I should but that requires doing a fair amount more work I didn’t want to do lol.
That’s fair, but I don’t think leaving off the ground ring really helps the problem. It’s the case that will short. It’s already at ground now, or hopefully is anyway. Of course even that, I don’t know if it’s as simple as hitting the fill bucket icon and selecting copper and clicking. I’ve never used the software.
I see no less than 8 places where traces have 90º turns. I’m no electronics engineer, but I’ve seen the guys who are argue this many times, no 90º turns.
Edit: Oops! My bad, 10 places.
Doesn't seem very open and shut to me at worst:
http://electronics.stackexchange.com/questions/226582/pcb-90-degree-angles
Some other discussions suggest the most practical reason for this may be that some older hardware and thus software didn't deal with creating these well.
Updated cart in post, I think 236. I think it's all set now. That one-click BOM tool is really neat. I really recommend giving it a try. It's worth 3 minutes to read the instructions. The authors todo list says they are working to support arrow too.
Alright, last last version before release unless someone spots an issue (better now then later).
Gonna check over the parts list and put together a direct shopping cart link.
Post 236 is my own, where is the latest parts list? Might want to copy and paste it here anyways so we can see it and the latest PCB side by side.
oops... 326: [quote=Flintrock] Here goes. Hopefully I didn't mess anything up. Your risk, not mine. Only buy and build what YOU want. I have nothing to do with it. :) Parts list for 16.8V input, 12V nominal output, driving 4p xhp-35 at 2.5A per LED, 576 khz, 10A total (can go higher, but it’s an experimental driver) The main parts:MCU: Attiny85 the normal one, attiny85-20SUR I believe is usually fine. V version is also fine I think. (However if driving with 4.2V an attiny85V should probably be used because this driver presently requires an LDO for the mcu even for 1S batteries and the LDO will need to operate below the lowest battery level, needs more thought though and wil require some resistor value changes) LDO: MIC5235 3.0V (other voltages CAN work, but require some resistor value changes)Buck IC: LM3409 10-MSOP-PowerPad (or EP)Inductor, must be 17.15*17.15mm or very close. 10uH absolute minimum inductance. 30mohm max resistance. Vishay IHLP6767GZER150M11 is a good choice since resistance matters most. It's very expensive though, $6!!, but other alternatives are about the same. Diode, "8PowerTDFN" (might be compatible with similarly named footprints?) STPS30M60DJF-TR has a low 0.5V Vf and low leakage current when hot. Mosfet:Powerflat 5x6 p-channel FET (PFET), Infineon BSC084P03NS3 G Balances low Rdson with low gate capacitance. Gate charge divided by voltage should be less than ~12nF at worst. Half that is better. Rds on should probably be less than 20mOhm at worst. Low Rdson is good for high power. Low gate charge is good for low-current efficiency. It's usually some tradeoff. Caps: C2 10.uF 0805, Vcc bypass 4V minimum, 6.3V or more highly preferred, 10% Cf 1uF 0603, Gate drive bypass, 16V 10%C1 10uF 1206 , LDO input bypass, 35V 10% Cf2 10uF 1206, Iadj voltage filter, 4V minimum (6.3 preferred). 10%, x7r preferred but 125C rated should do. Alternative: 220uF for soft mode transitions. Tantalum and high ESR (ohms even) are OK here.Cin 10uF 1206 or 1210, Input cap, 35V 10%, two minimum, 3 x 1206’s should fit. 4 might fit and is even better. <20% dissipation factor at 1Mhz, 10% prefered.Co 10uF 1206 or 1210, Output cap, 35V 10% One is enough but two is insurance. <10% dissipation factor (5 is better), with good performance up to 1Mhz. Just buy ten 1206 uF caps and you’re set. Cin and Co should be high quality caps. Coff 470pf 0603 35V Buck off-time cap.All caps should be ceramic unless stated, X7R or better strongly preferred (125C or higher rated) . Resistors: JMP 2010 0-ohm 1/10 W is fine. R1 220k 0603 for e-switch 22k for clicky maybe. (with OTC mods now under development, the clicky issue will dissappear)R2 12k 0603 for e-switch, 1.2k for clicky maybe.R5 4.7 ohm 0603 1/8 to 1/4 watt might be wise here, but 1/10 should be ok I think.BR for lighted tailcap 470-630 ohm so I’ve read, optional.Rf2 3.9K 0603 Rf3 2.7K 0603 (Could use 4.7k and 3.3k also for a little softer mode transitions with the 220uF cap)Roff 4.7k 0603 with the 470pf Cf, this will give very roughly 580 khz, which seems ok.Rsense, 2512, current sense resistors, X 3. 0.074 ohm each, 2W rated, adjusted for max current, see below.All resistors should be 1% tolerance, rated for high temperature, 155C preferred, 1/10 W or more unless specified RSenseMax current occurs at 0.248V drop across Rsense.So Rsense_total=0.248/Imax.But there are three resistors, so if they are the same, they should each be:Rses1=3*0.248/Imax. Err on the high side of resistance values to be safe.But no software adjustment can ever make the current higher than the max value set here. Ex: 2.5A for xph35*4= 10A total.Rses= 3*0.248/10=0.074 , closest match, 0.075 ok. Roff:To be written later. Iadj:Rf2, Rf3, Cf2, LDO voltage, and a pwm duty cycle all determine the current set point. Only duty cycle should really need to be adjusted though (through software modes) for current control. Max current is adjusted with the sense resistor, not with this. Of course software could limit the duty cycle, but that’s not the safest approach to limiting current. Soft mode transitions:To achieve slow (~0.33 s RC) you can use a Cf2 of 220uF and adjust speed by increasing or decreasing Rf2 and Rf3. Some options are:Rf2: 3.9K, Rf3: 2.7K (flintrock's favorite) ~0.35s RC timeRf2 4.7K, Rf3 3.3K ~.43s RC time requires one less new value. Much larger and the current control circuit gets an offset, but it should be < 0.7% offset with these values still. Twice as high could still be ok but I think these RC values should feel nice. PWM will be used to get lowest modes anyway so a small control offset is ok.These are chosen to prioritize resistors, but either matches the max control voltage to better than 1.2% after bias current correction. For best precision you can use a 1.02K and a 715ohm, but won’t get very soft mode transitions and probably won’t notice the precision improvement. If you’re using a 10uF cap anyway, then you can as well use these lower resistor values. LM3409 low voltage shutoffRuv1, Ruv2 are the voltage divider for buck IC shutoff. This is redundant with MCU shutoff. You can leave off Ruv1 entirely and use pretty much any value at all for Ruv2 then. This will disable this feature. You can also use Ruv2 36k and Ruv1 4.7k for a 2.7V/cell shutoff and a 2.9V turn on. The cart: Updated with one improved resistor pairing. Digikey carts will aparently expire and they only work on digikey. This is better: References Quantity digikey Description U1 1 ATTINY85-20SURCT-ND IC MCU 8BIT 8KB FLASH 8SOIC LDO 1 576-2783-1-ND IC REG LDO 3V 0.15A SOT23-5 U2 1 LM3409MY/NOPBCT-ND IC LED DRIVER CTRLR DIM 10MSOP L1 1 541-1287-1-ND FIXED IND 15UH 14A 14.4 MOHM SMD D1 1 497-12421-1-ND DIODE SCHOTTKY 60V 30A POWERFLAT Q1 1 BSC084P03NS3 GCT-ND MOSFET P-CH 30V 14.9A TDSON-8 C2 10 1276-2872-1-ND CAP CER 10UF 16V X7R 0805 Cf 1 311-1446-1-ND CAP CER 1UF 16V X7R 0603 Cf2,Cin,Co,C1 10 1276-6767-1-ND CAP CER 10UF 50V X7R 1206 Cf2 alternate 1 490-13970-1-ND CAP CER 220UF 6.3V X5R 1206 Coff 10 1276-1094-1-ND CAP CER 470PF 50V X7R 0603 JMP 1 YAG3380CT-ND RES SMD 0.0 OHM JUMPER 3/4W 2010 R1 10 311-220KHRCT-ND RES SMD 220K OHM 1% 1/10W 0603 R2 10 311-12.0KHRCT-ND RES SMD 12K OHM 1% 1/10W 0603 Roff 10 311-4.70KHRCT-ND RES SMD 4.7K OHM 1% 1/10W 0603 R5 10 RNCP0603FTD4R70CT-ND RES SMD 4.7 OHM 1% 1/8W 060 Rf2 10 311-3.90KHRCT-ND RES SMD 3.9K OHM 1% 1/10W 0603 Rf3 10 311-2.70KHRCT-ND RES SMD 2.7K OHM 1% 1/10W 0603 Rsns 3 696-1670-1-ND RES SMD 0.075 OHM 1% 2W 2512 The 10 uf 1206 Ci Co caps keep going on backorder. That's because they are cheap and seem to be really nice caps.These are an alternative, at twice the price, and slightly worse ESR, but still good and maybe available much faster: 1276-3103-1-ND, or 1276-3102-1-ND USING THE SHOPPING LIST:You can installhttps://1clickbom.com/ in firefox (doesn't work as well in chrome)And cut the table above and hit paste in the browser tool, and "complete" (hit complete several times actually, waiting for it to update between each, seems to help) to get shopping carts at all digikey, mouser, Newark, Farnell, (no arrow :() .. Click the add to cart icon on each to automatically create a shopping cart on any of them. Click "copy" and you get a table with part numbers from all of them. It's pretty neat actually. Of course a few parts are missing at mouser etc because these were chosen at digikey. Anyone clever might let this simmer a couple of days. TA please give it a good looking over. Also anyone else with expertise on the MCU side. Updates, changed C2 to 10uf and now 0805, as needed for LDO. Chanted R1 and R2 to work with 1.1V reference as now standard in bistro. [/quote]
but I don't want multiple places to maintain it. If I make changes, I will make them there.
Here's the shopping cart as generated from copying that table into one-click BOM.
http://www.digikey.com/short/3bvw7p
edit:so the quoting is terrible. Just see post 326.
I was just comparing prices at Arrow and Arrow is a fair amount cheaper on everything. The only issue is they only sell the FET in 5,000 increments. Too bad since it would knock off at least $5-8 if we could get everything from them.
Could get this one then:
https://www.arrow.com/en/products/search?q=+TPN4R712MD
It will have twice worse low power efficiency (maybe that comes to 0.4W minimum power if I remember right) and half the high power loss.
Sadly that one also appears to only be sold by in lots of 5000.
ah, missed that.
I updated post 326 with more clear instructions on Ruv1/Ruv2, assuming LVP in the IC won't be used for now. I've realize that if used, this needs to be setup for very high hysteresis, so if it turns off, it stays off until a power cycle, and furthermore you would need to have low to high mode order to have any hope of getting it to come back on. I guess the same is true for the mcu LVP though.
I also added some words about Coff, but I'm kind of thinking now any attempt to give math or explanation for tuning any of these things is probably more information than most people want to even see. Edit: Created an "adjustments" section for Rsense and soft transitions, and "expert tuning" section for everything else.
I will probably soon work up a calculation sheet with Vf correction (because it matters near direct drive) specifically for this build, just for fun. It could be good to start adjusting the OP, but wouldn't hurt if I had a second post. I don't know if it's possible for mods to insert a post. I doubt it (would change all post numbers).
Question:
How does the bleeder resistor situation work for this board? For a typical board, it bleeds current from batt+ to case "ground" and that case current returns to batt- through a tailcap led. However on this board the bleeder resistor connects directly from the batt+ contact to the batt- contact. It's just a battery short. There is no case path in the middle. I haven't looked yet, but I wonder how this works on the Texas Avenger too.
I haven't looked at how a lighted e-switch would work. It's a momentary so it won't short out an led like a tail cap switch will. I guess they're either always on or they'd need software control, but just speculating.
One thing I realized when working out new values for th Ruv1 and 2 is that the pad the via comes from not only never goes to batt-, but it's always at 8.4V above batt- in both 4S and 2S. Because of that the voltage divider (if ever used at all) would never need to be reconfigured. I never noticed because I wasn't considering to leave a voltage divider on anyway, and I'm still not sure I like the idea of pulling current (voltage is fine) off a middle voltage. It could unbalance cells over enough months. It could be something to have in mind though, maybe even for R1 for other SRK boards.
The bleeder in this case is not needed and most likely would not be used but there was room for it so why not. It could also be used for an indicator as well.
Although in this case you are correct, it is simply a short since the tailcap is not connected to ground. You could still wire it up but there is no need as you could directly tap the positive and ground at the tailcap. In fact I might add this to my tailcap MCPCB come to think of it.
In this particular case it’s most likely use would be an indicator LED installed near the switch for when the light is off. Something that could easily show you the button location. In fact I really like this idea and will have to see if it could be implemented on the BLF GT. Finding the side switch to turn a light on is always the hardest part.
The most important thing for the average person when it comes to the component list is an easy to follow list for 2s input and 1s or 2s output along with 4s input and outputs of 2s and 4s. Those are the most common uses I see.
The only real change most would make besides that is the sense resistors, which a simple to follow calculation or a simple list would do for that. Anyone building one of these should be able to figure out what they need with a few reference points or a basic calculation.
That's actually the direction I was going with it in my head, in almost the same steps.. yeah, could wire to tiny 0603 pads, but, why not...
The thing that seems slightly harder with e-switches is, well, with a clicky the switch shorts the tailcap light and turns it off. With a momentary, it doesn't. So if you want it to turn off when the light's on, I guess you need another control mechanism? Of course it could just stay on.
I figure the .05ma that the indicator LED would use pales in comparison to the 12,000 that is being shined out the front lol.
There is a spare pin available for a controlled indicator LED but why not have options? Plus it is easy accsess to both positive and ground for anything else that might be needed.
I guess it just seems less slick, but it's not really. Always on is fine.
So actually I was thinking a + pad next to Rsense on the driver board. Slightly dangerous for case shorts. Could put it after (right) of rsense, but it gets in the way of the star of Texas, or could make a hole. The tailcap won't actually have direct access to batt+, only to 4.2V in 2S and to 4.2V and 12.6V in 4S, and the quality of the ground connection depends how well the ground ring gets connected to the case. Also ins't it easier to wire the switch light from the driver compartment than the tailcap?