Help in Understanding LED Driver - The Planted Tank Forum
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post #1 of 10 (permalink) Old 06-20-2016, 10:23 AM Thread Starter
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Help in Understanding LED Driver

Hello All,

I'm in the process of making a DIY LED fixture for a planted bowl. I have bought 3 x Solderless Cree XTE Cool White chips. I read a lot about LED drivers but still I donít think I have fully understood their application. Please guide me with below doubts;

i) I understand that LEDs require constant current, so does it mean that the voltage remains a variable and it draws only required voltage to operate at given amps.

ii) In continuation to above query, is it ok to use a driver rated as "0.5VDC - 12VDC, 1amp" to light a single Cree LED which draws ~ 3V @ 1000mA. I know that this driver is perfect for lighting 3 ~ 4 XTE in series. But i want to understand what happens when only 1 XTE is connected to such driver

iii) Also if I have a power source of 24VDC 1amp which i'll input to Meanwell LDD 1000H, is it ok to connect 3 x CREE XTE in series to output of LDD. The LDD max output will be ~ 21VDC @ 1,000mA. Whereas the voltage required by 3 x XTEs are only ~ 9V @ 1,000mA

Thanks in advance
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post #2 of 10 (permalink) Old 06-20-2016, 12:35 PM
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i)"Requires" is a bit harsh LED's can be driven w/ constant current or constant voltage. CC is preferred..and yes a constant current driver is basically a voltage regulator that senses current and adjusts accordingly.
ii)same as if there are 3. Driver will ramp up voltage till it senses 1A..if .5v-12V @1A is the limit it may have a hard time doing 4 since the 3v is not set in stone. Natural variation ect may have the v(f) at 1000mA go beyond 3 v for each..
iii)yes
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post #3 of 10 (permalink) Old 06-21-2016, 12:04 PM Thread Starter
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thanks for clearing all the doubts Jeffkrol

Now can someone pls tell me what type of pwm dimmer to get for controlling Meanwell Ldd?
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post #4 of 10 (permalink) Old 06-21-2016, 01:55 PM
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Typhon
Storm
Storm X
bluefish
Bluefish mini
robotank
Any DIY Aduino types.
Modified tc-420

"A man with a watch knows what time it is. A man with two watches is never sure."
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post #5 of 10 (permalink) Old 06-22-2016, 06:32 AM Thread Starter
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Quote:
Originally Posted by jeffkrol View Post
Typhon
Storm
Storm X
bluefish
Bluefish mini
robotank
Any DIY Aduino types.
Modified tc-420
thanks jeffkroll, however the said parts are not easily available here, I may have to incur exorbitant shipping charges to get them.

Please have a look at this local ebay listing:
Capacitive Touch LED Dimmer PWM Control Switch Module Arduino BE0324 | eBay

Do you think this piece will suffice my need for dimming meanwell ldd 1000h?, Also whether can this board be powered with ~3v cell phone charger

Thanks
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post #6 of 10 (permalink) Old 06-22-2016, 01:22 PM
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Quote:
Originally Posted by da_vipin View Post
thanks jeffkroll, however the said parts are not easily available here, I may have to incur exorbitant shipping charges to get them.

Please have a look at this local ebay listing:
Capacitive Touch LED Dimmer PWM Control Switch Module Arduino BE0324 | eBay

Do you think this piece will suffice my need for dimming meanwell ldd 1000h?, Also whether can this board be powered with ~3v cell phone charger

Thanks
not sure but this should work. Manual "pot" PWM dimming board:
555 Timer LED Dimmer Circuit Kit..
Looks to be 1Khz at whatever voltage you feed it ..
and voltage (plug the circuit in w/ out the led/resistor) is 2.5V or greater..
SEE THIS for more info (substitute LDD PWM "plus" at "motor" plus.. common ground the negative):
http://www.instructables.com/id/Simp...lation-PWM-Wi/
C1 and C2 define the frequency..Not sure if there is a voltage loss across the circuit so youre 3V power supply may or may not be enough..(I suspect it is 3.3V anyways)
to get at least 2.5 volts out at "motor"..
Or you can get one of these by you.. Note the modification at post 9
https://www.plantedtank.net/forums/20...mer-ldd-h.html
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Last edited by jeffkrol; 06-22-2016 at 01:44 PM. Reason: info
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post #7 of 10 (permalink) Old 06-23-2016, 05:56 AM
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Question

Quote:
Originally Posted by da_vipin View Post
thanks jeffkroll, however the said parts are not easily available here, I may have to incur exorbitant shipping charges to get them.

Please have a look at this local ebay listing:
Capacitive Touch LED Dimmer PWM Control Switch Module Arduino BE0324 | eBay

Do you think this piece will suffice my need for dimming meanwell ldd 1000h?, Also whether can this board be powered with ~3v cell phone charger

Thanks
from where did you get those meanwell LDDs ?

buy arduino compatible board from here Arduino UNO R3 Compatible Development Board ATMEGA328P CH340G Free USB Cable | eBay or Arduino compatible UNO R3 development board w USB Cable (Dccduino)

and use arduino program from here https://www.plantedtank.net/forums/20...ting-code.html

Last edited by Arun.; 06-23-2016 at 06:07 AM. Reason: update
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post #8 of 10 (permalink) Old 06-23-2016, 08:20 AM Thread Starter
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Quote:
Originally Posted by jeffkrol View Post
not sure but this should work. Manual "pot" PWM dimming board:
555 Timer LED Dimmer Circuit Kit..
Looks to be 1Khz at whatever voltage you feed it ..
and voltage (plug the circuit in w/ out the led/resistor) is 2.5V or greater..
SEE THIS for more info (substitute LDD PWM "plus" at "motor" plus.. common ground the negative):
Simple (and dirty) Pulse Width Modulation (PWM) With 555 Timer
C1 and C2 define the frequency..Not sure if there is a voltage loss across the circuit so youre 3V power supply may or may not be enough..(I suspect it is 3.3V anyways)
to get at least 2.5 volts out at "motor"..
Or you can get one of these by you.. Note the modification at post 9
https://www.plantedtank.net/forums/20...mer-ldd-h.html
Thanks again jeffkroll, your inputs has tremendously helped me in steering ahead in learning curve.

I'll go ahead with your Manual PWM Dimmer hack for the time being since its only for a planted bowl.

So to sum it up, here's what i have planned;
The Parts:
i) 3 x CREE XTE
ii) Meanwell LDD 1000h
iii) Manual PWM Dimmer rated 12-24V 8A
iv) 24V 1A Power supply - will be used to drive both dimmer and meanwell ldd in parallel

The circuit:
i) The dimmer and LDD will be connected in parallel to PS.
ii) A jumper wire to be attached from "Gate" of MOSFET inside dimmer to "PWM in" of LDD
iii) The LEDs will be connected in series to LDD

Hopefully this scheme will work, please review the attached circuit.

However do you think that the output voltage at MOSFET gate will remain within LDD 'PWM in' limit of 6VDC even when the dimmer is operated at 24V

Thanks

Bump:
Quote:
Originally Posted by Arun. View Post
Thanks for the info Arun, I bought all the parts from Aliexpress. Waiting for delivery though...
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post #9 of 10 (permalink) Old 06-23-2016, 09:59 AM
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Quote:
Originally Posted by da_vipin View Post
Thanks again jeffkroll, your inputs has tremendously helped me in steering ahead in learning curve.

I'll go ahead with your Manual PWM Dimmer hack for the time being since its only for a planted bowl.

So to sum it up, here's what i have planned;
The Parts:
i) 3 x CREE XTE
ii) Meanwell LDD 1000h
iii) Manual PWM Dimmer rated 12-24V 8A
iv) 24V 1A Power supply - will be used to drive both dimmer and meanwell ldd in parallel

The circuit:
i) The dimmer and LDD will be connected in parallel to PS.
ii) A jumper wire to be attached from "Gate" of MOSFET inside dimmer to "PWM in" of LDD
iii) The LEDs will be connected in series to LDD

Hopefully this scheme will work, please review the attached circuit.
Looks fine

Quote:
Originally Posted by da_vipin View Post
However do you think that the output voltage at MOSFET gate will remain within LDD 'PWM in' limit of 6VDC even when the dimmer is operated at 24V

Thanks
There is a voltage regulator inside. Mine stays at 3.6V on the gate regardless of ps voltage
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post #10 of 10 (permalink) Old 06-23-2016, 03:51 PM
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Hi...i do not have much experience but as per my knowledge i would like to say that it Requires a bit harsh LED's can be driven with constant current or constant voltage. CC is preferred and yes a constant current driver is basically a voltage regulator that senses current and adjusts accordingly. Also same as if there are 3. Driver will ramp up voltage till it senses 1A..if .5v-12V @1A is the limit it may have a hard time doing 4 since the 3v is not set in stone.

complete pcb

Last edited by MarvKern; 07-07-2016 at 09:32 PM. Reason: typo
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