17mm & 20/26/27mm single-sided DD/FET driver release: A17DD-SO8 / A20DD-SO8 / etc

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Rufusbduck
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Best place to solder a dedicated ground would be across the 3 ground pins of the FET since that’s where most if the juice flows.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

ImA4Wheelr
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wight, would be great to get your thoughts on two items.

First is regarding using your 26mm board to experiment with adding a thermistor circuit?  These big multi-emitter lights need thermal protection more than pretty much every other light out three.  ToyKeeper is building a program for garrybunk that should be able to use it to throttle power down when the thermistor gets too hot.


I thinking such a circuit should look just like a voltage divider you taught me about except for the following:

  • R2 will be a thermistor instead of a resistor.
  • There should be a capacitor parallel to thermistor.  Probably can just be stacked on top of the thermistor if space is an issue.

It seems the power for the circuit should branch off the Vcc line.  It would be good if the ground for the thermistor was directly linked to the ground ring for good thermal connection.  I don't know what MCU pin pad to recommend.  I would think any available one except PB3.   I also don't know what thermistor or capacitor size to use.

Your 26mm board has some spare space.  That and the fact that it will tend to be used in big high powered lights makes it seem like a great candidate.  We will be get some insight with garrybunk's light, but that driver has a much different MCU Vcc circuit.


Secondly, what are your thoughts of paralleling a capacitor on R2 in a normal voltage divider circuit.  I think it would smooth out the signal and might resolve the premature triggers that I think I may have been getting on my Crelant 7G10 build.  I will be exploring this after I finish garrybunk's build.

EDIT: Clarified some wording.

wight
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ImA4Wheelr, you are correct that the circuit for using a thermistor should look like a voltage divider (because it is a voltage divider). I’m not certain which position will work best for us, I’ve seen diagrams with the thermistor in either position.

I don’t see what the point of the capacitor is (for either divider). I don’t expect for it to provide any smoothing.

Have you considered skipping the thermistor business and going with an all-in-one temp sensor? Microa has used LM45, RMM has been experimenting with MCP9700 (Post#625). MCP9700 sounds like a good one to me.

I did not include pads specifically for a temp sensing IC, but I did include pads. You may lay an MCP9700 across the pad attached to Pin3 and pickup GND right next to it. You’ll need an air wire to pickup Vcc but that’s it.

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)

wight
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In response to your edit… the MCU Vcc circuit on both boards (when used for 2s+) is very similar AFAIK: it’s just a Zener and a limiting resistor.

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)

ImA4Wheelr
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Excellent info.  Thanks wight.  You're right, there is plenty of space on your 26mm to easily air wire in such a circuit.  It wouldn't even have to be the air with the available open flat surface to run any wires needed.  That will work just fine.

I see what you mean about the circuits actually being similar on the Vcc feed now.

Regarding the parallel caps.  If they don't smooth, why do you think garrybunk's driver has them?

EDIT: I have no thoughts on the alternatives to thermistor.  I don't have an working knowledge in this area.

Hope you don't mind this discussion here.  Do you have a different thread you would prefer it in?  I can move my posts there if you do.  Here is a circuit diagram of some of garrybunk's driver:

wight
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I wouldn’t want to air-wire 0805 sized thermistors and resistors all the time, so if that turns out to be the thing to do I’d update the PCB. I doubt that it will be the thing to do though. Using a thermistor in a voltage divider is dependent on a known Vcc, so 1s use is impractical and 2s+ use requires the use of a known Zener value. The monolithic “sensor” IC is a much better route IMO.

As far as those caps go… good question. I don’t know the answer. I sometimes speculate that a fair number of the drivers we see have unnecessary components. I think that designers of lesser skill get a lot of “building block” circuits from datasheets and forums without a real understanding of what they do. They cobble these things together and get a functioning product and leave it at that. … that said, I could certainly be wrong in this case. I don’t have a very complete grasp of a lot of these concepts myself.

If your early LVP issues were happening in medium mode we could say that PWM might be causing something that needed to be smoothed. But early LVP with no PWM (HIGH/TURBO/whatever) on a linear light? I forgot that we were talking about a buck regulated light. Maybe we do need to smooth the divider. EDIT: I mean for your problem light, not over here.

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)

wight
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This discussion is fine here; I don’t know of anywhere better to have it. I guess you posted the diagram to show how the thermistor and smoothing cap are wired?

I can (now) imagine that the smoothing cap could have an effect on low voltage stepdown and low voltage shutdown when in modes other than 255/255 on a linear or DD driver with PWM. I’m not aware of problems with it now though, so we’ll have to see. For buck drivers I think it makes more sense because of the spiky way current is drawn from the batteries.

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)

ImA4Wheelr
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Thanks again wight.  Great info and thoughts as always.  I think I understand what you're saying about buck having different issues regarding voltage dividing.  I can see it will get real messy in here if we talk about your driver and buck.  Sounds like we should discuss buck voltage dividing in garrybunk's mod thread (since that will be actively pursued soon).

I really like the idea of getting true thermal management in the DD environment and your 26mm driver seems like the best candidate for experimenting with it.  When I get a chance do that, I will touch base with RMM so I don't reinvent the wheel.

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ImA4Wheelr wrote:
ToyKeeper is building a program for garrybunk that should be able to use it to throttle power down when the thermistor gets too hot.

More specifically, thinking about building a program… But I’m probably going to need actual hardware to test it on, or it’s very unlikely to work. Blind coding almost never goes well.

Regardless, I still doubt whether thermal protection is even relevant on a bike headlight. If the bike is moving, it’s unlikely to get hot enough to matter. I mean, unless it’s built really weird, like using a steel or plastic host… but IIRC this one is aluminum with heat fins and the intended use is to run it on medium or high (not maximum) during regular use. So, maybe 2.6 amps spread between two emitters. Doesn’t seem like it’s going to be an issue.

Rufusbduck
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Would it be possible to fix a starting voltage with a Zener and use the thermistor to alter that in comparison to Vref? Then the cold voltage is constant for the entire battery cycle and goes down only with heat.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

wight
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Rufusbduck wrote:
Would it be possible to fix a starting voltage with a Zener and use the thermistor to alter that in comparison to Vref? Then the cold voltage is constant for the entire battery cycle and goes down only with heat.
Sure, I think so. At that point you’ve got:
  • Zener
  • Limiting resistor
  • Thermistor
  • Other resistor for divider

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)

DB Custom
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Update on my Quad. I used a PH-08 from FastTech to put a quad in, with a solid copper pill and BLF17DD Ver 3.0. But I was having some flickering issues. So I pulled the V3 and put the A17DD-S08 with ToyKeepers newest Ramping firmware, bits commented out that didn’t apply to this light. Still flickered. So I pulled the tail cap apart and Voila! Dirty aluminum retaining ring and cheap pcb with dirty copper trace!

So, I cut a circle of copper from a bit of copper sheet Scott sent to me (Thanks again Scott! Wink ) and soldered a spring on it, bypassed the spring with a 22ga wire. Then filed down the aluminum retaining ring so it’s flat and new metal.

This A17DD-S08 driver allows the freshly charged Efest 35A to run 15.2A through the Quad XP-L V6 2C emitters! Folks, this is a pretty small light, making over 3000 OTF lumens! :bigsmile:

I Truly Do Love It When A Plan Comes Together!!!

(it’s a given, I do NOT have cold hands…)

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Um, the bad news is I only got about 7 seconds out of it on the lightbox at 4147 lumens, 3976 when it died, poof, just went out. So now I get to go back in and see just what happened. lol

wight
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DBCstm wrote:
Um, the bad news is I only got about 7 seconds out of it on the lightbox at 4147 lumens, 3976 when it died, poof, just went out. So now I get to go back in and see just what happened. lol
Aww crap. Smile

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)

DB Custom
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Yeah, but dang it’s thrilling for a light this size to pass 4000 lumens! :bigsmile:

Light works fine, just won’t sustain the top end.

DB Custom
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Just ran it 18 seconds at max level handheld, get’s REALLY hot, really quick! Still working, but shut it down.

It shut down when on the lightbox, headstanding, with all the heat rising into the copper right at the driver. Big Smile

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I put one of those spongy white thermal pad things on the MOSFET (came off the driver in my Olight Javelot) and just ran it for 45 seconds in hand.

This bad boy gets HOT! But it seems to be working. It’s been pointed out to me that 15A off 4V is in the 60Watt range or somewhat like a good soldering iron. Smile

Ok, so the 2 minute step-down is somewhat long.

wight
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Erm… I think it is possible that the PTC at the positive end of the cell overheated?

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)

DB Custom
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This is an Efest 35A, not protected. It is one of the new button tops but it has no protection to the best of my knowledge.

wight
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DBCstm wrote:
This is an Efest 35A, not protected. It is one of the new button tops but it has no protection to the best of my knowledge.
The PTC is a physical safety feature, it is not what you refer to as “protection”. AFAIK all cylindrical Li-Ion cells have that (as well as a CID I think).

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)

DB Custom
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Wow, learn something new every day! (I could have already known that, and forgotten it, and learned it, and forgotten it again)

Now I need to do some research, so I’ll be armed with more stuff to forget. Vicious circle, is it not?

wight
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DBCstm wrote:
Wow, learn something new every day! (I could have already known that, and forgotten it, and learned it, and forgotten it again)

Now I need to do some research, so I’ll be armed with more stuff to forget. Vicious circle, is it not?

Silly

One way figure out whether it’s the PTC is to remote-mount the battery. I know that this flashlight does not make it easy, but it’s probably possible with a sliding clamp to hold the cell, a nice jumper cable clamp for the GND/Bat- connection, and some copper rod or whatever for the BAT+ connection.

Or you could just solder some big hookup wire directly to the light engine.

I’m assuming that if it is the PTC then the problem is the heat from the emitters, not the cell self-heating or anything.

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)

DB Custom
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The PTC is a thermal switch to help prevent overheating of the cell causing pressure build-up. From what I’ve been able to find online, if the PTC is triggered the cell will most likely be useless. This cell is working fine, recharging fine, working some more. So it really is doubtful that it’s the PTC causing issue here. (Positive Thermal Coefficient) This is the primary information I found. And just now, looking to double check what I was writing, I found this information that contradicts the previous articles (4 different sources)

“Problem
Most commercial, cylindrical lithium-ion cell design are
equipped with a positive thermal coefficient (PTC)
current limiting switch to provide hazard protection
against short circuits external to the cell. This device,
shown in Figure 1, is thin annulus consisting of a
specially irradiated polyethylene laminated with a metal
on both sides [1]. When exposed to an overcurrent
situation, this normally conductive polymer heats up and
changes phases to become several orders of magnitude
more resistive. Once the short is removed, the PTC cools
down and returns to its electrically conductive state. This
device has been a very effective method of providing
reliable short circuit protection in low voltage battery
assemblies. “

This would explain why, after several seconds, the firmware caused a flash indicating power had been applied, even though I had not taken the light apart or opened it. The switch in the cell reset and power was again available.

So, is 15A+ the top end for the Efest 35A Purple cell? Leave it to me to have found that, huh? Silly

Now I will test the Sony VT C5. :bigsmile:

wight
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DBCstm wrote:
The PTC is a thermal switch to help prevent overheating of the cell causing pressure build-up. From what I’ve been able to find online, if the PTC is triggered the cell will most likely be useless. This cell is working fine, recharging fine, working some more. So it really is doubtful that it’s the PTC causing issue here. (Positive Thermal Coefficient) This is the primary information I found. And just now, looking to double check what I was writing, I found this information that contradicts the previous articles (4 different sources)

“Problem
Most commercial, cylindrical lithium-ion cell design are
equipped with a positive thermal coefficient (PTC)
current limiting switch to provide hazard protection
against short circuits external to the cell. This device,
shown in Figure 1, is thin annulus consisting of a
specially irradiated polyethylene laminated with a metal
on both sides [1]. When exposed to an overcurrent
situation, this normally conductive polymer heats up and
changes phases to become several orders of magnitude
more resistive. Once the short is removed, the PTC cools
down and returns to its electrically conductive state. This
device has been a very effective method of providing
reliable short circuit protection in low voltage battery
assemblies. “

This would explain why, after several seconds, the firmware caused a flash indicating power had been applied, even though I had not taken the light apart or opened it. The switch in the cell reset and power was again available.

So, is 15A+ the top end for the Efest 35A Purple cell? Leave it to me to have found that, huh? Silly

Now I will test the Sony VT C5. :bigsmile:

IMO the issue is that you are subjecting the cell to a very high temperature (although a 15A drain at the same time probably doesn’t help ;)). HKJ successfully tested the Efest ‘35A’ cells at 30A, with strong results at 20A.

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)

DB Custom
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The Sony C5, fresh off the charger, didn’t quite allow 14A (13.61-13.91) and showed 3784 lumens at the highest, dropping down to 3450 by the time it was too hot for me to hold my thumb opposing the switch. (54 seconds, as per the video I took while doing this.) I should also point out that I was taking a tail amperage reading with a 14” long 12Ga wire through the clamp meter while the light was in the light box. So the lumens output was lower than if the light had been assembled.

This light with it’s chunk of copper under the quad only dropped 340 lumens in 54 seconds at extreme power levels, I’d say that’s not bad at all!

Point here being that your A17DD-S08 driver is a very capable little single sided slimline device!

wight
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Hahahahaha, tell your hand thanks for taking one for the team! https://www.youtube.com/watch?v=qPr-xsQvhgw

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)

DB Custom
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The meter is set at X10 (so 10970), the number shown is then multiplied by .345 to get Lumens. This is the multiplier for my lightbox.

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Stock clicky DBCstm? ALOT of amps to be running thru a stock switch man

Still awesome as hell bro…all them amps! WOOO!

3000 lumen sleeper…guy is all, look at my light, and you MELT his with a click of the switch Big Smile

DB Custom
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It’s an e-switch with a ramping firmware and a sleep mode. Uses very little (some 40uA) current when not in use. A long press bypasses memory for the lowest position and hold, have to release to start ramping up from there. A double press goes straight to the max level. Single press from any position when on turns it off. Release the ramping and start again within a second and it reverses, otherwise it continues in the same direction if pressed again after one second. 64 steps, top to bottom in 2 seconds, or vice verse.

I find this very handy with the big draw lights, the most options to get the optimal light for the situation or conserve the cell or both.

Under the copper plate that holds the spring in the tailcap is a very strong magnet that holds the light even with this big chunk of Cu in the head. So I can also stop a pacemaker with it. Silly

And it does over 4000 with an Efest 35A, 4147 to be exact. Silly

Rufusbduck
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Holy hot stuff Batman, that thing is a portable reflow oven. Glad you found a use for the copper. Let me know if you see anything else in my builds(rare as they are) that you might use.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

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