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Old 01-03-2013, 03:05 PM   #76
tdcarter
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Quote:
Originally Posted by craftycoder View Post
I don't know what a buck puck is but I assure you the only thing you need to run LEDs other than this box is a current limiting resistor setup so that the maximum current allowed through the circuit is <= the max through the LEDs.
Sorry.. a buckpuck is a name brand of a LED constant current driver. Name just kind of means generic constant current to the DIY led community now. A buckpuck is when your supply voltage is higher the the forward voltage of the leds, a buckboost is a current limiter and voltage booster used when your supply voltage is lower then the leds required forward voltage.

A quick run-down of what I was referring too..
So a resistor will limit current, but only a specified amount at a specified voltage. Has to be calculated each/every time. Increase voltage and the current flow can increase too. A buckpuck (aka constant current supply) limits the supply but lets voltage float, upto an amount that is slightly less then the supply side. With a constant current supply there is no need for the resistor to limit the Led. As long as your string of leds have a forward voltage less then the supply, you can control their brightness by limiting current. If forward voltage is greater then supply, you can still limit current but the led's will not achieve max brightness.

If you pop open a high quality led light you won't find any current limiting resistors in line with the led's themselves. Using a resistor to save an led from runaway is an inexpensive way to do it when you know the supply voltage and have limited amounts of low light leds. But when you start talking high power led's, varying voltage supplies, resistors would not be a very efficent way to go. Now you'd have to worry about the heat the resistors generate and your losing supply power to that resistor, killing your batteries faster then necessary. Plus as the batteries drop voltage when they age the led's will dim since available current will drop due to the resistor being a fixed value. Again, resistor, cheap and easy for small led, constantly wastes energy, not effective for high power.

Onto the variable part.

Using pwm to flash the led's on/off faster then we can see is one way to dim them. There is where I have seen some pwm (dimmers) cause problems. The buckpuck or buckboost (ie the led driver) does not like the frequency that the dimmer is using. Not real common occurrence, but it happens. Low powered led's that are using resistors for current limit don't really care about the current being pulsed. But if you can just flat out limit the current, and by varying the current you adjust the brightness, it's even better and ultimately more efficient.

Clear as Mississippi mud? and more then you wanted to hear?
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Old 01-03-2013, 03:48 PM   #77
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I am familiar with the idea of constant current. I guess I just fundamentally disagree with the common knowledge. The definition of a constant current is a constant voltage through a constant resistance. Therefore, using a resistor to limit the current is no more inefficient than using a constant current supply as the resistor doesn't use extra current, it just limits it which is all the active constant current circuit is doing. What it DOES do is require you to set the resistor to a conservative value or risk blowing the semiconductor during transients. This actually means that on average you should use less power with a resistor compared to a constant current supply. The cost of this will be the max brightness you can attain.

So, if the complaint was that you need all the light possible and a resistor leads to LEDs being too dim, I'd buy it. Efficiency, I am not buying. Personally, I don't worry about maximum brightness. I'm putting on the aux lights because my main light is a giant steel grill in front of it to protect it from flying rocks and its covered with mud so I can't see the damn road until the next river crossing. If I was really concerned about max brightness I'd not ride in the mud.

My system does NOT boost the voltage so you will have to concern yourself with forward voltage drop if you have too many LEDS in series. I also doesn't do any voltage regulation (short of cutting out transients above 18V). My system therefore would not allow you to get "maximum" life span and "maximum" brightness out of your LEDs but they are still going to be damn bright and you will be able to control them from your phone from the campfire when you want to see what just flew into your can of Dinty Moore stew.

This will all be irrelevant if I can get a fast enough data feed from my current sensors to create an active constant current supply. If I can, I'll short out some wires on video and post it up for all to see. Then, I'll send you a virtual beer for the fine idea.
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Old 01-04-2013, 05:04 AM   #78
tdcarter
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This will all be irrelevant if I can get a fast enough data feed from my current sensors to create an active constant current supply. If I can, I'll short out some wires on video and post it up for all to see. Then, I'll send you a virtual beer for the fine idea.
Waiting on the beer... and the opportunity to purchase/install a High Tech Fuse Block...
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Old 01-06-2013, 02:54 PM   #79
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This is a report on constant current function requested. It works relatively well for moderately low resistant circuits. In this test I have a 10Ω load and it works very well, albeit a lot slower than an analog constant current supply. So, while my concerns about speed were well founded this is a reasonably useful way to control constant currents. Will this feature make it into the final design? I'm not sure... If I thought constant current was vital, I'd prefer to do it in the analog domain which is generally faster than doing things digitally. Is this a reasonably useful feature? Yes. It does still require that you add a little impedance to the circuit to prevent your LEDs from popping (because of the speed the circuit reacts), but much less than required without any constant current control.



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Waiting on the beer... and the opportunity to purchase/install a High Tech Fuse Block...
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Old 01-07-2013, 04:07 PM   #80
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Example showing interactive use of the constant current mode with an iPhone.

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Old 01-08-2013, 10:53 AM   #81
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I think i'll have to get one just because you use Rush for your background music.. :)
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Old 01-08-2013, 10:55 AM   #82
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I think i'll have to get one just because you use Rush for your background music.. :)
Being an ATL guy like me, you can get an early version even ;^)
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Old 01-08-2013, 12:35 PM   #83
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Sure enough, never saw that before. Mine will be considerably smaller than that one (but only 40A as well). It certainly has the significant advantage of being available for purchase.

The expandable card system we have and the programmability are a significant upgrade in terms of feature set... It's nice to know we are not alone.
Can you expand on this? I'm a user of the Disptach 1, and would love to learn about what your product offers vis-a-vis them so that I can consider your product!

Nate
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Old 01-08-2013, 01:13 PM   #84
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I've moved on from the card system to a completely encapsulated system without fuses (it uses digital circuit breakers instead). I decided the cards were just not tough enough for autos. I think the biggest differentiation is that this is bluetooth controlled and 100A. I am not familiar with the Dispatch except that I know it's real and this is still in R&D mode. Which is to say that it is not yet real. It gets a little more real each day though. Keep your eyes peeled to this thread. I've been posting my progress with videos as I reach milestones.

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Can you expand on this? I'm a user of the Disptach 1, and would love to learn about what your product offers vis-a-vis them so that I can consider your product!

Nate
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Old 01-08-2013, 01:31 PM   #85
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Originally Posted by craftycoder View Post
I am familiar with the idea of constant current. I guess I just fundamentally disagree with the common knowledge. The definition of a constant current is a constant voltage through a constant resistance. Therefore, using a resistor to limit the current is no more inefficient than using a constant current supply as the resistor doesn't use extra current, it just limits it which is all the active constant current circuit is doing.
All true if the "constant current supply" is not using PWM. The bucks use PWM ... if you are using that too to get your "constant current" then the efficiency should be similar.

Some systems for LEDs don't bother with a true constant current, they use the LED and light persistence to do the filtering on the PWM signal... leads to better efficiency.
---------------------------
A note on the horns...
On page 1 you said something like "One horn button - initial operation to the normal horn, after 1 second to the loud horn." Sorry but if someone wants the loud horn they want it now... not after any delay. In any emergency situation you want help NOW.

PS your definition .. well what happens if the resistance is not constant? EG a common light globe. Think about your Thévenin's and Norton's Theorems ! I stay away from definitions in most forums, they confuse rather than help?

----------------
There are some EMI regs that you may have to meet... FCC? Or some other gov agency.

Warin screwed with this post 01-08-2013 at 01:42 PM
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Old 01-08-2013, 01:43 PM   #86
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I think I am more likely to find the horn I normally tap, so I'm willing to use it knowing that I'll have a LOUD horn on the way. That was not my idea, but it is a good one. It may not be for you, but when fit hits the shan I won't find the loud horn if I rarely use it. The delay is welcome in that exchange.

Quote:
Originally Posted by Warin View Post
All true if the "constant current supply" is not using PWM. The bucks use PWM ... if you are using that too to get your "constant current" then the efficiency sould be similar.

---------------------------
A note on the horns...
On page 1 you said something like "One horn button - initial operation to the normal horn, after 1 second to the loud horn." Sorry but if someone wants the loud horn they want it now... not after any delay. In any emergency situation you want help NOW.

PS your definition .. well what happens if the resistance is not constant? EG a common light globe. Think about your Thévenin's and Norton's Theorems ! I stay away from definitions in most forums, they confuse rather than help?

----------------
There are some EMI regs that you may have to meet... FCC? Or some other gov agency.
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Old 01-08-2013, 02:19 PM   #87
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I'm pretty excited about this Crafty. This incorporated with DSM and running on a 7 inch tablet would be an awesome heads up display.
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Old 01-08-2013, 02:22 PM   #88
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I was thinking the same thing.

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I'm pretty excited about this Crafty. This incorporated with DSM and running on a 7 inch tablet would be an awesome heads up display.
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Old 01-08-2013, 02:23 PM   #89
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Old 01-08-2013, 02:35 PM   #90
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interesting... long time flashlight/LED nut here ...

here's an ancient pic testing forward voltage of a 5watt Luxeon LED with a vf of 5.99v. which used to be king of the hill in output. but those days are long past.




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