The Haiku: why I personally feel the 3S lights have surpassed the PD lights

[recDNA]

I always go for selector rings so I can confidently choose output level before turning on.

[nbp]

OK. So I just finished talking to the head of the electronics shop here at the lab--and he also has a lot of industry experience. And I also talked to another senior research associate who designed the master oscillator and our hyper-fast timing system. Here is the summary of what they both said in regards to potting--and they were both pretty much in agreement.

1. Potting is definitely a good thing if you need to protect from the environment--splashes, dust, oil, etc. And in fact some of the open electronics here at work (i.e. not in a case) is in fact potted, and the head of the electronics shop was very positive about their results. He felt that it would take EXTREME temperatures (like -40C or below) to experience thermal issues like I mentioned earlier.

2. Potting is a lot more advisable when some or all of the board components are the kind with wire leads (as opposed to surface mount), such as capacitors sticking up on two legs, classic standard barrel shaped resistors with the two axial leads, and etc, and when the electronics will experience extended vibration (like in a vehicle or on a motor).

3. Potting is also advisable if any of the board components are massive and are attached only with the solder connections (like an inductor, for example).

4. However, in the case where the board components are surface mount, and the board is well mounted and mechanically connected to a case, and where the electronics will not get wet, then potting is unnecessary because the surface mount components are so well connected to the board, and potting makes repair and trouble shooting of failures or other issues impossible.

I asked both of them about the specific application of flashlights, and both thought potting the electronics was unnecessary, but both also thought it certainly wouldn't hurt, and would add some extra level of vibration and shock resistance.

So, I think the really short summary is "it's all good."

This is a great post! Very informative and well balanced from both perspectives. Thanks for digging up this info and sharing it with us js!

[easilyled]

This is a great post! Very informative and well balanced from both perspectives. Thanks for digging up this info and sharing it with us js!

+1

[js]

Thanks guys! In retrospect, I should have talked to all these people FIRST and THEN posted a SINGLE post with all the info. LOL! Ah well, next time I'll do better. I've been a bit scattered lately for various reasons.

[nbp]

No worries. Do you think it would be good to split the posts on potting off into their own thread within the subforum to make them easier to find? They are only loosely associated with the 3S vs. PD discussion. Perhaps Don would be inclined to offer his thoughts on potting?

[scout24]

Perhaps out into the wilds that are "General Flashlight Discussion" if anywhere. One of the charms of the McG subforum for me is the delightful, generally informative side-trips that are taken in some of the threads.

[kaichu dento]

Thanks guys! In retrospect, I should have talked to all these people FIRST and THEN posted a SINGLE post with all the info. LOL! Ah well, next time I'll do better. I've been a bit scattered lately for various reasons.

Nah, this way is better. Instead of a single informational post, we get a conversation.

[nbp]

Nah, this way is better. Instead of a single informational post, we get a conversation.

Good point. I'm with Pete.

[nbp]

Perhaps Don would be inclined to offer his thoughts on potting?

Don, I have never taken apart one of your light engines. Do the more recent ones just have empty space in the can between the emitter PCB and the driver board? I recently tried my hand at building an Aleph LE. It went ok, but didn't work quite right. And I potted it, making it impossible to fix anything. I loosely followed an old build log you had done, and in that one you potted it. My main reason for doing so was heat transfer, not so much durability. Do you feel that having just air in there is a disadvantage when it comes to heat transfer? Does having the AA thermal epoxy inside the can and up against the star help that much with heat transfer vs. solely the small contact areas from the star to the can to the head? When I build another, should I forget about potting it to make sure I can access things if I have problems and not worry about heat? I'm not sure which the best way to go is. Thanks for your help!

[McGizmo]

Don, I have never taken apart one of your light engines. Do the more recent ones just have empty space in the can between the emitter PCB and the driver board? I recently tried my hand at building an Aleph LE. It went ok, but didn't work quite right. And I potted it, making it impossible to fix anything. I loosely followed an old build log you had done, and in that one you potted it. My main reason for doing so was heat transfer, not so much durability. Do you feel that having just air in there is a disadvantage when it comes to heat transfer? Does having the AA thermal epoxy inside the can and up against the star help that much with heat transfer vs. solely the small contact areas from the star to the can to the head? When I build another, should I forget about potting it to make sure I can access things if I have problems and not worry about heat? I'm not sure which the best way to go is. Thanks for your help!

nbp,
Let me qualify my comments as those from no expert on this matter.
I haven't used any thermal potting epoxy or thermal grease now in a number of years. In the present version of light engines, the two sided converter is suspended between the MCPCB and contact board by virtue of its four leads. With the efficiency of the converters and drive levels I use, I have no reason to believe the converter needs enhanced thermal relief and I have not heard of or encountered one instance of damage due to thermal excess. As far as thermal relief for the LED itself, the MCPCB's are much better at spreading out the heat than our original epoxied LED's and sinks and again less heat produced these days. In my current design of LE, the MCPCB is slightly above the castle points on the cam so when the LE is tightened into the head, the MCPCB is pressed up against a shoulder in the head for a good thermal path and then it is also pressed against the can which can pass heat through its physical contact with the head.

In the original LE's of the Aleph series, the epoxy served a structural and mechanical purpose as well as aid in thermal relief. There are obvious advantages to a good potting job in terms of protection of the components but then as you have stated, access to the components has been removed. If possible, I believe access to all components and parts of a design has great advantages and is worth incorporating.

[nbp]

Thanks Don, that is very helpful. On my next one I will likely not pot it, at least not until my skills significantly improve or the situation would call for it based on a specific need. Thank you.

[js]

So I thought I'd post my further experience in regards to the 3S vs. PD lights. It seems since I re-acquired an LS20 that I have re-trodden the exact same ground that I covered back when I first got my Haiku!

At first, as I posted, I was really really happy to have an LS20 again, and I EDC'd it for a number of weeks and admired and played with it regularly. But then, gradually, over time, I just stopped using it that much and mostly used my Haiku because, well, for all the reasons that I talk about in the first post of this thread!

I understand--I really really do--why people love the PD lights, and I felt strongly enough about it that I spent a lot of money to own one again. But, once again, I'm back in the same position of rarely using my LS20. My Haiku is my workhorse light. It is awesome, practical, convenient, and the High CRI LED in mine throws such a beautiful light. Nostalgia and regret and love of the Piston-Drive concept are what prompted me to buy an LS20 again, but it is still my considered opinion that the new lights have surpassed the PD lights. Just my personal opinion. YMMV!

[nbp]

The Haiku reigns supreme! Again!