I wear my sunglasses at night... I really do (Dout question)

[dcer10]

Hi all,

Is there any way to lower the intensity of the LEDs without soldering all new resistors or replacing the LEDs? I chose all ultra bright LEDs for my sequencer, which look amazing, but they blind me to the point that I cant see anything else :)

I would love to reduce their brightness without using a texta, or too much mechanical work on it if possible. Could a resistor be put before the board to reduce the current or would that make the ICs not work right??

Thanks,

John

[doc]

Hi,

I'm afraid the only "real good" way to reduce the brightness of the leds is a higher current limiting resistor.

Normally you have to change all resistores to a higher value. A resistor before the board isn't a good idea. I think, this won't work. The DOUTs may work with a little lower voltage (..don't know the minimum voltage of the HC series... you have to look at the datasheet) but your CORE will quit working if voltage drops.

There is one chance for you:

If you have all the GND lines of the leds seperate wired you can try to put another resister in the ground line of the LEDs. But be careful, because no other GND, especially no IC or cap, should be behind that resister. You also have to mention that through this resister a higher current is needed. You should try at least a 2W type for this.

You can easy calculate the load of the needed resistor:

Overall led current x voltage of led after the 220 resistor.

For example: You have 20 Leds with 20mA each. The Led voltage is 2V:

20 x 0,02 x 2 = 0,8W

This is not the exact formula and you should calculate about 50% extra safety to be on the safe side.

In my example I would use a 2W resistor.

Hope this helps

greets

Doc

[dcer10]

Hi Doc,

Thanks for the answer. All of the LEDs basically ground to two points on the DOUT so if I join them to one and add a resistor to it, then take the ground back to the core (will look for 1st ground point, maybe on the regulator??) would that help or will I blow myself up :)

Thanks,

John

[MRE]

Looking at the DOUT board, on the left of each 'bank' of resistors, is the ground point for that group of LEDs.. Technically, each of these 4 ground points is the same. So, if you were tie all of your LED grounds back to any ONE of these ground points, it would work fine.

So, I would suggest a variable resistor in which one leg of the resistor is tied to the ground, and then all of the LEDs are tied to the wiper. That way, you have full control over the brightness of all the LEDs at once (connected to that board). Just make sure its a decent sized VR, so that it will handle the current.

To make it easy (ie, you already have all your grounds on the DOUT board and dont want to muck it up again).. cut the trace on all 4 ground points on the board, then wire a series of solid core wire jumpers on the connector side of the cut to each of the grounds. Finally, insert a VR between the cut points of ONE of your cut traces.

DO NOT cut the part of the trace that grounds each chip! (or the extension connector for that matter!)

In fact, there is a bit of room on the far left of the board. Perhaps the next revision of the DOUT pcb could have these traces cut, with a set of holes, and a pad set for the pot on the left side of the board. That way, you can install a pot if you want, or simply install 4 jumpers if you dont?

[HL-SDK]

220 ohm is a bit low, I use 510 with my 50,000 mcd! white LED's... but they are bright enough to blind...

If you dont want to desolder, you might be able to use a resistor in between the anode and cathode of the LEDs... I dont know what value'd work well, lower values dimmer, higher brighter, but that will also change the voltage so they might just turn off