[WIP] 15mm PAM2803 w/ ATtiny13A rough layout / possibility

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wight
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[WIP] 15mm PAM2803 w/ ATtiny13A rough layout / possibility

I really don’t know if this will work. A lot of sacrifices to components have been made:

  • voltage divider deleted
  • uhm, actually maybe that was it?

So I layed out an ATtiny13A and what I think is an entire PAM2803 boost circuit in a 15mm PCB w/ 0.75mm electrical and physical keepouts around the edges… The inductor I used is way too small I think. You can see in the image that I measured a 5.5×5.0mm rectangle, this is closer to a realistic inductor I think. Those are the approximate footprint dimensions of the inductor from a Lux-Pro 2D boost driver, although that inductor has rounded corners. With luck a modified clip will fit. (modified to clear the inductor)

Components around the edge, going clockwise from the ATtiny:
ATtiny
Capacitor (Offtime)
Sense resistor
FET for PWM (which may be miswired, sue me)
Capacitor (Output)
Capacitor (Input)
Inductor
Capacitor (ATtiny Vcc decoupling cap) (maybe we can delete it)

In the center:
Schottky using 0805 footprint
PAM2803

Clearly this thing has a lot of tuning up to be done. It may not work at all. Ever. That said, after cleanup I think this design will closely follow the PCB Layout Guidelines from the datasheet for PAM2803.

As I’ve explained elsewhere after reading the datasheet, PAM2803 appears to have Overvoltage Protection which prevents it from boosting beyond around 5.12v. This is how we are able to bootstrap the ATtiny off of it, even while using PWM to interrupt power to the LED. With many boost circuits voltage would spike, but the datasheet clearly shows a graph scope image! for OVP which I think is clean enough for the ATtiny to be OK.

Here is the PAM2803 datasheet.

Here is v008 of the layout:

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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Edited by: wight on 02/07/2015 - 22:11
wight
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Reserved.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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ChibiM
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Can you give a possible suggestion what kind of light/host this can fit?

wight
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It’s a 15mm boost driver, potentially intended for 1xAA, 2xAA, and 1xCR123A applications. I have only a limited idea what hosts it fits in though. I was hoping other people would chime in on that, I have very few of those types of light.

Maybe Ultrafire C3 and SK68. Also take a look at comments in my recent 15mm DD+7135 driver thread maybe? http://budgetlightforum.com/node/36766

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driveX
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I have made some prototypes with 7mm inductor, linear moonlight, voltage monitoring and ramp programmable modes (I don’t have the linear ML and VM programmed in my firmware yet). The problem is that I don’t have enough time to play with it. I need to make one more version with more space for diode so maybe I’ll end with just 5mm inductor. My previous versions used small diode and it didn’t perform very well. I also made a nice board for ATTiny10 but I realized that it doesn’t have an eeprom too late :-/ I have some useless boards now.

ATTiny10 version (quite useless)

Demo video

djozz
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Nice! 15mm drivers open up the possibility of modding most AA-sized lights.

And if it is all going to work: will this driver have:

a) a decent efficiency compared to other boost drivers

b) a decent output current on a 1.2V NiMh battery, like over 1A through a XP-G2 emitter ?

In other words, apart from being able to have a custom UI (which is a wonderful perspective in a boost driver!Smile), does it also outperform the middle-of-the-road boost drivers that come with cheapie lights?

ChibiM
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Ah... I was under the impression its only for lithium cells!

so it can run of AA cells as well? thats great

wight
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driveX wrote:
I have made some prototypes with 7mm inductor, linear moonlight, voltage monitoring and ramp programmable modes (I don’t have the linear ML and VM programmed in my firmware yet). The problem is that I don’t have enough time to play with it. I need to make one more version with more space for diode so maybe I’ll end with just 5mm inductor. My previous versions used small diode and it didn’t perform very well. I also made a nice board for ATTiny10 but I realized that it doesn’t have an eeprom too late :-/ I have some useless boards now.
  • 7mm inductor is quite large, is there a benefit for this application?
  • What component size and footprint size are you using?
  • I think your layout is never compatible with SOIC programming clips, right?
  • I will study your layout, besides teh programming clip compatibility it looks nice to me.

djozz wrote:

Nice! 15mm drivers open up the possibility of modding most AA-sized lights.

And if it is all going to work: will this driver have:

a) a decent efficiency compared to other boost drivers

b) a decent output current on a 1.2V NiMh battery, like over 1A through a XP-G2 emitter ?

In other words, apart from being able to have a custom UI (which is a wonderful perspective in a boost driver!Smile), does it also outperform the middle-of-the-road boost drivers that come with cheapie lights?

Don’t get too excited djozz! The PAM2803 is only the normal boost controller we find on common boards such as DQG AA/AAA lights, Fenix E05 (& probably others), DX SKU#128084, Nanjg-110, and many others.

The answers to your questions are “maybe” and “no”. No, it will not put out 1A from a single NiMH. The datasheet has a good and easy to understand graph on that subject, please take a look. Efficiency? I expect that to be similar to other similar drivers such as the ones mentioned above. Take a look here for HKJ’s review of the 400mA Nanjg-110. It is not very efficient: no surprise!

ChibiM wrote:

Ah… I was under the impression its only for lithium cells!

so it can run of AA cells as well? thats great

No comment on running it with lithium cells. It is a boost controller with a cap of around 5v for output and a minimum of around 0.9v (startup) voltage for the input. It’s intended for applications where input voltage is lower than LED Vf. Generally speaking that means that it is intended for driving white LEDs on 1xAA, 2xAA, or possibly 1xCR123A.

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ChibiM
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But the first of its kind where you can flash your own firmware! On an AA driver!?

wight
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ChibiM wrote:

But the first of its kind where you can flash your own firmware! On an AA driver!?

Well, not the first to be created: driveX’s driver seems to be dated 10/14. Wink

But yes, mine may end up being the first publicly available one where you can flash your own firmware.

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wight
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Am I right in thinking that Pin5 (VOUT) is simply a voltage feedback pin?

The pin descriptions in the datasheet are not very useful. We’ve already got other pins for Switch and FB/SENSE, so I can’t imagine VOUT being anything but voltage monitoring…

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driveX
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Sure it should be a feedback for oscillator. It’s 5am now and I’m having finals at nine so I will get back to you later. Tomorrow probably, after getting some sleep Smile

wight
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driveX wrote:
Sure it should be a feedback for oscillator. It’s 5am now and I’m having finals at nine so I will talk back to you later. Tomorrow probably after getting some sleep Smile
Thanks driveX. I have updated my layout. For now I have assumed that VIN can have a small trace. Please let me know if you think that this is incorrect.

Good luck w/ your finals!

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wight
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v016

  • FET for PWM was miswired. I fixed it, I think..
  • Made a new 0805 footprint (based on the Eagle one) which I hope to be meaty enough for easy hand soldering and inspection. The pads are the same distance apart from each other, but they are both less long and less wide. The white tdocu markings showing the component outline are the same as the stock Eagle 0805 footprint.
  • If you are willing to aggressively shave your SOIC programming clip or give up onboard programming, a 5.0×4.5mm rectangular inductor will fit (or a 5.5mm round one). With a 4.0×4.0mm inductor an unmodified SOIC clip should be a snug fit.
  • I used Eagle’s big, stock, 0805 sized footprint for the Schottky diode. This should have enough space for an adequate one, but if you need to use a bigger one you’ll just have sacrifice the SOIC clip.
  • There are 3× 0805 components on the board with no identifier. These are all 10uF capacitors.
  • LED- is at the top next to Rs / LED+ is at the bottom on the end of the capacitor.

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H-Man
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What would happen if the driver was built with a high resistance sense resistor for a current a bit above the requirements of the drive and a barely glowing LED AND a FET in parrell with the sense resistor so to increase the output, the micro controller would have the FET turn on? I’m not sure that the PAM2805 will take kindly to this kind of treatment or if it would actually do anything for efficiency on lower modes.

I do horrible things to electronics in an effort to get them to do what I want.

wight
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H-Man wrote:
What would happen if the driver was built with a high resistance sense resistor for a current a bit above the requirements of the drive and a barely glowing LED AND a FET in parrell with the sense resistor so to increase the output, the micro controller would have the FET turn on? I’m not sure that the PAM2805 will take kindly to this kind of treatment or if it would actually do anything for efficiency on lower modes.
I’m not really sure where you’re attempting to go with that line of thinking.

With weak cells or 1xAA you’d get the normal current for 1xAA. It’s not limited by sense resistance at low input voltages.

With 2xAA and strong cells I assume you’d burn the PAM2805 when you turned on the FET.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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H-man, I have to completely agree with Alex here the circuit in the boards above is the correct use of this boost iC, can you link to a datasheet your looking at or why it is exactly you think adding those components would do anything different / better?

Can we back up (probably a topic for its own thread) but what is it your trying to do? Just have a higher current boost driver?

 RIP  SPC Joey Riley, KIA 11/24/14. Now I am become death, the destroyer of worlds.

H-Man
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wight wrote:
H-Man wrote:
What would happen if the driver was built with a high resistance sense resistor for a current a bit above the requirements of the drive and a barely glowing LED AND a FET in parrell with the sense resistor so to increase the output, the micro controller would have the FET turn on? I’m not sure that the PAM2805 will take kindly to this kind of treatment or if it would actually do anything for efficiency on lower modes.
I’m not really sure where you’re attempting to go with that line of thinking.

With weak cells or 1xAA you’d get the normal current for 1xAA. It’s not limited by sense resistance at low input voltages.

With 2xAA and strong cells I assume you’d burn the PAM2805 when you turned on the FET.


Don’t FETs of the size being used has an on resistance similar to that of the feedback resistor (~130 mOhm)?

The intent is to have the driver have a low mode without having it bounce off of the voltage limiter. My line of thinking is that with 2AA on lower modes, the PAM2805 would have to boost the voltage from ~2.4V to something below 3V with the FET off and then only have to boost to the relatively high voltage necessary to run the desired current through the LED when it is being pulsed. The current design has the PAM2805 bounceing off of the voltage limiter when the FET is off, right? That can’t be terribly efficient.

RE: The PAM2805 burning up: I shorted out the sense resistor on a boost driver that looks to be built around a PAM2805 or similar, it did not burn. There may have been some resistance in the circuit, but bypassing the sense resistor bumped current being pulled off of 2 eneloops from 1A to nearly 2A.

I do horrible things to electronics in an effort to get them to do what I want.

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Has anyone prototyped this circuit? The basic PAM2803 circuit can be harvested from this cheap driver. Actually, that driver can be connected to any BLF DD driver for prototyping.

one year rookie

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Can it be filed to fit a 14mm cavity? I wanted to put one in a brass AA light from Cnq / Banggood.

wight
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dthoang wrote:
Has anyone prototyped this circuit? The basic PAM2803 circuit can be harvested from this cheap driver. Actually, that driver can be connected to any BLF DD driver for prototyping.
IIRC I haven’t actually shared this driver yet. I haven’t ordered or built any. Thanks for linking to a cheap donor driver for the parts. Now I’m somewhat more interested!

Gunga wrote:
Can it be filed to fit a 14mm cavity? I wanted to put one in a brass AA light from Cnq / Banggood.
Maybe if you are very careful. You’ll probably break the GND ring on top and have to rely on the GND ring on the bottom for continuity between the GND vias. I thought that those lights used a 15mm driver?

H-Man wrote:
Don’t FETs of the size being used has an on resistance similar to that of the feedback resistor (~130 mOhm)?

The intent is to have the driver have a low mode without having it bounce off of the voltage limiter. My line of thinking is that with 2AA on lower modes, the PAM2805 would have to boost the voltage from ~2.4V to something below 3V with the FET off and then only have to boost to the relatively high voltage necessary to run the desired current through the LED when it is being pulsed. The current design has the PAM2805 bounceing off of the voltage limiter when the FET is off, right? That can’t be terribly efficient.

RE: The PAM2805 burning up: I shorted out the sense resistor on a boost driver that looks to be built around a PAM2805 or similar, it did not burn. There may have been some resistance in the circuit, but bypassing the sense resistor bumped current being pulled off of 2 eneloops from 1A to nearly 2A.

Hmm, I see what you were going for now. Personally I still think it’s a bad idea. The on-resistance is not a static value, or even “near static” like a passive resistor’s value (which does still change with temperature). On-resistance changes significantly based on both input voltage and load. Unless someone spells it out for me that this idea will reliably function, I am going to assume that it will not reliably function. Sad Ah, now I see that you’ve actually done an experiment.

Interesting. In that case, maybe the idea is viable. I still think that it will be prone to burning things. If the PAM280x doesn’t burn instantly it can still burn over time. Of course the next question is also whether anyone actually wants a 2-mode 1xAA / 2xAA driver? (I’m asking, not telling.)

As far as the bouncing off the voltage limiter business… I wouldn’t worry about it. These things have terrible efficiency in all cases I’m pretty sure…

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

H-Man
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wight wrote:
dthoang wrote:
Has anyone prototyped this circuit? The basic PAM2803 circuit can be harvested from this cheap driver. Actually, that driver can be connected to any BLF DD driver for prototyping.
IIRC I haven’t actually shared this driver yet. I haven’t ordered or built any. Thanks for linking to a cheap donor driver for the parts. Now I’m somewhat more interested!

Gunga wrote:
Can it be filed to fit a 14mm cavity? I wanted to put one in a brass AA light from Cnq / Banggood.
Maybe if you are very careful. You’ll probably break the GND ring on top and have to rely on the GND ring on the bottom for continuity between the GND vias. I thought that those lights used a 15mm driver?

H-Man wrote:
Don’t FETs of the size being used has an on resistance similar to that of the feedback resistor (~130 mOhm)?

The intent is to have the driver have a low mode without having it bounce off of the voltage limiter. My line of thinking is that with 2AA on lower modes, the PAM2805 would have to boost the voltage from ~2.4V to something below 3V with the FET off and then only have to boost to the relatively high voltage necessary to run the desired current through the LED when it is being pulsed. The current design has the PAM2805 bounceing off of the voltage limiter when the FET is off, right? That can’t be terribly efficient.

RE: The PAM2805 burning up: I shorted out the sense resistor on a boost driver that looks to be built around a PAM2805 or similar, it did not burn. There may have been some resistance in the circuit, but bypassing the sense resistor bumped current being pulled off of 2 eneloops from 1A to nearly 2A.

Hmm, I see what you were going for now. Personally I still think it’s a bad idea. The on-resistance is not a static value, or even “near static” like a passive resistor’s value (which does still change with temperature). On-resistance changes significantly based on both input voltage and load. Unless someone spells it out for me that this idea will reliably function, I am going to assume that it will not reliably function. Sad Ah, now I see that you’ve actually done an experiment.

Interesting. In that case, maybe the idea is viable. I still think that it will be prone to burning things. If the PAM280x doesn’t burn instantly it can still burn over time. Of course the next question is also whether anyone actually wants a 2-mode 1xAA / 2xAA driver? (I’m asking, not telling.)

As far as the bouncing off the voltage limiter business… I wouldn’t worry about it. These things have terrible efficiency in all cases I’m pretty sure…


If you PWM the FET, you can still use PWM in theory (in reality, it may fail hilariously.) I’ve tested a shorting of the sense resistor, I haven’t tested long enough to trust it but if the efficiency is still horrible, that point is moot because the whole point of this would be to try to improve efficiency. Are there no efficent boost ICs?

BACK ON TOPIC: At this point, just being available will make this the best boost diver for multimode AA/2AA lights because I don’t think there is a single microcontroller driven boost driver for AA/2AA/CR123 on the market right now.
Would there be any benefit to using a remote mounted toroid choke in this driver?

I do horrible things to electronics in an effort to get them to do what I want.

wight
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H-Man wrote:
If you PWM the FET, you can still use PWM in theory (in reality, it may fail hilariously.) I’ve tested a shorting of the sense resistor, I haven’t tested long enough to trust it but if the efficiency is still horrible, that point is moot because the whole point of this would be to try to improve efficiency. Are there no efficent boost ICs?

BACK ON TOPIC: At this point, just being available will make this the best boost diver for multimode AA/2AA lights because I don’t think there is a single microcontroller driven boost driver for AA/2AA/CR123 on the market right now.
Would there be any benefit to using a remote mounted toroid choke in this driver?

There are plenty of efficient boost ICs, but not with a 1.2v or 2.4v Vinput.

If nobody sees any problems with this driver as laid out in post #13 then I’ll review for design rule violations and release it as a WIP.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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Hi wight,

that’s a nice one. I like the idea of a “Nanjg 110 with modes”. I built some lights with the Nanjg 110 as it seems to be the best of the bunch of 1-cell-boost-drivers and I prefer Eneloop-torches for the kids.

-

Some ideas for the layout:

Why suddenly PAM2805? 2803 and 2805 are not pin compatible and your circuit in post 13 follows mostly the 2803 datasheet circuit, except for the capacitor between Pin-1 and GND. No such with the 2803. The 2805 has its input capacitor there, as Vin for the 2805 is Pin-1.
The output capacitor for 2803 is between Pin-5/Diode/LED+ and GND, so it in fact is at the same position as for the MCU capacitor. This Cap might be disposable, one could as well use a higher value for output capacitor (22yF) as the datasheet suggests for “high power” LED – I think they a referring to 750mA.

Any particular reason for PWM using MCU Pin-5? As Pin-6 is the usual rail for pwm in our firmwares and as we’re not using multiple rails on this one we might just stick to pin-6.

-

I want to do a test setup with a Nanjg 110 and a stripped Nanjg AK47 to see whether the design will work at all.

I have all parts except for the FET. Could someone please give me some specifications for the FET. I have only a faint idea what is needed here as up to now I don’t use FET/DD drivers.

One that I think might fit the pin layout and spec is
IRLML0030TRPbF
Power MOSFET
N-Channel
SOT-23-3
UDS 30V
UGS (th) +/-20V
Id 5.3A (4.3A at 70°)
RDS (on) 27mOhm (40mOhm at 4.5V)

That one ok, or any value that could be better than on this one? Or any other value that has to be observed?
Thanks a lot.

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To make part selection easier I made a more detailed partlist according to wight’s design as of now and following the recommendations in the PAM2803 datasheet. Suggestions and corrections are welcome.

PAM2803
SOT-23-6

Inductor
min. 2.2yH, 4.7yH recommended, DC resistance (DCR) as low as possible
4mm x 4mm / 5.4mm x 5mm

Diode
Schottky, min. 2A, Vf as low as possible

Input Capacitor
min. 2.2yF, X5R or X7R recommended
SMD0805

Output Capacitor
min. 6.8yF, 10-22yF recommended, X5R or X7R recommended
SMD0805, perhaps increase to SMD1206 for 10-22yF on a 17mm board

Current Sense Resistor (Rs)
~0.120 Ohm for 750mA (2cell)
SMD0805

ATTiny13A-SSU (MCU)
Package 8S1

Capacitor for the MCU
(might be unnecessary as being in parallel to Cout)
10yF, X5R or X7R
SMD0805

Off-Time-Capacitor (OTC)
1yF, X5R or X7R
SMD0805

MOSFET

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This seems to work.

I hooked up a stock Nanjg110 to an ATtiny13a, and a Cmcu, both remainder of a Nanjg AK47. I added an OffTimeCap between Pin-2 and GND. And I used the FET I described 2 posts before. I placed the FET on the pads for a 7135, cut the traces and rewired (better: re-blobbed) for the PWM signal from Pin-6.

I flashed a it with an offtime firmware with 4 modes.
And there was light.

First impressions:

It does work on two tested frequencies:
PWM at 4 kHz (9.6MHz CPU, divider 8, fuse 6a) had a strong whining, but mostly from the magnet on the Eneloop.
PWM at 18 kHz (4.8MHz CPU, divider 1, fuse 75) still produced a slight whining, hmm…

At 18kHz PWM values of 2 – 10 – 40 – 255 resulted in 12mA – 102mA – 198mA – 404mA with a single full and resting Eneloop. Keep in mind that this boost driver by design does not regulate anymore with 1 NiMH cell. See HKJ’s test for the Nanjg110, especially the first graph. So the current does degrade straight from the beginning in all modes. Results with 2 cells will be better for sure, but those later.

The 404mA at PWM 255 is about the same that resulted in driving the bare Nanjg110 on that LED, which I did before I hooked the setup together. So the FET with PWM does not seem to loose much energy here.

So far, so good.

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Short version: nanjg 110 is boosting voltage fed to mcu and FET whose gate is pwm controlled by Attiny13A, correct? Could you use a BLF tiny10 DD(or any BLF DD) stacked on the 110 this way?

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HarleyQuin
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Rufusbduck wrote:
Short version: nanjg 110 is boosting voltage fed to mcu and FET whose gate is pwm controlled by Attiny13A, correct? Could you use a BLF tiny10 DD(or any BLF DD) stacked on the 110 this way?

Short version: Yes, that’s what it does.

BLF DDs: I can’t say, I didn’t follow the development and specs of the DD/FET drivers. But in theory, if you isolate the needed parts and feed them with the 110’s output, perhaps.

Oshpark Boards:
HQ ProgKey: Universal Driver Programming Key . Boost: HQ 15mm/17mm programmable boost driver with ATtiny13A
46mm Triple-Channel: BLF SRK FET v3 . 17mm Linear: HQ10D / HQ4D / HQ4S . Contact Boards: 22/24/26mm

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So is your test (above^^) essentially a mockup of wight’s board, or is it a different design altogether? Could wight’s board be mostly populated by stripping a 110 and an AK47?

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Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

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Basically my test is derived from wight’s idea.
But I went along the datasheet of the PAM2803, as it seems wight has somewhere along the path mixed up the PAM2803 and the PAM2805 (see my comment in post#23), which are not pin-compatible.
The Nanjg110 seems to have the PAM2803, as the board is designed after that datasheet.
So I took
- a Nanjg110
- a stripped AK47 (for ATtiny13A, Cout)
- added 1yF OffTimecap (but the standard STAR firmware values dont work and need to be tweaked)
- added a IRLML0030TRPbF N-Channel MosFET
and that was it.

In the meantime I tested the stock Nanjg110 with several other diodes and inductors with interesting results (gaining efficiency with 2 cells and gaining output with 1 cell). Got a last diode today, will post altogether in some days.

I’d be interested to know if there is a better FET that could be used.

Oshpark Boards:
HQ ProgKey: Universal Driver Programming Key . Boost: HQ 15mm/17mm programmable boost driver with ATtiny13A
46mm Triple-Channel: BLF SRK FET v3 . 17mm Linear: HQ10D / HQ4D / HQ4S . Contact Boards: 22/24/26mm

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Hmm Interesting. I might have to start playing around with this too.

Unfortunately I can’t help with Fet options, I’m a blind bat when it comes to reading spec sheets.

My Favorite Modded Lights: X6R, S8 , X2R , M6, SP03

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

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