yes, providing it's heatsinked, driving an led by voltage is safe to do...


So please don't bring 20ma little leds into the argument. Because then I agree and you know that.
522  Community / Products and Services / Re: Hi, We are launching ChipCrate to give you parts to make one project a month on: March 05, 2014, 11:24:46 pm
You supply a pi or arduino for a small fee, we supply the board?

What kind of board? Breadboard? Citcuit board?  A clipboard?  A wooden board?  Water boarding?  Lol
523  Using Arduino / General Electronics / Re: Arduino a Transistor and the right resitstor on: March 05, 2014, 09:06:38 pm
A 220ohm would be plenty of current...

Do you have it wired correctly?
524  Community / Website and Forum / Nick Gammon? on: March 05, 2014, 04:23:09 pm
I've not seen any posts from him in a while  smiley-eek

Health issues? Did he leave?
525  Using Arduino / General Electronics / Re: input voltage = forward voltage = no resistor required? on: March 05, 2014, 07:04:24 am
Quote
Mike although correct, is also wrong if you can keep the temperature at a constant which difficult to do with leds under a watt or so.
No Mike is also correct and correct.
It is totally impractical to keep a power LED at a constant temperature.
Even if you could keep a constant temperature, you can not stop the forward voltage changing with the age of the device.

However this is nothing to do with this thread as the LEDs involved are not power LEDs, they are just normal low current LEDs with built in resistors so no external resistors, or other form of current control, are required.

Nope mike is partly right... heatsink the led and it wont, just you can't really do that with low power leds (eg 5mm)
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