mm95z71
New member
$.29? Ouch. I don't blame you for keeping your electricity usage low. Thank God for natural gas reserves in OK. I'm right at $.08 per kwh.
DIY LEDs - The write-up
- Thread starter JohnL
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$.29? Ouch. I don't blame you for keeping your electricity usage low. Thank God for natural gas reserves in OK. I'm right at $.08 per kwh.
mdisalvo55
New member
I just glued down my 6 LEDs from the Rapidled.com 6 premium LED DIY kit. I wired up the driver (didn't ground it, is this okay?). Then I touched the positive wire to the positive side of an LED, and the negative to the negative of the same LED...I was assuming I could do this..but it looks like I blew the light. Will I be okay to wire the 5 I still have to the driver or do I need the replacement?
der_wille_zur_macht
Team RC
What driver are you using? Did you adjust anything on it prior to your experiment?
stugray
Premium Member
mdisalvo55,
"then I touched the positive wire to the positive side of an LED, and the negative to the negative of the same LED"
Sorry! I have posted before to never do this with a Constant Current driver.
When you turn it on Open circuited ( no Load ), it will turn up to it's maximum voltage trying to get to the target current.
Then when you abruptly apply the load ( LED ) the LED sees the max voltage of the driver & POOF!
Did that twice before I figured it out & I am supposed to know better.
Hook em up first then turn it on.
DWZM - did you see my comment on the last page about an even Cheaper way to drive a string? probably should have posted in on your driver thread.
Stu
"then I touched the positive wire to the positive side of an LED, and the negative to the negative of the same LED"
Sorry! I have posted before to never do this with a Constant Current driver.
When you turn it on Open circuited ( no Load ), it will turn up to it's maximum voltage trying to get to the target current.
Then when you abruptly apply the load ( LED ) the LED sees the max voltage of the driver & POOF!
Did that twice before I figured it out & I am supposed to know better.
Hook em up first then turn it on.
DWZM - did you see my comment on the last page about an even Cheaper way to drive a string? probably should have posted in on your driver thread.
Stu
mdisalvo55
New member
The meanwell LPC-35-700 that came in the kit...I didn't adjust anything, is there something I should have adjusted?
mdisalvo55
New member
stugray-Thanks for the info, I figured that was what I did...price I pay for being so curious. Am I safe to wire up the 5 that are still good then? Since I'm going to order another LED, I was wondering how many can I power with this driver?
stugray
Premium Member
"You're safe up to 12 LEDs on a meanwell "
Be careful. There are a LOT of different Meanwells.
I cant tell what model from the pic.
Tell us the models number from the case of the driver.
Sammy113 is correct if it is a ELN-60-48.
In THAT case you need to turn it down, but that looks like a CC 700mA or something similar.
EDIT:
I found it , it is a LPC-35-700W
So it can drive 12 XR-Es at a max of 33.6 Watts
Stu
Be careful. There are a LOT of different Meanwells.
I cant tell what model from the pic.
Tell us the models number from the case of the driver.
Sammy113 is correct if it is a ELN-60-48.
In THAT case you need to turn it down, but that looks like a CC 700mA or something similar.
EDIT:
I found it , it is a LPC-35-700W
So it can drive 12 XR-Es at a max of 33.6 Watts
Stu
mdisalvo55
New member
Thanks for all the help!
der_wille_zur_macht
Team RC
And be sure you know the properties of the driver, in terms of min/max output and what current it's set to!
Yeah, still trying to wrap my head around how that would/wouldn't work. Wouldn't the flicker from the lumpy rectified 60hz A/C be visible to the human eye, even if the LEDs managed to not self-destruct? Plus, is it really worth it to spend for an UPS to regulate the voltage, vs. a few bucks for a driver?
Crazy35111
New member
Any thoughts on which is better to use as a splash guard for the led fixture...glass or plexiglass?
Crazy35111
New member
Wondering about the effects it has on the lighting
laverda
Well-known member
Considering most people through away old UPSs instead of buying new batteries for them, you can get them for free.
stugray
Premium Member
"Wouldn't the flicker from the lumpy rectified 60hz A/C be visible to the human eye,"
We dont see the flicker of 60Hz Incandescent.
A properly ( should have said FULL WAVE in the OP ) rectified AC wave would look more like 120Hz On/Off.
" even if the LEDs managed to not self-destruct?"
No reason they would if the string was long enough.
"Plus, is it really worth it to spend for an UPS to regulate the voltage, vs. a few bucks for a driver?"
Yes because a UPS ( power conditioner ) could drive dozens of these strings at a time.
Each string could be dimmed with it's own Triac.
Still just thinking & waiting for someone to tell me what I missed.....
Stu
We dont see the flicker of 60Hz Incandescent.
A properly ( should have said FULL WAVE in the OP ) rectified AC wave would look more like 120Hz On/Off.
" even if the LEDs managed to not self-destruct?"
No reason they would if the string was long enough.
"Plus, is it really worth it to spend for an UPS to regulate the voltage, vs. a few bucks for a driver?"
Yes because a UPS ( power conditioner ) could drive dozens of these strings at a time.
Each string could be dimmed with it's own Triac.
Still just thinking & waiting for someone to tell me what I missed.....
Stu
kcress
New member
What you missed...
You might still see flicker because unlike an incandescent that is hot and takes a finite amount of time to cool a LED really would go on and off. So what happens is if you look right at the tank you won't see any flickering but as you walk by the tank you can see it flickering out of the corner of your eye. That can be very annoying.
Also, you cannot run them as bright as you can with a driver because the peak voltage of a sinewave will over volt and hence over current the LEDs. So as you turn down the voltage to the point where the peaks aren't harmful or fatal to the LEDs the rest of the time the LEDs are under driven - a lot-. The result is that AC driving the LEDs results in less output. Something like 20% if I remember correctly.
Lastly you may end up with some dangerous voltages available or non-isolated voltages. Of course if you make sure everything is seriously covered and g r o u n d e d it can still be safe.
I have one of the original AC driven LED flood lights that you screw into a standard socket. It cost me about $300, is all clear, so you can see the resistors and bridge rectifiers and it totally SUX. A single CREE would triple eclipse it.
You might still see flicker because unlike an incandescent that is hot and takes a finite amount of time to cool a LED really would go on and off. So what happens is if you look right at the tank you won't see any flickering but as you walk by the tank you can see it flickering out of the corner of your eye. That can be very annoying.
Also, you cannot run them as bright as you can with a driver because the peak voltage of a sinewave will over volt and hence over current the LEDs. So as you turn down the voltage to the point where the peaks aren't harmful or fatal to the LEDs the rest of the time the LEDs are under driven - a lot-. The result is that AC driving the LEDs results in less output. Something like 20% if I remember correctly.
Lastly you may end up with some dangerous voltages available or non-isolated voltages. Of course if you make sure everything is seriously covered and g r o u n d e d it can still be safe.
I have one of the original AC driven LED flood lights that you screw into a standard socket. It cost me about $300, is all clear, so you can see the resistors and bridge rectifiers and it totally SUX. A single CREE would triple eclipse it.
der_wille_zur_macht
Team RC
This tangent has raised a subject I'm a little curious about. What's in the "first half" of a meanwell driver? In my DIY driver adventures I've come across reference designs that show a DC/DC chip being used with a bridge rectifier and a cap to generate a DC voltage:
Of course for a chip with a low voltage requirement (like this one) you'd need a transformer before the circuit to step the voltage down. Besides having some of the problems kcress is raising, what else is wrong with that? efficiency? Is it "harder" on the IC? Do the meanwells use a simple design like this or something more complicated? When I look at the complexity of the PCB in the DC power supply I'm using, it' strikes me as WAY more junk than would fit inside the case for a meanwell driver, so I'm curious.
Of course for a chip with a low voltage requirement (like this one) you'd need a transformer before the circuit to step the voltage down. Besides having some of the problems kcress is raising, what else is wrong with that? efficiency? Is it "harder" on the IC? Do the meanwells use a simple design like this or something more complicated? When I look at the complexity of the PCB in the DC power supply I'm using, it' strikes me as WAY more junk than would fit inside the case for a meanwell driver, so I'm curious.
Santoki
Shimmer Addict
der_wille_zur_macht
Team RC
While we're on the subject, I'll add to that something that's been repeated many times but is still important: If you're using the ELN60-48 model, it's TOO POWERFUL at the max current setting. You MUST open it up and turn down the current trimpot BEFORE turning it on with LEDs attached. The best practice is probably to turn it down all the way, wire things up, turn the rig on, measure current, and adjust the pot upwards if needed.
Also, the ELN60-48 is commonly used with 12 LEDs. That's fine for the typical LEDs we're using. If you want fewer (or more, I guess) keep in mind that it's only spec'd to operate in constant current mode between 24 and 48 volts. So DON'T wire it to a single LED! Even if you have the trimpots turned all the way down, according to the specs, it can't operate in constant current for less than 24v, which is roughly 7 typical LEDs.
And since the XP-G is becoming more common, it bears noting that it runs at a lower Vf than XR-E or Rebels - so people using XP-G should check the datasheet and check their math.
Also, the ELN60-48 is commonly used with 12 LEDs. That's fine for the typical LEDs we're using. If you want fewer (or more, I guess) keep in mind that it's only spec'd to operate in constant current mode between 24 and 48 volts. So DON'T wire it to a single LED! Even if you have the trimpots turned all the way down, according to the specs, it can't operate in constant current for less than 24v, which is roughly 7 typical LEDs.
And since the XP-G is becoming more common, it bears noting that it runs at a lower Vf than XR-E or Rebels - so people using XP-G should check the datasheet and check their math.
widmer
Drug Enthusiast
Question:
Does anyone forsee any problem with having ~15 ft of cord between my 24V DC power supply and the buck pucks? I know that on the buck puck data sheet it says that there should be a capacitor on the input side if it's greater than 18" which I can do. But is there any problem with going way beyond 18"? I was going to use standard 14 awg lamp cord...
This is pretty exciting, just got the confirmation email that LEDSupply is sending the Cree 8 degree optics, which should cast a ~12" diameter beam at 5 or so feet, which is exactly what I need at long last...
Does anyone forsee any problem with having ~15 ft of cord between my 24V DC power supply and the buck pucks? I know that on the buck puck data sheet it says that there should be a capacitor on the input side if it's greater than 18" which I can do. But is there any problem with going way beyond 18"? I was going to use standard 14 awg lamp cord...
This is pretty exciting, just got the confirmation email that LEDSupply is sending the Cree 8 degree optics, which should cast a ~12" diameter beam at 5 or so feet, which is exactly what I need at long last...
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