I like to make sure the FET is placed towards the center, trying to allow the positive lead some room to be away from the edge of the board. I know this can lead to issues with the FET being too close to the ATiny to allow a re-flash, but I’ve trimmed that side of my clip to make it skinny to facilitate this. I don’t usually flash on the board anyway, but like to allow the possibility to change firmware later
By keeping that positive LED pad clear it’s easier to keep it from grounding out on a pill. I also like to cut away the shelf in that area on the pill to make sure it doesn’t still contact the actual pad. I do NOT want a 30A capable cell shorting out in my light!
I’ve used about 25 of these FET drivers so far and am loving the power level they bring to the table. The hot cells like a 20R or C4 give full blown output, control can be found through use of PF’s or other less potent cell chemistry, enabling the user to limit a 6A+ light to 4A or so through proper cell selection. Simple as changing batteries.
One last thing I’ve started doing is to apply coverage of critical components with a coating of Arctic Alumina Thermal Adhesive. This is like extending the silicone sleeve to ensure contact cannot be made, thus further easing my mind on possible shorts and adding some support to the LED leads on the board. A very thin layer of AATA is easy insurance anywhere something might possibly touch.
All good points Dale! Yes - I tried to position the FET more to the left and up (in the pics), but it slid downward when the solder paste liquified - probably should hand solder the FET to better control it's final set position... I gotta incorporate all of these points in the OP somewhere... Thanx!
You may have done the most qty of these boards than anybody, including Richard.
You need to watch out for a short from LED+ to the pad under the FET, too. Not worth it to protect against a short in one spot if it causes one in another. I make sure the FET has the pad well covered and then solder the LED+ wire right up against the FET body, if the edge of the pad on the board and the edge of the pad on the FET line up that leaves plenty of clear space out to the + pad.
edit: and if the pill needs work for clearance to the + wire's solder pad, then the pill needs work. Lots of pills have a far wider step that is needed.
I mount my FET all the way to the right to allow room for the clip, I just finished up 10 of these and I think this method is about the best (the best I’ve found so far anyway), the 17dd is siliconed in place so theres no chance of a short to the host board from the components on the bottom, power and ground are pulled threw the connections on the top there.
Ignore the extra wire there, its for hooking up a power supply for testing and is removed before buttoning it up. I cant wait to run out of these old 17’s and order the new revision to make it easier to hook up the switch wire. Also note how I do the GND connection with a piece of braid directly to the FET source leg, I also scrape away the mask around the leg so its got more copper to solder to.
Yeah Comfy, valid point there. By moving the FET away from the positive LED pad it also ensures the LED negative out that covers a large portion of the bottom of the FET cannot touch the positive pad. Lot of high amperage bits on this small board!
CK, all good points there as well for piggybacking. When I piggyback these I like to use Teflon coated wires for the power to the BLF board and double Teflon wires for ground. This gives me 3 very sturdy legs holding the BLF board away from contact, allowing it to float as it were. With the double wires attaching ground, it’s ground supply is ample. I’ll make note of using the ground leg of the FET though, good point that.
Edit: By the way Tom, in the pics above the FET needs to move to the Right and up, towards the MCU and away from the LED + pad. Sometimes I re-flow this side of the board using a solder paste mask from Texas Pyro. Then hand solder the other side. While I always use the mask for the FET side, sometimes I just use the soldering iron to make the contacts one at a time in order to not have to use the stove top in the kitchen for one driver. I have a 6” round 1/8” thick 304SS plate that I put on the glass induction element, re-flow on top of that at a 4 1/2 setting then remove to a 3” cube of 6061 for quick cooling. The tiny diode and the capacitor are the most tedious when soldering with an iron, but then I’m using the big round/oval bevel tip as well. lol And no magnification.
I've read and looked at the OP now a couple of times. The way you have laid out your pictures the content in them along with parts lists and a little description on whats being done has really given me the urge to give this a go. There are lots of other threads similar to this out there but this just seems right. Thanks Tom E.
Have anyone found a way to get rid of the whine in the middle modes now? Ive just been using STAR firmware that you get from RMM. I thought comfychair had found a way to get rid of the whine on the SRK BLF DD driver, but there is a jungle of information out there about these drivers now.
If these could become 100% silent in all modes that would be great. Id even take low/slow PWM over whine.
Ohhh - I'm still using phase correct but these ol ears can't hear it.. Hhmm - gonna have to change. Forgot details how to convert and not sure of side effects - still can use low PWM value of 1?
Previously DrJones was the only one doing FW for momentary drivers, and the 'sleep' method he uses means the LEDs do not turn off completely in the 0% mode (that's the only way to turn off a momentary driver since the +/- remains connected at all times). Jonny does something different in his code (which of course I don't understand) that fully puts the MCU to sleep after the button is released. None of that matters or has ever affected the clicky drivers.
I've been shopping at our local Spotlight and come home with this. Before I open it do you guys think this will do the job. Apart from the color it appears identical to the one Tom E linked to earlier.
Still very new to DIY drivers and seems like it is really cool! Can someone tell me a little about this driver’s specs? RMM’s site does not really provide enough info, like how many amps, input voltage, etc. I really want to build one because it is called BLF! Thanks for your help!
It is direct drive like the now obsolete/out of production east-092, but with an easily reflashed controller. So depending on what firmware you give it, it'll work in either clicky switch lights or momentary electronic switch lights. The number & level of modes and the PWM frequency all depends on which firmware you use.
The FET (basically just like a relay, but with no moving parts) has been chosen to give the lowest possible resistance, so with a hot INR/IMR cell you'll see something like 6.5-7 amps to a single XML2, or 11-12A to a triple from a single cell.
Interesting… Thank you for the explanation. Would I need something like what Tido (https://budgetlightforum.com/t/-/744 ) has to program the firmware?
One question that I am interested in is the momentary switch. How do I use these? They are rated .5A and do not stay on after I press on them. Does the FET turn on and off every time there is an electrical connection or something? These switches are SO tiny, versatile, and come in METAL! O:
The momentary switch only grounds one tiny pin on the MCU, it doesn't carry any current. The firmware in the MCU monitors that pin for button presses and then follows its instructions on what it should do. Power & ground are always connected at all times, the MCU turns the FET on or off (pr pulsed at a very fast rate to give the lower modes). When the FET is off, no current flows.
MRsDNF - it does sure look the same. Hope the heat and airflow are the same though.. Guess this is kind of a risk though because there's no specs to speak on these things, besides the wattage I suppose, and the 300W rating does match mine.
Mine is stickered with: Heat Blow Tool, 300W 120v/60hz. Model: HG-100, Made in Taiwan
But it doesn't have the official description that yours has: BADA-BING, BADA-BOOM, so yours must be better .
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