I measured resistance from PBx pins to both VCC and GND on an unconnected MCU. I got varying results but the lowest was in the 4 to 5 mega ohms range. Things are probably different when it’s mounted on a driver.
I didn’t think about the zener case either. In any case I’d guess that a driver with the LDO solution would provide more stable readings than one with the zener solution, or at least differently. The zener does what it does, it’s passive, but the output pin of the LDO probably behaves differently when there is no input voltage.
The off time cap is measured before it gets any voltage. The cap doesn’t get charged until the pin it sits on is set to output high in the firmware, at least this is the normal method in “standard” driver designs if things haven’t changed lately.
Updated cart above. To give an idea how powerful that browser tool I linked is.. it generated this for me from my table above, and populated my shopping carts for all of them:
(NOTE THIS IS NOW DEMONSTRATION ONLY, NOT CORRECT COMPONENTS)
References
Qty
Description
Manufacturer
MPN
Manufacturer
MPN
Digikey
Mouser
RS
Newark
Farnell
U1
1
IC MCU 8BIT 8KB FLASH 8SOIC
Atmel
ATTINY85-20SUR
ATTINY85-20SURCT-ND
556ATTINY8520SUR
68T3811
LDO
1
IC REG LDO 3V 0.15A SOT23-5
Microchip
MIC5235-3.0YM5-TR
576-2783-1-ND
998MIC52353.0YM5TR
71Y1742
U2
1
IC LED DRIVER CTRLR DIM 10MSOP
Texas Instruments
LM3409MY/NOPB
LM3409MY/NOPBCT-ND
926LM3409MY/NOPB
7615678
14R4586
1735797
L1
1
FIXED IND 15UH 14A 14.4 MOHM SMD
Vishay Dale
IHLP6767GZER150M11
541-1287-1-ND
70IHLP6767GZER150M1
7487615
13T1269
1845594
D1
1
DIODE SCHOTTKY 60V 30A POWERFLAT
STMicroelectronics
STPS30M60DJF-TR
497-12421-1-ND
511STPS30M60DJFTR
8290456
97W2993
2325863
Q1
1
MOSFET P-CH 30V 14.9A TDSON-8
Infineon
BSC084P03NS3GATMA1
Infineon
BSC084P03NS3GATMA1
BSC084P03NS3 GCT-ND
726BSC084P03NS3EG
C1
1
CAP CER 10UF 25V X7S 0805
Murata
GRM21BC71E106KE11L
490-10496-1-ND
81GRM21BC71E106KE1L
8851764
96Y9268
2611935
C2
10
CAP CER 0.1UF 16V X7R 0603
Yageo
CC0603KRX7R7BB104
311-1088-1-ND
603CC603KRX7R7BB104
6698763
68R4769
432210
Cf
1
CAP CER 1UF 16V X7R 0603
Yageo
CC0603KRX7R7BB105
311-1446-1-ND
603CC603KRX7R7BB105
68R4770
1458900
Cf2,Cin,Co
10
CAP CER 10UF 50V X7R 1206
Kemet
C1206C104M5RACTU
Kemet
C1206C104M5RACTU
1276-6767-1-ND
603CC206KKX5R8BB106
14N2184
2581103
Cf2 alternate
1
CAP CER 220UF 6.3V X5R 1206
Murata
GRM31CR60J227ME11L
490-13970-1-ND
81GRM31CR60J227ME1L
55Y9932
2494472
Coff
10
CAP CER 470PF 50V X7R 0603
Samsung
CL10B471KB8NNNC
1276-1094-1-ND
7665238
JMP
1
RES SMD 0.0 OHM JUMPER 3/4W 2010
Yageo
RC2010JK-070RL
YAG3380CT-ND
603RC2010JK070RL
98K7919
9235523
R1 eswitch
10
RES SMD 360K OHM 1% 1/10W 0603
Yageo
RC0603FR-0736KL
311-360KHRCT-ND
603RC0603FR073K6L
68R0080
1799338
R1 clickie
10
RES SMD 36K OHM 1% 1/10W 0603
Yageo
RC0603FR-0736KL
311-36.0KHRCT-ND
603RC0603FR073K6L
68R0080
1799338
R2 eswitch
10
RES SMD 47K OHM 1% 1/10W 0603
Yageo
RC0603FR-0747KL
311-47.0KHRCT-ND
603RC0603FR074K7L
5047363
68R0098
2146120
R2clk, Roff
10
RES SMD 4.7K OHM 1% 1/10W 0603
Yageo
RC0603FR-0747KL
311-4.70KHRCT-ND
603RC0603FR074K7L
5047363
68R0098
2146120
R5
10
RES SMD 4.7 OHM 1% 1/8W 060
Vishay
MCT06030C4708FP500
Vishay
MCT06030C4708FP500
RNCP0603FTD4R70CT-ND
594MCT06030C4701FP5
96Y9432
2614446
Rf2
10
RES SMD 3.9K OHM 1% 1/10W 0603
Yageo
RC0603FR-07390KL
311-3.90KHRCT-ND
603RC0603FR0739KL
5046916
68R0081
2143821
Rf3
10
RES SMD 2.7K OHM 1% 1/10W 0603
Yageo
RC0603FR-07270KL
311-2.70KHRCT-ND
603RC0603FR0727KL
68R0067
2136427
Rsns
3
RES SMD 0.075 OHM 1% 2W 2512
International Resistive
LRC-LR2512LF-01-R075-F
International Resistive
LRC-LR2512LF-01-R075-F
696-1670-1-ND
66LR2512LFR075F
7717792
88K2583
1254661
It's also possible to feed it alternate MPN's for each row so that the cart will get filled for all vendors.
Ah.. yes, Now I remember being confused about THAT when I saw it before. I now got C1 and OTC confused... well, because there is no OTC in this driver! Never mind. C1 is I guess only a bypass and maybe useful for the bleeder. Somehow I had that right in my parts description, just a not-so momentary lapse of reason.
Very nice work, I am busy today but I will sit down and check out those items later along with tweaking the driver to see about removing the jumper and squeezing a 1206 cap in there.
Also curious how arrow will compare in the final price outcome. Particularly with free shipping they have now.
I honestly have only ever made one order from mouser, all I remember about it is that it was just so so. Prices were a bit higher then digikey, the website was far harder to navigate then digikey (although massively better then arrow) and the shipping cost was a bit cheaper but not significantly so IIRC.
My biggest issue with shipping is that out of all the orders I have made shipping is generally at least $10 for some parts that weigh all of an ounce and should cost all of $3 to ship.
When I only need $7 worth of parts and spend $10 on shipping, that should have cost $3, that bothers me.
Not to mention that to date Arrow has been cheaper on 90% of parts I have compared (they also have a price guaranty apparently, although not sure how it works).
Mouser is in Mansfield, you could drive over and pick stuff up and pay zero shipping.
They also have an option to use USPS for shipping at the lower rates, it’s not really clear though and you almost have to ask for it.
I buy almost all my components from Mouser. Have built hundreds of FET drivers with parts from them, a few times I’ve gotten stuff from DigiKey and the shipping costs were similar. Then the DigiKey site got difficult to access and I quit using them altogether.
Yeah so I was getting things all mixed up with the OTC momentarily and yet C1 does seem to play a role in this and the point of adding a controlled resistance maybe is even more clear. There's some weird stuff going on there. Without C1 I wouldn't think R1 matters for OTC, it just the highest resistance path to ground. Reading the docs it's not at all clear to me that attiny will shut down consistently, but I don't know. It seems like going with a 10x or 100x higher capacitor for OTC and a parallel resistor would put the discharge RC time entirely into our control and decouple it from all the side effects of every voltage and leakage in the whole system. I bet all this stability voodoo of minor changes here and there just dissappear. It also should allow to get rid of R1 and R2 entirely in direct drive non-zener lights without impacting OTC.
I'm seeing now this could be tested in a 1S non zener light without changes just by removing R1 and shorting the R2 pin to the OTC pin to create the RC. Then just have to choose the right OTC and R2 for desired RC. I've got a $0.50 0805 220uF cap picked out already. There may be cheaper options at 100uF or so.
So this thing is basically an analogish driver with a digital click controller and took a little thought (we'll still have to see) to cram that together. However, it's also possible to ditch the MCU entirely and just replace the Iadj stuff with just an ldo, pot, cap and resistor or two. The pot could be mounted in place of the e-switch for a fully analog light. Of course clicks have some use, always knowing really what mode you're in, so you know what to expect for heat and runtime, and some features like battery monitoring, thermal control etc are nice. But simplicity and analog control are also very attractive features that us humans tend to find comfortable. I don't know how hard it would be to find a nice pot knob that could fit on say a Q8. As for battery monitoring, we could undervoltage shuttoff back to the LM3409 (lol, I just asked about removing it, not even gone yet). And I think the LM3409 has some kind of thermal shuttoff built in as I recall, maybe pretty extreme though.
Interesting, I knew they were in Texas but didn’t know they were in DFW.
Although Mansfield is still a good drive from me. DFW is a huge place and just keeps getting bigger! You can drive for 1.5 - 2 hours in some places and still be in DFW! And thats without traffic.
Now at 3 in the morning on a toll road on the other hand, that time can be cut down to about 20 minutes…….
I use digikey simply because their website makes sense and you can narrow down the parts you are looking for far easier. Mouser is several steps behind when it comes to this.
In my case I best it would cost me the same in gas to pick it up as to ship it.
In this size at least yes. I momentarily forgot that earlier when I was looking at circuits instead of the board, and with all the discussion of it. I might raise the idea in another thread.
Yep, and it makes it a simple place to test this RC idea. Once my hot air station gets sorted, I might just give it a go. I've got all the bits, enough for two to compare for that matter.
Yes, so I'm not sure this is settled. I went with 360k/47k because we had strong confirmation of 36k/4.7k working well for 4S clicky. That will give the same divider obviously, and there are no OTC issues, so I thought that should be fine. Most of the early adopters will have the 220k on hand if needed anyway, so worst case is we change it and learn. Anyway, we can certainly change the part list if we're sure. I'm still not.
So I’m probably missing it, but I just can’t see how that lower right quadrant could ever be ground. The upper right is + and the upper left is - and in 4s all other battery contacts are not ground. (the ground of a battery maybe, but not the ground, any raised voltage will due for the uv pin). I’m assuming there will be a jumper connecting the bottom two pads then.
For 2 S one of each of the bottom right and bottom left must be plus and minus. The mid voltage plane must be at the tail. There’s no other possible way. But I can’t imagine why the lower right would be ground. That would require connecting diagonal pads which is not simple to even do. The only thing that makes sense in 2S the lower right is connected to hot and lower left to ground, with vertical jumpers or traces on each side.
I’m wondering if you forgot to flip the board over in your head when you said that’s ground. If I’m confused, ok, but if I’m not, the jumper thing is real simple so maybe worth double checking.
I still think we should redo the voltage divider to whatever is ideal for the voltage in this case. Very few people have the components on hand for high voltage builds as it is so not a big deal to start over in this case.
Am I right that 4x the R2 should be roughly what we need to get the same reference voltage for the MCU with 4x the voltage?
So it would seem that an 47k/880k ish would be what we need?
Mostly because I do not know what reference existing firmware’s are using. It needs to be setup for whatever they are using now, which I think is the 1.1V reference.
Changing the reference is over the head of most people (including me) so it needs to work with whatever it is setup for now. Calibrating it is pretty simple by comparison.
Obviously other solutions will be needed for smaller boards, and I know you're always thinking about that. But with how silly simple this is.. I'd just worry about that later. It's solved here.
Never mind, that's not even right. In 2s tube lights there's only hot there.