DIY LED driver for reef lighting

[SpacedCowboy]

SpacedCowboy, just for curiosity's sake, if the caps on the 24v line were to be changed, does it stay at 1uF or does its value change?

Thank you.

I'm not sure I understand the question... If it changes, then it obviously has to change [grin]

If you mean, can you replace them with a single 3uF cap as DWZM posited, I don't think it's too critical - a regulated PSU will already have that capacitor on its output, sized according to the PSU. Use any combination (1x3uF, 3x1uF, 1x1uF or none) IMHO

Simon

 

[SpacedCowboy]

Is it my imagination, or has this thread just gone sticky ? If so, congrats to DWZM

Simon

 

[Dejavu]

Congrats on being voted December's Thread of the Month:celeb3::celeb2::celeb1:

 

[Misled]

Top of the Hill!!!! Congrats DWIZUM!!!!! :thumbsup:

 

[TheFishMan65]

Congrats!!

I did the combined capacitor. One large one I think it was 10-25uF on the 34V.

 

[artemm]

yes, i guess you are all 100% right about current limits. With li-ion the battery was the limiter actually. I completelly overlooked it.

So, i am gone for a while to find out how to build a very small and cheep active current limiter.

 

[sailfish]

Congrats DWZM on Thread of the Month!!

Parts are on order to build one of these and I was able to find a board from a nice chap here on RC. Will keep you posted as to the progress.

 

[der_wille_zur_macht]

So, i am gone for a while to find out how to build a very small and cheep active current limiter.

You might want to read this thread:

http://reefcentral.com/forums/showthread.php?t=1759758

(I kid, I kid!)

 

[chrisfowler99]

Ooh...sticky...congrats!

 

[TheFishMan65]

DWZM endless loops can get you into real trouble if there is not a way out

 

[bluebayou]

Congrats DWZM! and thanks so much for all your help and time.

 

[imagex]

Another question guys... ok on a powersupply with 24v 6.5a how many 3 boards can i run?? and also is it 1a per cat4101 or is it configured on the pcb to run 1a per board? or actually 700ma as the way it's configured.. cause usually it's .7a per string correct? so each cat4101 need .7a or is it the .7a to the pcb with 3 cat4101? cause i'm trying to run a array with 6 maxed out boards would a 6.5a be sufficient?

 

[S&KGray]

Another question guys... ok on a powersupply with 24v 6.5a how many 3 boards can i run?? and also is it 1a per cat4101 or is it configured on the pcb to run 1a per board? or actually 700ma as the way it's configured.. cause usually it's .7a per string correct? so each cat4101 need .7a or is it the .7a to the pcb with 3 cat4101? cause i'm trying to run a array with 6 maxed out boards would a 6.5a be sufficient?

The rated max of the CAT4101 is 1A, but I think at least 1 person has pushed it a little above that. The LED current is set by the value of the Rset resistor; there is a table on page 7 of the CAT4101 datasheet that lists values for Rset and the corresponding LED current. Most people are using an Rset of 768 ohms for 700mA LED current; an Rset of 549 ohms will give you 1A LED current.

The current is per CAT4101 so total current per board would be x3.

I believe it is recommended to choose a power supply so that you are using up to 80% of its max amperage. So for a 6.5A power supply, you should try not to use over 5.2A.

For 6 boards at 1A per string you would be using 3A per board, total of 18A. You would need a power supply that puts out about 22A.

For 6 boards at 900mA per string you would be using 2.7A per board, total of 16.2A . You would need a power supply that puts out about 20A or you could use 3 of the 6.5A supplies (each one driving 2 boards). You would be using 5.4A out of 6.5A or 83%, but that should be okay.

Anyone feel free to chime in if I am giving the wrong info.

 

[der_wille_zur_macht]

That's perfectly correct and I agree with your assessment that you'd want three of the common 6.5A supplies to run six 3-up boards at 1A.

 

[imagex]

so basically 2 per 6.5a power supply correct?? but thats at a 1a perspective if at .7a then i could run 3 x 3up boards right?? wowsers well was thinking it was per board well that puts a whole different view on this project..

 

[twinreef]

2.1 * 3 = 6.3 that will be over the 80% of its max amperage.

 

[kcress]

Don't get toooOOOOoooOO hung up on the, "don't fully load your power supply", rule. 80% is a guide line. 82,,85 isn't going to cause a big problem. 80% would typically be good efficiency and not going to thermally put one on the edge. 90% would be too little room for comfort though. As you crowd the 80% line cooling needs to be thought about. Make sure your design allows ample air flow through and around the supply.

 

[jrsaindo]

the pwm signal on these drivers would only be a 5v correct?? so if i took a 7805 off the powersupply and run it to a 555 then run it into the pot then the drivers then it would work fine?

The PWM in the spec sheet states that the logic high and low levels are 1.30V and .40V respectively.

 

[TheFishMan65]

No it says that the low maximum value (guaranted off) is 0.4 volts and the minimum high level (guaranted on) is 1.3 volts. So between 0.4 ad 1.3 we do not know how it will behave.

 

[RCBrooke]

The 0.4v - 1.3v range, I'm not sure if it applies here but is it the same phenomenon the causes the step drop off that was talked about on the meanwell dimming? Maybe it was steep cut-off? Oh well, hopefully you guys know what I'm asking even if I said it badly.

Randy