small 3xp7 driver?

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NightOwl™

Newly Enlightened
Joined
Jun 8, 2011
Messages
41
Bicycle light- The NightOwl-

Hi everyone!

This will be my first post 🙂
I'm trying to do a really small driver suitable for three ssc P7 in series.
I've been looking around at different data sheets to find what is best for my project, but it is really hard to find what I'm looking for, remember I'm a noob 🙂

Background information:
To power my driver and leds I got a battery with this setup 14.8v 8.8Ah.
I also want the driver to have a PWM input, so I can use a pre set from a extern uCPU
something like the TPS61042, but @ 2.8A ?
 
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Re: small 3xp7 driver

Hi, and a very warm welcome to CPF !
Check out Taskled drivers. I am sure there is something there for you. May I ask for what purpose is the light intended for, perhaps I or others can come up with ideas and suggestions to get you on the right track.
 
Re: small 3xp7 driver

Thank you!

well I think that the drives at taskled is too big but I will take a look.
I'm working on a bicycle light that will rock all the Swedish night riders, and perhaps international riders as well?
if I make my own driver then it could fit with the rest on my circuit board instead of having two separate thingies. 😱
okay, picture time!
first up, the design. 3 xp7
cnc machined housing and handlebar mount in aluminum.
Roughly 90*30 mm and 50 mm high (without the mounts)


Beamshot: with CPF 'standards'

 
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Re: small 3xp7 driver

Will you be driving those P7's at rated max current ? Them P7's get mighty hot very quickly if the bike is at a standstill or not going fast enough. Thermal driver shutdown may result if heat isn't rid of fast enough. Have you checked out the Shark Buck 2.8A driver from The Sandwich Shoppe ? It can easily handle the 14.8 V you have and is built like a tank. You can even add a 20K log pot and do some fancy dimming if you like. It is a single mode driver only. Make sure you adequately heat sink the driver. The Shark is a lot smaller than Taskled's offerings and may fit, I'm not sure about the chassis you have there though, perhaps a bit bigger. The light you have on the bicycle with the beam shot, what driver were you using for that. Have you also considered using the Cree XM-L's instead ? they can take 3A easily and in my opinion run a bit cooler and consume less from he bat. Anyway, good luck !
 
Re: small 3xp7 driver

Yep, 2.8A.
I know, they do get hot! but don’t worry I got that covered. 🙂
I've made some serious testing with my housing and it keeps a rather cool temperature.
Thanks for you tip, I will check out the sandwich Shoppe asap.
im planning to make five-six lights with the ssc p7 and then give the cree XM-L a shot.
I bought a few 2.8A drivers from Der Witchel here at CPF


[edit]
I measured the driver that I'm using now with the shark buck and the shark is only 5mm smaller. still too big :/
 
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Re: small 3xp7 driver

" regardless of V out?"

Perhaps you meant V in.
With my experience in the constant current buck drivers I have used, a constant maximum rated current depends on the voltage differential of Vin to the driver and the total forward voltage of all the leds combined. being a buck driver, there must be a minimum voltage differential for the driver to be within regulation. I have at many times used drivers that were rated at 2.8A but were outputting 2.4 or less as the differential voltage got down to 1-1.5 volt. As soon as I upped the Vin, the driver was indeed outputting the rated amperage. In your design of using a 14.8 volt battery, should not pose a problem at all. Just make sure that on a full charge, some batteries go to 18v and beyond. Make sure the driver can handle that.
 
Re: small 3xp7 driver

ah Vin, of course, I was rather tired yesterday :tired:
I think I found what I was looking for, the ME 5583 seems to do everything I ask for.
3A constant output current
up to 95% efficiency
3.6v - 32v input
Vout . adjustable from 1.235v to 21v
PWM control circuit is able to adjust the duty ratio​
linearly from 0 to 100%.

next problem, where do I find it ? GAH!:ohgeez:
 
Re: small 3xp7 driver

Hi NightOwl,

May I ask you What's the sizes of the driver compartment you are thinking of? Will it be located behind the p7 in the middle of you light? Where the push switch will be located?
 
Re: small 3xp7 driver

The driver compartment will be in a kind of box (max 20*60*15). from this driver box will there be three cabels, one from the battery and one to the leds and the last one to a controll located somewhere close to the handle.
 
Re: small 3xp7 driver

NightOwl™;3665200 said:
I'm working on a bicycle light that will rock all the Swedish night riders, and perhaps international riders as well
Click to expand...

In case of rocking all the riders worldwide you'd better choose XM-L instead of P7 🙂

Concerning your question: I use LT3755 with IRF7832 FET in my headlamps with 3 x XM-L in series from 2S2P LiIon. The converter is in the same housing wih the remote button and its dimentions are 30mm x 32mm x 10mm. In turbomode overdrive the LEDs get 4+ amps and the only component on the converter board that becomes slightly warm at this 40+ W consumption is Shottky rectifier.
 
Re: small 3xp7 driver

Taobao web stores. I am a Chinese lives in Hong Kong. I bought 5 pieces at the price RMB$3.00/pc not including shipping charges.
 
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Re: small 3xp7 driver

ah, I stayed in Kowloon last year, I search'd like a fool for a shop where I could buy componets like this, but never found one 🙂
But... Taobao is all in Chinese! (I didn't learn that much 🙂)
 
Re: small 3xp7 driver

Because of so many items of the electronic components, you have to communicate with the shop keeper to check whether they have STOCK, PRICE and MINIMUM ORDER QUANTITY before you place your order. Sadly to say, some shops are selling salvaged chips for brand new even fake chips. You are living so far away that it is quite boring if claiming is required.
 
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