http://www.digikey.com/classic/Ordering/AddPart.aspx?WT.z_cid=Shared_Cart is not the link for the shared cart, it’s the URL after you’ve clicked the shared link and parts have been added, you need to use the shortened link from the pop-up box. Or right-click/copy the link as given in the Oshpark projects thread.
Save yourself some trouble and order the resistors in batches of 100 at a time, it's only $1.22/100. The 19.1k can be used for both the voltage divider and the gate pulldown (R4). There's no reason not to use R4, anything from 10k to 20k is too high to have any negative effect on the signal to the FET, but will make sure there's no residual charge left at the gate during the time when the MCU has commanded the FET 'off'.
In response to your question on the R3 value, I believe 100ohm is about the bare minimum and 150 is to high. Your not noticing any ill effects with that one, skipping modes or not switching when it should? Have you tested it with both physical clickies and momentary button setup’s?
I’d be more than happy to drop a few 130ohm 0805’s in a regular mail envelope for you, I have a strip of 1000. PM me your address if I can hook you up.
Your soldering is extremely clean. I use an iron so I get a good amount of extra solder everywhere when I do it, yours look very professional!
Sorry - been out all day - wifey and I had a car accident this eve - she was driving... No one hurt, but more like a strong fender bender.
I do have qty 100 130 ohm resistor on order from yesterday, from California, so hoping later half of this week, so I'll be set. Thanks for the offer though .
Haven't noticed any issues - only used/tested in a conventional reverse clickie. Actually I should have cleaned the board with iso. alcohol, but didn't. The hot air reflow method is great! Love it! The heat gun I use is cheap, like under $10-$20 maybe? It's a "StampAbilities Heat Embossing Gun". This is one example: ebay-stampabilities-heat-embossing-gun. A friend had several he uses for small PC board projects in hobby rocketry and other side-work projects, and he gave me one.
I gotta fix that link. Thanx comfy!! Just tried to copy the link RufusbDuck had... HHmm...
Oops, updated again from comfy (includes 130 ohm resistors) I updated the DigiKey parts list link in the OP - please try again, thanx!!
I adjust the distance I hold it from the board - this gun has no adjustments at all. I was leary of this, but why my friend loves using these things is it's pretty low speed on the air, unlike conventional hot air guns. In the few boards I did, it happened only once on the diode which is the smallest high sitting SMD, but only happened because I did not have enough solder on the pad. All I did was add solder paste, push it in good, then it worked fine.
I guess I should experiment with the different sized nozzles. I’ve only ever done one component at at time, and hold it in place with tweezers. With full air, it’s soldered down in seconds.
Turn the fan down and the heat up. I use the fan on around #4 and the temp at 310-330, I don't know what the actual temp is but nothing melts but the solder and nothing gets blown off.
Ohh - I do all parts on a side at once. I use gentle circular patterns with the heat gun, until all solder contacts turn nice and shiny. This embossing heat gun is very simple - I've even used it for LED reflows. Think he bought it at Michaels, here: michaels.com/surebonder-proheater-tool, but it's labeled different now.
I have the 858D as well…I set mine at 300, lowest air setting, when I start I start farther back, let the heat soften the flux in the solder, it makes it tacky and the components don’t blow off the pads, once nice and warm close in to reflow the individual components
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.
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