DIY LED driver for reef lighting

Aqua@Home said:
1. Analog dim by directly driving the IADJ pin with a voltage source from 0V
to 1.24V
2. Analog dim by placing a potentiometer between IADJ pin and Gnd.

Am following the circuit design posted by der_wille_zur_macht. How do I decide on what value of pot should be used to do the pwm?
Click to expand...

The LM3409 spec sheet calls for a 250k ohm pot between the Iadj pin and ground. You can use the pot for ANALOG DIMMING and a separate 5v pwm signal for PWM DIMMING. I built a driver spec'd for 3,000ma but i use the 250k pot to turn down the current to 2100ma and use the 5v pwm signal to dim further down from there. Both dimming schemes can be employed at the same time, making this driver a very flexible design.
 
O2Surplus said:
The LM3409 spec sheet calls for a 250k ohm pot between the Iadj pin and ground. You can use the pot for ANALOG DIMMING and a separate 5v pwm signal for PWM DIMMING. I built a driver spec'd for 3,000ma but i use the 250k pot to turn down the current to 2100ma and use the 5v pwm signal to dim further down from there. Both dimming schemes can be employed at the same time, making this driver a very flexible design.
Click to expand...

Will the pot value have to be changed when the driving current is changed from 3A to 1A?

I am building 1A circuit.

Also could you share your pwm circuit? I can see if I can employ that in my circuit. Please..
 
der_wille_zur_macht said:
Not I! Switching to your I2C boards, or something very similar to it.

I'm thinking about putting a spot on the board for resistors/fuses for parallel strings but the catch there is you'd be designing for a specific number of strings and it's not really a big deal to have those components external to the board. Does anyone else think this would be useful?
Click to expand...

Hi DWZM

Couple of questions if I may on this....

Scenario...6/7/8 strings off 1 lm3409 with 3/4 led's on each...

Would each string be independantly controllable from say an arduino through the driver ?

Also, if allowing for 8 strings off each board i doubt that anyone would need more than that, and i would say less in most cases ?

If you have already designed the parallel boards will you be posting sch/brd files ?

Plus if I may pick your brains a little more...as I mentioned in an earlier post, I'm no ee and looking at the xls worksheet for component choice, I am assuming that RD at the bottom of the sheet is resistance differential ? If so, across which points is this estimated ?

Cheers

John
 
Last edited:
BTW...I think its a great idea looking at it from a modular point of view.

Plus... each module could be daisy chained with power and control in a sort of master/slave set up.

This is referring to DWZM's post on parallel strings from an LM3409 :)
 
Last edited:
O2Surplus said:
DEVS

Here's a dual CAT driver that will work. As it is, both channels are independent of each other. If you want to Parallel the channels, just connect the negative side of your LED string to both negative terminals on the board. I included pots with both chips for current adjustment. All you'd have to do is balance the load between the two CAT chips by adjusting each one to drive half your target current. For example- Say you want to drive a string of six XPG's to 1400 ma. Connect the string to one channel only, power-up, and adjust the current to 700ma. Now connect to the other channel only, power up, and adjust it for 700ma output. finally connect both channels and check the current, It should now be around your target of 1400ma.This design is nice because you're not forced to parallel drive if you don't need to, plus it has a 5V reg included for powering up the driver for situations where there is not a controller providing the 5V turn on signal or dimming signal. Feel free to mod it any way you like.
Click to expand...

Much appreciated O2, but i've since been reading up on the LM3409, so I think I'm gonna be going with that.

Cheers

John
 
Question to Terahz (or anyone else that would happen to know):

If I have multiple I2C boards and want to dim them together (all at the same time); can I set the addresses the same on the I2C bus? Will they all recognize the coding from the Arduino and perform as if they were on a unique address or will there be a conflict?
 
Now, imagine that your business depended on those chips. :)

Send me the exact part number and I will check with some of our other sources. How many do you need?
 
Thanks Shirley just ordered them from Newark! Also thank you Landsailor. While I'm handing out thanks also Thank you DWZM, TheFishman65, terahz, and every body else that has a hand in this and all the many other DIY projects here at Reef Central. I've been a long time lurker here and over the years my interests have ebb and flowed in this hobby but I always know this is the place to go when I need help or good information.
 
That doesn't surprise me. I buy reels of contacts from an authorized dealer in France for about 60% less than I can buy them in the US.

The stupid part is that they are made in the USA! How on earth, they can be manufactured here, shipped to and from Europe, and still cost 40% of where we used to buy them is beyond my comprehension.
 
if a 48v-150 watt-3.2amp power supply is used to supply the lm3409hv drivers and the leds have Vf of 3.4 each driver can run around 12-14 leds is this correct dont have a calculater handy right now? and if i run them at 750ma this power supply should be able to supply the volts and amps for up to 4 of the lm3409hv drivers is this correct?
i am a little confused about the whole volts milliamps watts amps thing i just want to make sure my thinking is correct
james
 
shirley386 said:
Question to Terahz (or anyone else that would happen to know):

If I have multiple I2C boards and want to dim them together (all at the same time); can I set the addresses the same on the I2C bus? Will they all recognize the coding from the Arduino and perform as if they were on a unique address or will there be a conflict?
Click to expand...

It might work. I haven't tried it though, and from what I read it depends on the i2c client (the DAC in this case).

Porgy Bait said:
Anybody know if any company has the Cat1401 chips in stock? Most say that they won't have any until Sept.
Click to expand...
http://www.findchips.com/avail?part=CAT4101

Landsailor said:
The stupid part is that they are made in the USA!
Click to expand...
Even though OnSemi has factories in the US, I'd be really surprised if the CATs are indeed made in the USA.

jc286006 said:
if a 48v-150 watt-3.2amp power supply is used to supply the lm3409hv drivers and the leds have Vf of 3.4 each driver can run around 12-14 leds is this correct dont have a calculater handy right now? and if i run them at 750ma this power supply should be able to supply the volts and amps for up to 4 of the lm3409hv drivers is this correct?
i am a little confused about the whole volts milliamps watts amps thing i just want to make sure my thinking is correct
james
Click to expand...
3.4V * 12-14 LEDs = 40.8V-47.6V, the 14 count is pushing it.

4 strings at 750ma will be 3A. I strongly advise against using a 3.2A PSU under a constant load of 3A. My personal limit would be about 2.5A. In other words, I wouldn't put more than 3 strings on it.

To sum it up, I would put at most 3 strings of at most 13 LEDs (with 3.4Vf) on this power supply (assuming it can actually regulate the specs you list under load)
 
thanks terahz i didnt have a calculater handy when i posted this but you have answered my question !!!! its better to be under the max to be safe!!! but i was just trying to get my head straight about how the volts amps works in trying to figure out how many drivers and how many power supplies you needfor a build
thanks for clearing it up for me
james
 
You must log in or register to reply here.

Similar threads

C
DIY Stand for Flatback Hexagon Tank
Replies
2
Views
764
Drummer98
Drummer98
T
Looking for a specific tank build - EZTube.com sent me here
Replies
6
Views
537
Reefing102
Reefing102
Emanuel92
What lighting for S. haddoni and E. quadricolor?
2
Replies
20
Views
1K
Hong Kong
Hong Kong
C
Scored a complete setup for $100
Replies
13
Views
1K
griss
griss
R
Red tufty algae - Asparagopsis - any expert advice for removal?
Replies
14
Views
2K
rallibon
R
Back
Top