I’m new to the forum but an acquaintance of mine from LPF (where I’m a veteran member) who spends a lot of time here sent me this way. I just ordered a SRK with the XM-L2 U2 emitters from CNQG and I’d like to drive those emitters as close to 3A as possible.
I REALLY like the ability to select which modes you want and the fact that you have a fast strobe available.
So, will the driver be 3.05A as in the OP or 2.8A as in a later post? If it is only going to be 2.8A, what all is involved in bumping up the current? I assume just paralleling on more smd regulators?
It will probably be 2.8A, the 380 mA regulators just are not available at cost effective prices. To boost the current to 3A you would need to add another regulator chip to each channel.
I’m sorry for the silly question but being the inept person I am when it comes to electronics l have to ask. This driver I think is designed for an electronic switch? Will it work with a normal on off tailcap switch?
It's just a momentary pushbutton, non-latching. Like on a TV remote. The switch grounds a pin and the driver does whatever it's programmed to do until the switch is pressed again.
I got in some new rev PC boards (that did not have the solder mask screwups that OSHPARK’s board fabricators did on the first ones… they monkeyed with several people’s boards on that panel). I built one up with some 350 mA driver chips from Fastech. Seems to work well. You lose about 60 lumens per LED going from 2.8A to 3.05A per LED…
I got a better measurement of the parasitic drain… it averages around 6 microamps… about 666 times less than the stock SRK driver (over 4 milliamps). Should drain 4 x 2600 mAh cells in around 200 years. The stock SRK will drain the cells in around 3 months.
That is awesome! Weren't 7135s supposed to leak some current when not switched on? Is that not the case, or did you add some type of switch in between the battery and 7135s?
Biggest disadvantage of this driver is that it didn’t show up about 3-4 months ago, in the golden age of SRK
Now, with Supfire M6 and Solarstorm/FandyFire Warrior, SRK is fading away…
I have noticed that the lead frames on ’7135 chips are particularly fragile. I’ve left behind lots of them when trying to unsolder them. Also broken them when bending the leads down.
The behavior of the chips is not specified under the conditions of having the Vdd pin pulled to ground. Something tells me there is no pulldown on the output FET gate. Without the Vdd circuit being powered on, the gate might be floating. I suspect it is only an issue with chips from some manufacturers.
That spec is a boiler plate typical spec manufacturers use when they don’t want to measure the actual value. It takes a lot of megabuck tester time to measure those low currents.
For the AMC7135, it also applies when the Vdd pin is being driven high. The current the chips draw when being operated with Vdd low (assuming the chip is not leaking current through the output pin) is actually in the nanoamps. Going from 1 chip to 24 chips the board current increased less than 0.5 microamps. If the chip is leaking current, it may be a couple of milliamps. Designing a product that depends upon unspecified chip operation is a no-no, but sometimes you gotta do what you gotta do with the parts that are available, and maybe have to live with the consequences of what you actually get.
The same thing applies to things like AVR chip ADC inputs. They spec them at microamps, but I have never seen one draw more than a few nanoamps.