perikaruppan
Member
thanks fishman. what shall be power resistor ratings required? driving the chip at 500ma
DIY LED driver for reef lighting
- Thread starter der_wille_zur_macht
- Start date
TheFishMan65
New member
About
40.5 volts (supply) - 21 (LEDs - double check drop at 500 ma) gives 19.5 drop on the resistor
Now current, voltage, and resistance are related as Volt = current * resistance (V = IR).
So 19.5 = R * .5 or resistance of 39 ohm. A little less and the chip has to drop some which should be OK. A little more and you may have to turn up your power supply. This is assuming the chip doesn't need some operating room. Can't remember right now. One of the ones discussed here needed 2 volts.
40.5 volts (supply) - 21 (LEDs - double check drop at 500 ma) gives 19.5 drop on the resistor
Now current, voltage, and resistance are related as Volt = current * resistance (V = IR).
So 19.5 = R * .5 or resistance of 39 ohm. A little less and the chip has to drop some which should be OK. A little more and you may have to turn up your power supply. This is assuming the chip doesn't need some operating room. Can't remember right now. One of the ones discussed here needed 2 volts.
der_wille_zur_macht
Team RC
Maybe it's just me, but I can't see going through this much trouble just to turn it on for a second and say "yep it didn't fry my LEDs" especially since we know the ZXLD chip is picky about matching input voltage to the load it'll actually be running when installed. If it were me, I'd just wire it up to the number of LEDs you'll be running on it when it's installed in your system and test it. If you're worried about some malfunction frying your string of LEDs, just put a fuse in series with the LEDs while you test.
Otherwise, if you come up with some test circuit that's made up of a combination of LEDs and power resistors, you'll probably have to re-test when you finally wire it to the LED load it'll actually be running, to see if it's dropping an acceptable voltage, driving the LEDs at the right current, not overheating, etc.
Otherwise, if you come up with some test circuit that's made up of a combination of LEDs and power resistors, you'll probably have to re-test when you finally wire it to the LED load it'll actually be running, to see if it's dropping an acceptable voltage, driving the LEDs at the right current, not overheating, etc.
perikaruppan
Member
thats fishman and DWZM.
I accept with you der. So I will fire up 12LEDS with a 1A fuse in series.
+PWR ---> 1A Fuse ----> LED String ----> -PWR
I accept with you der. So I will fire up 12LEDS with a 1A fuse in series.
+PWR ---> 1A Fuse ----> LED String ----> -PWR
kcress
New member
perikaruppan; I hate to say this but you should NOT bother to use that 48V supply at all. That is like using a sledgehammer to hang a picture on the wall. It's entirely the WRONG tool. You live in the land of power supplies! Go find a 24VDC supply.
The chance of a slightly wrong move blowing all your LEDs or your driver board are greatly increased using your existing supply.
If you do get it working, without disaster befalling you, you'll have a system running that is less efficient than a MH installation. "Why'd you bother?" sort of deal.
The chance of a slightly wrong move blowing all your LEDs or your driver board are greatly increased using your existing supply.
If you do get it working, without disaster befalling you, you'll have a system running that is less efficient than a MH installation. "Why'd you bother?" sort of deal.
TheFishMan65
New member
kcress,
I have to disagree. Why is it wrong with 12 LEDs?
I will agree that there MAYBE a slightly higher risk of damge while building, but not if he understands the issues.
Why do you think it will be inefficient? 12 LEDS at about 3.5 volts is 42 volts. The 40 volt will need to be turned up some (or maybe not since 3.5 is just a guess). So it should be fairly effieicient.
I have to disagree. Why is it wrong with 12 LEDs?
I will agree that there MAYBE a slightly higher risk of damge while building, but not if he understands the issues.
Why do you think it will be inefficient? 12 LEDS at about 3.5 volts is 42 volts. The 40 volt will need to be turned up some (or maybe not since 3.5 is just a guess). So it should be fairly effieicient.
der_wille_zur_macht
Team RC
kcress, I read it that he's testing with 6 LEDs for fear of blowing more, then will be running the drivers with more LEDs when it's actually over his tank. Maybe I'm wrong though.
TheFishMan65
New member
I read this as testing with 12.
der_wille_zur_macht
Team RC
TheFishMan65
New member
I thought he modified that after our responses. Hey, pericaruppan what number of LEDs are you going to test with. Also would you remind me of what LEDs you are using.
thanks
thanks
SpacedCowboy
New member
Google how you will, I doubt you'll find either a simpler or a cheaper driver circuit than I posted back on page 13 (post #302). It's 4 components!
Simon.
@shackscs: The meanwell LPC35 put out 9v minimum, which will cook a single led.
Doesnt explain how you killed 5 of the others in series.
@thefishman: the meanwell ELN60 are adjustable via internal screws.
They are rated at 1.3amp, but factory can be out. (mine are dialed 950ma).
The LPC35 are different beast, totally sealed, IP67 waterproofing.
No adjustment or dimming.
---
Was there any further news on Macroblock MBI6651 ?
Sure Electronics have their 700ma board for $3.99
Wondering if easier to ask them to make 1000ma or 1400ma for xpe/xpg.
Doesnt explain how you killed 5 of the others in series.
@thefishman: the meanwell ELN60 are adjustable via internal screws.
They are rated at 1.3amp, but factory can be out. (mine are dialed 950ma).
The LPC35 are different beast, totally sealed, IP67 waterproofing.
No adjustment or dimming.
---
Was there any further news on Macroblock MBI6651 ?
Sure Electronics have their 700ma board for $3.99
Wondering if easier to ask them to make 1000ma or 1400ma for xpe/xpg.
perikaruppan
Member
sorry Fishman, DWZM and Kress... for the delayed response.. live in a +12hr time zone!!!
Well first of all i went with the thought of DWZM that if i test it right with a resitor and when i do it will the string of 12 then if it blows i wont be able to solve the problem.. might as well test it will the 12 string.
Kress not using my regular power supply, purchased a brand new MEANWELL SMPS - 48V/7.3A = 350W power supply to power up my LED string. There is an adjuster pin using which i can reduce it to 40.5V or max it to 51V.
I reduced it to 41V and strung in 10 LEDs as that is what the spread sheet indicated.
keeping my fingers crossed... i kept the switch pretty far off from the Setup and like testing a bomb, i switch ON the supply and RAN a few yards!!! and IT WORKED!!!... all the 12 LEDS GLOWED well. But with a problem!!!
The problem the ZXLD chip got hot pretty fast in abt 30-40 seconds itself.. so i turned off the lights. and then turned them on and off in short phases and tested the Voltage and current across the LEDS ... whola it was 3.77V (=37.7V, with a drop of about 3.3V across the system) and the current was the estimated 500mA.
Now what is going wrong here? do i need to ADD one more LED to the string to reduce the voltage across them? will that help?
Well here are the specs of the components used on teh ZXLD:
RSense - 0.33 Ohms / 1 Watt
Capacitor - 10uF / 63V Rating
Inductor - 220uH (Resistor model, not the coil one)
ADJ pin - did the circuit with a transistor and resistor as indicted by DWZM and the spec sheet, and left the input to the Resistor Pin (PWM) floating.
DIODE - BAT49 (http://www.datasheetcatalog.org/datasheet/stmicroelectronics/3297.pdf)
And one more thing, when i tested for the current across the LED, when i kept the multimeter probes over the LED only that LED dimmed drastically, is this alright? or will i be damaging the LED?
actually what worries me the most is that i made 8 ZXLDs in a PCB of 100mmX100mm!!! tiny it is : and it is estimated to control 84 LEDS.. now that makes me scared.
Now what can i do to reduce the heat?
Well first of all i went with the thought of DWZM that if i test it right with a resitor and when i do it will the string of 12 then if it blows i wont be able to solve the problem.. might as well test it will the 12 string.
Kress not using my regular power supply, purchased a brand new MEANWELL SMPS - 48V/7.3A = 350W power supply to power up my LED string. There is an adjuster pin using which i can reduce it to 40.5V or max it to 51V.
I reduced it to 41V and strung in 10 LEDs as that is what the spread sheet indicated.
keeping my fingers crossed... i kept the switch pretty far off from the Setup and like testing a bomb, i switch ON the supply and RAN a few yards!!! and IT WORKED!!!... all the 12 LEDS GLOWED well. But with a problem!!!
The problem the ZXLD chip got hot pretty fast in abt 30-40 seconds itself.. so i turned off the lights. and then turned them on and off in short phases and tested the Voltage and current across the LEDS ... whola it was 3.77V (=37.7V, with a drop of about 3.3V across the system) and the current was the estimated 500mA.
Now what is going wrong here? do i need to ADD one more LED to the string to reduce the voltage across them? will that help?
Well here are the specs of the components used on teh ZXLD:
RSense - 0.33 Ohms / 1 Watt
Capacitor - 10uF / 63V Rating
Inductor - 220uH (Resistor model, not the coil one)
ADJ pin - did the circuit with a transistor and resistor as indicted by DWZM and the spec sheet, and left the input to the Resistor Pin (PWM) floating.
DIODE - BAT49 (http://www.datasheetcatalog.org/datasheet/stmicroelectronics/3297.pdf)
And one more thing, when i tested for the current across the LED, when i kept the multimeter probes over the LED only that LED dimmed drastically, is this alright? or will i be damaging the LED?
actually what worries me the most is that i made 8 ZXLDs in a PCB of 100mmX100mm!!! tiny it is : and it is estimated to control 84 LEDS.. now that makes me scared.
Now what can i do to reduce the heat?
TheFishMan65
New member
perikaruppan,
When you are testing the current are placing one probe on each of the '-' and '+' plus of the LED. This is the way I read the above. You must break the string and place the meter in series with the LEDs. Voltage is measured in parallel. This would also explain why the LED dimmed when you tested current. Most of it got bypassed around the LED through the meter.
Your are dropping .5 amps * (41 - 37.7) = 1.65 watts across the chip. I would not think that would be a problem, but I have not used the chip. I would place the meter in series to measure current. Then lower the voltage until you start to see a drop in current. Then raise about 1/2 volt above this limit. You may need to add another LED depending on how far you can lower the power supply. Then see how hot it gets.
Also 10 or 12 LEDs. '41v and strung 10 LEDs' or '12 LEDs GLOWED'. Depending on the answer you may need to adjust some of my math above.
When you are testing the current are placing one probe on each of the '-' and '+' plus of the LED. This is the way I read the above. You must break the string and place the meter in series with the LEDs. Voltage is measured in parallel. This would also explain why the LED dimmed when you tested current. Most of it got bypassed around the LED through the meter.
Your are dropping .5 amps * (41 - 37.7) = 1.65 watts across the chip. I would not think that would be a problem, but I have not used the chip. I would place the meter in series to measure current. Then lower the voltage until you start to see a drop in current. Then raise about 1/2 volt above this limit. You may need to add another LED depending on how far you can lower the power supply. Then see how hot it gets.
Also 10 or 12 LEDs. '41v and strung 10 LEDs' or '12 LEDs GLOWED'. Depending on the answer you may need to adjust some of my math above.
der_wille_zur_macht
Team RC
Agreed. It basically comes down to this - if all else remains the same, the heat produced by the (linear) IC will be proportional to the voltage drop across it, i.e. the difference between input voltage and output voltage. So, first, make sure you're measuring current correctly. Next, if it's getting too hot, reduce the drop. You can do that by adding more LEDs (if the drop is big enough) or reducing the supply voltage.
perikaruppan
Member
sorry typo error.. it is 10 LEDS only.
So can i take the last lead from the LED -ve pin into the -ve power supply, and place the Meter betwen this is series to measure the current right?.
I will also add another LED in series to see what happens. need to do some more soldering then..
Adding another LED makes it 11 @3.77 = 41.47, so the drop assuming needs to be zero across the IC, then the Voltage should be about 3.72, is this correct?
or will there be some voltage drop across the IC?
i am currently at the lowest voltage in my power supply 41, so i cant reduce it any further to determine the drop in current. So the only option is to add more LEDs across. But the spec sheet given by them tells not more than 10 LEDs for 41V - might be calculation error?
So can i take the last lead from the LED -ve pin into the -ve power supply, and place the Meter betwen this is series to measure the current right?.
I will also add another LED in series to see what happens. need to do some more soldering then..
Adding another LED makes it 11 @3.77 = 41.47, so the drop assuming needs to be zero across the IC, then the Voltage should be about 3.72, is this correct?
or will there be some voltage drop across the IC?
i am currently at the lowest voltage in my power supply 41, so i cant reduce it any further to determine the drop in current. So the only option is to add more LEDs across. But the spec sheet given by them tells not more than 10 LEDs for 41V - might be calculation error?
TheFishMan65
New member
Yes, that is the way to measure current.
I am not sure the drop can be an absolute 0 with this chip. There maybe some drop across the IC. Measure the current as you turn the voltage down. When it starts to drop then turn it back up. 1/2 Volt on the IC should be fine.
The 10 LED at 41V maybe at the maximum current. In that case the drop across each LED would be a little more. Still that would be 4.1V across an LED, too much. Can you point me to the speck sheet.
Where is the 41 volt limit coming from. Maybe I am missing something. The ZXLD1366 will allow a 60 volt inpout.
I am not sure the drop can be an absolute 0 with this chip. There maybe some drop across the IC. Measure the current as you turn the voltage down. When it starts to drop then turn it back up. 1/2 Volt on the IC should be fine.
The 10 LED at 41V maybe at the maximum current. In that case the drop across each LED would be a little more. Still that would be 4.1V across an LED, too much. Can you point me to the speck sheet.
Where is the 41 volt limit coming from. Maybe I am missing something. The ZXLD1366 will allow a 60 volt inpout.
