DC-DC Converters ... who has the best price?

[Knuckles]

http://item.taobao.com/auction/item_detail-0db2-7c2f3e11df20ebc467e065ba5edd8f13.htm

Max 60V in and adj V out

1" x 2" x 1/2" ... slim 8)

22.00 CNY = $3.23 USD
Now that's CHEAP!

 

[Russell]

http://item.taobao.com/auction/item_detail-0db2-7c2f3e11df20ebc467e065ba5edd8f13.htm

Max 60V in and adj V out

1" x 2" x 1/2" ... slim 8)

22.00 CNY = $3.23 USD
Now that's CHEAP!

But what CURRENT can it deliver?

-R

 

[full-throttle]

3Amax

Good find! How can they possibly be so cheap??

 

[amberwolf]

Probably minimum order of ten bajillion. :lol:

 

[Russell]

Probably minimum order of ten bajillion. :lol:

Plus shipping

-R

 

[amberwolf]

And maybe they're all the ones that failed QC. Oh, wait, do they even *do* QC?

 

[auraslip]

If you wanted to start making enclosures for these and selling them to ebikers like ebike.ca it'd be worth it to buy a few and check out the quality!

In my experience even if the minimum order quantity is high (1000s) they will still ship you a few if you want to to "quality testing". You just gotta convince them that you really might follow through on the big orders...

Damn I could make a pretty penny on ebay selling these if I knew more about electronics

 

[Knuckles]

Keywin has them for $6.20 USD ... I just ordered 4 modules.

My Chinese buddy!

Apparently he sells "chit loads" of these for LED drivers ... also for "low V" controller VR circuitry.

Can't wait to hack it! :lol:

 

[full-throttle]

And maybe they're all the ones that failed QC. Oh, wait, do they even *do* QC?

Some do, some are very advanced with their procedures. But they charge $$ for the privilege.

 

[pdf]

Sorry for the late post. What voltage can a MagicShine use? Want to run one off a 36v battery. Battery pack is 7.2v, but i assume there must be an onboard regulator. I infer from some of the postings that people are using 12v. Is that correct?

 

[John in CR]

Why do they make these things with such narrow ranges of input voltage? How is a DC/DC converter better than the 12VDC out switching supply I use that can accept 110-220VAC and I've tested it as low as 37VDC as the input and still got the solid 12V out?

 

[docnjoj]

Sorry for the late post. What voltage can a MagicShine use? Want to run one off a 36v battery. Battery pack is 7.2v, but i assume there must be an onboard regulator. I infer from some of the postings that people are using 12v. Is that correct?

I asked Dr Bass that same question and I believe he said 8-14 volts for MagicShine. He uses 4 of them! I'll bet the trees burst into flame as he goes by.
otherDoc

 

[Kingfish]

I have Qty-2 of the KKP60MT312. The MPS for BBC is taking longer than expected therefore I am executing on Plan-B to get me through the night.

The Application Notes for the device have been attached. Note that the USA importer does not carry the required heatinks - and we are on our own. :?

View attachment VKP60MT312-app-notes.pdf
Primary Use:
Pull up to 3A off the V1 3.3V circuit to power up to three UniqueFire X8 Cree XP-G R5 300L HP-LED Flashlights. The output voltage will be trimmed-up to 4.0V with a resistor value of 220 Ohm.

Questions:

• May I presume the Trim Resistor wattage as being ¼ W?
• Input: 15S LiPo, therefore 54-63V and within spec; I’m in good shape. I suspect I may require some input filtering; small cap & inductor, yes?
• If the flashlights are off, can the DC converter still draw power? I think the answer is no, though I seek validation.
• The maximum efficiency for the XP-G R5 is between 1 and 1.5A. I’d like to limit that to 1A each, therefore I am asking for is a current-limiting circuit, either individually per light or as a whole. Does this make sense? :?
• The total wattage (sans internal losses) is 4.0V * 3A = 12W, yes?
• If so, then the additional heat generated is 12 * 8.2 = 98.4*C, is that right? Maybe I should mount it beneath my seat. :lol:

Thanks in advance for advice. KF

 

[amberwolf]

Note that the USA importer does not carry the required heatinks - and we are on our own. :?

Have you looked at various CPU heatsinks? Lots of them would work, if you are willing to drill the holes in them for bolting on.

I skipped the bolts, myself:

 

[tycreek]

Wow... Hot enough for a heat sink? I've been running a C&D Technologies DC-DC converter for months with 3 Cree's on the 3v tap and haven't noticed any heat issues (looks like that one in AW's post). I'm bench testing with smaller same converter (60 vs. 100); 3 P7 cree on the 3v and 2 MC-E on the 12 w/flasher and had the flasher on quite a bit in a hot garage and the only heat change I observed was from the LED's not the converter. FWIW... 2 P7 Crees can put out a lot of light as a headlight if focused and are more than needed as a taillight with a red dispersing lens cover.

When a DC/DC converter nears the footprint of a separate battery ... hum...

 

[Kingfish]

AW: Man that is impressive! I take it in AZ you need that kind of relief.

Tycreek: So your lights are self-regulating on current?

Am I over-thinking this?

I figure 3 Crees as:

• 1 Flood
• 1 as a Blinky
• 1 Spare/Dual-light

Rear Lighing:

• Peel off 100mA to power two "AA" Blinkies.

You guys instill a lot of confidence! :wink:
Truly, thanks! KF

 

[amberwolf]

I used the heatsink because I had it, and because I know that in the ambient temperatures of over 105F we still get some days right now, it's harder for a small surface area like the DC-DC has to shed the heat generated from running the headlight at almost 2A, near it's max on one 12V line, and beyond it's max in pulses (several amps for an instant and then ramping down to about 1-2A, every 2/3 of a second or so) on the other when using the turn signals (plus that side has the taillight on all the time for around 500-750mA, a third of max, and occasional brakelights for 2/3 max, 1A-1.25A, PLUS the over-max turnsignals at the same time sometimes).

I havent' tried calculating heat generation by it, but since even with the heatsink I used, the HS is warm, I feel better with it on there. Also, mine is enclosed partly within the "fairing" plastics on the bars now, so more heat will probably be retained than otherwise.

It might nto actually be necessary for one. But as I only have the one 12V DC-DC, I'd rather be safe than sorry. I can always build a simple new one based on the Roman Black stuff, but I'd rather not.

 

[Kingfish]

Roman Black stuff? Wot be that?

This is like the 4th time I have dug around for a heatsink for this device - and this time I found a supplier in California; too late to call them now, but will do come Monday. Here's the link:

• HDM-HS

I just typed into Bing: heatsink "2.3 x 2.4" and there it was. These guys make a bunch of different power modules in brick format, though they are the only ones with this heatsink. Dunno the price. Regular stock material would probably be cheaper. If it's not over $10 I'll prolly grab two.

In the Pacific Northwest-Western Washington we get maybe one or two days that are in the high 90's or above 100 (and when it does I freak people out by wearing black ) so heat is not that big of a deal here. But who knows - I might move...
and decide to be your neighbor next month

Just kidding... maybe

Thanky, KF

 

[tycreek]

Tycreek: So your lights are self-regulating on current?

Well... good question!
NO! I beleive they are bare P7 Cree LED's.

Haven't blown anything yet and we've many days over 100deg here. None of my plastic surrounds have melted etc... All looks just like it did when I put it together. Here's info on what I did: http://endless-sphere.com/forums/viewtopic.php?f=6&t=18691&start=15#p286256
Still haven't hooked up the turn signal LED's ... a busy summer!

 

[amberwolf]

Roman Black has designed a few DC-DC circuits, and they're very easy to make. Given a good math and electronics knowledge it would also be possible to recalculate any of his circuits for other voltages. I'm crappy with math but eventually can figure things out after I get them wrong enough times.

http://romanblack.com/smps/smps.htm#apps
There are a few variations already present, along with explanations.

As for heatsinks, unless you are looking for one specifically for others to be able to just order up and use with the same DC-DC you have, then the DIY route with a PC CPU heatsink would seem faster just to get you going (unless you don't have any stuff like that lying around).

 

[Kingfish]

Tycreek: You know – I always wondered if those dies could be directly wired. You have me inspired to go fetch one of those big 5” diameter flamed headlamp holders and put a Cree in it. Have to figure out to route the heat away though.
Thanks for sharing!

AW: I like the Hippyware link. My favorite is the BMP Hider; paint me a nerd, I’m into raster – and hiding a file in the header made for a good belly laugh.

The Minimalist design is a great concept. I’ll have to study that circuit you suggested; electronics is not my forte. I bet I said that already.

Heatsinks:
You have me thinking about tearing into one of my dead pcs; a Dell that experienced a short life of only four years. Appalling. I had a laptop from them in the same era that had to have the motherboard replaced annually; it too no longer boots. Might be able to salvage that Heatsink for the Flame headlamp. Oh now it’s in my head and I cain’t let go of it!

Links:
http://customdynamics.com/headlights.htm ; also these guys…
http://www.kustomwerks.com/metric/images/products/07m_part5.pdf
Whadda ya think? Stuff a Cree 4X in there where the 55W bulb would go. It would need some serious heat-pipe. 8)

Awesome stuff guys! Thanks KF

 

[kjparker]

Tycreek: So your lights are self-regulating on current?

Well... good question!
NO! I beleive they are bare P7 Cree LED's.

Haven't blown anything yet and we've many days over 100deg here. None of my plastic surrounds have melted etc... All looks just like it did when I put it together. Here's info on what I did: http://endless-sphere.com/forums/viewtopic.php?f=6&t=18691&start=15#p286256
Still haven't hooked up the turn signal LED's ... a busy summer!

So just so I understand correctly, your direct driving the cree's from the dc - dc converter? Hmm, I might have to try that. P7's are becoming increadibly cheap these days!

 

[tycreek]

So just so I understand correctly, your direct driving the cree's from the dc - dc converter? Hmm, I might have to try that. P7's are becoming increadibly cheap these days!

I did adjust the vout down a bit from 3.3v to 3.2v with a trim resistor ... maybe that somehow limits current? The cree's also worked perfectly fine and achieved essentially the same vout with a 1ohm resistor on the output pin. In reading it seemed a resistor was needed to limit current... but I have 3 P7 LED's connected directly in parallel to the adjusted output. Figured I could trim up Vout in cold weather (like now) and down when hot (then). I've not touched it again since I set it as the light output is quite enough.

On the planned 12v Cree's there's resistors inline because the flasher wouldn't flash without them. I've a little more to prove out with the 12v Cree's when life slows down a bit.

WARNING: Make sure you wear eye protection when messing with LED's! Seriously, if they pop, stuff flies! I've not exploded a Cree yet... but many other types of LEDs have thrown a top at me!

 

[Kingfish]

...
This is like the 4th time I have dug around for a heatsink for this device - and this time I found a supplier in California; too late to call them now, but will do come Monday. Here's the link:

• HDM-HS

I just typed into Bing: heatsink "2.3 x 2.4" and there it was. These guys make a bunch of different power modules in brick format, though they are the only ones with this heatsink. Dunno the price. Regular stock material would probably be cheaper. If it's not over $10 I'll prolly grab two.

...

:x These guys at Rantec.com do not answer emails or phones. I searched extruded aluminum heatsinks but did not find an exact match; close though - very close and likely might have worked, except - I got bit by the eBat bug and had to go on a hunt and found this:

Heat Sink

Hopefully the search will still work. Anyways - this is almost exactly the precise dimensions for the device. At $1 each (used) + shipping, I bought two. I'll let you know how it works out when I gets them :wink:

Cheers, KF

 

[Kingfish]

Hey I just wanted to drop a note that I received my heat sinks about two weeks ago. I have been waiting on the flashlight clamps to arrive before proceding; those came in today.

Quick question about the VKP60MT312:
I have the application notes open and I'm looking at the source Vin, and the output V1. I have decided not to adjust the output voltage; just keep it at 3.3V so I can run all my battery lights at the same-ol-same voltage (KISS). With two Crees mounted I hardly think I'll be short on candlepower 8)

Would it make sense to put a filter cap on the In and Out of the device?

I'm at http://www.RadioShack.com: The lowest they have is a 10µF 16V 20% Tantalum (for the output @ 3.3V). If I run the Cree on Flashy mode that might goof with the current. How about maybe a 100µF 35V 20% Electrolytic might do it? I think I have a spare 100V 100µF Electrolytic for the Input.

The whole list is:
Up to 3 Crees @ 1A each, and two blinky rear tail lights pulling µAs.

Whatch think? Would that be suitable? Or am I over-thinking :?
Thanks, KF